WO2025210434A1

WO2025210434A1 - External device operation and communication

Info

Publication number: WO2025210434A1
Application number: PCT/IB2025/053006
Authority: WO
Inventors: Andrew T. Fried; Sakethram Karumuri; Charles M NOWELL; Eric P. MINNERATH; Jacob P. KOMAREK
Original assignee: Medtronic Inc
Current assignee: Medtronic Inc
Priority date: 2024-04-03
Filing date: 2025-03-21
Publication date: 2025-10-09
Anticipated expiration: 2026-10-03

Abstract

Systems and techniques for managing communication and charging from an external instrument are described. In one example, an external instrument includes communication circuitry and processing circuitry. The processing circuitry can control the communication circuitry to connect to the external device via the first communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the first communication channel, and control the communication circuitry to transmit the encrypted passthrough data to the medical device via a second communication channel. The processing circuitry can control an operational state of the external instrument based on reception of the encrypted passthrough data or the command. In some example, the operational state may be an operational state of recharge circuitry.

Description

EXTERNAL DEVICE OPERATION AND COMMUNICATION

CROSS-RELATED REFERENCE

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/574,058, filed April 3, 2024, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The disclosure relates to medical device communication, and more specifically to communication with a wearable or implantable medical device on a patient.

BACKGROUND

[0003] Medical devices may be external or implanted and may be used to monitor patient signals such as cardiac activity, biological impedance and to deliver electrical stimulation therapy to patients via various tissue sites to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson’s disease, diabetes, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis and other conditions. In some examples, the medical devices may communicate with one or more external devices. The communications may include programming the device to operate according to a patient condition as well as transmitting updates on the patient status to, for example, a clinician caring for the patient. In some examples, medical devices may include a rechargeable electrical power source, or may be powered directly by transmitting energy through tissue. In other examples, a medical device may receive power from a primary cell battery (non-rechargeable) or from line power.

SUMMARY

[0004] In general, the disclosure describes systems, devices, and techniques to manage communication and charging operation between external devices (e.g., a recharger, a patient programmer, clinician programmer, an application on a patient programmer, or an external computing device), and medical devices such as a wearable or implantable medical device. The communication for the systems of this disclosure may include a communication channel between one external device and another external device. These external devices may include any external devices configured to be involved with the operation of a medical device. Generally, an external device may include any device that can send or receive a signal or information directly or indirectly to or from the medical device. An external device may include a recharger, a programmer, or even computing device (e.g., tablet computer or hand-held computer) that communicates with the medical device through another device. In some examples, one of the external devices may be referred to as an external instrument when it is configured to interact directly with the medical device (e.g., a recharging device, a programmer, or a wireless sensor).

[0005] In some examples, a first communication channel is configured to transfer passthrough data from the external device to an external instrument, where the external instrument then funnels the passthrough data to the medical device without accessing that passthrough data. For example the passthrough data may be encrypted, but the medical device has a key to decrypt the passthrough data instead of the external instrument having a key. In this manner, the passthrough data may be encrypted before it is sent to the external instrument and stays encrypted until after it has been received by the medical device. The first communication channel may also act to transfer the passthrough data from the external instrument to the medical device. In some examples, the first communication channel may transfer a command from the external device directly to the recharger via an encrypted channel. For example, the command may include instructions that request one or more certain operations of the recharger. In some examples, the second communication channel, between the external instrument and the medical device may have one or more authorization levels and be authorized to convey different levels of information.

[0006] In some examples, the external instrument may adjust an operational state of the recharge circuitry of the external instrument based on reception of the passthrough data and/or the command. For example, the external instrument may switch from a charging state to a communication state in response to receiving the passthrough data. The external instrument may operate in a single shot communication mode (e.g., an example communication mode) in which the external instrument pauses charging, sends a single message to the medical device, and then resumes charging after the single message has been sent. In some examples, the external instrument may operate in telemetry-only mode (e.g., an example communication mode) in which the external instrument may pause charging, communicate with the medical device, and then resume charging after receiving a second command from the external device or a timeout condition occurs. The external instrument may switch between the charging mode, one or more communication modes, and/or an idle mode based on the type of data received from the external device, internal instructions stored by the recharger, or even communication from the medical device. In any case, the external instrument may switch between charging and communication modes in order to deliver energy and data to the medical device without interference. In some examples, the medical device can deliver electrical stimulation to various anatomical regions, such as a tibial nerve, sacral nerve, spinal cord, etc.

[0007] In one example, an external instrument includes communication circuitry configured to establish a first communication channel with an external device and a second communication channel with a medical device; and processing circuitry configured to: control the communication circuitry to connect to the external device via the communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the communication channel; control an operational state of the external instrument based on reception of at least one of the encrypted passthrough data or the command; and control the communication circuitry to transmit the encrypted passthrough data to the medical device via the second communication channel.

[0008] In another example, a method includes controlling, by processing circuitry of an external instrument, communication circuitry of the external instrument to connect to an external device via a first communication channel and a second communication channel with a medical device, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the first communication channel; controlling, by the processing circuitry, the communication circuitry to transmit the encrypted passthrough data to the medical device via the second communication channel; and controlling, by the processing circuitry, an operational state of the external instrument based on reception of at least one of the encrypted passthrough data or the command.

[0009] In another example, a non-transitory computer-readable storage medium storing instructions that, when executed, causes processing circuitry of an external instrument to control communication circuitry of the external instrument to connect to an external device via a first communication channel and a medical device via a second communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the communication channel; control the communication circuitry to transmit the encrypted passthrough data to the medical device via a second communication channel; and control an operational state of recharge circuitry of the external instrument based on reception of at least one of the encrypted passthrough data or the command, wherein the recharge circuitry is configured to transmit energy to the medical device.

[0010] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. l is a conceptual diagram illustrating an example medical system of this disclosure that includes an implantable medical device located near an ankle of a patient. [0012] FIG. 2 is a block diagram illustrating an example communication configuration for a system according to one or more techniques of this disclosure.

[0013] FIG. 3 is a conceptual diagram illustrating an medical system of this disclosure that includes an implantable medical device located near a pelvis of a patient. [0014] FIG. 4 is a block diagram illustrating example components of an example medical device.

[0015] FIG. 5 is a block diagram illustrating example components of an example recharger.

[0016] FIG. 6 is a flow chart illustrating an example mode for system operation for a single shot communication process.

[0017] FIG. 7 is a flow chart illustrating an example mode for system operation of a telemetry-only communication process.

[0018] FIG. 8 is a state diagram illustrating example states of a recharger.

DETAILED DESCRIPTION

[0019] The disclosure describes systems, devices, and techniques for facilitating communication between external devices (e.g. a clinical programmer, a client programmer, an onsite server, or an offsite server, a recharger, a wireless recharging device, a patient programmer, clinician programmer, or an application on a patient programmer) and medical devices such as a wearable or implantable medical device. These external devices may include any external devices configured to be involved with the operation of a medical device. Generally, an external device may include any device that can send or receive a signal or information directly or indirectly to or from the medical device. An external device may include a recharger, a programmer, or even computing device (e.g., tablet computer or hand-held computer) that communicates with the medical device through another device. In some examples, one of the external devices may be referred to as an external instrument when it is configured to interact directly with the medical device (e.g., a recharging device, a programmer, or a wireless sensor). Direct interaction may include directly sending a signal to, or receiving a signal from, the medical device.

[0020] Medical devices may be programmed using external programmers (e.g., clinician programmers and patient programmers) and, for rechargeable medical devices, receive charging energy from the external device. For example, an implantable medical device may receive energy wirelessly from an external and wireless charging device via an energy charging modality such as inductive charging. However, the medical device may not be able to receive data from the external instrument (a recharger or a programmer) during a recharge session because the inductive charging may interfere with the wireless communication of data and/or the single antenna of the medical device may be configured to receive inductive power instead of communication. In some examples, the external instrument may be configured to communicate with the external instrument (e.g., a recharger or a programmer) using a communication modality that the medical device is not capable of using (e.g., Bluetooth or other RF telemetry). Although the external instrument may act as an intermediary to send that communication from an external device (e.g., another external instrument or an external device that requires the external instrument to interact with the medical device) to the medical device, the external instrument may not be able to transmit communications to the medical device during a recharging session.

[0021] As described herein, the system may employ techniques that can enable the external instrument to facilitate communications and recharging sessions with the medical device. These techniques may operate in the background without interrupting the user experience. In some examples, an external device (e.g. an offsite server, an onsite server, a clinician programmer, or a patient programmer) is connected to an external instrument (e.g., a recharger, wireless recharger communicator, a patient programmer, clinician programmer, or an application on a patient device). In some examples, the external instrument may serially either communicate to or charge the medical device (e.g. not communicate or charger at the same time to prevent communication issues.) In some examples, a patient may have the external instrument strapped near the medical device, e.g., to the ankle of the patient for a tibial implanted device, when the system is using a Clinician Programmer or Patient Programmer to communicate to the medial device. The external instrument can then utilize different communication modalities between the external device(s) and the external instrument and between the external instrument and the medical device.

[0022] The communication for the systems of this disclosure may include a communication channel between an external device and an external instrument. In some examples, a first communication channel is configured to transfer passthrough data from the external device to the recharger (e.g., an example of an external instrument). The first communication channel may transfer the passthrough data from the external instrument to the medical device in an encrypted channel within the first communication channel (e.g., encrypted passthrough data). In some examples, the first communication channel may transfer a command from the external device to the external instrument. In some examples, the passthrough data may be encrypted before it is sent to the external instrument and stays encrypted until after it has been received by the medical device. In other words, the external instrument can re-transmit the received encrypted passthrough data to the medical device, but the external instrument cannot decrypt or otherwise interpret the content of the encrypted data. In this manner, the encrypted data cannot directly instruct the external instrument to perform any functions. The command, in contrast, sent to the external instrument may also be encrypted, but at a different authorization level such that the external instrument can decrypt the command and operate as instructed by the command.

[0023] Although the external instrument may not be able to decrypt the passthrough data, the external instrument may still be configured to alter an operational state of the external instrument, such as the recharge circuitry or communication circuitry, based on reception of the encrypted passthrough data or the content of the command. For example, the external instrument may operate in single shot communication mode in which the external instrument may pause charging, send a single message to the medical device, and then resume charging. In another example, the external instrument may operate in telemetry-only mode in which the external instrument may pause charging, communicate with the medical device, then resume charging after receiving a second command or timeout condition. These different communication modes may be selected by the external instrument based on the type of data received, depending on the data received from the external device, or some combination thereof. For example, the external instrument may switch to either communication mode in response to receiving the passthrough data or in response to receiving a direct instruction to transmit data such as via the command. The external instrument may select the single shot communication or the telemetry-only mode based on the quantity of passthrough data received, the frequency of passthrough data received, or some other characteristic indicative of which communication mode would be beneficial for transmitting data to the medical device while also limiting the interruption to the recharging session.

[0024] In some examples, the first communication channel is Bluetooth or another telemetry modality that may not be compatible with the medical device. In this manner, the external instrument can receive data through one of those communication channels and then transmit that data to the medical device using a different communication modality such as inductive telemetry. In some examples, the external instrument and the medical device have one coil each that may be used to transmit and/or receive energy and/or data. In some examples, the external instrument and the medical device each have one or two coils, such as a respective energy transmission coil and communication coil (e.g., coils that may be tuned to different frequencies or circuits that may re-tune the coil to perform a function as needed). In some examples, the medical device is a tibial stimulator that delivers electrical stimulation to a tibial nerve. However, the medical device may be configured to deliver stimulation to other anatomical targets and/or deliver other types of therapies.

[0025] As discussed herein, the external instrument may operate using different types of operational modes. These different operational modes may specify how the external instrument switches between recharging (or an idle state) and communication states, or between different communication states, or between different power states, or any other types of operational modes. In some examples, in a single-shot telemetry mode an external instrument may temporarily pause charging of a medical device to transmit passthrough data then return to charging the medical device after the passthrough data has been sent. The passthrough data may be received at the external instrument through a first communication channel. The passthrough data may stay encrypted from the external device (e.g. a programmer) and be decrypted by the medical device using an encryption key that the external instrument does not have access to. As such, the external instrument can only handle encrypted passthrough data instead of decrypt and read the passthrough data. As another example, in a telemetry-only mode, an external instrument may suspend charging of a medical device to transmit passthrough data then await receipt of a second command or a timeout condition before returning to charging the medical device. The passthrough data may be received at the external instrument through a first communication channel. The command to enter the telemetry-only mode may be sent through the first communication channel. A portion of the first communication channel, such as an encrypted channel, may be encrypted and un-decryptable by the external instrument such that the external instrument may not interpret, copy, or otherwise retain the data sent via the encrypted channel. The passthrough data may be an example of a data packet that the external instrument cannot decrypt.

[0026] The external instrument may be configured to transmit the passthrough data to the medical device (e.g., an implantable medical device, or IMD) via a second communication channel. A portion of the second communication channel may be unencrypted, or decryptable by the external instrument such that the external instrument may interpret the command sent over the second communication channel. Another portion of the first communication channel, such as the encrypted channel, may be encrypted and un-decryptable by the external instrument such that the external instrument may not interpret, copy, or otherwise retain the data sent via the encrypted channel (e.g., the encrypted passthrough data).

[0027] The systems and devices of this disclosure may provide advantages. For example, the external instrument can be configured to form first and second communication channels in which the passthrough data of the encrypted channel is encrypted prior to and relayed by the external instrument. A command may be received using first communication channel and may be decrypted and interpreted by the external instrument (e.g., a wireless recharger). This configuration can provide enhanced security for the operation of the medical device because the external instrument can send secure messages between an external device and the medical device. In addition, the systems can manage the switching between recharging and communication transmission to medical devices in order to deliver data in a timely manner while also completing recharging of the medical device also in a timely manner. The external instrument can perform this switching even when receiving encrypted passthrough data that the external instrument cannot interpret. For example, the external instrument can initiate different communication modes, such as a telemetry-only mode that priorities communicating passthrough data or a single shot telemetry mode that reduces latency in the recharging session. The systems of this disclosure may provide advantages by more efficiently managing the switching between recharging and data transmission to a medical device which can be hidden from the user to enhance user experience even when operational modes of the external instrument are changed.

[0028] FIG. 1 is a conceptual diagram illustrating an example medical system 100 of this disclosure that includes an implantable medical device located near an ankle of a patient. The example of system 100 in FIG. 1 includes implantable medical device (IMD) 110, external instrument 150, and one or more external devices 112.

[0029] In some examples, external instrument 150 may also be referred to as a recharger as shown in the example of FIG. 1, but may be or include a wireless recharger communicator, programmer, patient programmer, clinician programmer, external recharging device, or external computing device in other examples. These examples of external instrument 150 are all external devices that are configured to interact directly with IMD 110 (e.g., send signals to or receive signals from a medical device). External instrument 150 as shown in FIG. 1 includes one or more coils, external transfer coil 126 and internal transfer coil 128. External instrument 150 may be used to program or adjust settings of IMD 110 and may also recharge an electrical energy storage device, such as a battery, of IMD 110 (not shown in FIG. 1). In other examples, external instrument 150 may also include a mobile phone, tablet computer, a wearable computing device or similar computing device that includes processing circuitry configured to execute programming instructions to communicate with IMD 110 and/or external devices 112. Such a computing device may communicate with IMD 110 to adjust therapy and/or sensing parameters, download recorded data, and the other functions described in this disclosure. In some examples, such a computing device may additionally or alternatively be connected to external transfer coil 126 or include an internal transfer coil 128. External instrument 150 may also communicate with one or more external devices 112. External devices 112 may be configured to send or receive information to any other external devices, external instrument 150, or IMD 110. However, external devices 112 may not be configured to send or receive information directly to or from IMD 110. Instead, external devices 112 may be configured to interact with IMD 110 through external instrument 150. [0030] IMD 110 may include sensing circuitry configured to detect biological signals from the patient; electrical stimulation circuitry configured to deliver electrical stimulation to target tissue of the patient, communication circuitry, processing circuitry configured to control the operation of circuitry of IMD 110 and other circuitry (not shown in FIG. 1) configured to perform the functions described in this disclosure. IMD 110 may output the sensed data via communication circuitry (not shown in FIG. 1). In this disclosure, IMD 110 may referred to as medical device 110, implantable medical device (IMD) 110 or, in the example of a neurostimulation medical device, may be referred to as implantable neuro stimulator (INS) 110.

[0031] The communication circuitry may be configured to communicate with rechargers in system 100. In some examples, the communication circuitry may establish a first communication channel with external instrument 150. In some examples, the communication circuitry may also establish a second communication channel with IMD 110. The communication circuitry of IMD 110, as well as communication circuitry of external instrument 150, external devices 112, and other devices of system 100 may be configured to establish the first communication channel and the second communication channel on the communication link using time division multiplexing. By multiplexing the information for each communication channel over the same communication link, the respective data for each communication channel may be interleaved together over time. [0032] The second communication channel may transfer information at a first authorization level and/or a second authorization level. In some examples, the first communication channel is a secure communication channel established based on a first encryption key, and the second communication channel is a secure communication channel established based on a second encryption key. IMD 110 may communicate via inductive communication or another protocol such as a wireless protocol (e.g., Bluetooth™, Bluetooth Low Energy (BLE), or a protocol using the Medical Implant Communication System (MICS) band) to a number of different instruments, such as, for example, an additional medical device, a patient programmer, a clinician programmer, a programming fob, or another device. The inductive communication, or inductive connection, may be referred to as, or including, a communication channel in some examples.

[0033] In some examples, a first authorization level may provide access to more capabilities of IMD 110 than the other authorization levels. In some examples, external instrument 150 may establish the second communication channel in which external instrument 150 only acts as a relay to transfer data at the first authorization level. In some examples, the first authorization level may only authorize sending and receiving queries and status information about the transfer of passthrough data. In some examples, IMD 110 may communicate with external device 112 via the encrypted channel acting as a relay such that external device 112 may receive information about the power transfer function, such as the electrical energy storage level of a battery, or a power transfer rate. In some examples, where the encrypted channel acts as a relay, IMD 110 may additionally or alternatively communicate information commands and information that change the operation of the medical device worn by, or implanted in, the patient, such as a parameters that define a therapy delivery program. In some examples, the authorization level on the different channel may transfer information about the power transfer function, such as the electrical energy storage level of a battery, or a power transfer rate. In some examples, the other authorization levels may be decrypted and/or interpreted by the external instrument 150 to modulate the operation of external instrument 150.

[0034] Communication related to power transfer may limit external instrument 150 to receive and transfer information such as battery current, battery discharge level, power transfer efficiency and similar system metrics and information. A variety of system metrics may be available to external instrument 150 from computations of power and heat and from metrics communicated from IMD 110. Processing circuitry of system 100, e.g., processing circuitry of external instrument 150, processing circuitry of external devices 112, and/or processing circuitry of IMD 110, may calculate any of the values described herein. These metrics may include but are not limited to: battery current, power transfer efficiency, IMD efficiency and other similar metrics. Analysis of system characterization data that the IMD efficiency, which may be measured by IMD 110 and communicated to external instrument 150, may be an example indicator of when external transfer coil 126 is concentric with transfer coil 116.

[0035] As noted above, at the same time, IMD 110 may communicate with one or more other devices over one or more additional communication channels at a different authorization level. Each communication channel may have a separate authorization level and may have separate encryption keys. For example, a clinical programmer may establish a communication channel with an authorization level that allows the clinical programmer to change operating parameters, set or change therapy modes, set up patient data collection, receive detailed patient sensing data, and other similar functions. In some examples, the authorization level may enable external instrument 150 to act as a relay to passthrough the data from the clinical programmer to IMD 110. In some examples the clinician programmer may be near IMD 110, e.g., in the same room. In other examples, the clinician programmer may be at a remote location, operated by a caregiver, and communicate via external devices 112, or some other communication device. Similarly, a patient programmer may communicate at a third authorization level with a more limited set of functions, such as may be able to cause IMD 110 to increase or decrease stimulation amplitude and intensity, but may be unable to change a programmed therapy protocol. In other words, a first authorization level may configure external instrument 150 to act as a relay to transfer passthrough data from external device 112 to IMD 110. A second authorization level may enable external instrument 150 to read some or all of the data communicated through external instrument 150. The data of the second authorization level may configure or alter an operation of external instrument 150 to implement telemetry-only mode, which may enable a bulk transfer of data. Some examples of items in an information set, which may be transferred via the first or second authorization levels, may include: data, operating status, operating commands, and therapy parameters that define delivered therapy such as amplitude, pulse width, frequency, burst length, and other parameters that define therapy. Some examples of items in an information set may also include configuration of sense circuitry in the medical device, identifying information e.g., related to identifying the patient, the computing device, location and similar identification information, power information, firmware update commands, memory access commands, and configuration of closed loop therapy algorithms. [0036] Some other examples of roles and associated authorization levels for communication channels may include any one or more of clinician, patient, recharger, firmware update, security level change, and remote. In some examples, the programming instructions for processing circuitry of system 100 may reduce or limit conflicting commands and other information transfer between the two or more communication channels, which may have different roles. For example, processing circuitry of system 100, e.g., of external instrument 150, IMD 110 or some other processing circuitry, may reduce or limit a patient programmer from trying to decrease a parameter at the same time a clinician programmer is trying to increase the parameter. In other examples, one or more roles may be restricted based on the role of an established communication channel, e.g., the patient programmer may not establish a communication channel during a firmware update. In other examples, the number of channels may be restricted, e.g., only two channels may connect at the same time, or no more than three channels may connect at the same time.

[0037] In some examples, computing devices of system 100 may be configured to identify, open, and close a secure communications channel to and from IMD 110. Each secure channel may be independent from each other in channel establishment, generated encryption keys, and authorization roles, as noted above. In some examples, each channel may have a channel validity timer, which is set to a configured value at the time the recharger, e.g., external instrument 150, establishes a communication channel with IMD 110. In other words, the communication circuitry may be configured to establish the secure communication based on an encryption key for the duration of a communication session. The encryption for the encrypted channel, and the associated authorization level, may be time limited to the communication session for each channel.

[0038] In some examples, the channel validity timer may be reset upon each successful decryption of subsequent messages, or based on some other communication event, effectively extending the communication session. When the timer for a channel expires, that channel may be invalidated and subsequent commands may not be processed. In the event a channel timer expires, a user of external instrument 150 may request to open a new channel to issue subsequent commands or the recharger may reopen a new channel automatically in the background.

[0039] In some examples, authorization to transfer information may be granted upon a successful channel open command. The authorization is valid for the duration of the channel validity timer. Channel validity may be set to a configured value of ten minutes, five minutes, twenty minutes, or any number of other values. In some examples, the channel validity time for each channel may be the same, or may be different, from other channels and based on authorization level. In some examples, upon successfully decrypting a user command processing circuitry of one or more of the computing devices of system 100 may reset the channel validity timer. The channel validity timer may count down from the set time and at zero, may cause the processing circuitry to revoke the channel validity and authorization. After the channel validity and authorization have been revoked, any subsequent commands may result in a non-decryptable message and commands are not executed. The programming instructions for the processing circuitry of system 100 may not respond to application commands and other messages when channel encryption keys are invalid/expired. In some examples, the processing circuitry may set a register and/or output an error message. In some examples, when IMD 110 is reset or security level is changed the communication channels may also be reset, which may clear the channel encryption keys and set the channel state to “unused.” Each computing device may then re-negotiate encryption keys to establish and continue secure communication over the established communication channel. [0040] In the example of a rechargeable power source, the rechargeable power source of IMD 110 may include one or more capacitors, batteries, or other components, e.g., chemical, or electrical energy storage devices (not shown in FIG. 1). Example batteries may include lithium-based batteries, nickel metal-hydride batteries, or other materials. The rechargeable power source may be replenished, refilled, or otherwise capable of increasing the amount of energy stored after energy has been depleted. The energy received from transfer coil 116 may be conditioned and/or transformed by a charging circuit. The charging circuit may then send an electrical signal used to charge the rechargeable power source when the power source is fully depleted or only partially depleted.

[0041] External instrument 150 may be used to recharge the rechargeable power source within IMD 110 implanted in the patient. External instrument 150 may be a handheld device, a portable device, or a stationary charging system. External instrument 150 may include components necessary to charge IMD 110 through tissue of the patient. External instrument 150 may include external transfer coil 126 and internal transfer coil 128. In other examples, external instrument may only include internal primary coil 128 and omit the use of external transfer coil 126, may have multiple internal and external coils, or may omit internal transfer coil 128 and use external transfer coil 126.

[0042] External instrument 150 may include a housing to enclose operational components such as a processor, memory, user interface, telemetry circuitry, power source, and charging circuit configured to transmit energy to transfer coil 116 inside IMD 110 via external transfer coil 126 and/or internal transfer coil 128. Although a user may control the recharging process with a user interface of external instrument 150, external instrument 150 may alternatively be controlled by another device, e.g., an external programmer, a computing device of external devices 112, where such external device may include a tablet computer, laptop, or other similar computing device. In other examples, external instrument 150 may be integrated with an external programmer, such as the patient programmer carried by the patient.

[0043] External instrument 150 and IMD 110 may utilize any wireless power transfer techniques that are capable of recharging the power source of IMD 110 when IMD 110 is implanted within the patient. In some examples, system 100 may utilize inductive coupling between primary coils (e.g., internal transfer coil 128 or external transfer coil 126) and secondary coils (e.g., transfer coil 116) of external instrument 150 and IMD 110. In inductive coupling, internal transfer coil 128 (or external transfer coil 126) is placed near implanted IMD 110 such that internal transfer coil 128 (or external transfer coil 126) is aligned (e.g. coaxially) with transfer coil 116 of IMD 110. External instrument 150 may then generate an electrical current in internal transfer coil 128 based on a selected power level for charging the rechargeable power source of IMD 110.

[0044] When the primary coils (e.g., internal transfer coil 128 or external transfer coil 126) and the secondary coils (e.g., transfer coil 116) are aligned, or partially aligned, the electrical current in the primary coils may magnetically induce an electrical current in transfer coil 116 within IMD 110. Since the secondary coils are associated with and electrically coupled to the rechargeable power source, the induced electrical current may be used to increase the voltage, or charge level, of the rechargeable power source. Although inductive coupling is generally described herein, any type of wireless energy transfer may be used to transfer energy between external instrument 150 and IMD 110. [0045] External transfer coils 126 and internal transfer coil 128 may include a wound wire (e.g., a coil) (not shown in FIG. 1). The coil may be constructed of a wire wound in an in-plane spiral (e.g., a disk-shaped coil). In some examples, this single or even multilayers spiral of wire may be considered a flexible coil capable of deforming to conform with a non-planar skin surface. The coil may include wires that electrically couple the flexible coil to a power source and a charging module configured to generate an electrical current within the coil. External transfer coil 128 may be external of the housing of external instrument 150 such that external transfer coil 128 may be placed on the skin of the patient proximal to IMD 110. In some examples, external transfer coil 128 may be disposed on the outside of the housing or even within housing.

[0046] Either internal transfer coil 126 and/or external transfer coil 128 of system 100 may include a heat sink device (not shown in FIG. 1). In the example of system 100, external instrument 150 is the power transmitting unit and IMD 110 is the power receiving unit. IMD 110 may be in a flipped or non-flipped position.

[0047] External instrument 150 may include a user interface to receive control inputs from a user, such as the patient, medical professional, or other caregiver. External instrument 150, and any computing device of system 100, may include a touch-screen user interface. The user interface of external instrument 150 may also provide information to a user, including whether IMD 110 is ON and delivering therapy, whether external instrument 150 is wirelessly communicating with IMD 110 and other information which external instrument 150 may transfer or receive. [0048] In some examples, external instrument 150 may be configured to transfer data. External instrument 150 may be configured to transfer data by inductively linking the primary coils (e.g., internal transfer coil 128 or external transfer coil 126) and the secondary coils (e.g., transfer coil 116). In some examples, the primary coils and the secondary coils may be inductively linked when the primary coils and the secondary coils are aligned, or partially aligned, wherein the electrical current in the primary coils may magnetically induce an electrical current in transfer coil 116 within IMD 110. Data may be inductively transmitted between the primary coils and the secondary coils through frequency modulation of the current or amplitude modulation of the current. In some examples, the primary coils and/or the secondary coils may have a default optimization for receiving power. In some examples, the primary coils and/or the secondary coils may have a default optimization for receiving data. In some examples, the primary coils and/or the secondary coils may have a sufficient band pass range such that the coils are able to receive both power and data in their default tuning status. In some examples, the primary coils and/or the secondary coils may be tuned into a selective data receiving state wherein the default state changes from a power receiver default to a data receiver default for a temporary period of time. In some examples, the primary coils and/or the secondary coils may be tuned into a selective power receiving state wherein the default state changes from a data receiver default to a power receiver default for a temporary period of time. [0049] The example of FIG. 1 is a side view of a patient’s leg showing IMD 110 as a leadless neurostimulation device near the ankle adjacent to tibial nerve 104. IMD 110 may be implanted through the patient’s skin and cutaneous fat layer via incision 102. In some examples, incision 102 may be relatively small (e.g., about one to three cm) to improve patient outcomes and decrease healing time. In some examples, incision 102 may above tibial nerve 104 on a medial aspect of the patient’s ankle. While incision 102 is shown approximately horizontal to the length of tibial nerve 104, other incisions 102 or implantation techniques could be used according to physician preference such as a longitudinal to the length of tibial nerve 104 or at a 45 degree angle relative to tibial nerve 104. The example of FIG. 1 describes IMD 110 for tibial nerve stimulation. In other examples, the techniques of this disclosure may apply to other rechargeable devices, such as implantable neurostimulation system for use in spinal cord stimulation therapy, deep brain stimulation, as well as to other types of medical devices without limitation.

[0050] IMD 110 may be positioned adjacent to the region defined by flexor digitorum longus and soleus in which tibial nerve 104 is contained and implanted adjacent and proximal to a fascia layer. One or more electrodes of IMD 110 may face toward tibial nerve 104. Though not shown in FIG. 1, IMD 110 may also connect to one or more leads comprising one or more electrodes (not shown in FIG. 1).

[0051] IMD 110 may be constructed of any polymer, metal, or composite material sufficient to house the components of IMD 110. In this example, IMD 110 may be constructed with a biocompatible housing, such as titanium or stainless steel, or a polymeric material such as silicone or polyurethane, and surgically implanted at a site in patient near tibial nerve 104, in some examples, while in other examples, implanted near the pelvis, abdomen, or buttocks. The housing of IMD 110 may be configured to provide a hermetic seal for components, such as a rechargeable power source. In addition, the housing of IMD 110 may be selected of a material that facilitates receiving energy to charge the rechargeable power source.

[0052] During normal operation after implantation, an electrical stimulation signal may be transmitted between one or more electrodes through the fascia layer. The electrical signal may be used to stimulate tibial nerve 104 which may be useful in the treatment of overactive bladder (OAB) symptoms of urinary urgency, urinary frequency and/or urge incontinence, or fecal incontinence.

[0053] One type of therapy for treating bladder dysfunction includes delivery of electrical stimulation to a target tissue site within a patient to cause a therapeutic effect during delivery of the electrical stimulation. For example, delivery of electrical stimulation from IMD 110 to a target therapy site, e.g., a tissue site that delivers stimulation to modulate activity of tibial nerve 104, spinal nerve (e.g., a sacral nerve), a pudendal nerve, dorsal genital nerve, an inferior rectal nerve, a perineal nerve, or branches of any of the aforementioned nerves, may provide a therapeutic effect for bladder dysfunction, such as a reduction in frequency of bladder contractions. In some cases, electrical stimulation of tibial nerve 104 may modulate afferent nerve activities to restore urinary function.

[0054] FIG. 2 is a block diagram illustrating an example communication configuration for a system according to one or more techniques of this disclosure. System 200 of FIG. 2 is an example of system 100 described above in relation to FIG. 1 and may have the same characteristics and functions as described above for system 100. For example, medical device 210 may be similar to IMD 110, external instrument 250 may be similar to external instrument 150, and external device 212 may be similar to external device 112. [0055] In some examples medical device 210, also referred to as device 210 or implantable medical device (IMD) 210, may be an implantable or wearable device or an implantable neuro stimulator as described above in relation to FIG. 1. In other examples, medical device 210 may also include medical systems that are capital equipment that may be neither body worn nor implantable. Some examples of capital equipment may include a surgical navigation system, a blood oxygen monitoring system, a robotic surgery system and other types of capital equipment. For example, a robotic surgery system may establish a communication channel with a first provider, e.g., a surgeon in an international location, as well as with a provider that is local and may be in the same operating room as the robotic surgery system.

[0056] External instrument 250 may comprise processing circuitry 230, communication circuitry 256, and charging circuitry 268. In some examples, external instrument 250 may be referred to as a recharger for medical device 210. Communication circuitry 256 of external instrument 250 may be configured to establish encrypted channel 202 between external device 212 medical device 210 through external instrument 250. Communication circuitry 256 of external instrument 250 may be configured to establish first communication channel 204 between external device 212 and external instrument 250. In some examples, communication circuitry 256 of external instrument 250 may be configured to establish second communication channel 206 between external instrument 250 and medical device 210. Second communication channel 206 may have first authorization level 203 (not shown in FIG. 2) and second authorization level 205. In some examples, second communication channel 206 may include three or more different authorization levels. Although the example of FIG. 2 only illustrates two communication channels (204 and 206) to simplify the description, there may be any number of channels, e.g., two or more channels for each of first communication channel 204 and second communication channel 206.

[0057] In some examples, processing circuitry 230 of external instrument 250 may manage communication circuitry 256 to open and establish first communication channel 204 and second communication channel 206. First communication channel 204 may transfer information from external device 212 to external instrument 250. In some examples, external instrument 250 may decrypt at least some of the data received via first communication channel 204. Encrypted channel 202 may act as an encrypted passthrough to transfer an encrypted passthrough data (e.g., encrypted payload) from external device 212 to external instrument 250 and then may additionally transfer the encrypted passthrough data from external instrument 250 to medical device 210. In this manner, external instrument 250 can act as an intermediary. Encrypted channel 202 enables external instrument 250 to act as a relay and a converter such that external instrument 250 cannot decrypt or read this passthrough data of encrypted channel 202.

[0058] In some examples, encrypted channel 202 may be described as end-to-end encrypted transfer of data. In some examples, external instrument 250 accepts passthrough data, which may be an encrypted payload, from external device 212 via encrypted channel 202 and then transmits the passthrough data to medical device 210 via encrypted channel 202 without decrypting the data. In some examples, external instrument 250 may not have the encryption key encrypted channel 202 and as is unable to decrypt the passthrough data. External instrument 250 may be described as a converter as the passthrough data is transferred from external device 212 to external instrument 250 via a wireless protocol (e.g., Bluetooth™, Bluetooth Low Energy (BLE), or a protocol using the Medical Implant Communication System (MICS) band) or some other wired (e.g. Universal Serial Bus (USB)) or wireless communication protocol. External instrument 250 may then convert the data from the wirelessly received data to data which may be transferred inductively from external instrument 250 to medical device 210. In some examples, the inductive communication may utilize Medical Device Radiocommunications Service (MICS) standard, Bluetooth™ Low Energy (BLE) standard, or any other communication standard suitable to transfer data between a medical device and a device external to the body.

[0059] In some examples, the passthrough data transferred via encrypted channel 202 may be commands to change operating parameters, set or change therapy modes, set up patient data collection, receive detailed patient sensing data, and other similar functions. In some examples, the passthrough data may additionally or alternatively be firmware, software, or other updates to medical device 210.

[0060] In some examples, external instrument 250 may additionally or alternatively not notify an operator of external instrument 250 that data is being transmitted via encrypted channel 202 to improve a client interface with external instrument 250. In some examples, external instrument 250 may be recharging the internal components of medical device 210 and receive a request from external device 210 to update medical device 210 then processing circuitry 230 may disable charging circuitry 268 and processing circuitry 230 may enable communication circuitry 256 to form encrypted channel 202 to transfer the passthrough data. During the transfer of the passthrough data, processing circuitry 230 may continue to provide a readout to an operator that external instrument 250 is operating nominally (e.g. recharging normally) and upon completion of the transfer of the passthrough data, processing circuitry 230 may disable communication circuitry 256 and re-enable charging circuitry 268.

[0061] In some examples, first communication channel 204 and second communication channel 206 may be described as a man-in-the-middle transfer of data. In some examples, external instrument 250 accepts data, such as a command (e.g. a command to change a status of external instrument 250) from external device 212 via communication channel 204 and then may transmit the data, or an alternation or transformation of the data, to medical device 210 via communication channel 206. In some examples, external instrument 250 may have a decryption key for information transmitted over first communication channel 204. In some examples, external instrument 250 may re-encrypt or may additionally or alternatively encrypt the information then transmitted over second communication channel 206. In some examples, first communication channel 204 may use a wireless protocol (e.g., Bluetooth™, Bluetooth Low Energy (BLE) or any other suitable protocol to transfer data between devices) or some other wired (e.g. USB) or wireless communication protocol. In some examples, second communication channel 206 may use an inductive transfer system from external instrument 250 to medical device 210. In some examples, communication channels 204 and 206 may utilize the same telemetry modality.

[0062] In some examples, the data transferred via first communication channel 204 may be information from external device 212 to alter a status of external instrument 250 (e.g. putting external instrument 250 into a telemetry-only mode, putting external instrument 250 into a single shot telemetry mode) or to update external instrument 250 (e.g. firmware or software). In some examples, the data transferred via second communication channel 206 may be information from external instrument 250, and may additionally or alternatively, be information passed through from external device 212. The information sent through communication channel 206 may alter a status of medical device 210.

[0063] In some examples, external instrument 250 may notify an operator of external instrument 250 that data is being transmitted via first communication channel 204 or second communication channel 206. In some examples, external instrument 250 may not notify an operator of external instrument 250 that data is being transmitted via first communication channel 204 or second communication channel 206. In some examples, external instrument 250 may be recharging the internal components of medical device 210 and receive a request from external device 212 via first communication channel 204 to enter telemetry only mode then processing circuitry 230 may disable charging circuitry 268 and processing circuitry 230 may enable communication circuitry 256 to form communication channel 206. Communication channel 206 enable continuous communication over and may additionally or alternatively form encrypted channel 202 to enable continues encrypted communication over encrypted channel 202 as discussed above. In some examples, communication circuity 256 may utilize a wireless protocol (e.g., Bluetooth™, Bluetooth Low Energy (BLE), inductive communication, Wi-Fi™ or a protocol using the Medical Implant Communication System (MICS) band) and/or a wired protocol (e.g. Universal Serial Bus (USB)). In some examples, during the transfer of the passthrough data, processing circuitry 230 may provide a readout to an operator that external instrument 250 is transferring data. In some examples, during the transfer of the passthrough data, processing circuitry 230 may continue to provide a readout to an operator that external instrument 250 is operating nominally (e.g. recharging normally). External instrument 250 may then wait to receive a request from external device 210 to exit telemetry only mode or wait for external instrument 250 to reach a timeout condition whereafter, processing circuitry 230 may disable communication circuitry 256 and reenable charging circuitry 268.

[0064] FIG. 3 is a conceptual diagram illustrating a medical system of this disclosure that includes an implantable medical device located near a pelvis of a patient. In the example shown, system 300 includes IMD 372 configured to deliver spinal cord stimulation (SCS) therapy and external instrument 350, in accordance with one or more techniques of this disclosure. Although the techniques described in this disclosure are generally applicable to a variety of medical devices including external devices and IMDs, application of such techniques to IMDs and, more particularly, implantable electrical stimulators (e.g., neurostimulators) will be described for purposes of illustration. More particularly, the disclosure will refer to an implantable SCS system for purposes of illustration, but without limitation as to other types of medical devices or other therapeutic applications of medical devices. In the example of FIG. 3, system 300 includes IMD 372 with antenna 316, external instrument 350, and external device 312, which may be similar to examples of IMD 110, 210 with secondary coil 116, external instrument 150, 250, and external device 112, 212 described above in relation to FIGS. 1 and 2 and may have the same or similar functions and characteristics. [0065] As shown in FIG. 3, system 300 includes an IMD 372, leads 330A and 330B, and external instrument 350 shown in conjunction with a patient 305, who is ordinarily a human patient. In the example of FIG. 3, IMD 372 is an implantable electrical stimulator that is configured to generate and deliver electrical stimulation therapy to patient 305 via one or more electrodes of electrodes 332A and 332B, respectively on leads 330A and/or 330B (collectively, “leads 330”), e.g., for relief of chronic pain or other symptoms. In other examples, IMD 372 may be coupled to a single lead carrying multiple electrodes or more than two leads each carrying multiple electrodes, or leadless, as in the example of IMD 110 depicted in FIG. 1. IMD 372 may include an electrical connector configured to connect to the electrical leads, e.g., in the header of IMD 372.

[0066] IMD 372 may be a chronic electrical stimulator that remains implanted within patient 305 for weeks, months, or even years. In other examples, IMD 372 may be a temporary, or trial, stimulator used to screen or evaluate the efficacy of electrical stimulation for chronic therapy. In one example, IMD 372 is implanted within patient 305, while in another example, IMD 372 is an external device coupled to percutaneously implanted leads.

[0067] In the example of FIG. 3, external instrument 350 may be placed near IMD 372 to communicate and/or transfer power to IMD 372. In some examples, external instrument 350 may be held in place by a belt or straps 352. In some examples belt 352 may include a pouch that accepts external instrument 350. Any of the computing devices of system 300 may include a user interface. Examples of the user interface may include indicator lights, audio feedback, or graphics displayed on a graphical user interface (GUI) such as a tablet computer, smart phone 354, wearable computing device 355 or similar device.

[0068] As described above in relation to FIGS. 1 and 2, in some examples, a user, such as a clinician or patient 305, may interact with a user interface of external instrument 350 or external device 312, to program IMD 372, download collected patient data, and similar interactions. Communication circuitry, which may be substantially equivalent to communication circuitry 256 of FIG. 2, of system 300, located on any of IMD 372 and the rechargers of system 300 may establish one or more communication channels on a communication link. The communication channels may share the communication link using time division of the link bandwidth. Each communication channel may be configured to transfer information based on an associated information set. In some examples, the one or more communication channels may be substantially similar to first communication channel 204 and/or second communication channel 206 and may have one or more encrypted channels within the one or more communication channels, the one or more encrypted channels may be substantially similar to encrypted channel 202. In this manner, communication channels 204 and 206 may, together, act to transmit the same encrypted passthrough data from medical device 212 indirectly to medical device 210. [0069] Programming of IMD 372 may refer generally to the generation and transfer of commands, programs, or other information to control the operation of IMD 372. In this manner, IMD 372 may receive the transferred commands and programs from external instrument 350 to control stimulation, such as electrical stimulation therapy (e.g., informed pulses), control stimulation (e.g., control pulses), haptic stimulation, sensing and other operating parameters. When recharging, external instrument 350 may communicate to IMD 372 with a more limited information set than a patient programmer or clinician programmer.

[0070] For example, a clinician programmer may transmit therapy stimulation programs, evoked compound action potential (ECAP) test stimulation programs, stimulation parameter adjustments, therapy stimulation program selections, ECAP test program selections, user input, or other information to control the operation of IMD 372 as described above in relation to FIGS. 1 and 2. A patient programmer device, or wearable computing device 355 and mobile computing device 354 with processing circuitry executing an application configured to control the operation of IMD 372, may communication with a more limited information set and at a different authorization level than a clinical programmer.

[0071] As described above in relation to FIG.l, information may be transmitted between external instruments of system 300 and IMD 372. Therefore, IMD 372 and the external instruments may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, radiofrequency (RF) telemetry and inductive coupling, but other techniques are also contemplated. In some examples, external instrument 350 includes a communication head, e.g., external transfer coil 126 depicted in FIG. 1, that may be placed proximate to the patient’s body near the IMD 372 implant site to improve the quality or security of communication between IMD 372 and external instrument 350. Communication between the rechargers of system 300 and IMD 372 may occur during power transmission or separate from power transmission. [0072] In some examples, the stimulation signals, or pulses, may be configured to elicit detectable ECAP signals that IMD 372 may use to determine the posture state occupied by patient 305 and/or determine how to adjust one or more parameters that define stimulation therapy. The processing circuitry of IMD 372 may cause the stimulation signals to also deliver haptic stimulation, e.g., stimulation above a perception threshold of patient 305, to provide patient feedback, such as feedback on the quality of alignment between the primary and secondary coils.

[0073] The techniques of this disclosure may also apply to other devices, including wearable devices that may be located elsewhere on patient 305. Some examples of IMD 372 may include devices implanted pectorally for deep brain stimulation (DBS), near the tibial region (e.g. to stimulate a tibial nerve such as IMS 110 of FIG. 1 to stimulate tibial nerve 104 of FIG. 1), near the buttocks or flank for sacral neuromodulation, near the heart for cardiac therapy and/or monitoring, and other locations.

[0074] In other words, although in one example IMD 372 takes the form of an SCS device, in other examples, IMD 372 takes the form of any combination of DBS devices, sacral neuromodulation (SNM) devices, implantable cardioverter defibrillators (ICDs), pacemakers, cardiac resynchronization therapy devices (CRT -Ds), left ventricular assist devices (LVADs), implantable sensors, orthopedic devices, or drug pumps, as examples. Moreover, techniques of this disclosure may be used to determine parameters that affect stimulation thresholds (e.g., perception thresholds and detection thresholds) associated any one of the aforementioned IMDs and then use a stimulation threshold to inform the intensity (e.g., stimulation levels) of therapy. For example, changing stimulation parameters such as the number of pulses in a burst, the number of bursts over a duration, the pulse width of a pulse in a burst, the ON-time, the OFF-time, a pattern of pulses over a duration and other parameters may change the intensity as well as the efficacy of the therapy to relieve the symptoms.

[0075] As with IMD 110 described above in relation to FIG. 1, IMD 372 may be constructed of any polymer, metal, or composite material sufficient to house the components of IMD 372 (e.g., components illustrated in FIG. 2) within patient 305. In this example, IMD 372 may be constructed with a biocompatible housing, such as titanium or stainless steel, or a polymeric material such as silicone, polyurethane, or a liquid crystal polymer, and surgically implanted at a site in patient 305 near the pelvis, abdomen, or buttocks. In other examples, IMD 372 may be implanted within other suitable sites within patient 305, which may depend, for example, on the target site within patient 305 for the delivery of electrical stimulation therapy. The outer housing of IMD 372 may be configured to provide a hermetic seal for components, such as a rechargeable or non-rechargeable power source. In addition, in some examples, the outer housing of IMD 372 is selected from a material that facilitates receiving energy to charge the rechargeable power source.

[0076] IMD 372 may deliver electrical stimulation energy, which may be constant current or constant voltage pulses, for example, to one or more target tissue sites of patient 305 via one or more electrodes 332A and 332B (collectively electrodes 332) of implantable leads 330. In the example of FIG. 3, leads 330 carry electrodes that are placed adjacent to the target tissue of spinal cord 320. One or more of electrodes 332 may be disposed at a distal tip of a lead 330 and/or at other positions at intermediate points along the lead. Leads 330 may be implanted and coupled to IMD 372. Electrodes 332 may transfer electrical stimulation generated by an electrical stimulation generator in IMD 372 to tissue of patient 305. Electrodes 332 may also sense bioelectrical signals of patient 305.

[0077] Although leads 330 may each be a single lead, lead 330 may include a lead extension or other segments that may aid in implantation or positioning of lead 330. In some other examples, IMD 372 may be a leadless stimulator with one or more arrays of electrodes arranged on a housing of the stimulator rather than leads that extend from the housing, as shown in IMD 110 of FIG. 1. In addition, in some other examples, system 300 may include one lead or more than two leads, each coupled to IMD 372 and directed to similar or different target tissue sites.

[0078] Electrodes 332A and 332B of leads 330 may be electrode pads on a paddle lead, circular (e.g., ring) electrodes surrounding the body of the lead, conformable electrodes, cuff electrodes, segmented electrodes (e.g., electrodes disposed at different circumferential positions around the lead instead of a continuous ring electrode), any combination thereof (e.g., ring electrodes and segmented electrodes) or any other type of electrodes capable of forming unipolar, bipolar or multipolar electrode combinations for therapy. Ring electrodes arranged at different axial positions at the distal ends of lead 330 will be described for purposes of illustration.

[0079] The deployment of electrodes 332A and 332B via leads 330 is described for purposes of illustration, but arrays of electrodes may be deployed in different ways. For example, a housing associated with a leadless stimulator may carry arrays of electrodes, e.g., rows and/or columns (or other patterns), to which shifting operations may be applied. Such electrodes may be arranged as surface electrodes, ring electrodes, or protrusions. As a an alternative, electrode arrays may be formed by rows and/or columns of electrodes on one or more paddle leads. In some examples, electrode arrays include electrode segments, which are arranged at respective positions around a periphery of a lead, e.g., arranged in the form of one or more segmented rings around a circumference of a cylindrical lead. In other examples, one or more of leads 330 are linear leads having 8 ring electrodes along the axial length of the lead. In another example, the electrodes are segmented rings arranged in a linear fashion along the axial length of the lead and at the periphery of the lead.

[0080] The stimulation parameter set of a therapy stimulation program that defines the stimulation pulses of electrical stimulation therapy by IMD 372 through the electrodes of leads 330 may include information identifying which electrodes have been selected for delivery of stimulation according to a stimulation program, the polarities of the selected electrodes, i.e., the electrode combination for the program, voltage or current amplitude, pulse frequency, pulse width, pulse shape of stimulation delivered by the electrodes. These stimulation parameters values that make up the stimulation parameter set that defines pulses may be predetermined parameter values defined by a user and/or automatically determined by system 300 based on one or more factors or user input.

[0081] Similarly, sensing bioelectrical signals may use a variety of combinations of electrodes on leads 330, the housing of IMD 372, or other sensors connected directly or indirectly to IMD 372. In some examples IMD 372 may measure and detect other bioelectrical signals from patient 305 including cardiac activity, thoracic impedance, water retention and other signals. In some examples, lead 330 includes one or more sensors configured to allow IMD 372 to monitor one or more parameters of patient 305, such as patient activity, pressure such as blood pressure, temperature, or other characteristics. The one or more sensors may be provided in addition to, or in place of, therapy delivery by lead 330.

[0082] Although FIG. 3 is directed to SCS therapy, e.g., used to treat pain, in other examples system 300 may be configured to treat any other condition that may benefit from electrical stimulation therapy. For example, system 300 may be used to treat tremor, Parkinson’s disease, epilepsy, a pelvic floor disorder (e.g., urinary incontinence or other bladder dysfunction, fecal incontinence, pelvic pain, bowel dysfunction, or sexual dysfunction), obesity, gastroparesis, or psychiatric disorders (e.g., depression, mania, obsessive compulsive disorder, anxiety disorders, and the like). In this manner, system 300 may be configured to provide therapy taking the form of deep brain stimulation (DBS), peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), cortical stimulation (CS), pelvic floor stimulation, gastrointestinal stimulation, or any other stimulation therapy capable of treating a condition of patient 305. In other examples, IMD 372 takes the form of any combination of deep brain stimulation (DBS) devices, implantable cardioverter defibrillators (ICDs), pacemakers, cardiac resynchronization therapy devices (CRT-Ds), left ventricular assist devices (LVADs), implantable sensors, orthopedic devices, drug pumps and so on.

[0083] IMD 372 is configured to deliver electrical stimulation therapy to patient 305 via selected combinations of electrodes carried by one or both of leads 330, alone or in combination with an electrode carried by or defined by an outer housing of IMD 372. The target tissue for the electrical stimulation therapy may be any tissue affected by electrical stimulation, which may be in the form of electrical stimulation pulses or continuous waveforms. In some examples, the target tissue includes nerves, smooth muscle, or skeletal muscle. In the example illustrated by FIG. 3, the target tissue is tissue proximate spinal cord 320, such as within an intrathecal space or epidural space of spinal cord 320, or, in some examples, adjacent nerves that branch off spinal cord 320. Leads 330 may be introduced into spinal cord 320 in via any suitable region, such as the thoracic, cervical, or lumbar regions. Stimulation of spinal cord 320 may, for example, reduce or limit pain signals from traveling through spinal cord 320 and to the brain of patient 305. Patient 305 may perceive the interruption of pain signals as a reduction in pain and, therefore, efficacious therapy results. In other examples, stimulation of spinal cord 320 may produce paresthesia which may be reduce the perception of pain by patient 305, and thus, provide efficacious therapy results.

[0084] IMD 372 is configured to generate and deliver electrical stimulation therapy to a target stimulation site within patient 305 via the electrodes of leads 330 to patient 305 according to one or more therapy stimulation programs. A therapy stimulation program defines values for one or more parameters (e.g., a parameter set) that define an aspect of the therapy delivered by IMD 372 according to that program. For example, a therapy stimulation program that controls delivery of stimulation by IMD 372 in the form of pulses may define values for voltage or current pulse amplitude, pulse width, pulse rate (e.g., pulse frequency), electrode combination, pulse shape, etc. for stimulation pulses delivered by IMD 372 according to that program. In some examples, parameters may include sequences of pulses, for example a “burst” of pulses with gradually increasing current magnitudes, or some other sequence. In some examples, IMD 372 may deliver therapy for a given duration and stop delivering therapy for a given duration. In other words, parameters of the electrical stimulation therapy may include an ON-time and an OFF-time. In some examples, an ON-time may be a few seconds or minutes and the OFF- time may also be for a few seconds or minutes. The ON-time may be equal to the OFF- time in some examples, while in other examples the ON-time and the OFF-time may be unequal durations.

[0085] In some examples, IMD 372 may be configured to deliver control stimulation to patient 305 via a combination of electrodes of leads 330, alone or in combination with an electrode carried by or defined by an outer housing of IMD 372 to detect ECAP signals (e.g., control pulses and/or informed pulses). The tissue targeted by the stimulation may be the same or similar tissue targeted by the electrical stimulation therapy, but IMD 372 may deliver stimulation pulses for ECAP signal detection via the same, at least some of the same, or different electrodes. Since control stimulation pulses may be delivered in an interleaved manner with informed pulses (e.g., when the pulses configured to contribute to therapy interfere with the detection of ECAP signals or pulse sweeps intended for posture state detection via ECAP signals do not correspond to pulses intended for therapy purposes), a clinician and/or user may select any suitable electrode combination for informed pulses. Like the electrical stimulation therapy, the control stimulation may be in the form of electrical stimulation pulses or continuous waveforms. [0086] In one example, each control stimulation pulse may include a balanced, biphasic square pulse that employs an active recharge phase. However, in other examples, the control stimulation pulses may include a monophasic pulse followed by a passive recharge phase. In other examples, a control pulse may include an imbalanced bi-phasic portion and a passive recharge portion. Although not necessary, a bi-phasic control pulse may include an interphase interval between the positive and negative phase to promote propagation of the nerve impulse in response to the first phase of the bi-phasic pulse. The control stimulation may be delivered without interrupting the delivery of the electrical stimulation informed pulses, such as during the window between consecutive informed pulses. The control pulses may elicit an ECAP signal from the tissue, and IMD 372 may sense the ECAP signal via two or more electrodes on leads 330. In cases where the control stimulation pulses are applied to spinal cord 320, the signal may be sensed by IMD 372 from spinal cord 320. [0087] In the example of FIG. 3, IMD 372 described as performing a plurality of processing and computing functions. However, external instrument 350, mobile computing device 354, wearable computing device 355 and/or external device 312 instead may perform one, several, or all of these functions. IMD 372 may relay sensed signals to external instrument 350 for analysis via a communication channel analogous to second communication channel 206 of FIG. 2, and external instrument 350 transmits instructions to IMD 372 to adjust the one or more parameters defining the electrical stimulation therapy based on analysis of the sensed signals via a communication channel analogous to second communication channel 206. In some examples, IMD 372 may additionally or alternatively relay sensed signals to external device 312 via a communication channel analogous to encrypted channel 202 of FIG. 2 such that external device 312 may receive encrypted data from IMD 372 without external instrument 350 decrypting the data. In some examples, IMD 372 may additionally or alternatively alter a mode of external instrument 350 such that external instrument 350 is in a telemetry only mode or a single shot mode as described in FIG. 2.

[0088] FIG. 4 is a block diagram illustrating example components of the medical device as described above. Implantable medical device (IMD) 410 may be an example of IMD 110, IMD 210, or IMD 372 of FIGS 1, 2, and 3 respectively. IMD 410 of FIG. 4 is described as an implantable medical device, but the same functions, characteristics and techniques may also apply to other type of wearable or portable medical devices.

[0089] In the example illustrated in FIG. 4, IMD 410 includes housing 419 which may contain coil 416, power source 418, processing circuity 430, memory 432, therapy and sensing circuitry 434, communication circuitry 436, one or more sensors 437, recharge circuitry 438, temperature sensor 439, and encryption/ decry ption circuitry 440. IMD 410 may be connected to electrodes 417. In other examples, IMD 410 may include a greater or a fewer number of components, e.g., in some examples, IMD 410 may not include sensors 437 or temperature sensor 439. In general, IMD 410 may comprise any suitable arrangement of hardware, alone or in combination with software and/or firmware, to perform the various techniques described herein attributed to IMD 410 and processing circuitry 430, and any equivalents thereof.

[0090] Processing circuitry 430 of IMD 410 may be implemented as one or more processors, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. IMD 410 may include a memory 432, such as random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, comprising executable instructions for causing the processing circuitry 430 to perform the actions attributed to this circuitry.

[0091] Moreover, although processing circuitry 430, therapy and sensing circuitry 434, communication circuitry 436, recharge circuitry 438, and temperature sensor 439 are described as separate modules, in some examples, some combination of processing circuitry 430, therapy and sensing circuitry 434, communication circuitry 436, recharge circuitry 438, and temperature sensor 439 are functionally integrated. In some examples, processing circuitry 430, therapy and sensing circuitry 434, communication circuitry 436, recharge circuitry 438, and temperature sensor 439 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units. For example, components of IMD 410 may be implemented as separate circuits in some examples. In other examples, two or more components of IMD 410 may be implemented on a single integrated circuit, e.g., including processing circuitry 430, memory 432, therapy and sensing circuitry 434, communication circuitry 436, and other components of IMD 410. In this disclosure, therapy, and sensing circuitry 434 may be referred to as therapy circuitry 434.

[0092] Memory 432 may store therapy programs or other instructions that specify therapy parameter values for the therapy provided by therapy circuitry 434 and IMD 410. In some examples, memory 432 may also store temperature data from temperature sensor 439, instructions for recharging rechargeable power source 418, thresholds, instructions for communication between IMD 410 and an external instrument (such as external instrument 150, 250, or 350 of FIGS. 1, 2, and 3 respectively), or any other instructions required to perform tasks attributed to IMD 410. Memory 432 may be configured to store instructions for communication with and/or controlling one or more temperature sensors of temperature sensor 439. In various examples, memory 432 stores information related to determining the temperature of housing 419 and/or exterior surface(s) of housing 419 of IMD 410 based on temperatures sensed by one or more temperature sensors, such as temperature sensor 439, located within IMD 410.

[0093] For example, memory 432 may store programming settings such as parameters for electrical stimulation therapy output, e.g., magnitude, pulse width, and so on. Memory 432 may store parameters and other settings for the delivery of haptic stimulation. Settings may be individualized based on patient preference and/or patient physiology. For example, a stimulation intensity that is above the perception threshold for a first patient may be different than the stimulation intensity that may be above the perception threshold for a second patient. In some examples, a patient may find a particular frequency to be annoying or painful and therefore, may request a different frequency setting when receiving haptic stimulation as feedback.

[0094] Instructions stored at memory 432 when executed by processing circuitry 430 may determine whether a sensed bioelectrical signal is valid, such as and ECAP or other signal in response to an output electrical stimulation therapy event. Memory 432 may store programming instructions that when executed by processing circuitry 430 cause processing circuitry 430 to cause electrical stimulation circuitry therapy circuitry 434 to deliver electrical stimulation therapy to a target nerve of a patient. Memory 432 may also store instructions on encrypting and decrypting communications to be sent via communications circuitry 436 to an external instrument (such as external instrument 150, 250, or 350 of FIGS. 1, 2, and 3 respectively), as well as instructions for establishing a communication channel over communication channels, as described above in relation to FIGS. 1 - 3.

[0095] Therapy and sensing circuitry 434 may generate and deliver electrical stimulation under the control of processing circuitry 430. Therapy and sensing circuitry 434 may also output non-therapy stimulation, such as control pulses and haptic stimulation. In some examples, processing circuitry 430 controls therapy circuitry 434 by accessing memory 432 to selectively access and load at least one of the stimulation programs to therapy circuitry 434. For example, in operation, processing circuitry 430 may access memory 432 to load one of the stimulation programs to therapy circuitry 434. In such examples, relevant stimulation parameters may include a voltage amplitude, a current amplitude, a pulse rate, a pulse width, a duty cycle, or the combination of electrodes 417A, 417B, 417C, and 417D (collectively “electrodes 417”) that therapy circuitry 434 may use to deliver the electrical stimulation signal as well as sense biological signals. In other examples, IMD 410 may have more or fewer electrodes than the four shown in the example of FIG. 4. In some examples, electrodes 417 may be part of or attached to a housing of IMD 410, e.g., a leadless electrode. In other examples, one or more of electrodes 417 may be part of a lead implanted in or attached to a patient to sense biological signals and/or deliver electrical stimulation, as described above in relation to FIG. 1.

[0096] In some examples, one or more electrodes 417 connected to therapy circuitry 434 may connect to one or more sensing electrodes 417, e.g., attached to housing of IMD 410. In some examples electrodes 417 may be configured to detect an evoked motor response caused by the electrical stimulation therapy event, or other bioelectrical signals such as ECAPs, impedance and so on.

[0097] IMD 410 also includes components to receive power to recharge rechargeable power source 418 when rechargeable power source 418 has been at least partially depleted. As shown in FIG. 4, IMD 410 includes coil 416 and recharge circuitry 438 coupled to rechargeable power source 418. Recharge circuitry 438 may be configured to charge rechargeable power source 418 with the selected power level determined by either processing circuitry 430 or an external charging device, such as external computing IMD 110 described above in relation to FIG. 1. Recharge circuitry 438 may include any of a variety of charging and/or control circuitry configured to process or convert current induced in coil 416 into charging current to charge power source 418. For example, recharge circuitry 438 may include measurement circuitry configured to determine a magnitude of current received by secondary coil 416, a magnitude of current delivered to power source 418, and other measurements. Recharge circuitry 438 may send such measurements to processing circuitry 430 to be used in system metrics, and sent to the external instrument (such as external instrument 150, 250, or 350 of FIGS. 1, 2, and 3 respectively) via communication circuitry 436.

[0098] Secondary coil 416 may include a coil of wire or other device capable of inductive coupling with a primary coil disposed external to the patient. Although secondary coil 416 is illustrated as a simple loop of in FIG. 4, secondary coil 416 may include multiple turns of conductive wire. Secondary coil 416 may include a winding of wire configured such that an electrical current may be induced within secondary coil 416 from a magnetic field. The induced electrical current may then be used to recharge rechargeable power source 418.

[0099] Recharge circuitry 438 may include one or more circuits that process, filter, convert and/or transform the electrical signal induced in the secondary coil to an electrical signal capable of recharging rechargeable power source 418. For example, in alternating current induction, recharge circuitry 438 may include a half-wave rectifier circuit and/or a full-wave rectifier circuit configured to convert alternating current from the induction to a direct current for rechargeable power source 418. The full-wave rectifier circuit may be more efficient at converting the induced energy for rechargeable power source 418. However, a half-wave rectifier circuit may be used to store energy in rechargeable power source 418 at a slower rate. In some examples, recharge circuitry 438 may include both a full-wave rectifier circuit and a half-wave rectifier circuit such that recharge circuitry 438 may switch between each circuit to control the charging rate of rechargeable power source 418 and temperature of IMD 410.

[0100] Rechargeable power source 418 may include one or more capacitors, batteries, and/or other energy storage devices. Rechargeable power source 418 may deliver operating power to the components of IMD 410. In some examples, rechargeable power source 418 may include a power generation circuit to produce the operating power. Rechargeable power source 418 may be configured to operate through many discharge and recharge cycles. Rechargeable power source 418 may also be configured to provide operational power to IMD 410 during the recharge process. In some examples, rechargeable power source 418 may be constructed with materials to reduce the amount of heat generated during charging. In other examples, IMD 410 may be constructed of materials and/or using structures that may help dissipate generated heat at rechargeable power source 418, recharge circuitry 438, and/or secondary coil 416 over a larger surface area of the housing of IMD 410.

[0101] Although rechargeable power source 418, recharge circuitry 438, and secondary coil 416 are shown as contained within the housing of IMD 410, in some implementations, at least one of these components may be disposed outside of the housing. For example, in some implementations, secondary coil 416 may be disposed outside of the housing of IMD 410 to facilitate better coupling between secondary coil 416 and the primary coil of external charging device. In other examples, power source 418 may be a primary power cell and IMD 410 may not include recharge circuitry 438 and recharge coil 416.

[0102] Processing circuitry 430 may also control the exchange of information with an external instrument using communication circuitry 436. Processing circuitry 430 may transmit operational information and receive therapy programs or therapy parameter adjustments over an established secure communication channel via communication circuitry 436. Also, in some examples, IMD 410 may communicate with other implanted devices, such as stimulators, control devices, or sensors, via communication circuitry 436. Communication circuitry 436 may include one or more antennas 437 configured to communicate with the external instrument (such as external instrument 150, 250, or 350 of FIGS. 1, 2, and 3 respectively), e.g., for power transfer or for data transfer with the other devices. In addition, communication circuitry 436 may be configured to control the exchange of information related to sensed and/or determined temperature data, for example temperatures sensed by and/or determined from temperatures sensed using temperature sensor 439. In some examples, communication circuitry 436 may communicate using inductive communication, and in other examples, communication circuitry 436 may communicate using RF frequencies separate from the frequencies used for inductive charging.

[0103] In the example of FIG. 4, communication circuitry 436 includes circuitry 440 configured to manage encryption and decryption and may also execute some of the other functions related to establishing communications channels described in in this disclosure. In other examples, the encryption functions of circuitry 440 may be handled by processing circuitry 430, by some other circuitry of IMD 410, or by any combination thereof.

[0104] Communication circuitry 436 may be configured to support wireless communication. For example, communication circuitry 436 may be configured to support wireless communication using Bluetooth™ (e.g., BLE and other versions of Bluetooth™, including future versions of Bluetooth™), Wi-Fi™, Near-Field Communication (NFC), Near Field Magnetic Induction (NFMI), Long Term Evolution, 5th generation (LTE/5G), or MedRadio (MICS: Medical Implant Communication Service, MEDS: Medical External Device Service, MB AD: Medical Body Area Network)) between IMD 410 and another computing device, e.g., external instrument 150, 250, or 350 or alternatively external device 112, 212, or 312 of FIGS. 1, 2, and 3 respectively of system 100, 200 or 300 described above in relation to FIGS. 1 - 3. In some examples, communication circuitry 436 supports a communication frequency that may correspond to a high frequency or radio frequency, which may be a radio frequency established via Bluetooth, Wi-Fi, Near-Field Communication (NFC), 175KHz inductive communication, or MICS, for example. Communication circuitry 436 may be configured to receive an inductive sting. Processing circuitry 430 of IMD 410 may receive, as updates to programs (e.g., at least one program parameter), values for various stimulation parameters such as magnitude and electrode combination, from external instrument (such as external instrument 150, 250, or 350 of FIGS. 1, 2, and 3 respectively) via communication circuitry 436. In addition, communication circuitry 436 may communicate with an external medical device via proximal inductive interaction of IMD 410, e.g., during recharging. Communication circuitry 436 may send and receive information on a continuous basis, at periodic intervals, or upon request from the recharger. In some examples, communication circuitry 436 may also be referred to as telemetry circuitry in this disclosure.

[0105] In some examples, communication circuitry 436 may be configured to receive communications or data via secondary coil 416. This data may be received using the same configuration of secondary coil (e.g., tuned to the same frequency) or include tuning circuitry that can adjust the resonant frequency of secondary coil to receive and/or transmit information to another device, such as to an external instrument using inductive coupling. In other examples, communication circuitry 436 may be coupled to a different coil than secondary coil 416 for receiving and/or transmitting information.

[0106] In some examples, processing circuitry 430 may transmit additional information to external charging device related to the operation of rechargeable power source 418, e.g., at a more limited authorization level than for sending and receiving operational programming instructions or parameters. For example, processing circuitry 430 may use communication circuitry 436 to transmit indications that rechargeable power source 418 is completely charged, rechargeable power source 418 is fully discharged, the amount of charging current output by recharge circuitry 438 e.g., to power source 418, or any other charge status of rechargeable power source 418. In some examples, processing circuitry 430 may use communication circuitry 436 to transmit instructions to the external charging device, including instructions regarding control of the charging session, for example instructions to lower the power level or to terminate the charging session, based on the determined temperature of the housing/external surface 419 of the IMD.

[0107] Processing circuitry 430 may also transmit information to external charging device that indicates any errors with rechargeable power source 418 that may reduce or limit rechargeable power source 418 from providing operational power to the components of IMD 410. In various examples, processing circuitry 430 may receive, through communication circuitry 436, instructions for algorithms, including formulas and/or values for constants to be used in the formulas that may be used to determine the temperature of the housing 419 and/or exterior surface(s) of housing 419 of IMD 410 based on temperatures sensed by temperature sensor 439 located within IMD 410 during and after a recharging session performed on rechargeable power source 418. [0108] FIG. 5 is a block diagram illustrating example components of the external instrument of FIGS. 1 - 3. External charging device 550 in of FIG. 5 is an example of external instrument 150, 250, and 350 described above in relation to FIGS. 1 - 3 and may have the same or similar functions. As described above, in some examples, external instrument 550 may be a hand-held device, while in other examples, external instrument 550 may be a larger or a non-portable device. In addition, in other examples external instrument 550 may be included as part of an external programmer or include functionality of an external programmer. As shown in the example of FIG. 5, external instrument 550 includes two separate components. Housing 524 encloses components such as a processing circuitry 530, memory 552, user interface 554, communication circuitry 556, power source 560, and audio output circuitry 570. Charging head 526, also referred to as a charging wand 526, may include charging circuitry 558, temperature sensor 559, and coil 548. Housing 524 is electrically coupled to charging head 526 via charging cable 529. In some examples, housing 524 may also include charging circuitry 568 and coil 528, which may be an example of coil internal transfer coil 128 described above in relation to FIG. 1.

[0109] In some examples, separate charging wand 526 may facilitate positioning of coil 548 over secondary coil 116 of IMD 110 of FIG. 1, or coil 416 of FIG. 4. In some examples, charging circuitry 568 and/or coil 528 may be integrated within housing 524. In other examples, external instrument 550 may not include charging wand 526. Coil 548 may be referred to as external transfer coil, which may be substantially equivalent to external transfer coil 126 of FIG. 1. Coil 528 may be referred to as external transfer coil, which may be substantially equivalent to external transfer coil 128 of FIG. 1. Coil 548 and coil 528 may also be referred to as transfer coils, primary transfer coils, energy transfer coils, data transfer coils, or antenna. In some examples, coil 548 and 528 may transfer energy, data, or both. In this manner, external instrument 550 (e.g., an example recharger), may include one or more coils within housing 524 or include one or more coils outside of the housing 524.

[0110] External charging device 550 may also include one or more temperature sensors, illustrated as temperature sensor 559, similar to temperature sensor 439 of FIG. 4. As shown in FIG. 5, temperature sensor 559 may be disposed within charging head 526. For example, charging head 526 may include one or more temperature sensors positioned and configured to sense the temperature of coil 548 and/or a surface of the housing of charging head 526. In some examples, external instrument 550 may not include temperature sensor 559. In other examples, one or more temperature sensors of temperature sensor 559 may be disposed within housing 524, such as located to sense the temperature of primary coil 528 and/or charging circuitry 568.

[oni] In general, external instrument 550 comprises any suitable arrangement of hardware, alone or in combination with software and/or firmware, to perform the techniques ascribed to external instrument 550, and processing circuitry 530, user interface 554, communication circuitry 556, and charging circuitry 558 of external instrument 550, and/or any equivalents thereof. In various examples, external instrument 550 may include one or more processors, such as one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components.

[0112] Similar to IMD 110 and 410 described above in relation to FIGS. 1 and 4, components of external instrument 550 shown in FIG. 5 may be implemented as separate circuitry, or combined into one or more integrated circuits. In other words, although processing circuitry 530, communication circuitry 556, charging circuitry 558, and temperature sensor 559 are described as separate modules, in some examples, processing circuitry 530, communication circuitry 556, charging circuitry 558, and/or temperature sensor 559 are functionally integrated. In some examples, processing circuitry 530, communication circuitry 556, charging circuitry 558, and/or temperature sensor 559 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0113] External instrument 550 also, in various examples, may include a memory 552, such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, a hard disk, a CD- ROM, comprising executable instructions for causing the one or more processors to perform the actions attributed to external instrument 550. Memory 552 may store instructions that, when executed by processing circuitry 530, cause processing circuitry 530 and external charging device 550 to provide the functionality ascribed to external instrument 550 throughout this disclosure, and/or any equivalents thereof, including information sets 534 for authorization levels (e.g. first authorization level 203 and second authorization level 205), as described above in relation to FIG. 1 and 2. For example, memory 552 may include instructions that cause processing circuitry 530 to control the power level used to charge IMD 410 of FIG. 4, as communicated from IMD 410 via a communication channel, e.g., second communication channel 206 described above in relation to FIG. 2. Memory 552 may include a record of selected power levels, sensed temperatures, determined temperatures, or any other data related to charging rechargeable power source 418, described above in relation to FIG. 4.

[0114] User interface 554 may include buttons, a keypad, indicator lights, a microphone for voice commands, a display, such as a liquid crystal (LCD), light-emitting diode (LED), or cathode ray tube (CRT) and audio output circuitry.

[0115] In some examples, the display of user interface 554 may be a touch screen. As discussed in this disclosure, processing circuitry 530 may present and receive information relating to the charging of rechargeable power source 418 via user interface 554. For example, user interface 554 may indicate when charging is occurring, quality of the alignment between primary coil 528 or 548 and the secondary coil of the IMD, the selected power level, current charge level of power source 418, duration of the current recharge session, anticipated remaining time of the charging session, sensed temperatures, or any other information. In some examples, processing circuitry 530 may receive some of the information displayed on user interface 554, e.g., via communication circuitry such as communication circuitry 556. In some examples, user interface 554 may provide an indication to the user regarding the quality of alignment between coil 416, depicted in FIG. 4 and coil 548, based on one or more system metrics, such as the charge current to the battery of the IMD.

[0116] Processing circuitry 530 may also receive user input via user interface 554. The input may be, for example, in the form of pressing a button on a keypad or selecting an icon from a touch screen. The input may change programmed settings, start, or stop therapy, request starting or stopping a recharge session, a suitable level of charging, or one or more statistics related to charging power source 418 (e.g., the cumulative thermal dose). In this manner, user interface 554 may allow the user to view information related to the operation of IMD 410.

[0117] Charging circuitry 558 may include one or more circuits that generate an electrical current within primary coil 548. Charging circuitry 558 may generate an alternating current of specified amplitude and frequency in some examples. In other examples, charging circuitry 558 may generate a direct current. In any case, charging circuitry 558 may be capable of generating electrical signals, and subsequent magnetic fields, to transmit various levels of power to IMD 410. In this manner, charging circuitry 558 may be configured to charge power source 418 of IMD 410 with the selected power level. [0118] Power source 560 may deliver operating power to the components of external instrument 550. Power source 560 may also deliver the operating power to drive primary coil 548 or primary coil 528 during the charging process. Power source 560 may include a battery and a power generation circuit to produce the operating power. In some examples, a battery of power source 560 may be rechargeable to allow extended portable operation. In other examples, power source 560 may draw power from a wired voltage source such as a consumer or commercial power outlet.

[0119] Processing circuitry 530 may, when requested, transmit any stored data in memory 552 for review or processing, such as transmitting the stored data to external devices 112 depicted in FIG. 1 via encrypted channel 202 as depicted in FIG. 2. Processing circuitry 530 may be configured to access memory, such as memory 432 of IMD 410 and/or memory 552 of external instrument 550, to retrieve information comprising instructions, formulas, and determined values for one or more constants. As described above in relation to FIGS. 1 - 4, processing circuitry 530 and communication circuitry 556 may establish one or more secure communication channels over a communication link. In some examples, processing circuitry 530 may act as a relay to transfer passthrough data via an encrypted channel, such as encrypted channel 202 of FIG. 2, such that communication circuitry 556 is incapable of decrypting the information and merely transfers the passthrough data from an external device to an IMD. In some examples, processing circuitry 530 may act as a man-in-the-middle and is able to encrypt and decrypt transferred information during a communication session, and may pass data through communication channels such as first communication channel 204 and second communication channel 206 of FIG. 2, such that communication circuitry 556 is capable of decrypting the data. In the example of FIG. 5, instructions for establishing the communication channel, handling the encryption handshaking, setting, and resetting the communication session timers, storing encryption keys and other similar functions may be stored at memory 552 (e.g., encryption circuitry 532). In other examples, (not shown in FIGS. 4 and 5) the encryption keys and/or encryption instructions may be stored in a separate encrypted memory in communication with processing circuitry 430 or 530. [0120] In some examples, communication circuitry 556 may establish a second communication channel directly to an implantable medical device, (e.g. IMD 110 of FIG.

1, IMD 210 of FIG. 2, IMD 372 of FIG. 3, or IMD 410 of FIG. 4). Communication circuitry 556 may establish the second communication channel with different authorization levels. In some examples external device, e.g., of systems 100, 200 or 300 described above in relation to FIGS. 1 -3, may transfer information with IMD 210 via communication channel via external instrument 250.

[0121] Communication circuitry 556 may support wireless communication between IMD 110 of FIG. 1 and external instrument 550 under the control of processing circuitry 530. Communication circuitry 556 may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. In some examples, communication circuitry 556 may be substantially similar to communication circuitry 436 of IMD 410 of FIG. 4 and/or communication circuitry 256 of IMD 210 of FIG. 2, providing wireless communication via an RF or proximal inductive medium. In some examples, communication circuitry 556 may include an antenna 557, which may take on a variety of forms, such as an internal or external antenna. Although communication circuitry 556 may each include dedicated antennas for communications between these devices, communication circuitry 556, 436, and 256 may instead, or additionally, be configured to utilize inductive coupling from coils 416 and 548 to transfer data.

[0122] Examples of local wireless communication techniques that may be employed to facilitate communication between external instrument 550 and IMD 410 include radio frequency and/or inductive communication according to any of a variety of standard or proprietary communication protocols, or according to other communication protocols such as the IEEE 802.1 lx or Bluetooth specification sets. In this manner, other external devices may be capable of communicating with external instrument 550 without needing to establish a secure wireless connection.

[0123] FIG. 6 is a flow chart illustrating an example mode of operation of a single shot communication process for a system. Single shot process 600, which may be referred to as process 600 or single shot communication process 600 enables an external device (e.g. external device 112, 212, 312 of FIGS. 1-3) to communicate a one-off message to an IMD (e.g. 112, 212, 312, 410 of FIGS. 1-4) via communication channels (e.g. first communication channel 204, second communication channel 206, and encrypted channel 202 (which may be a sub-channel or encrypted payload within the other channels) of FIG. 2) of an external instrument (e.g. 150, 250, 350, 550 of FIGS. 1-3, and 5) (e.g. a recharger, a patient programmer, clinician programmer, or an application on a patient programmer). In other examples, encrypted channel 202 (or the encrypted passthrough data) may be transmitted via a different and distinct) encrypted channel between medical device and external instrument and/or between the external instrument and external device. In the example shown, the one-off message may be communicated as passthrough data wherein the external instrument may be incapable of decrypting the data. In some examples, the one-off message may be communicated as alternative data wherein the external instrument may be capable of decrypting the data. Portions of process 600 may be performed by individual devices from that perspective of the device.

[0124] In the example shown, FIG. 6 includes receiving encrypted data at the external device (602), sending the encrypted data from the external device to the external instrument (604), receiving the encrypted data at the external instrument (606), switching the external instrument to telemetry mode (608), sending the encrypted data to the IMD via an inductive connection (610), receiving the encrypted data at the IMD and sending a confirmation to the external instrument (612), and then sending the confirmation from the external instrument to the external device and switching the charger from telemetry mode and back to another mode such as resuming the recharging session (614).

[0125] Receiving encrypted data at the external device (602) may include the external device creating the data to be sent to the IMD and encrypting the data prior to transmission. In some examples, the external device may be a clinical programmer or patient programmer. In other examples, the external device may be a remote server, a local server, application on a smartphone, or other program which may allow for selection of parameters by a clinician or a patient. In some examples, receiving the data at the external device may comprise receiving the data from an outside source, such as a remote clinician programmer or a server. In some examples, the server can be onsite, or the server can be offsite. In some examples, receiving encrypted data at the external device may comprise the external device receiving the data from an outside source, such as a clinician programmer in a pre-encrypted format wherein the pre-encrypted format is such that the IMD is able to decrypt the data. In some examples, the data may arrive at the external device in an unencrypted format wherein the external device thereafter encrypts the data.

[0126] Sending the encrypted data from the external device to the external instrument (604) and receiving the encrypted data at the external instrument (606) may include processing circuitry 530 instructing communication circuitry 556 of the external instrument to form encrypted channel 202 of FIG. 2 between the external device and the IMD wherein the external instrument acts as a relay. In some examples, the relay functionality enables the external instrument to receive the data, temporarily cache the data, and thereafter transmit the data. Communication circuitry 556 may be incapable of decrypting the information of encrypted channel 202 and merely transfers the passthrough data from an external device to an IMD.

[0127] Prior to transfer of the data, processing circuitry 530 may switch the external instrument to telemetry mode (608) such that charging circuity 558 is disabled and communication circuitry 556 is enabled. Disabling charging circuity 558 prior to enabling communication circuitry 556 may optimize the data transfer rate as coils 528 and 548 may be optimized for data transfer or energy transfer. In some examples, multiple coils 528 and 548 may be used such that charging circuity 558 may stay enabled when enabling communication circuitry 556. In some examples, communication circuitry 556 may additionally or alternatively use a wireless transfer protocol that does not interfere with charging circuity 558(e.g., Bluetooth™, Bluetooth Low Energy (BLE), or a protocol using the Medical Implant Communication System (MICS) band). In some examples, the telemetry mode is a single shot telemetry mode such that once confirmation of receipt is received at any of the external instrument or the external device, second communication channel 206 and/or encrypted channel 202 may close. In some examples, the single shot telemetry mode will allow a single packet of information. In some examples, the single shot telemetry mode will allow a single temporary stream of information prior to closure. [0128] Sending the encrypted data to the IMD via an inductive connection (610) may include communication circuitry 556 transferring the passthrough data to the IMD via an inductive connection over second communication channel 206. Once the passthrough data has been transferred, the passthrough data can be cleared from memory 552.

[0129] Receiving the encrypted data at the IMD and sending a confirmation to the external instrument (612) may include the IMD receiving the passthrough data via communication circuitry 436 and decrypting the data via encryption circuity 440. IMD may send a confirmation of receipt, or may additionally or alternatively send a confirmation of successful decryption, back to the external device via first communication channel 204.

[0130] Sending the confirmation from the external instrument to the external device and the charger exiting telemetry mode (614) may include the external instrument receiving the confirmation via second communication channel 206 and sending the confirmation message to the external device via first communication channel 204. In some examples, the confirmation may be encrypted such that only the external device may interpret the confirmation. In some examples, the confirmation may be transferred via encrypted channel 202 such that only the external device may interpret the confirmation. Upon delivery of the confirmation message, processing circuitry 530 may instruct communication circuity 556 of the external instrument to halt transfer of information thereby ending second communication channel 206 and/or encrypted channel 202. Processing circuitry 530 may instruct charging circuitry 568 to resume charging IMD. In some examples, a user interface of the external instrument may not indicate that a transfer of data occurred or that the external instrument was not recharging for a period of time. In some examples, the single shot process 600 may immediately, or shortly thereafter, repeat to send a second or additional message.

[0131] FIG. 7 is a flow chart illustrating an example mode of operation of a telemetry-only communication process for the system. Telemetry-only mode 700, which may be referred to as sustained communication process 700, or telemetry-only communication 700 enables an external device (e.g. external device 112, 212, 312 of FIGS. 1-3) to communicate a series of messages to an IMD (e.g. 112, 212, 312, 410 of FIGS. 1-4) via a communication channel (e.g. first communication channel 204, second communication channel 206, or encrypted channel 202 of FIG. 2) of an external instrument (e.g. 150, 250, 350, 550 of FIGS. 1-3, and 5). In the example shown, the series of messages may be communicated as passthrough data wherein the external instrument may be incapable of decrypting the data. In some examples, the series of messages may be communicated as alternative data wherein the external instrument may be capable of decrypting the data. Portions of process 600 may be performed by individual devices from that perspective of the device.

[0132] In the example shown, FIG. 7 includes transmitting a command from the external device to the external instrument (702), the external instrument receiving the command (704), the external instrument switching to telemetry-only mode (706), the external instrument facilitating transmission of passthrough data from external device to IMD (708), the IMD receiving the passthrough data (710), and the external instrument switching from telemetry only mode in response to receiving a second command or timeout condition (712).

[0133] Transmitting a command from the external device to the external instrument (702) may comprise processing circuity 530 controlling communication circuitry 556 to form a first communication channel 204 between the external device and the external instrument. In some examples, the first communication channel 204 may be encrypted such that the external instrument may decrypt the data and interpret the data. In some examples, encrypted channel 202 may operate within first communication channel 204 and encrypted channel 202 may not be able to be decrypted by the external instrument. [0134] The external instrument receiving the command (704) may comprise the communication circuitry 556 receiving and interpreting the command. In some examples, the communication circuitry 556 may send the command to processing circuity 530. In some examples, processing circuity 530 may store the received command in memory 552. In some examples, encryption circuitry 532 may decrypt the data, enabling processing circuitry 530 to act upon the received data.

[0135] Upon receipt of the command at processing circuity 530, the external instrument may switch to telemetry-only mode (706). Processing circuity 530 may switch the external instrument to telemetry-only mode by disabling or inactivating charging circuitry 558 and enabling communication circuity 556 to form encrypted channel 202 to enable passthrough data to be sent in bulk. In some examples, communication circuity 556 may enable other data, which is not passthrough data, to be sent in bulk across second communication channel 206. Communication circuitry 556 may transmit the data to IMD by inductively linking coils 528 or 548 of external instrument 550 with coil 416 of IMD 410. In some examples, coils 416, 528, and 548 may dynamically adjust their preferred frequency to optimize data transfer when in telemetry-only mode as this may increase a bulk data transfer rate.

[0136] The external instrument transmitting passthrough data from external device to IMD (708) and the IMD receiving the passthrough data (710) may comprise communication circuitry 556 sending passthrough data through encrypted channel 202 in bulk without closing encrypted channel 202 after data transfer completes. In some examples, the passthrough data may be data from the external device, wherein the external device may be a clinical programmer, a client programmer, an onsite server, or an offsite server. In some examples, communication circuitry 556 may send other data through second communication channel 206 in bulk without closing communication channel 206 after data transfer completes.

[0137] The external instrument leaving telemetry only mode upon receiving a second command or timeout condition (712) may comprise the external instrument closing first communication channel 204, second communication channel 206, and/or encrypted channel 202 upon receipt of a second command which indicates a requested closure of the telemetry-only mode or a timeout condition. The second command may be a command from the external device to stop data transfer. The second command may be sent upon completion of the bulk passthrough data transfer or may be sent if there is an error detected in the data transfer stream. In some examples, processing circuitry 530 of external instrument may record a time since the last data was transferred across second communication channel 206 and if the time since the last data was transferred exceeds a threshold then a timeout threshold has been reached. Once a timeout threshold has been reached, the second communication channel 206 may be closed. Once second communication channel 206 is closed, external instrument 550 may deactivate the inductive communication of communication circuitry 556 and re-enable the inductive charging of charging circuitry 558.

[0138] FIG. 8 is a state diagram illustrating potential states of an external instrument (e.g. 150, 250, 350, 550 of FIGS. 1-3, and 5). The external instrument will enter idle state 802 by default. A current operational state of the external instrument is controlled by the state diagram and its processes. The operational state of the external instrument may be influenced by commands sent from an external device (e.g. external device 112, 212, 312 of FIGS. 1-3) which controls what data is sent between which devices based on commands of a physician and/or a patient.

[0139] In the example shown, the external instrument may be in idle state 802, telemetry state 802, 810, investigative state 806, or charging state 808. Idle state can lead to telemetry state 804 through single shot telemetry request 812, telemetry-only mode request 814, end transmission request 816, or charging request 818. Investigative state 806 can succeed and lead to charging state 808 through charging connection success 820. Charging state 808 can lead to telemetry state 810 through single shot telemetry request 822, telemetry-only mode request 824, end transmission request 826, or charging completion 828.

[0140] Idle state 802 may comprise the external instrument not being connected to any other device or being connected only to the external device. In some examples, in idle state 802 a user interface of the external instrument may indicate that the external instrument is idling. In some examples, in idle state 802 the external instrument may be continuously checking for commands from the external device. In some examples, in idle state 802 the external instrument may be in a lower power mode awaiting an interrupt command form the external device.

[0141] Telemeting states 804 and 810 will be discussed together. In some examples, telemetry states 804, 810 may comprise a single shot telemetry process such as described above in FIG. 6. The single shot telemetry process may be a result of single shot telemetry request 812. In some examples, telemetry state 804, 810 may comprise a telemetry-only communication process such as described above in FIG. 7. The telemetry- only communication process may be a result of telemetry-only mode request 814, 824. Once the single shot telemetry process has completed or the telemetry-only communication process has timed out or received an end session request, such as a second command, then end transmission request 816, 826 may end telemetry states 804, 810. End transmission request 816, 826 may end telemetry states 804, 810 as described above in FIGS. 6-7. In some examples, in telemetry states 804, 810 a user interface of the external instrument may indicate that the external instrument is idling, or may indicate that the external instrument is charging, or may indicate that the external instrument is telemetry data. In some examples, the indication of the user interface may be pre-selected based on the patient or physician’s preferences. In some examples, the indication of the user interface may be actively-selected based on the patient or physician’s preferences or based on past interactions between the patient and the programmer. In some examples, the preferences may be to improve a user-friendliness or a style of the recharger.

[0142] Investigative state 806 may include the charger activating and deactivating its inductive coils (e.g. primary coils) to determine whether there is another inductive coil (e.g. secondary coils) nearby to which it can inductively couple. In some examples, the charger may enter the investigative state 806 through charging request 818 wherein the external instrument or the external device request that the external instrument electrically connect with the IMD (e.g. 112, 212, 312, 410 of FIGS. 1-4) to transfer it power. In some examples, the coupling may be a frequent occurrence (e.g. multiple times a day or nearly continuous energy transfer, when the medical device requires high levels of power). In some examples, the coupling may be an infrequent occurrence (e.g. once a week, once a month, or once per year) wherein a low battery signal from the IMD indicates to a patient or physician that the external instrument needs to be moved near the IMD and thereafter charging request 818 will put the external instrument into investigative state 806. If the external instrument finds with and inductively couples with the IMD or is able to establish communication with the IMD then charging connection success 820 occurs and the external instrument enters charging state 808 whereas if the external instrument does not inductively couple with the IMD or communicate with the IMD then charging connection success 820 does not occur. In some examples, if connection success 820 does not occur, then the external instrument returns to idle state 802. In other examples, if the investigative state 806 fails the external instrument may proceed to charging the IMD without regard for if the IMD is responsive to communication or inductively coupled (e.g. some IMDs are very small, can be deep in the body, and/or may have depleted batteries.). [0143] In some examples, once the external instrument has successfully completed charging of the IMD, charging completion 828 may occur which returns the external instrument state to idle state 802. In some examples, charging completion 828 may occur wherein the external instrument should be removed, even if the external instrument has not successfully completed charging of the IMD (e.g. if an update is required, the external instrument may exit charging to transfer data). In some examples, in investigative state 806 a user interface of the external instrument may indicate that the external instrument is idling, or may indicate that the external instrument is charging, or may indicate that the external instrument is in the investigative state. In some examples, the indication of investigative state may be spinning LEDs and beeping. In some examples, the indication of the user interface may be pre-selected based on the patient or physician’s preferences. In some examples, the indication of the user interface may be actively-selected based on the patient or physician’s preferences or based on past interactions between the patient and the programmer. In some examples, the preferences may be to improve a user- friendliness or a style of the recharger. In some examples, the user interface may indicate to the user that the device must be moved closer to the implant location such that a connection may be made between the external instrument and the IMD.

[0144] The techniques of this disclosure may also be described in the following examples.

[0145] Example 1. A external instrument, the device comprising: communication circuitry configured to establish a first communication channel with an external device and a second communication channel with a medical device; and processing circuitry configured to: control the communication circuitry to connect to the external device via the communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the communication channel; control an operational state of the external instrument based on reception of at least one of the encrypted passthrough data or the command; and control the communication circuitry to transmit the encrypted passthrough data to the medical device via the second communication channel.

[0146] Example 2. The instrument of example 1, wherein the second communication channel has a first authorization level and a second authorization level. [0147] Example 3. The instrument of any of examples 1 and 2, wherein the encrypted passthrough data is encrypted before the communication circuitry receives the encrypted passthrough data, wherein the encrypted passthrough data is configured to be decrypted by the medical device instead of the external instrument, and wherein the communication circuitry is configured to transmit the encrypted passthrough data to the medical device. [0148] Example 4. The instrument of any of examples 1 through 3, further comprising recharge circuitry configured to transmit energy to the medical device, wherein the second communication channel comprises an inductive connection, and wherein the processing circuitry is further configured to: control the recharging circuitry to switch the operational state from a first mode to a temporary telemetry mode based on reception of the encrypted passthrough data; control the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection, wherein the communication circuitry is configured to receive a confirmation of receipt of the encrypted passthrough data from the medical device via the inductive connection; control the communication circuitry to send the confirmation to the external device via the first communication channel; and control the recharging circuitry to switch from the temporary telemetry mode to the first mode based on receiving the confirmation.

[0149] Example 5. The instrument of example 4, wherein the first mode is one of a recharging mode or an idle mode.

[0150] Example 6. The instrument of any of examples 1 through 5, further comprising recharge circuitry configured to transmit energy to the medical device, wherein the second communication channel comprises an inductive connection, wherein the communication circuitry is configured to receive a first command from the external device, and wherein the processing circuitry is configured to: control the recharging circuitry to switch the operational state from a first mode to a telemetry-only mode based on receipt of the first command; control the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection; control the communication circuitry to wait for one of a second command from the external device or a timeout condition; and responsive to receiving the second command or the time condition occurs, control the recharging circuitry to switch from the telemetry-only mode to the first mode.

[0151] Example 7. The instrument of any of examples 1 through 6, wherein the medical device is an implantable electrical stimulation device. [0152] Example 8. The instrument of any of examples 1 through 7, wherein the medical device is configured to deliver electrical stimulation to a tibial nerve of a patient. [0153] Example 9. The instrument of any of examples 1 through 8, wherein the external device is configured to program the medical device via the encrypted passthrough data routed through the external instrument by the processing circuitry of the external instrument.

[0154] Example 10. The instrument of any of examples 1 through 9, wherein the first communication channel is a Bluetooth connection.

[0155] Example 11. The instrument of any of examples 1 through 10, further comprising: recharge circuitry configured to transmit energy to the medical device, an inductive energy transmission coil connected to the recharge circuity and configured to transmit the energy to a secondary coil in the medical device; an inductive data transmission coil connected to the communication circuity and configured to transmit data to the medical device via the second communication channel; and an antenna connected to the communication circuitry and configured to exchange data with the external device via the communication channels.

[0156] Example 12. A method comprising: controlling, by processing circuitry of an external instrument, communication circuitry of the external instrument to connect to an external device via a first communication channel and a second communication channel with a medical device, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the first communication channel; controlling, by the processing circuitry, the communication circuitry to transmit the encrypted passthrough data to the medical device via the second communication channel; and controlling, by the processing circuitry, an operational state of the external instrument based on reception of at least one of the encrypted passthrough data or the command.

[0157] Example 13. The method of example 12, wherein the second communication channel has a first authorization level and a second authorization level.

[0158] Example 14. The method of any of examples 12 and 13, wherein the encrypted passthrough data is encrypted before the communication circuitry receives the encrypted passthrough data, wherein the encrypted passthrough data is configured to be decrypted by the medical device instead of the external instrument, and wherein the method further comprises transmitting, by the communication circuitry, the encrypted passthrough data to the medical device. [0159] Example 15. The method of any of examples 12 through 14, wherein the external instrument comprises recharge circuitry configured to transmit energy to the medical device, wherein the second communication channel comprises an inductive connection, and wherein the method further comprises: controlling the recharging circuitry to switch the operational state from a first mode to a temporary telemetry mode based on reception of the encrypted passthrough data; controlling the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection, wherein the communication circuitry is configured to receive a confirmation of receipt of the encrypted passthrough data from the medical device via the inductive connection; controlling the communication circuitry to send the confirmation to the external device via the communication channel; and controlling the recharging circuitry to switch from the temporary telemetry mode to the first mode based on receiving the confirmation.

[0160] Example 16. The method of any of examples 12 through 15, wherein the external instrument comprises recharge circuitry configured to transmit energy to the medical device, and wherein the second communication channel comprises an inductive connection, and wherein the method further comprises: receiving, by the communication circuitry, a first command from the external device, controlling the recharging circuitry to switch the operational state from a first mode to a telemetry-only mode based on receipt of the first command; controlling the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection; controlling the communication circuitry to wait for one of a second command from the external device or a timeout condition; and responsive to receiving the second command or the time condition occurs, controlling the recharging circuitry to switch from the telemetry-only mode to the first mode.

[0161] Example 17. The method of any of examples 12 through 16, wherein the medical device is an implantable medical device configured to deliver electrical stimulation to a tibial nerve of a patient.

[0162] Example 18. The method of any of examples 12 through 17, wherein the external device is configured to program the medical device via the encrypted passthrough data routed through the external instrument by the processing circuitry of the external instrument.

[0163] Example 19. The method of any of examples 12 through 18, wherein the external instrument comprises recharge circuitry configured to transmit energy to the medical device, and wherein the method further comprises: transmitting, by an inductive energy transmission coil connected to the recharge circuity, the energy to a secondary coil in the medical device; transmitting, by an inductive data transmission coil connected to the communication circuity, data to the medical device via the second communication channel; and exchanging, by an antenna connected to the communication circuitry, data with the external device via the communication channel.

[0164] Example 20. A non-transitory computer-readable storage medium storing instructions that, when executed, cause processing circuitry of an external instrument to: control communication circuitry of the external instrument to connect to an external device via a first communication channel and a medical device via a second communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the communication channel; control the communication circuitry to transmit the encrypted passthrough data to the medical device via a second communication channel; and control an operational state of recharge circuitry of the external instrument based on reception of at least one of the encrypted passthrough data or the command, wherein the recharge circuitry is configured to transmit energy to the medical device.

[0165] In one or more examples, the functions described above may be implemented in hardware, software, firmware, or any combination thereof. For example, the various components of FIGS. 1 - 4, processing circuitry 430 and processing circuitry 530 may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardwarebased processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer- readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that may be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium. [0166] The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that may, over time, change (e.g., in RAM or cache). By way of example, and not limitation, such computer-readable storage media, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or other computer readable media. In some examples, an article of manufacture may include one or more computer-readable storage media.

[0167] Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Combinations of the above should also be included within the scope of computer-readable media.

[0168] Instructions may be executed by one or more processors, such as one or more DSPs, general purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” and “processing circuitry,” as used herein, may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0169] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware. [0170] Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A external instrument, the instrument comprising: communication circuitry configured to establish a first communication channel with an external device and a second communication channel with a medical device; and processing circuitry configured to: control the communication circuitry to connect to the external device via the communication channel, wherein the communication circuitry is configured to receive encrypted passthrough data and a command from the external device through the communication channel; control an operational state of the external instrument based on reception of at least one of the encrypted passthrough data or the command; and control the communication circuitry to transmit the encrypted passthrough data to the medical device via the second communication channel.

2. The instrument of claim 1, wherein the second communication channel has a first authorization level and a second authorization level.

3. The instrument of any of claims 1 and 2, wherein the encrypted passthrough data is encrypted before the communication circuitry receives the encrypted passthrough data, wherein the encrypted passthrough data is configured to be decrypted by the medical device instead of the external instrument, and wherein the communication circuitry is configured to transmit the encrypted passthrough data to the medical device.

4. The instrument of any of claims 1 through 3, further comprising recharge circuitry configured to transmit energy to the medical device, wherein the second communication channel comprises an inductive connection, and wherein the processing circuitry is further configured to: control the recharging circuitry to switch the operational state from a first mode to a temporary telemetry mode based on reception of the encrypted passthrough data; control the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection, wherein the communication circuitry is configured to receive a confirmation of receipt of the encrypted passthrough data from the medical device via the inductive connection; control the communication circuitry to send the confirmation to the external device via the first communication channel; and control the recharging circuitry to switch from the temporary telemetry mode to the first mode based on receiving the confirmation.

5. The instrument of claim 4, wherein the first mode is one of a recharging mode or an idle mode.

6. The instrument of any of claims 1 through 5, further comprising recharge circuitry configured to transmit energy to the medical device, wherein the second communication channel comprises an inductive connection, wherein the communication circuitry is configured to receive a first command from the external device, and wherein the processing circuitry is configured to: control the recharging circuitry to switch the operational state from a first mode to a telemetry-only mode based on receipt of the first command; control the communication circuitry to transmit the encrypted passthrough data to the medical device via the inductive connection; control the communication circuitry to wait for one of a second command from the external device or a timeout condition; and responsive to receiving the second command or the time condition occurs, control the recharging circuitry to switch from the telemetry-only mode to the first mode.

7. The instrument of any of claims 1 through 6, wherein the medical device is an implantable electrical stimulation device.

8. The instrument of any of claims 1 through 7, wherein the medical device is configured to deliver electrical stimulation to a tibial nerve of a patient.

9. The instrument of any of claims 1 through 8, wherein the external device is configured to program the medical device via the encrypted passthrough data routed through the external instrument by the processing circuitry of the external instrument.

10. The instrument of any of claims 1 through 9, wherein the first communication channel is a Bluetooth connection.

11. The instrument of any of claims 1 through 10, further comprising recharge circuitry configured to transmit energy to the medical device.

12. The instrument of claim 10, further comprising an inductive energy transmission coil connected to the recharge circuity and configured to transmit the energy to a secondary coil in the medical device.

13. The instrument of any of claims 1 through 12, further comprising an inductive data transmission coil connected to the communication circuity and configured to transmit data to the medical device via the second communication channel.

14. The instrument of any of claims 1 through 13, further comprising an antenna connected to the communication circuitry and configured to exchange data with the external device via the communication channels.

15. A non-transitory computer-readable storage medium storing instructions that, when executed, cause the processing circuitry of the external instrument to perform functions of any of claims 1 through 14.