EP3758665A1

EP3758665A1 - Mechanical cardio pulmonary resuscitation machine

Info

Publication number: EP3758665A1
Application number: EP19761531.3A
Authority: EP
Inventors: Sara Lindroth; Erik Von Schenck; Anders Nilsson; Jonas Lagerström; Bjarne Madsen Härdig; Thomas Falk
Original assignee: Stryker Corp
Current assignee: Stryker Corp
Priority date: 2018-02-28
Filing date: 2019-02-26
Publication date: 2021-01-06
Anticipated expiration: 2039-02-26
Also published as: EP3758665A4; EP3758665B1; WO2019168825A1

Abstract

An exemplary embodiment of a mechanical cardiopulmonary resuscitation ("CPR") device can include a piston, a driver coupled to the piston configured to extend and retract the piston and a controller. The controller can be configured to cause the driver during a session to at least position the piston at a reference position, extend the piston from the reference position to a compression position to compress a chest of a patient, return the piston from the compression position to the reference position, retract the piston from the reference position to a retreat position, the retreat position including the piston at a distance away from the reference position whereby the patient's chest can expand without active decompression of the patient's chest, the piston retracted to the retreat position at least once before the end of the session, and return the piston from the retreat position to the reference position.

Description

MECHANICAL CARDIO PULMONARY RESUSCITATION

MACHINE

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

[01] This patent application claims priority from U.S. Provisional Patent Application Serial No. 62/636,772, filed on February 28, 2018, the contents of which is incorporated herein by reference in its entirety.

BACKGROUND

[02] In certain types of medical emergencies a patient’s heart stops working. This stops the blood flow, without which the patient may die. Cardio Pulmonary Resuscitation (CPR) can forestall the risk of death. CPR includes performing repeated chest compressions to the chest of the patient so as to cause their blood to circulate some. CPR also includes delivering rescue breaths to the patient. CPR is intended to merely maintain the patient until a more definite therapy is made available, such as defibrillation. Defibrillation is an electrical shock deliberately delivered to a person in the hope of correcting their heart rhythm.

[03] Guidelines by medical experts such as the American Heart Association provide parameters for CPR to cause the blood to circulate effectively. The parameters are for aspects such as the frequency of the compressions, the depth that they should reach, and the full release that is to follow each of them. The depth is sometimes required to exceed 5 centimeters (cm) (2 inches (in.)). The parameters also include instructions for the rescue breaths.

[04] Traditionally, CPR has been performed manually. A number of people have been trained in CPR, including some who are not in the medical professions just in case. However, manual CPR might be ineffective, and being ineffective it may lead to irreversible damage to the patient’s vital organs, such as the brain and the heart. The rescuer at the moment might not be able to recall their training, especially under the stress of the moment. And even the best trained rescuer can become quickly fatigued from performing chest compressions, at which point their performance might be degraded. Indeed, chest compressions that are not frequent enough, not deep enough, or not followed by a full decompression may fail to maintain blood circulation.

[05] The risk of ineffective chest compressions has been addressed with CPR chest compression machines. Such machines have been known by a number of names, for example CPR chest compression machines (CCCM), mechanical CPR devices, cardiac compressors and so on.

[06] CPR chest compression machines repeatedly compress and release the chest of the patient. Such machines can be programmed so that they will automatically compress and release at the recommended rate or frequency, and can reach a specific depth within the recommended range. The repeated chest compressions of CPR are actually compressions alternating with releases of a compression element, such as a piston or belt. Conventional CPR machines start from a starting point, apply the chest compression, then release the compression element back to its starting point to reset and be ready to apply another chest compression, when needed, or according to a protocol. The start position of the compression element is near or physically touching the patient’s chest.

[07] Some CPR machines can even exert force upwards during the“release” or decompressions, pulling the chest higher than it would be while at rest - a feature that is called active decompression. Active decompression applies a force to promote the patient’s chest to expand after an applied chest compression. During active decompression in embodiments of a CCCM with a piston with a suction cup, the suction cup creates a vacuum with the patient’s chest and applies a force directed away from the anterior surface of the patient’s chest to promote chest expansion beyond the chest’s starting resting height between chest compressions.

[08] Patients who are not breathing do not have a chest that expands during CPR treatment. When CPR is successful, the patient spontaneously resumes natural ventilation. Or, during a CPR session, the rescuer administers ventilation therapy to the patient either manually or with a ventilator, and the patient’s chest expands with the ventilation. Unfortunately, conventional CPR devices do not lift the compression element away from or otherwise release the chest compression element from the patient’s chest to allow for chest expansion, which impedes the patient’s ventilation and lowers the likelihood of success of the treatment.

BRIEF SUMMARY

[09] An exemplary embodiment of a mechanical cardiopulmonary resuscitation ("CPR") device can include a piston, a driver coupled to the piston configured to extend and retract the piston and a controller. The controller can be configured to cause the driver during a session to at least position the piston at a reference position, extend the piston from the reference position to a compression position to compress a chest of a patient, return the piston from the compression position to the reference position, retract the piston from the reference position to a retreat position, the retreat position including the piston at a distance away from the reference position whereby the patient's chest can expand without active decompression of the patient's chest, the piston retracted to the retreat position at least once before the end of the session, and return the piston from the retreat position to the reference position.

[10] In some embodiments, the controller can be further configured to cause the driver to retract the piston to the retreat position after each return to the reference position from the compression position. Additionally and/or alternatively, the controller can be further configured to initiate a pause, wherein during the pause the piston is not extended to the compression position and the piston is retracted to the retreat position. Additionally and/or alternatively, the controller can be further configured to retain the piston in the retreat position for a preset amount of time.

[H] Some embodiments of the CPR device can include a user interface configured to receive a selection of a pause mode, wherein the controller is configured to generate a pause signal when the selection of the pause mode is received and further configured to cause the driver to retract the piston to the retreat position. Additionally and/or alternatively, some embodiments can include a suction cup removably attached to the piston at a piston end.

[12] In some embodiments, retraction of the piston from the reference position to the retreat position includes an application of 22.24 newtons (N) (five pounds (lb)) or less of force. Additionally and/or alternatively, the distance between the retreat position and the reference position is less than 6 centimeters. Additionally and/or alternatively, the distance between the retreat position and the reference position is at least 3 centimeters. Additionally and/or alternatively, the distance between the retreat position and the reference position is approximately 1 centimeter.

[13] An exemplary embodiment of a non-transitory computer-readable storage medium storing one or more programs which, when executed by at least one processor of a system to assist a rescuer to perform, during a session, successive cardiopulmonary resuscitation (“CPR”) compressions on a chest of a patient by using a system that includes a piston and a driver, the programs can result in operations comprising positioning the piston at a reference position, extending the piston from the reference position to a compression position to compress a chest of a patient, returning the piston from the compression position to the reference position, retracting the piston from the reference position to a retreat position, the retreat position including the piston at a distance away from the reference position whereby the patient's chest can expand without active decompression of the patient's chest, the piston retracted to the retreat position at least once before the end of the session; and returning the piston from the retreat position to the reference position.

[14] Additionally and/or alternatively, the programs can result in operations further comprising retracting the piston to the retreat position after each return to the reference position from the compression position. Additionally and/or alternatively, the programs can result in operations further comprising initiating a pause, wherein during the pause the piston is not extended to the compression position and the piston is retracted to the retreat position. Additionally and/or alternatively, the programs can result in operations further comprising retaining the piston in the retreat position for a preset amount of time

[15] Additionally and/or alternatively, the system can further includes a user interface configured to receive a selection of a pause mode, wherein the programs result in operations further comprising generating a pause signal when the selection of the pause mode is received and retracting the piston to the retreat position.

[16] Some embodiments of a CPR device can include a compression belt, a driver coupled to the compression belt configured to tighten and loosen the compression belt about a chest of a patient, and a controller configured to cause the driver during a session to at least: tighten the compression belt from a reference position to a compression position to compress a chest of a patient, wherein the reference position includes a compression belt reference length, return the compression belt from the compression position to the reference position, loosen the compression belt from the reference position to a retreat position, the retreat position including the compression belt having a retreat length longer than the reference length whereby the patient's chest can expand, the compression belt loosened to the retreat position at least once before the end of the session, and tighten the compression belt from the retreat position to the reference position.

[17] Additionally and/or alternatively, the controller can be further configured to loosen the compression belt to the retreat position after each return to the reference position from the compression position. Additionally and/or alternatively, the controller can be further configured to initiate a pause, wherein during the pause the compression belt is not tightened to the compression position and the compression belt is loosened to the retreat position. Additionally and/or alternatively, the controller can be further configured to retain the piston in the retreat position for a preset amount of time. Additionally and/or alternatively, the CPR device can further include a user interface configured to receive a selection of a pause mode, wherein the controller is configured to generate a pause signal when the selection of the pause mode is received and cause the driver to loosen the compression belt to the retreat position.

[18] These and other features and advantages of this description will become more readily apparent from the following Detailed Description, which proceeds with reference to the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[19] FIG. 1 is a diagram of components of an abstracted CPR chest compression system according to the present disclosure.

[20] FIG. 2 is an exemplary CPR chest compression system including a piston and a suction cup according to the present disclosure. [21] FIG. 3 is an exemplary compression mechanism and exemplary time diagram of a CPR session.

[22] FIG. 4 is an exemplary time diagram of a sample sequence of CPR chest compressions that includes a pause and a retreat to a retreat position.

[23] FIG. 5 is an exemplary time diagram of a sample sequence of CPR chest compressions that includes a retreat to a retreat position following each return to a reference position.

[24] FIG. 6 is an exemplary flow chart for illustrating methods.

[25] FIGS. 7A-C are exemplary diagrams of components of an abstracted CPR machine that includes a piston.

[26] FIGS. 8A-C are exemplary diagrams of components of an abstracted CPR machine that includes a belt.

[27] FIGS. 9A-B are exemplary diagrams of components of an abstracted CPR machine that includes a piston and a suction cup.

DETAILED DESCRIPTION

[28] The present disclosure relates to CPR chest compression machines, methods and software that can perform automatically a series of Cardio-Pulmonary Resuscitation (“CPR”) chest compressions on a patient and can include a compression element having a retreat position, also referred to as a ventilation position, that allows for ventilation of a patient’s chest, such as a gap or space between the surface of the compression element and the patient’s chest, without applying any force or active decompression on the patient’s chest.

[29] The disclosed mechanical CPR machines with the compression element having the retreat position can improve oxygenation of the patient during CPR therapy. The CPR machines can further simplify the ability to adjust the patient during therapy and/or the CPR machine during use, if needed. By moving the compression element to a retreat position away from the patient’s chest to allow for chest expansion from ventilation, the compression element is not placing a load on the patient’s chest during the ventilation and ventilation delivery become easier because there is no opposing force working against the chest expansion/chest rise. The rescuer can more easily deliver ventilation, either manually or through use of a ventilator, when the patient’s chest is allowed to freely rise, as needed, without the opposing force of the chest compression element pushing against the patient’s chest.

[30] Further, the rescuer can observe or monitor the patient’s ventilation and chest rise throughout CPR therapy and can adjust CPR administration if the ventilation is not occurring as needed or expected. The patient can be correctly positioned or re positioned to maximize the benefit of the chest compressions. Further, the position of the CPR machine can also be adjusted when the compression element is in the retreat position which can improve the proper placement of the compression element to contact the patient’s chest in the ideal or recommended position. The patient’s clothes could be removed when the chest compression element is in the retreat position, if needed, or if not previously removed, to help facilitate improved CPR therapy administration. Moving the chest compression element to the retreat position allows the rescuer to more easily and quickly detect if the patient experiences return of spontaneous circulation (ROSC) which may indicate a change in the administered therapy. Even further, if the CPR machine is used during imaging, such as x-ray for example, lifting the compression element away from the patient’s chest may allow more accurate and precise imaging results, which improves patient outcomes. One example is use of the CPR machine during cardiac surgery, such as angiography and/or angioplasty in which imaging is used as a guide to help the technician or surgeon, respectively, and the CPR machine can block or obstruct imaging techniques. Embodiments are now described in more detail.

[31] Fig. 1 illustrates an example schematic block diagram of a mechanical CPR device 100. As will be understood by one skilled in the art, the mechanical CPR device 100 may include additional components not shown in Fig. 1. The mechanical CPR device 100 includes a controller 102, which may be in electrical communication with a chest compression mechanism or device 104. The chest compression mechanism 104 can include a compression element, that compresses a chest of a patient, such as a piston based chest compression device or a belt driven device that wraps around a chest of a patient. The compression element in Fig. 1 includes a piston 106 and a contact member 154. Chest compression elements for CPR machines can also include compression arms, such as one or more rigid or semi-rigid arms and/or a compression element and belt combination. The rigid or semi-rigid arms apply a force onto the anterior surface of the patient’s chest in a manner similar to that of the piston-style chest compression element. The belt-style chest compression element is often a flexible but resilient and tough material that tightens around some portion of the patient’s chest to force its compression element to against the patient’s chest to apply the chest compression. Alternatively, the belt holds a compression element, such as a plunger or piston element above the patient’s chest and tightens the belt on either side of the plunger or position to cause the force to move the plunger or piston toward the patient’s chest. The belt can be made of any suitable material.

[32] Contact member 154 can include a suction cup, a compression pad, or other device configured to make contact with a patient's chest. The chest compression mechanism 104 can further include a contact surface 116 configured to make contact with a patient's chest. The contact surface 116 can be disposed on the piston 106 or the contact member 154. The chest compression mechanism 104 further can include retention structure 108 including one or more legs 110 and/or a support portion 112 configured to be placed underneath a patient 114.

[33] The chest compression mechanism 104 may include a driver 118 configured to drive the compression mechanism 104 to cause the compression mechanism 104 to perform compressions to a chest of patient 114. The controller 102, as will be discussed in more detail below, provides instructions to the chest compression mechanism 104 to operate the chest compression mechanism 104 at a number of different rates, depths, heights, duty cycles. Example chest compression instructions or protocols include a series of compressions with intermittent releases in which a compression element is moved away from or otherwise released from the patient’s chest to a retreat position, also referred to as a retreat position, that allows for ventilation of a patient’s chest, such as a gap or space between the surface of the compression element and the patient’s chest, without applying any force or active decompression on the patient’s chest. During these “releases” between chest compressions, the patient’s chest may expand from natural ventilation whether spontaneous or ongoing, or from manual, rescuer administered ventilation from manual ventilation (“rescue breathes”) or from a ventilation device like a ventilator.

[34] The controller 102 may include a processor 120, which may be implemented as any processing circuity, such as, but not limited to, a microprocessor, an application specific integration circuit (ASIC), programmable logic circuits, etc. The controller may further include a memory 122 coupled with the processor 120. Memory can include a non-transitory storage medium that includes programs 124 configured to be read by the processor 120 and be executed upon reading. The processor 120 is configured to execute instructions from memory 122 and may perform any methods and/or associated operations indicated by such instructions. Memory 122 may be implemented as processor cache, random access memory (RAM), read only memory (ROM), solid state memory, hard disk drive(s), and/or any other memory type. Memory 122 acts as a medium for storing data 126, such as event data, patient data, etc., computer program products, and other instructions.

[35] Controller 102 may further include a communication module 128. Communication module 128 may transmit data to a post-processing module 130. Alternately, data may also be transferred via removable storage such as a flash drive. While in module 130, data can be used in post-event analysis. Such analysis may reveal how the CPR machine was used, whether it was used properly, and to find ways to improve future sessions, etc.

[36] Communication module 128 may further communicate with other medical device 132. Other medical device 132 can be a defibrillator, a monitor, a monitor- defibrillator, a ventilator, a capnography device, or any other medical device. Communication between communication module 128 and other medical device 132 could be direct, or relayed through a tablet or a monitor-defibrillator. Therapy from other device 132, such as ventilation or defibrillation shocks, can be coordinated and/or synchronized with the operation of the CPR machine. For example, compression mechanism 104 may pause the compressions for delivery of a defibrillation shock, afterwards detection of ECG, and the decision of whether its operation needs to be restarted. For instance, if the defibrillation shock has been successful, then operation of the CPR machine might not need to be restarted. Additionally and/or alternatively, the other medical device 132 can include a ventilator and the ventilator can send instructions to the controller 102 to coordinate chest compressions and ventilation. For example, the controller 102 may cause the compression mechanism 104 to pause compressions and/or the compression element to be moved away from or otherwise released from the patient’s chest to the ventilation position, such that a ventilation by the ventilator can occur and the patient’s chest can rise naturally during the ventilation.

[37] The controller 102 may be located separately from the chest compression mechanism 104 and may communicate with the chest compression mechanism 104 through a wired or wireless connection 134. The controller 102 also electrically communicates with a user interface 136. As will be understood by one skilled in the art, the controller 102 may also be in electronic communication with a variety of other devices, such as, but not limited to, another communication device, another medical device, etc.

[38] The chest compression mechanism 104 may include one or more sensors configured to transmit information to controller 102. For example, chest compression mechanism 104 can include a physiological parameter sensor 138 for sensing a physiological parameter of a patient and to output a physiological parameter sensor signal 140 that is indicative of a dynamic value of the parameter. The physiological parameter can be an Arterial Systolic Blood Pressure (ABSP), a blood oxygen saturation (Sp02), a ventilation measured as End-Tidal C02 (ETC02), a temperature, a detected pulse, etc. In addition, this parameter can be what is detected by defibrillator electrodes that may be attached to patient, such as ECG and impedance.

[39] Additionally and/or alternatively, the chest compression mechanism 104 can include a height sensor 142 configured to sense the height of the patient’s chest and to output a height signal 144, which is indicative of the resting height of the patient’s chest. Additionally and/or alternatively, the controller 102 can receive the height signal 144 and calculate a reference position, also referred to as a start position, for the compression mechanism 104. Additionally and/or alternatively, the chest compression mechanism can include a movement sensor 146 configured to sense movement of the patient’s chest and to output a movement signal 148, which may indicate ventilation movement of the patient’s chest. Additionally and/or alternatively, the chest compression mechanism 104 can include a pressure sensor 150 configured to sense area(s) of pressure of the contact surface with the patient's chest and to output a pressure signal 152, which is indicative of a dynamic value of pressure against the patient's chest.

[40] Operations of the mechanical CPR device 100 may be effectuated through the user interface 136. The user interface 136 may be external to or integrated with a display. For example, in some embodiments, the user interface 136 may include physical buttons located on the mechanical CPR device 100, while in other embodiments, the user interface 136 may be a touch-sensitive feature of a display. The user interface 136 may be located on the mechanical CPR device 100, or may be located on a remote device, such as a smartphone, tablet, PDA, and the like, and is also in electronic communication with the controller 102. In some embodiments, controller 102 can receive a pause input from the user interface 136 and, responsive to the pause input, cause the compression mechanism 104 to move to a retreat position to allow a patient’s chest to rise, to allow the rescuer to position or reposition the patient or the CPR machine, and for all other stated and discovered benefits of temporarily providing additional space between the patient’s chest and the compression element. Responsive to the pause input, the controller 102 can move and retain the compression mechanism 104 in the retreat position for a preset amount of time or CPR can be manually restarted by a rescuer taking an additional action, such as releasing a pause button or otherwise inputting an instruction received by the controller 102 to resume chest compressions.

[41] During a CPR session of compressions, controller 102 can generate or receive an instruction (either pre-programmed or customized based on any parameters or other data) to drive the compression mechanism 104 from a reference position towards the patient’s chest to a compression position to administer a chest compression. The reference position can be a specific and pre-defmed position or can be calculated or estimated based on sensed input or other patient and/or rescuer data. The same or a subsequent instruction can also drive the compression mechanism 104 to move back away from the patient’s chest after the applied chest compression. The chest compression mechanism 104 can be moved to a retreat position away from the patient’s chest. The retreat position is different than the reference position of the compression mechanism 104 and allows for the patient’s chest to expand. Moving the chest compression mechanism 104 to the retreat position does not require or force the patient’s chest to expand but instead allows for the opportunity for the patient’s chest to expand during ventilation. The chest compression mechanism 104 can remain at the retreat position until the next chest compression begins. In some examples, the chest compression mechanism 104 is returned to the reference position from the retreat position before the next chest compression begins. Alternatively, the chest compression mechanism 104 begins the next chest compression from the retreat position. In a series of chest compressions, the CPR machine can use a combination of chest compressions that begin from both the reference position and the retreat position either according to a protocol or as needed.

[42] Moving the chest compression mechanism from the compression position to the retreat position can occur between each administered chest compression or between multiples of chest compressions, for example. Alternatively, moving the chest compression element to the retreat position can also occur manually or as needed and can be triggered either by user prompts, such as pushing a button on the user interface 136 or otherwise inputting data to indicate to the controller 102 to move the compression mechanism 104 to the retreat position, or automatically by sensed data, such as data automatically sensed by one or more sensors electrically coupled to the CPR machine, such as one or more patient physiological sensors including but not limited to physiological parameter sensor 138.

[43] The retreat position of the compression mechanism 104 is a position that allows for ventilation of the patient’s chest, such as a gap or space between the surface of the compression mechanism 104, such as contact surface 116 disposed on the piston 106 or the contact member 154, and the patient’s chest. The gap can vary between chest compressions, can be a set value, or any be adjustable. In some embodiments, the gap can be between 0.5-6 centimeters to allow the ventilation to occur. The retreat position can be a range of values or positions with respect to the patient’s chest and may change over the course of the CPR therapy. Activating the retreat position of the chest compression element can occur in different ways and a CPR machine can offer a user multiple options for activating the retreat position or alternatively automatically activing the retreat position without user interaction. For example, the CPR machine can include a pause button or other type of user input to drive the compression element to the retreat position rather than return to the reference position after one or more administered chest compressions.

[44] FIG. 2 shows a CPR system 200 including a retention structure 202. The retention structure 202 includes a central member 204, a first leg 206, a second leg 208, and a support portion 210 configured to be placed underneath a patient. Central member 204 is coupled with first leg 206 and with second leg 208 via joints 214 and 214, respectively. In addition, the far ends of legs 206, 208 can become coupled with edges 216, 218 of support portion 210. These couplings form the retention structure 202 that retains a patient. In this particular case, central member 204, first leg 206, second leg 208 and support portion 210 form a closed loop, in which the patient is retained.

[45] Central member 204 includes a battery that stores energy, a motor that receives the energy from the battery, and a compression mechanism that can be driven by the motor. The compression mechanism is driven up and down by the motor using a rack and pinion gear. The compression mechanism includes a compression element, such as a piston 220 that emerges from central member 204, and can compress and release the patient’s chest. Piston 220 is sometimes called a plunger. Here, piston 220 terminates in a contact member 222 having a contact surface 224. The contact member 222 can include a suction cup 226. In this case the battery, the motor and the rack and pinion gear are not shown, because they are completely within a housing of central member 204.

[46] FIG. 3 shows two cooperating diagrams 302, 304. Diagram 304 is bridged with diagram 302 by an arrow 306. Diagram 302 shows a retention structure 308 that retains a patient 310. A controller 312 controls a compression mechanism that includes a plunger 314. In this embodiment, plunger 314 does not have a suction cup at the end, although a suction cup can be included in other embodiments.

[47] A specific point 316 of plunger 314 is also indicated. Specific point 316 can be chosen anywhere on plunger 314; and it is arbitrarily chosen to be at the lowest point of plunger 316, so that its time trajectory will match the compression depth during the compressions and releases. Diagram 34 is a time diagram that shows the depths of CPR compressions and releases 318.

[48] Diagram 304 shows a time diagram of the elevation of specific point 316. Specific point 316 starts the compressions from a first elevation, also referred to as zero, initial position, start position, or reference position A of plunger 314, also referred to as piston 314. Reference position A can be the point at which a compression mechanism is near or in physical contact with a patient's chest in its resting position, without compression of the patient's chest. Reference position A can be determined manually by an operator or detected by a CPR system. Additionally and/or alternatively, reference position A can be the position from which depth of CPR compressions are measured. Additionally and/or alternatively, reference position A can be a patient's resting chest height, as determined manually by an operator or detected by a CPR system. The start or reference position may vary based on the patient’s size, cardiac condition, sensed physiological parameters, movement (either from transport or medical conditions like seizures or muscle spasms), and/or any other factors.

[49] During a first series or group of CPR compressions and releases 320, piston 314 repeatedly extends and returns between reference position A and compression position B. As shown in FIG. 3, piston 314 is extended from reference position A to a compression position B to compress a chest of patient 310. Piston 548 is returned from compression position B to reference position A.

[50] After first series 320, piston 314 is returned to the reference position A and a first pause 322 starts. During first pause 322, piston 314 is retracted a distance H away from the reference position A to a retreat position C, also referred to as ventilation position. Piston 314 is not extended to compression position B during first pause 322. Retreat position C can be higher than the chest resting height and/or reference position A such that, for example, the patient's chest can expand during ventilation. Retreating to retreat position C, however, does not actively decompress a patient's chest.

[51] Pause 322 can last for a preset amount of time or CPR can be manually restarted by a rescuer taking an additional action, such as releasing a pause button or otherwise inputting an instruction received by a controller to resume chest compressions. When pause 322 ends, piston 314 returns to reference position A and a second group of compressions (not shown in FIG. 3) begins. In some embodiments, piston 314 extends directly from retreat position C to compression position B. In some embodiments, piston 314 extends first from retreat position C to reference position A and then to compression position B to minimize any impact on a patient's chest. In some embodiments, piston 314 can pause momentarily, for example a fraction of a second, at reference position A before extending to compression position B.

[52] In some embodiments, the distance H between retreat position C and reference position A can be between 0.5 cm to 1 cm. In some embodiments, the distance H between retreat position C and reference position A can be up to 6 cm. In some embodiments, the distance H between retreat position C and reference position A can be greater than 6cm.

[53] Retreating to retreat position C at least once during a session of administration of CPR chest compressions to a patient can ensure that there is no load on a patient's chest to allow for natural or manual ventilation. It can therefore facilitate the provision of rescue breaths and/or ventilations. For example, ventilation might cause the chest to rise a little, but a CPR system paused at reference position A does not accommodate for this temporary chest rise. However, retreating to retreat position C during a pause for ventilation will accommodate for the rise. It can allow an operator of a CPR system to more easily see if air is entering a patient's chest and lungs as intended prior to continuing chest compressions and to further observe if the patient starts to breath by him or herself.

[54] Retreating to retreat position C can further allow for less visual obstruction in a catheterization laboratory during angiography or angioplasty if a compression mechanism used includes radiopaque material. Retreating to retreat position C can further permit adjustment of a compression mechanism if placement is not correct or the patient has shifted during a CPR session. Retreating to retreat position C can additionally allow for removal of clothes on the upper body if an operator initially forgot to remove clothing prior to starting the CPR session. Retreating to retreat position C can additionally allow for correcting placement of defibrillator pad(s). [55] Referring now to FIG. 4, another embodiment of a session of administration CPR chest compressions to a patient including at least one retreat to a retreat position. FIG. 4 shows a time diagram 400 of a CPR session of chest compressions and releases. A first group of compressions and releases 402 is followed by a first pause 404, which is then followed by a second group of compressions and releases 406, a second pause 408, and a third group of compressions and releases 410 as part of a sequence in a CPR session.

[56] A CPR system can pause compressions during a CPR session to administer ventilations, via a rescuer or a ventilator, and/or for detection of return of spontaneous circulation (ROSC). Pausing can be periodic, according to a schedule, responsive to an instruction received from a ventilator, and/or responsive to an input by an operator to a user interface. For example, controller 102 can receive a selection of a pause mode from user interface 136 and generate a pause signal. Additionally and/or alternatively, controller 102 can initiate a pause. The time length of a pause can last a predetermined amount of time and/or the length of a pause can be determined by an operator. For example, controller 102 can initiate the end of a pause and return to compression and release cycle and/or controller 102 can receive an end pause signal from a user interface and initiate return to the compression and release cycle.

[57] During first group of compressions and releases 402, second group of compressions and releases 406, and third group of compressions and releases 410, a compression mechanism, not shown, moves from a reference position A to a compression position B and returns to reference position A at least twice successively. During first pause 404 and second pause 408, the compression mechanism moves to a retreat position C from reference position A. After first pause 404 and second pause 408 ends, the compression mechanism returns to reference position A and continues the next group of compressions and releases.

[58] Referring now to FIG. 5, another embodiment of a session of administering CPR chest compressions to a patient including at least one retreat to a retreat position is shown. FIG. 5 shows a time diagram 500 of a session of CPR chest compressions and releases, wherein the session includes a group of compression and releases 502 during which, after each return to a reference position A from a compression position B, a compression mechanism, not shown, moves to a retreat position C. The compression mechanism then returns to reference position A and a next compression and release cycle begins, wherein the next compression and release cycle also includes moving to the retreat position C. In other words, the compression mechanism moves to the retreat position C after each compression during at least two successive compressions and releases in the CPR session.

[59] FIG. 6 is a flow chart 600 illustrating methods of CPR chest compressions in accordance with the present disclosure. At step 602, a compression mechanism moves to a reference position and at step 604, the compression mechanism moves to a compression position. At step 606, the compression mechanism returns to the reference position. At step 608, the compression mechanism moves to a retreat position.

[60] As shown in flow chart 600, in some embodiments the method 600 includes returning to step 602 to repeat the cycle of moving to the retreat position after each return to the reference position from the compression position. Additionally and/or alternatively, as also shown in flow chart 600, in some embodiments, the method 600 includes performing a group of compression and releases, having no movement to a retreat position, at step 610 and then returning to step 602 for an additional compression and release cycle including movement to a retreat position.

[61] Moving to retreat position C at least once during a session of administering sets of CPR chest compressions to a patient can be used in conjunction with a mechanical CPR system having any compression element, including but not limited to compression mechanisms including a piston, a compression pad or other pads, a suction cup, and/or a belt. As shown in FIGS. 7A and 7B, if a compression mechanism 700 includes a piston 702, the movement of compressions and releases of a patient's chest 704 between reference position A and compression position B can include extension and retraction of the piston 702 between a reference position at HA and a compression position at HB. The piston is very near or touches the patient’s chest at the reference position HA. The patient’s chest is compressed when the piston is in the compression position at HB. The movement to retreat position C and return to reference position A can include retraction and extension of the piston 2802 respectively as shown in FIGS. 7C and 7A between a retreat position at He and reference position at HA. The retreat position at He is shown to be moved farther away from the patient’s chest than the reference position at HA and leaves a gap or a space between the piston and the patient’s chest.

[62] As shown in FIGS. 8A and 8B, if a compression mechanism 800 includes a belt 802, the movement of compressions and releases between reference position A and compression position B can include tightening and loosening of the belt 802 between a reference position having a belt length LA and a compression position having a belt length LB. When the belt is in the reference position having the belt length LA, the belt touches or is very near to the patient’s chest without applying force. When the belt 802 is in the compression position having the belt length LB_, the belt applies compression force to the patient’s chest. After compression, the belt 802 is then released or retracted to move the compression mechanism away from the patient’s chest which causes the compression mechanism to be spaced apart from the patient’s chest to a retreat position at a belt length Lc. Alternatively, the belt 802 is released or retracted to cause the compression element to simply move with the patient’s chest rise and not obstruct it although it may not create a physical space between the compression element and the patient’s chest in this example. The movement to retreat position C and return to reference position A can include loosening and tightening of the belt respectively as shown in FIGS 8C and 8A between a retreat position at Lc and reference position at LA.

[63] As noted earlier, retreating to a retreat position does not result in active decompression of a patient's chest, even if the compression mechanism includes a suction cup. As shown in FIG. 9A, a compression mechanism 900 including a piston 902 and a suction cup 904 at a reference position with the compression element very near or touching the patient’s chest 906. FIG. 9B shows the compression mechanism 900 at a retreat position, wherein the piston 902 retreating to a retreat position occurs within the suction cup 904 such that no active decompression of the chest 906 occurs. In other words, the suction cup 904 is not moved and does not force any upwards movement of the chest 906. In the retreat position, the suction cup 904 remains in contact, and still has a vacuum seal, with the chest 906 while the piston 902 is moved away from the patient's chest 3006, for example to allow for natural expansion of the patient's chest 906 during ventilation. The force applied to lift the piston 902 is below the threshold force required for active decompression. Additionally and/or alternatively, the retraction of the compression mechanism 900 to the retreat position can include an application of 22.24 newtons (5 pounds) or less of force such that no active decompression of the chest occurs.

[64] This description includes one or more examples, but that does not limit how the invention may be practiced. Indeed, examples or embodiments of the invention may be practiced according to what is described, or yet differently, and also in conjunction with other present or future technologies.

[65] A person skilled in the art will be able to practice the present invention in view of this description, which is to be taken as a whole. Details have been included to provide a thorough understanding. In other instances, well-known aspects have not been described, in order to not obscure unnecessarily the present invention.

[66] Other embodiments include combinations and sub-combinations of features described herein, including for example, embodiments that are equivalent to: providing or applying a feature in a different order than in a described embodiment, extracting an individual feature from one embodiment and inserting such feature into another embodiment; removing one or more features from an embodiment; or both removing a feature from an embodiment and adding a feature extracted from another embodiment, while providing the advantages of the features incorporated in such combinations and sub-combinations.

[67] The following claims define certain combinations and subcombinations of elements, features and steps or operations, which are regarded as novel and non- obvious. Additional claims for other such combinations and subcombinations may be presented in this or a related document.

Claims

CLAIMS What is claimed:

1. A mechanical cardiopulmonary resuscitation ("CPR") device, comprising: a piston;

a driver coupled to the piston configured to extend and retract the piston; and a controller configured to cause the driver during a session to at least:

position the piston at a reference position;

extend the piston from the reference position to a compression position to compress a chest of a patient;

return the piston from the compression position to the reference position; retract the piston from the reference position to a retreat position, the retreat position including the piston at a distance away from the reference position whereby the patient's chest can expand without active decompression of the patient's chest, the piston retracted to the retreat position at least once before the end of the session; and return the piston from the retreat position to the reference position.

2. The CPR device of claim 1, wherein the controller is further configured to cause the driver to:

retract the piston to the retreat position after each return to the reference position from the compression position.

3. The CPR device of claim 1, wherein the controller is further configured to: initiate a pause, during the pause the piston is not extended to the compression position and the piston is retracted to the retreat position.

4. The CPR device of claim 1, wherein the controller is further configured to: retain the piston in the retreat position for a preset amount of time.

5. The CPR device of claim 1, further comprising a user interface configured to receive a selection of a pause mode, wherein the controller is configured to generate a pause signal and cause the driver to retract the piston to the retreat position when the selection of the pause mode is received.

6. The CPR device of claim 1, wherein retraction of the piston from the reference position to the retreat position includes an application of 22.24 newtons or less of force.

7. The CPR device of claim 1, wherein the distance between the retreat position and the reference position is less than 6 centimeters.

8. The CPR device of claim 1, the distance between the retreat position and the reference position is at least 3 centimeters.

9. The CPR device of claim 1, the distance between the retreat position and the reference position is approximately 1 centimeter.

10. The CPR device of claim 1, further comprising a suction cup removably attached to the piston at a piston end.

11. A non-transitory computer-readable storage medium storing one or more programs which, when executed by at least one processor of a system to assist a rescuer to perform, during a session, successive cardiopulmonary resuscitation (“CPR”) compressions on a chest of a patient by using a system that includes a piston and a driver, the programs result in operations comprising:

positioning the piston at a reference position;

extending the piston from the reference position to a compression position to compress a chest of a patient;

returning the piston from the compression position to the reference position; retracting the piston from the reference position to a retreat position, the retreat position including the piston at a distance away from the reference position whereby the patient's chest can expand without active decompression of the patient's chest, the piston retracted to the retreat position at least once before the end of the session; and

returning the piston from the retreat position to the reference position.

12. The non-transitory computer-readable storage medium storing one or more programs of claim 11, wherein the programs result in operations further comprising: retracting the piston to the retreat position after each return to the reference position from the compression position.

13. The non-transitory computer-readable storage medium storing one or more programs of claim 11, wherein the programs result in operations further comprising: initiating a pause, wherein during the pause the piston is not extended to the compression position and the piston is retracted to the retreat position.

14. The non-transitory computer-readable storage medium storing one or more programs of claim 11, wherein the programs result in operations further comprising: retaining the piston in the retreat position for a preset amount of time.

15. The non-transitory computer-readable storage medium storing one or more programs of claim 11, wherein the system further includes a user interface configured to receive a selection of a pause mode, wherein the programs result in operations further comprising:

generating a pause signal and retracting the piston to the retreat position when the selection of the pause mode is received.

16. A mechanical cardiopulmonary resuscitation ("CPR") device, comprising: a compression belt;

a driver coupled to the compression belt configured to tighten and loosen the compression belt about a chest of a patient; and

a controller configured to cause the driver during a session to at least:

tighten the compression belt from a reference position to a compression position to compress a chest of a patient, wherein the reference position includes a compression belt reference length;

return the compression belt from the compression position to the reference position;

loosen the compression belt from the reference position to a retreat position, the retreat position including the compression belt having a retreat length longer than the reference length whereby the patient's chest can expand, the compression belt loosened to the retreat position at least once before the end of the session; and

tighten the compression belt from the retreat position to the reference position.

17. The CPR device of claim 16, wherein the controller is further configured to:

loosen the compression belt to the retreat position after each return to the reference position from the compression position.

18. The CPR device of claim 16, wherein the controller is further configured to:

initiate a pause, wherein during the pause the compression belt is not tightened to the compression position and the compression belt is loosened to the retreat position.

19. The CPR device of claim 16, wherein the controller is further configured to:

retain the piston in the retreat position for a preset amount of time.

20. The CPR device of claim 16, further comprising a user interface configured to receive a selection of a pause mode, wherein the controller is configured to generate a pause signal when the selection of the pause mode is received and cause the driver to loosen the compression belt to the retreat position.