WO2014128668A1

WO2014128668A1 - Ventilator synchronized to an intermittently connected patient

Info

Publication number: WO2014128668A1
Application number: PCT/IB2014/059195
Authority: WO
Inventors: William Anthony TRUSCHEL; Christina Michele VOGLER
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-02-25
Filing date: 2014-02-24
Publication date: 2014-08-28

Abstract

A ventilator includes a breathing circuit (36) with a patient interface including a sensor (22) for measuring a flow signal. Two triggering mechanisms (60, 62) are configured to monitor a frequency response of the flow signal to sense patient connection and to determine when a change in a flow signal response meets one or more threshold conditions to enable a trigger event. A breathing apparatus (54 )is synchronized with the trigger event to enable breathing assistance for a patient.

Description

VENTILATOR SYNCHRONIZED TO AN INTERMITTENTLY

CONNECTED PATIENT RELATED APPLICATION DATA:

This application claims priority to commonly assigned provisional application serial No. 61/768,575, filed February 25, 2013, incorporated herein by reference.

BACKGROUND:

Technical Field

This disclosure relates to medical instruments and more particularly to devices and methods for triggering a ventilator by sensing subtle user interactions, e.g., using mouth, lip or tongue movements.

Description of the Related Art

Medical ventilators are employed to mechanically move breathable air into and out of the lungs for patients who are physically unable to breathe, or breathe insufficiently.

Ventilators may be employed in intensive care medicine, home care, and emergency medicine and in anesthesia (as a component of an anesthesia machine). In its simplest form, a modern positive pressure ventilator includes a compressible air reservoir or turbine, air and oxygen supplies, a set of valves and tubes, and a disposable or reusable "patient circuit". The air reservoir is pneumatically compressed several times a minute to deliver room-air, or in most cases, an air/oxygen mixture to the patient. If a turbine is used, the turbine pushes air through the ventilator, with a flow valve adjusting pressure to meet patient-specific parameters. When overpressure is released, the patient will exhale passively due to the lungs' elasticity, the exhaled air being released usually through a one-way valve within the patient circuit called the patient manifold.

Ventilators may be electronically controlled by an embedded system to permit exact adaptation of pressure and flow characteristics to an individual patient's needs. Fine-tuned ventilator settings also serve to make ventilation more tolerable and comfortable for the patient. A patient circuit may consist of one or more tubes. A tube could be used for only inhaled air; a tube could be used for only exhaled air and another tube could be used for oxygen or a nebulized drug treatment. Furthermore, the tube(s) may consist of a retractable catheter intended for the purposes of suctioning secretions. The patient circuit could be simplified by using one tube for multiple functions such as delivered and exhaled air with an exhalation device. Furthermore, the oxygen delivery can be mixed and combined with the inhaled air outside of the patient circuit. Determined by the type of ventilation needed, the patient-end of the circuit may be either noninvasive or invasive.

Noninvasive methods, which are adequate for patients who require a ventilator only while sleeping and resting, mainly employ a nasal mask. Invasive methods require intubation, which for long-term ventilator dependence will normally be a tracheotomy cannula, as this is much more comfortable and practical for long-term care than larynx or nasal intubation.

Mouthpiece ventilation is a form of noninvasive ventilation that combines positive pressure ventilation with a modified breathing circuit, typically using an angled mouthpiece to interface with the patient's lips and mouth. Often neuromuscular disease patients or other patients will require diurnal intermittent mechanical ventilator support. The ventilator only needs to deliver therapy when the patient has connected to the ventilator through the use of an angled mouthpiece or flexible straw. SUMMARY

In accordance with the present principles, a ventilator includes a breathing circuit with a patient interface including at least one sensor for measuring a flow signal. Two triggering mechanisms are configured to monitor a frequency response of the flow signal to sense patient connection and to determine when a change in a flow signal response meets one or more threshold conditions to enable a trigger event. A breathing apparatus is synchronized with the trigger event to enable breathing assistance for a patient.

A ventilator system includes a processor, memory coupled to the processor and a breathing circuit with a patient interface including at least one sensor for measuring a flow signal. A touch triggering mechanism is stored in memory and configured to monitor a frequency response of a flow signal to determine a patient connection. An air flow triggering mechanism is stored in memory and configured to monitor the frequency response of the flow signal due to breathing by a patient through the patient interface. An interpretation module is conflgured to initiate breathing cycles in a breathing apparatus based upon a response triggered by one or both of the touch triggering mechanism and the air flow triggering mechanism meeting one or more threshold conditions.

A method for ventilator synchronization based on patient attachment or detachment to an interface includes monitoring a flow signal through an interface; obtaining a frequency response of the flow signal; in accordance with the frequency response, determining whether a triggering threshold has been achieved using a first triggering mechanism configured to monitor the frequency response of the flow signal to sense patient connection and a second triggering mechanism to monitor the frequency response of the flow signal due to air flow changes through the interface; and when a triggering threshold has been achieved, triggering synchronized breathing cycles to enable or disable breathing assistance for a patient. These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

This disclosure will present in detail the following description of preferred

embodiments with reference to the following figures wherein:

FIG. 1 is a block/flow diagram showing a ventilator system having triggering mechanisms for determining patient connection activities (e.g., attachment or detachment) in accordance with one embodiment;

FIG. 2 is a block/flow diagram showing a system/method for filtering a frequency response of compensated flow in a ventilator in accordance with the present principles;

FIG. 3 is a graph showing frequency response (dB) verses frequency (Hz) for a kiss filter for mouthpiece ventilation in accordance with the present principles;

FIG. 4 is a graph showing frequency response (dB) verses frequency (Hz) for a differential flow filter for mouthpiece ventilation in accordance with the present principles;

FIG. 5 is a diagram showing flow measurement processed to graphically highlight patient attachment and detachment events in accordance with the present principles;

FIG. 6 is a diagram showing flow measurement processed to graphically highlight an insufficient touch trigger but a sufficient differential flow trigger to sense patient attachment in accordance with the present principles;

FIG. 7 is a block/flow diagram showing a system/method for determining whether threshold conditions have been met to initiate a touch trigger in accordance with the present principles; FIG. 8 is a block/flow diagram showing a system/method for determining whether threshold conditions have been met to initiate a differential flow trigger in accordance with the present principles;

FIG. 9 is a block/flow diagram showing a system/method for determining whether threshold conditions have been met to initiate an early exit (patient detachment) in accordance with the present principles;

FIG. 10 is an illustrative state diagram showing ventilator monitoring activities for mouthpiece ventilation in accordance with the present principles; and

FIG. 11 is a flow diagram showing a method for ventilator synchronization based on patient attachment or detachment with a mouthpiece in accordance with illustrative

embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

In accordance with the present principles, ventilators, systems and methods are provided that employ improved triggering mechanisms for initiating therapy. A ventilator may remain in a "standby" low power state until a patient is ready to receive therapy. The ventilator includes signal processing algorithms that enable the therapy to be initiated by the patient's connection to the ventilator. Because the patients often have little ability to generate negative inspiratory pressure with use of normal diaphragmatic efforts, the algorithms are provided to detect touch (e.g., mouth, tongue and lip movements) of the patient.

In one embodiment, two triggering mechanisms are provided together to improve reliability of sensing patient activities (e.g., attachment to a patient circuit or interface, such as, a mouthpiece). One triggering mechanism includes a flow signal within a preset frequency band (touch trigger or KISS TRIGGER™) and another triggering mechanism includes a flow measurement above a predetermined frequency (air flow or differential trigger).

It also should be understood that the present principles will be described in terms of medical instruments; however, the teachings of the present principles are much broader and are applicable to any air flow instrument configured with a sensitive triggering mechanism. In some embodiments, the present principles are employed in triggering a ventilator device but may be applied to any device that provides intermittent respiratory therapy.

The elements depicted in the FIGS, may be implemented in various combinations of hardware and software and provide functions which may be combined in a single element or multiple elements.

The functions of the various elements shown in the FIGS, can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which can be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and can implicitly include, without limitation, digital signal processor ("DSP") hardware, read-only memory ("ROM") for storing software, random access memory

("RAM"), non-volatile storage, etc.

Moreover, all statements herein reciting principles, aspects, and embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative system components and/or circuitry embodying the principles of the present embodiments. Similarly, it will be appreciated that any flow charts, flow diagrams and the like represent various processes which may be substantially represented in computer readable storage media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Furthermore, present embodiments can take the form of a computer program product accessible from a computer-usable or computer-readable storage medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable storage medium can be any apparatus that may include, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk - read only memory (CD-ROM), compact disk - read/write (CD-R/W), Blu-Ray™ and DVD.

Referring now to the drawings in which like numerals represent the same or similar elements and initially to FIG. 1, a ventilator system 10 is illustratively shown in accordance with one embodiment. System 10 includes a programmable ventilator 12 which preferably includes one or more processors 14 and memory 16 for storing programs and applications. It is to be understood that other types of ventilators may be employed that use a trigger device(s) to initiate therapy. The processor 14 may include or be part of a control unit which supervises and/or manages functions of the ventilator 12. Memory 16 may store software modules, such as a control module 52, that assist in the control and regulation of ventilator functions. In one embodiment, the memory 16 stores a flow response module 48 configured to monitor, interpret and filter a flow response signal from a flow sensor(s) 22 located in a patient interface 30, such as a mouth piece, tube or other breathing interface. The flow sensor 22 may be located anywhere in a patient circuit 36 (e.g., mouthpiece, at a vent outlet, etc.) to detect types of user activity consistent with a desire for treatment or therapy. The flow response module 48 filters the flow response signal to determine whether a user has attached or detached to the mouthpiece or patient interface 30 on the patient circuit 36.

While the present embodiments will be described in terms of flow, it should be understood that the triggering mechanisms may employ one or more of pressure, acceleration and/or flow to determine whether a patient has connected with or disconnected with the mouth piece 30. As such, the flow sensor 22 may include a pressure sensor, an accelerometer, a flow sensor or any other useful sensor or device.

The flow response module 48 performs one or more filter operations, logic operations, etc., as will be described to determine a frequency response of the flow sensor 22 output. The filtered output is analyzed for particular patient activities consistent with the initiation or cessation of treatment as determined by a trigger interpretation module 50. The filtered response output from the flow response module 48 is received by the trigger interpretation module 50 to be analyzed to determine if measured changes in a standby signal or flow signal of the flow sensor 22 are consistent with an attempt by a patient 32 to connect to the mouth piece 30. The trigger interpretation module 50 checks the filtered response against threshold conditions to determine whether, e.g., a patient' s mouth, lips or tongue have engaged the mouthpiece 30 or if airflow has changes a threshold amount for a given period of time.

The trigger interpretation module 50 includes one or more triggering mechanisms or methods. In blocks 60 and 62, first and second spontaneous triggering mechanisms associated with mouth piece ventilation (mpv) are provided. The triggering mechanisms 60, 62 complement each other to reliably detect an engagement between a patient's mouth and a patient circuit. Mouth piece ventilation is designed to operate by producing a small signal flow at all times when the patient is not connected. The triggering mechanisms 60, 62 are designed to analyze disruptions in the signal flow for specific frequency content, which indicate a patient connection (or disconnection).

The present triggering mechanisms 60, 62 are sensitive enough to allow a patient to easily trigger the device with his lips, mouth or tongue without requiring a large flow change from some diaphragmatic effort. In one embodiment, the first triggering mechanism 60 is associated with instantaneous changes or shorter timescale changes in the standby signal, and the second triggering mechanism 62 is associated with longer timescale changes in the standby signal. In a particularly useful embodiment, the first triggering mechanism 60 is triggered by an absolute value of the difference between a flow response filtered with a 1^st order 1 1 Hz low pass filter and a 2^nd order 3 Hz low pass filter. This response is associated with mechanical movement of the patient to connect with the mouth piece 30. The second triggering mechanism 62 is triggered by a computed difference between an average flow over time and an instantaneous change in flow over a threshold amount. The initiation of ventilator therapy may be initiated when either or both triggering mechanisms have been triggered. Other configurations, which may include additional or other triggering mechanisms are also contemplated.

Ventilator 12 includes a control module 52 that synchronizes breathing cycles for the patient 32. The control module 52 controls one or more mechanical devices including, e.g., a pressure device 54. The pressure device 54 may include a compressible air reservoir, turbine, or air/oxygen supply, and a set of valves and tubes, etc. connecting to the patient circuit 36. The pressure device 54 may be pneumatically compressed to deliver air or an air/oxygen mixture to the patient 32. If a turbine is employed, the turbine pushes through a flow valve to adjust pressure to meet patient-specific parameters. The pressure device 54 provides pressure differentials to assist in patient breathing.

The ventilator device 12 preferably includes a display 18 for viewing measurements, providing virtual control (e.g., touchscreen, etc.), plotting responses, etc. Display 18 may also permit a user to interact with the ventilator 12 and its components and functions, or any other element within the system 10. This is further facilitated by a digital interface 20 which may include a keyboard, mouse, a joystick, a haptic device, or any other peripheral or controls 34 to permit user feedback from and interaction with the ventilator 12.

Referring to FIG. 2, an illustrative system/method for filtering a flow sensor response is shown for the two mechanisms 60, 62 or FIG. 2. The triggering mechanism 60 may be referred to as a KISS TRIGGER™, a touch trigger or a frequency band trigger since it senses patient contact. The frequency band trigger employs a pseudo bandpass filter to filter a response of compensated total flow through a mouthpiece or patient interface in block 102. The response may be scaled before and/or after a low pass filter 106 in blocks 104 and 108 to ensure compatibility with other processes and computations (e.g., a subtraction operation in block 112). The low pass filter 106 may include a 2^nd order 3 Hz low pass filter.

The compensated flow response 102 is also subjected to another low pass filter 110. The low pass filter 110 filters with a 1^st order 11 Hz low pass filter. A difference between the outputs of the filter 106 and the filter 110 is computed in block 112 and an absolute value is taken of the result to provide a kiss energy (kiss flow deviation (KissFlowDev)) in block 116. The pseudo bandpass filter for kiss energy may be achieved by the absolute value of the difference between flow response filtered with a 1^st order 11 Hz low pass filter and a 2^nd order 3 Hz low pass filter.

The kiss energy may be in units of liters per minute (1pm) and scaling is preserved during processing with these units. A kiss or touch trigger is activated as an event when the kiss energy is greater than a threshold for a minimum duration. The resulting frequency response of the bandpass filters 106 and 110 (frequency response of mpv kiss filter) is illustratively shown in FIG. 3.

The triggering mechanism 62 may be referred to as a differential flow trigger, an airflow trigger or a threshold frequency trigger where a flow measurement above a predetermined frequency triggers a response in accordance with sensed changes in flow. The differential flow trigger uses a pseudo high pass filter. The high pass filter is realized by computing an absolute value in block 125 of a difference computed in block 124 between the low pass filter 110 (1^st order 11 Hz low pass filter) and a running average of most recent flow data points stored in an array 118. The array may store any number of data points, but for simplicity a 64 element array may be employed. In block 120, an average flow is computed for the elements in the array to output an average flow in block 122. The result is called a differential flow value (flow deviation (FlowDev)) in block 126 and is preferably in 1pm units with scaling. A differential flow trigger is defined as an event when the differential flow (126) is greater than a threshold for a minimum duration. The resulting frequency response of the filter 110 (frequency response of mpv diff filter) is shown in FIG. 4.

Referring to FIG. 5, the frequency band trigger algorithm is configured to detect the attachment and detachment of the patient's mouth on a mouthpiece. Signal processing in this algorithm produces an energy signal that spikes when the user interacts with the mouthpiece or interface. The algorithm is designed to respond quickly to the user's movement, respond to any movements of the mouth or tongue once the patient is attached and respond to normal diaphragmatic efforts if the patient is capable. The kiss energy will also spike when the user detaches from the mouthpiece and this will indicate a scenario when the patient leaves early and the volume measurement is inaccurate for updating the control loops.

A flow measurement device 202 (e.g., sensor(s)) collected flow data, and a signal processing algorithm 204 performs the steps as set forth in FIG. 2 to determine when the kiss energy threshold and/or the differential flow energy threshold have been exceeded in the flow data. The signal processing algorithm 204 receives the flow measurement data as described with reference to FIG. 2 (from block 102) and processes the received signal over set intervals to determine changes. A graph 206 illustratively shows an attachment and detachment of a patient's mouth with the mouthpiece (30, FIG. 1). A first peak 208 indicates when the patient's mouth touches the mouthpiece and a subsequent triggering of flow operation is indicated by peak 210. Likewise, a machine cycle indicating flow is shown by peak 212 and a peak 214 shows patient detachment. Peaks 208 and 210 are consistent with attachment (kiss and flow) and peaks 212 and 214 are consistent with detachment (flow and kiss). The properties of the peaks (magnitude and duration) can be employed to separately indicate attachment or detachment. For example, a change in flow of 3 1pm for one or more breathing cycles can be employed as a flow trigger and/or an abrupt response of adequate energy can be employed as a KISS TRIGGER™.

Referring to FIG. 6, the signal processing algorithm 204 is shown triggering the ventilator based upon flow alone. Graph 222 shows a frequency band trigger or KISS TRIGGER™ signal 224 without sufficient energy to trigger. However, machine flow 228 exceeds a flow trigger 226 (e.g., 3 1pm) to enable ventilator operation. The signal processing algorithm 204 receives flow measurement data as described with reference to FIG. 2 (from block 102) and processes the received signal over set intervals to determine changes. The flow trigger is designed to detect patient connections that occur so methodically or lethargically that there is not enough kiss energy to cause a fast trigger. The air flow trigger uses a running average of flow and looks for deviations from that running average. It is designed to be slower than the frequency band trigger.

Referring to FIG. 7, a method for determining whether kiss triggering thresholds are met is shown in accordance with one illustrative embodiment. In block 302, permission (permit) is set to false. Permission is granted to trigger when the status of the permit changes to true. A permit counter (PermitCntr) and a trigger counter (TriggerCntr) are set to zero. Exhale time (Etime) is initialized to zero. The method of FIG. 7 may be iterative and the process steps updated or repeated every interval (e.g., 10 ms). Initialization of these parameters are preferably performed at an inhale to exhale (IE) transition.

In block 304, a permission (Permit) check is made. If permission is granted, the process continues to block 306. If permission is not granted, the process continues with block 310.

In block 306, a determination is made as to whether the kiss flow deviation

(KissFlowDev) is greater than a threshold. KissFlowDev may be the output of block 116 in FIG. 2. The threshold may be expressed in 1pm or other units depending on the measurements type. In one embodiment, the threshold is 3 1pm although other thresholds may be employed. If KissFlowDev is greater than the threshold, the trigger counter is incremented in block 308; otherwise, it is decremented in block 312 (and the program path returns to the beginning). If incremented in block 308, a check as to whether the trigger counter is greater than 2 is made. This ensures the KissFlowDev activity is sustained over a given period (e.g., at least 20 ms) before triggering. If the trigger counter is greater than 2 (or some other threshold duration), Trigger is set to true in block 330 and triggering may occur (the program path returns to the beginning). If the trigger counter is not greater than 2 (or some other threshold duration) in block 314, the program path returns to the beginning.

If permit is not granted in block 304, Etime is incremented in block 310. In block 316, a check is performed to determine whether Etime is greater than 2 times (or other factor) the inhale time (Itime). If yes, than Permit is set to true in block 318. Otherwise, in block 320, a determination is made as to whether the KissFlowDev activity is less than a threshold (e.g., less than 0.5 1pm). If the KissFlowDev is less than the threshold, than the permit counter is incremented in block 322. Then in block 326, the permit counter is checked to see if a sufficient count has been achieved (e.g., 30). If a sufficient count has been achieved, Permit is set to true in block 328, and the program path returns to the beginning. If a sufficient count has not been achieved in block 326, the program path returns to the beginning. If the

KissFlowDev is greater than the threshold in block 320, than the permit counter is

decremented in block 324, and the program path returns to the beginning. Blocks 320 and 326 ensure stability in the kiss signal to set the trigger Permit to true. This would be expected when the patient is disconnected from the circuit. If the signal is still noisy, the permit can still be granted if sufficient time in expiratory phase expires.

Referring to FIG. 8, a method for determining whether differential flow triggering thresholds are met is shown in accordance with one illustrative embodiment. In block 402, permission (Permit) is set to false. Permission is granted to trigger when the status of the permit changes to true. A permit counter (PermitCntr) and a trigger counter (TriggerCntr) are set to zero. The method of FIG. 8 may be iterative and the process steps updated or repeated every interval (e.g., 10 ms). Initialization of these parameters are preferably performed at an inhale to exhale (I:E) transition. In block 404, a permission (Permit) check is made. If permission is granted, the process continues to block 406. If permission is not granted, the process continues with block 410. In block 406, a determination is made as to whether the flow deviation (FlowDev) is greater than a threshold. FlowDev may be the output of block 126 in FIG. 2. The threshold may be expressed in 1pm or other units depending on the measurement type. In one embodiment, the threshold is 3 1pm although other thresholds may be employed. If FlowDev is greater than the threshold the trigger counter is incremented in block 408; otherwise, it is decremented in block 412 (and the program path returns to the beginning). If incremented in block 408, a check as to whether the trigger counter is greater than 5 is made. This ensures the FlowDev activity is sustained over a given period (e.g., at least 50 ms) before triggering. If the trigger counter is greater than 5 (or some other threshold duration), trigger is set to true in block 422 and triggering may occur (the program path returns to the beginning). If the trigger counter is not greater than 5 (or some other threshold duration) in block 414, the program path returns to the beginning.

If Permit is not granted in block 404, a determination is made as to whether the FlowDev activity is less than another threshold (e.g., less than 2 1pm). If the FlowDev is less than the threshold, than the permit counter is incremented in block 416. Then, in block 418, the permit counter is checked to see is a sufficient count has been achieved (e.g., 40). If a sufficient count has been achieved, Permit is set to true in block 420, and the program path returns to the beginning. If a sufficient count has not been achieved, the program path returns to the beginning. If the FlowDev is greater than the threshold in block 410, then the program path returns to the beginning. Blocks 410 and 418 hold off the capability of the machine to trigger via the differential flow trigger until the flow has stabilized by holding the Permit to the value false. As block 410 and 418 indicate, the flow needs settle to within 2 1pm of the average flow before a flow deviation is qualified and the permit is set to true. While the permit is false, all threshold crossings are ignored.

Referring to FIG. 9, a method to detect when the patient has disconnected from the ventilator is shown in accordance with one illustrative embodiment. In block 502, an early exit flag (EarlyExitFlag) is set to false. This is preferably set after a second inhalation cycle (IPAP). Counter (Cntr) is set to zero and Itime is set to zero. The method of FIG. 9 may be iterative and the process steps updated or repeated every interval (e.g., 10 ms). Initialization of these parameters are preferably performed at an inhale to exhale (I:E) transition.

In block 504, Itime is incremented. In block 506, a conditional check is made as to whether the early exit flag is false, Itime is greater than 30, breathing is not mandatory (this can be set by a clinician based on the patient) and kiss permission (Permit) is granted. If any one of these conditions is false, the process returns to the beginning. If the specified conditions are true, the process continues.

If the KissFlowDev is not greater than the threshold (e.g., 7.5 1pm) in block 508, then the permit counter is decremented in block 510, and the program path returns to the beginning. If the KissFlowDev is greater than the threshold (e.g., 7.5 1pm) in block 508, then the permit counter is incremented in block 512.

In block 514, the counter is checked to see is a sufficient count has been achieved (e.g., 2). If a sufficient count has been achieved, EarlyExitFlag is set to true in block 516, and the program path returns to the beginning. If a sufficient count has not been achieved in block 514, the program path returns to the beginning.

Referring to FIG. 10, a state diagram shows states of a ventilator running the triggering methods in accordance with the present principles. In a first state 602, the system resets triggering algorithms and resets permits. In state 604, during expiratory positive airway pressure (EPAP), wait for an inspiratory positive airway pressure (IPAP) permit. In this state 604, signals are processed and permit logic is executed (see FIGs. 2, 7 and 8). A transition 605 is made to state 606 if at least one of: a kiss permit is granted, flow permit is granted or a time for a timed breath has elapsed true. In state 606, a trigger is permitted in the EPAP phase. Signals are processed, permit logic is executed and trigger logic is executed, as described (see FIGs. 2, 7 and 8).

A transition 607 is made to state 608 if at least one of a kiss permit is granted and a kiss trigger is enabled; a flow permit is granted and a flow trigger is enabled; or a time has elapsed for a timed breath. In state 608, in the IPAP phase, the system waits for an EPAP permit. Signals are processed, and a check is made for an early exit flag (see FIG. 9). A transition 609 is made to state 610 if at least one of: 300 ms (or other time) has elapsed or an immediate cycle has been forced by user action or other action, e.g., the vent uses a High Inspiratory Pressure (HIP) alarm to protect the patient from barotrauma. If this threshold is exceeded, the device will immediately cycle to EPAP. In state 610, in IPAP phase, the ventilator is permitted to cycle. Signals are processed, and a check is made for an early exit flag (see FIG. 9).

A transition to state 604 is made, if one of a VCV cycle, vol target cycle or a forced cycle are called for. The VCV cycle and Vol Target Cycle are designations given when the device has met or exceeded the target tidal volume. Thus it is appropriate to cycle to EPAP, or if a High Inspiratory Pressure alarm is detected, it is also appropriate to cycle to EPAP.

It should be noted that the therapy is terminated by safety limits in pressure and volume, to prevent barotraumas and volutrauma, respectively. In this form of ventilation, the cycles result in an exit to standby awaiting the next patient connection.

Referring to FIG. 1 1, a method for ventilator synchronization based on patient attachment or detachment with a patient interface (e.g., mouthpiece) is shown in accordance with the present principles. In block 702, a flow signal is monitored through a mouthpiece. In block 712, a frequency response is obtained for the flow signal.

In block 722, in accordance with the frequency response, it is determined whether a triggering threshold has been achieved using a first triggering mechanism configured to monitor the frequency response of the flow signal to sense patient touch and a second triggering mechanism to monitor the frequency response of the flow signal due to air flow changes through the mouthpiece.

In block 724, a kiss or touch trigger is evaluated. For example, a first band pass filter is configured to filter the frequency response and a second bandpass filter is configured to filter the frequency response such that an absolute value of a difference between filtered responses is compared to a threshold to determine if a patient has attached to the mouthpiece. The first band pass filter may include a second order 3 Hz low pass filter, and the second bandpass filter may include a first order 11 Hz low pass filter.

In block 726, a differential flow or air flow trigger is evaluated. For example, a band pass filter is configured to filter the frequency response and a computed average flow stored in memory based on recent flow measurements such that an absolute value of a difference between a filtered response and the computed average flow is compared to a threshold to determine if a patient has attached to the mouthpiece. The band pass filter may include a first order 11 Hz low pass filter.

In block 728, when a triggering threshold has been achieved, synchronized breathing cycles are triggered to enable or disable breathing assistance for a patient. One or both of the trigger mechanisms may be employed to enable breathing assistance/therapy.

In block 730, detachment from the mouthpiece by the patient may be determined based upon measured air flow changes using an early exit mechanism. When an early exit is determined, the breathing apparatus stops (therapy ends).

In interpreting the appended claims, it should be understood that:

a) the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim;

b) the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements;

c) any reference signs in the claims do not limit their scope;

d) several "means" may be represented by the same item or hardware or software implemented structure or function; and

e) no specific sequence of acts is intended to be required unless specifically indicated.

Having described preferred embodiments for ventilator synchronized to an

intermittently connected patient (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the disclosure disclosed which are within the scope of the embodiments disclosed herein as outlined by the appended claims. Having thus described the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.

Claims

CLAIMS:

1. A ventilator, comprising:

a breathing circuit (36) with a patient interface including at least one sensor (22) for measuring a flow signal;

at least two triggering mechanisms (60, 62) configured to monitor a frequency response of the flow signal to sense patient connection and to determine when a change in a flow signal response meets one or more threshold conditions to enable a trigger event; and a breathing apparatus (54) synchronized with the trigger event to enable breathing assistance for a patient.

2. The ventilator as recited in claim 1, wherein the at least one sensor (22) includes one of a flow sensor, an accelerometer and a pressure sensor.

3. The ventilator as recited in claim 1, wherein the patient connection is sensed based upon a measured change in energy in the frequency response of the flow signal over a threshold duration.

4. The ventilator as recited in claim 3, further comprising a first band pass filter (106) configured to filter the frequency response and a second bandpass filter (110) configured to filter the frequency response such that an absolute value of a difference between filtered responses is compared to a threshold to determine if a patient has attached to the patient interface.

5. The ventilator as recited in claim 4, wherein the first band pass filter (106) includes a second order 3 Hz low pass filter and the second bandpass filter (110) includes a first order 11 Hz low pass filter.

6. The ventilator as recited in claim 3, further comprising a band pass filter (110) configured to filter the frequency response and a computed average flow stored in memory based on recent flow measurements such that an absolute value of a difference between a filtered response and the computed average flow is compared to a threshold to determine if a patient has attached to the patient interface.

7. The ventilator as recited in claim 6, wherein the band pass filter (110) includes a first order 11 Hz low pass filter.

8. The ventilator as recited in claim 1, further comprising an early exit mechanism (506) configured to determine detachment from the patient interface by the patient based upon measured air flow changes.

9. The ventilator as recited in claim 1, wherein the at least two triggering mechanisms (60, 62) include a frequency band trigger and a frequency threshold trigger for changes sensed based upon a measured change in energy in the frequency response of the flow signal over a threshold duration.

10. A ventilator system, comprising:

a processor (14);

memory (16) coupled to the processor; a breathing circuit (36) with a patient interface including at least one sensor (22) for measuring a flow signal;

a touch triggering mechanism (60) stored in memory and configured to monitor a frequency response of a flow signal to determine a patient connection;

an air flow triggering mechanism (62) stored in memory and configured to monitor the frequency response of the flow signal due to breathing by a patient through the patient interface; and

an interpretation module (50) configured to initiate breathing cycles in a breathing apparatus based upon a response triggered by one or both of the touch triggering mechanism and the air flow triggering mechanism meeting one or more threshold conditions.

11. The ventilator system as recited in claim 10, wherein the at least one sensor (22) includes one of a flow sensor, an accelerometer and a pressure sensor.

12. The ventilator system as recited in claim 10, wherein the patient is sensed based upon a measured change in energy in the frequency response of the flow signal over a threshold duration.

13. The ventilator system as recited in claim 10, wherein the touch triggering mechanism (60) includes a first band pass filter (106) configured to filter the frequency response and a second bandpass filter (110) configured to filter the frequency response such that an absolute value of a difference between filtered responses is compared to a threshold to determine if a patient has attached to the patient interface.

14. The ventilator system as recited in claim 13, wherein the first band pass filter (106) includes a second order 3 Hz low pass filter and the second bandpass filter (110) includes a first order 11 Hz low pass filter.

15. The ventilator system as recited in claim 10, wherein the air flow triggering mechanism (62) includes a band pass filter (110) configured to filter the frequency response and a computed average flow stored in memory based on recent flow measurements such that an absolute value of a difference between a filtered response and the computed average flow is compared to a threshold to determine if a patient has attached to the patient interface.

16. The ventilator as recited in claim 15, wherein the band pass filter (110) includes a first order 11 Hz low pass filter.

17. The ventilator as recited in claim 10, further comprising an early exit mechanism (506) configured to determine detachment from the patient interface by the patient based upon measured air flow changes.

18. The ventilator as recited in claim 10, wherein the touch triggering mechanism (60) includes a frequency band trigger and the air flow triggering mechanism (62) includes a frequency threshold trigger, wherein the touch triggering mechanism and the air flow triggering mechanism sense changes based upon a measured change in energy in the frequency response of the flow signal over a threshold duration.

19. A method for ventilator synchronization based on patient attachment or detachment to an interface, comprising:

monitoring (702) a flow signal through an interface;

obtaining (712) a frequency response of the flow signal;

in accordance with the frequency response, determining (722) whether a triggering threshold has been achieved using a first triggering mechanism configured to monitor the frequency response of the flow signal to sense patient connection and a second triggering mechanism to monitor the frequency response of the flow signal due to air flow changes through the interface; and

when a triggering threshold has been achieved, triggering (728) synchronized breathing cycles to enable or disable breathing assistance for a patient.

20. The method as recited in claim 19, wherein the first triggering mechanism includes a first band pass filter (106) configured to filter the frequency response and a second bandpass filter (1 10) configured to filter the frequency response such that an absolute value of a difference between filtered responses is compared to a threshold to determine if a patient has attached to the interface.

21. The method as recited in claim 20, wherein the first band pass filter (106) includes a second order 3 Hz low pass filter and the second bandpass filter (110) includes a first order 11 Hz low pass filter.

22. The method as recited in claim 19, wherein the second triggering mechanism includes a band pass filter (1 10) configured to filter the frequency response and a computed average flow stored in memory based on recent flow measurements such that an absolute value of a difference between a filtered response and the computed average flow is compared to a threshold to determine if a patient has attached to the interface.

23. The method as recited in claim 19, wherein the band pass filter (110) includes a first order 11 Hz low pass filter.

24. The method as recited in claim 19, further comprising determining (730) detachment from the interface by the patient based upon measured air flow changes using an early exit mechanism.