CPR CHEST COMPRESSION MONITOR WITH REFERENCE SENSOR

Abstract

Methods and devices for chest compression depth measurement for CPR performed on infants.

Claims

1-20. (canceled)

21. A method for delivering cardiopulmonary resuscitation (CPR) chest compressions to a patient by a rescuer, the method comprising: positioning an anterior segment of a wrap-around structure comprising a first motion sensor on the sternum of the patient, the first motion sensor configured to generate a first motion signal; positioning a posterior segment of the wrap-around structure comprising a second motion sensor on the back of the patient, the second motion sensor configured to generate a second motion signal; providing chest compressions to the patient such that the first motion sensor moves in fixed relation with the sternum of the patient and the second motion sensor moves in fixed relation with the back of the patient during the chest compressions; and allowing for active decompression of the chest by the wrap-around structure after each chest compression.

22. The method of claim 21, further comprising operating an associated control system configured to receive the first motion signal and the second motion signal.

23. The method of claim 22, wherein the associated control system is configured to calculate at least one of a depth of chest compression delivered by the rescuer or a release parameter indicative of active decompression.

24. The method of claim 23, wherein the associated control system provides feedback regarding the depth of chest compression or the release parameter indicative of active decompression.

25. The method of claim 24, further comprising modifying delivery of the chest compressions based upon the feedback.

26. The method of claim 22, further comprising inputting information related to a size of the patient into the associated control system.

27. The method of claim 22, wherein the associated control system determines a size of the patient in response to receiving an indication from the rescuer that the wrap-around structure is disposed about the patient.

28. The method of claim 21, further comprising selecting at least one of: an appropriate size of the wrap-around structure and a resilience at a point of use of the wrap-around structure.

29. The method of claim 21, further comprising adjusting the wrap-around structure in response to a determination of a size of the patient.

30. The method of claim 21, wherein providing chest compressions to the patient comprises holding the anterior segment and the posterior segment in fixed relation to the body of the patient by the thumbs and fingers of the rescuer during the chest compressions.

31. The method of claim 21, wherein providing chest compressions to the patient comprises placing the hands of the rescuer around the thorax of the patient such that the thumbs of the rescuer are over the sternum of the patient and onto the anterior segment of a wrap-around structure and the fingers of the rescuer are on the back of the patient and positioned on the posterior segment of the wrap-around structure.

32. The method of claim 21, wherein providing chest compressions to the patient includes squeezing the thorax of the patient with the thumbs pressing on the sternum of the patient to push the sternum toward the spine.

33. The method of claim 21, wherein positioning the anterior segment and the posterior segment includes providing an input to the associated control system to indicate that the anterior segment and the posterior segment are in contact with the patient.

34. The method of claim 33, wherein the associated control system is a defibrillator that includes one or more input devices for receiving input from the rescuer.

35. The method of claim 34, wherein the one or more input devices include a keyboard, one or more soft-keys, and/or a touchscreen.

36. The method of claim 21, wherein the wrap-around structure is biased to an open configuration.

37. The method of claim 24, wherein the feedback provides an indication to the rescuer to adjust one or more parameters the chest compressions and/or release of the anterior segment during chest compressions.

38. The method of claim 37, wherein the one or more parameters include at least one of: a rate of the chest compressions, a depth of the chest compressions, and a release velocity of the chest compressions.

39. The method of claim 24, wherein the feedback includes a positive advisory in response to chest compressions that are adequate desired chest compression goals.

40. The method of claim 24, wherein the feedback includes a negative advisory in response to chest compressions that are inadequate or too excessive compared to the desired chest compression goals.

41. The method of claim 40, wherein the desired chest compression goals are based on a determined size of the patient and include at least one of: a chest compression depth, a chest compression rate, and a release velocity.

42. The method of claim 24, wherein the feedback includes at least one of visual prompts, audio prompts, and haptic prompts.

43. The method of claim 21, wherein the first motion sensor and second motion sensors are accelerometers that generate acceleration signals corresponding to acceleration of the chest and acceleration of the back of the patient during the chest compressions.

44. The method of claim 21, wherein the first motion sensor and second motion sensors are velocity sensors.

45. The method of claim 21, wherein the first motion sensor is a magnetic field sensor and the second motion sensor is a magnetic field generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 illustrates the two-thumb technique for accomplishing CPR compressions on an infant.

[0008] FIG. 2 illustrates placement of the new chest compression depth monitoring system on an infant cardiac arrest victim.

[0009] FIG. 3 illustrates the two-thumb technique for accomplishing CPR compressions on an infant while the system of FIG. 2 is installed on the infant.

[0010] FIG. 4 illustrates the frame in isolation.

[0011] FIGS. 5A, B and C illustrate the compression frame during compressions of the infants thorax.

[0012] FIG. 6 illustrates a wrap-around frame which can be fitted on an infant cardiac arrest victim.

[0013] FIG. 7 illustrates a variation of the frame, applied to infant cardiac arrest victim over the shoulders of the infant.

[0014] FIG. 8 illustrates a frame for use in the system which can be easily modified to adjust the resilience of the frame.

[0015] FIG. 9 illustrates a frame for use in the system, which can be adjusted to fit infants of various sizes.

DETAILED DESCRIPTION OF THE INVENTIONS

[0016] FIG. 1 illustrates the two-thumb technique for accomplishing CPR compressions on an infant. The infant is shown supine, supported on a surface. A CPR provider has placed his hands around the infant's thorax, placing his thumbs over the infant's sternum with his fingers wrapping over the axillary area under the infant's arms and around the infant's back. In this method, the CPR provider squeezes the infant's thorax, with the thumbs pressing on the sternum, to push the sternum toward the spine. These compression should be accomplished at a rate of 100 compressions per minute and a depth of 1.5 inches (3.8 cm)(or about one-third of the total thickness of the thorax).

[0017] FIG. 2 illustrates placement of the new chest compression depth monitoring system on an infant cardiac arrest victim 1. The system includes a first sensor 2 located over the sternum and a second sensor 3 located on the back. These two sensors are mounted on a frame 4, which, as illustrated, is a U-shaped frame defining an open space which accommodate the infant. The sensors are mounted on the frame such that, with the frame disposed about the infant's thorax, the sensors may be properly located over the sternum and opposite the sternum on the infant's back. The sensors are operably connected to an automatic external defibrillator (AED) 5 through cable 6. The AED box 5 includes a control system, a display and speaker, and a defibrillator. The display and speaker are operable for providing visual or audio feedback to the CPR provider regarding the depth and rate of the compressions provided by the CPR provider, and comprise means for providing feedback to the CPR provider. The AED also includes an input device, such as a keyboard, soft-keys or touchscreen (which may also be used as the display). The control system (a computer) is programmed to interpret the acceleration signals to calculate compression depth and/or velocity (specifically, release velocity), and generate visual displays and/or audio prompts to be displayed or played to guide the CPR provider. (The control system also analyzes ECG signals obtained from ECG electrodes, not shown, to determine if defibrillating shock should be applied, and may prompt the user to apply shock or automatically operate the defibrillator to apply shock to the infant patient.) The control system can also be provided in a stand-alone device, without the defibrillator function. The control system comprises at least one processor and at least one memory including program code with the memory and computer program code configured with the processor to cause the system to perform the functions described throughout this specification.

[0018] FIG. 3 illustrates the two-thumb technique for accomplishing CPR compressions on an infant while the system of FIG. 2 is installed on the infant. As in FIG. 2, the frame 4 is disposed about the thorax of the infant, with the first sensor 2 disposed over the sternum of the infant and the second sensor 3 (see FIG. 2) disposed on or under the back of the infant. The rescuer is shown with his/her thumbs over the first sensor, trapping the first sensor between the rescuer's thumbs and the infant's sternum, and the fingers of both hands wrapped around the infant's thorax, preferably trapping the second sensor between the fingers of the rescuer and the back of the infant.

[0019] FIG. 4 illustrates the frame in isolation. The frame may take on many forms, and is illustrated as a U-shaped frame 4, comprising two laterally extending elements 7 and 8 joined by an arcuate segment 9. The sensors 2 and 3 are mounted near the tips 10 and 11 of extending elements, so that they can easily be located with the first sensor 2 disposed over the sternum of the infant and the second sensor 3 disposed on or under the back of the infant. The frame construction assures proper placement of the sensors on the anterior and posterior surface of the infant, so that motion signals from each sensor can be used to measure the chest wall motion induced by the CPR compressions accomplished by the CPR provider, taking into account any anterior/superior motions of the infants entire thorax attendant to the two-thumbs technique. The frame is preferably resilient and biased to an open configuration (as large or larger than the thickness of the infant's chest), such that after each compression, it resiliently returns to an open position, but may instead be merely flexible such that upon release of the chest by the CPR provider the frame expands due to the natural resilience of the infant's chest. The frame is illustrated as an open U-shaped frame, but may be most any shape useful to properly locate the sensors above and below the infant's thorax and convenient to dispose about the infant's thorax. So, for example, the frame may be an oval which completely encircles the thorax. The frame may be provided in various sizes, with each size chosen to suit a range of infants and small children of various sizes, or it may be provided in single size suitable for a wide range of patient sizes.

[0020] If the system is intended to impart some expansive force on the chest between compression down strokes, during the release phase or upstroke of a compression, the inner surfaces of the extending segments of a resilient frame, which inner surfaces may include the inner surfaces of the sensor assemblies (or housings, if they are discrete from the extending segments), may be covered or coated with an adhesive layer suitable for adhering the extending segments to the thorax of the infants. The adhesive may be limited to the tips of the extending segments, such that only the tips of the extending segments adhere to the chest wall. With this construction, with each release of compression force, the resilient expansion of the frame with exert expansive force on the chest wall, and provide a degree of active decompression between each compression.

[0021] FIGS. 5A, B and C are cross sections of the frame, illustrating the action of the frame on the thorax of the infant. As shown in FIG. 5A, the frame is slipped over the infant's chest, such that the anterior sensor 2 is disposed directly over the sternum 12, and the posterior sensor 3 is located under the spine 13. The CPR provider squeezes the infants chest, using the two-thumbs technique, to achieve the compressed state illustrated in FIG. 5B. FIG. 5B represents the compression stroke or compression phase of the compression cycle. Upon release, the infants chest will expand, as shown in FIG. 5C, to its original thickness. Where the interior surfaces of the extending segments are adhesive, the resilient expansion of the frame lead to an expansive force applied to the chest, which hastens the expansion of the chest during the release phase of the compression cycle.

[0022] FIG. 6 illustrates a version of the frame which wraps entirely around the infant cardiac arrest victim. In FIG. 6, the frame 4 may be provided in a length exceeding the circumference of the infant, and sufficient to entirely surround the infant's thorax (practically, the wrap around frame will be provided in a single length long enough to surround infants of various sizes). As with the frames of the earlier figures, the frame of FIG. 6 is resiliently biased to open to a circumference larger than the circumference of the infant. The frame may have an initial configuration which is substantially flat, in which case it is folded up and around the infant's thorax as shown, and adjusted to obtain a close fit with the infant's thorax before compressions are initiated. The frame may instead have an initial configuration which is substantially circular, in which case it is spread open to accommodate the infant's thorax and adjusted to obtain a close fit with the infant's thorax before compressions are initiated. The anterior sensor 2 may be releasably fixed to the frame, with hook and loop fastener or other fastener, so that it can be relocated to the infant's sternum when the frame is adjusted to fit about the infant.

[0023] FIG. 7 illustrates a variation of the frame, applied to infant cardiac arrest victim over the shoulders of the infant. The frame of FIGS. 2 through 4 can of course be fitted over one shoulder of the infant, at the option of the CPR provider. The frame 14 of FIG. 7 comprises a front portion 15 and back portion 16, with an opening between the two to accommodate the infant's head. From the side or lateral aspect, the frame is U-shaped. As with the frame of FIGS. 2 through 4, this frame may be resilient and biased to an open position, with the distance between the sensors in the open, relaxed configuration being slightly greater than the anterior-posterior thickness of the infant's thorax. The sensors 2 and 3 are mounted on the frame, with the anterior sensor 2 mounted on the front portion and the posterior sensor 3 mounted on the back portion. As illustrated, viewed from the front or anterior aspect, the front portion is V-shaped, with the vertex 17 of the V, where the anterior sensor 2 is located, disposed over the sternum of the infant. The posterior sensor 3 located directly below the anterior sensor, on the back portion and located at the back of the infant. The vertex of the V serves as an easily recognizable landmark for the user when applying the frame to the infant, but the frame may be made in other configurations that permit the frame to be slipped over the infant's head (for example, a bib or pinafore), and provide for locating the anterior sensor over the infant's sternum.

[0024] The frame can be provided in a single size chosen to fit most infants subject to the two-thumb technique, and configured with a resilience and expansive force suitable for applying active compression/decompression for most infants, or the frame can provided in a variety of sizes, leaving to a CPR provider to select an appropriate size and/or resilience at the point of use, or adjust size and/or resilience of the frame at the point of use when the size of the actual patient is known. Should it be desirable to adjust these properties, the frame can be modified as illustrated in FIGS. 8 and 9. FIG. 8 illustrates a frame for use in the system which can be easily modified to adjust the resilience of the frame. The frame 21 holds the anterior and posterior sensors 2 and 3 at the tips of anterior and posterior extending elements 7 and 8. The frame 21 is resilient, and manufactured to exert a first level of expansive force when released from compression. The frame comprises one or more additional layers 22, 23 and 24, which are also resilient. The additional layers are secured to the underlying layers with adhesive or a mechanical interlock, such that they are releasable secured to underlying layers and may be removed easily by the CPR provider. To adjust the resilience of the frame, one or more releasable layers may be removed, thus weakening the frame and reducing its resilience.

[0025] FIG. 9 illustrates a frame for use in the system, which can be adjusted to fit infants of various sizes. The laterally extending segments 7 and 8 are connected to each other through an expandable ratcheting mechanism 25. The ratcheting assembly may be used to expand or collapse the laterally extending segments 7 and 8 to size the device to a particular infant cardiac arrest victim. As with the U-shaped frames illustrated above, the sensors 2 and 3 are disposed within or on the tips of the extending segments.

[0026] The sensors may include any sensor technology suitable for determining compression depth. Accelerometers may be used, as described in Halperin, U.S. Pat. No. 6,390,996 and Palazzolo, U.S. Pat. No. 7,122,014. In this case, the anterior sensor may be an accelerometer-based chest compression monitor as described in Halperin and Palazzolo, and the posterior sensor can be a reference accelerometer or another accelerometer-based chest compression monitor. The accelerometers are capable of producing acceleration signals corresponding to the acceleration of the chest and the acceleration of the back, and the control system is operable to integrate the acceleration signal received from the accelerometers, integrating and combining those signals to determine the depth of chest compression and produce a measured depth signal. The control system is also programmed to report the measured depth to the CPR provider through the display or audio output, or compare the measured depth signal to a desire depth of compression and report to the CPR provider whether the achieved depth of compression meets or fails to meet the desired depth. Velocity sensors may also be used, in which case the control system is programmed to process the velocity signal received from the velocity signals to achieve the same ends. Also, the control system may be programmed to process the acceleration signals to determine the compression velocity, release velocity, and compression rate to produce corresponding signals, and provide reports and feedback to the CPR provider regarding these parameters.

[0027] Magnetic motion sensors, such as those which use an electromagnetic source and sensor, described in Geheb, et al., Method and Apparatus for Enhancement of Compressions During CPR, U.S. Pat. No. 7,220,235 (May 22, 2007) and Centen, et al., Reference Sensor For CPR Feedback Device, U.S. Pub. 2012/0083720 (Apr. 5, 2012), may also be used to determine compression depth. In this case, the one sensor is a magnetic field sensor, and the other sensor is replaced by a magnetic field generator (a permanent magnet or an electromagnet), and the control system is operable to receive and process distance information from the electromagnetic sensor to determine compression depth, release velocity, and compression rate. These and any other means for determining compression depth, compression rate, and release velocity may be used.

[0028] The control system is programmed to receive signals corresponding to motion of the chest wall and motion of the thorax (motion of the back, as sensed by the sensor 3, and determine the depth of compression achieved during CPR based on those signals. (In the magnetic sensing embodiment, the control system is programmed to determine the depth of compression achieved during CPR based signals from the magnetic field sensor.) The control system is programmed to generate a signal corresponding to the determined chest compression depth which may be used to provide a display indicating achieved chest compression, or may be used by other equipment. The control system is further programmed to compare the determined depth of compression with predetermined desired chest compression goals, and provide feedback to a CPR provider regarding the adequacy of chest compression depth, including whether achieved chest compression depth is inadequate, adequate, or excessive as compared to the predetermined goals. The feedback can include audio or visual prompts to compress more deeply, prompts to compress at a faster or slower rate, and prompts to quickly and completely release the chest of the patient after each compression. The feedback can also include haptic feedback, provided when compression depth is adequate, inadequate, or excessive, through vibrators disposed on the frame.

[0029] The system can be adapted to determine an initial measurement of the patients chest. The sensors mentioned above may be used, or additional sensors may be added to the frame, to measure the patient's chest prior to the start of chest compressions. This information can be use to advise a CPR provider to limit expansive motion of the frame during release (to limit the active decompression)(limiting the expansive motion of the frame during release can be accomplished merely by holding the frame between compressions, and not allowing it to fully expand), and to advise the CPR provider regarding the adequacy of chest compressions based on the size of the patient. The distance between the sensors 2 and 3 can be determined, using signals from the sensors, where applicable. For example, where the sensors are a magnetic field sensor and a magnetic field generator, the position of the magnetic sensor in the magnetic field generated by the magnetic field generator can be determined.

[0030] Additional sensors may be used to size the patient. Distance sensors and proximity sensors at the tips of the frame, near sensor 2, for example, can determine the distance from the frame tip to the patient, and thereby calculate the size of the patient. This system may require operator input, to inform the system when the frame is disposed about the patient such that the bottom frame tip and sensor 3 are in place below the patient, so that the control system can then calculate the patient chest height based on the known distance between the frame tips and the measured distance between the upper frame tip and the chest wall of the patient. In another system, strain sensors disposed on or within the frame can be used to determine the shape of the frame, and thus the distance between the frame tips. For example, a shape monitoring cable (item 26 in Figure comprising linear arrays of fiber Bragg gratings may be disposed on or within the frame, and a control system may operate a light source and light sensors to determine the shape of the frame. This system may require operator input, to inform the system when the frame is disposed about the patient such that the bottom frame tips and sensor 2 and sensor 3 are in contact with the patient, so that the control system can then calculate the patient chest height based shape of the frame as determined by the shape monitoring cable. Shape monitoring cables suitable for use in this embodiment may also include piezo-electric strain gauges and other forms of strain gauges.

[0031] For the frame of FIG. 9, an optical, magnetic or capacitive encoder or other position sensor 27 can be used to determine the position of ratcheting segments relative to each other, and from this information the control system can determine the distance between the tips and the chest height of the patient. Again, with operator input informing the system when the frame is disposed about the patient such that the bottom frame tips and sensor 2 and sensor 3 are in contact with the patient, the control system can then calculate the patient chest height based on the encoder reading. Thus, for the initial determination of the size of the patient, sensors mounted on the frame tips, encoders disposed on an adjustable portion of the frame, a shape monitoring cable disposed on the frame, and any other suitable means of determining the distance between the frame tips can be used, in conjunction with input from the CPR provider indicating that the frame tips are in close proximity to the patient/s thorax.

[0032] In each case, the initial measurement of the size of the patient's thorax can be use by the control system to select advisory parameters, such as the amount of compression desired, and the amount of active decompression desired, for the patient based on patient size, and generate advisory prompts to the CPR provider based on patient size. The compression depth targets for infants should be about ? of the infant's chest height, and the appropriate chest compression goals can be selected by the control system programmed to calculate the chest compression goals based on the measured size of the patient. Thus, for CPR compressions performed on small children, the control system would be programmed to provide a positive advisory (that compression are adequate) or a negative advisory (that compression are excessive, or active decompression too expansive) for small compressions and active decompressions, and also programmed to provide a positive advisory (that compression are adequate) or a negative advisory (that compression are excessive, or active decompression too expansive) for slightly larger compressions and active decompressions for CPR performed on a larger child.

[0033] In use, a CPR provider will place the frame around the thorax of an infant cardiac arrest victim, with one sensor on the victim's chest, over the victim's sternum, and the second sensor under the infant's spine. The CPR provider will then grasp the infant's thorax with both hands, placing his thumbs over the infant's sternum and extending his fingers around the thorax, in the two-thumbs position. The CPR provider will perform CPR compressions, using the two-thumbs technique, pressing down on the chest, keeping the anterior sensor between his thumbs and the victim's chest, so that the sensor moves up and down in fixed relation with the patient's chest, and keeping the posterior sensor between his fingers and the victim's spine, or at least keeping the posterior extending element between his fingers and the patient's back so that the posterior sensor moves up and down in fixed relation with the patient's back. The CPR provider will operate an associated control system, and energize the sensors, to analyze the sensor signals to determine chest compression depth, velocity of the compression monitor (including release velocity), and the rate of compression, compare the determined chest compression depth, release velocity and/or compression rate to the desired values, and operate an output device to provide prompts indicating whether the determined chest compression depth, release velocity and/or compression rate meets or fails to meet the desired values. The control system may also be operated to compare the measured depth of compression to a desired depth of compression and report to the CPR provider whether the achieved depth of compression meets or fails to meet the desired depth. Prior to the start of compressions, the CPR provider may optionally bring the anterior frame and posterior frame into contact with the body, and provide input to the control system that the anterior frame and posterior frame are in contact with the body.

[0034] The frame may be used to perform CPR compressions, including active compression/decompression, with or without the compression depth monitoring components of the system. The frame, with an adhesive surface on at least a portion of the interior surface of the anterior segment, can be installed about the thorax of a patient such that the adhesive secures the anterior segment to the patient's chest wall, over the sternum (that is, the preferred compression point). With the frame installed, CPR compressions are performed. Upon release of each compression, the resilient frame will resiliently expand toward its open configuration, thereby imparting some expansive force on the chest wall. If the patient is prone on a supportive surface, only the anterior segment need be adhesive. If the patient is held up, or prone on a soft surface, the posterior segment interior surface may be adhesive as well. This method may be used on adults and pediatrics as well as infants.

[0035] When used to provide CPR compressions with active compression/decompression the method entails providing the frame having an anterior segment and a posterior segment, and sized and dimensioned to fit at least partially around the thorax of the cardiac arrest victim with adhesive on a portion of the anterior segment is adhesive and, optionally, on the posterior segment, and installing the frame about the thorax of a cardiac arrest victim such that the adhesive secures the anterior segment to the cardiac arrest victim's chest wall. After installation, the CPR provider performs CPR chest compressions on the cardiac arrest victim, allowing the frame to expand between compressions to provide active decompression, with the resilience of the frame acting to restore the frame toward its relaxed opened position and thus exert upward pulling force on the thorax.

[0036] While the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. Though illustrated for use with infants and the two-thumb compression technique, the devices may be used the two-finger technique, and the devices may sized and dimensioned for adult use, and used in otherwise standard CPR compressions. The elements of the various embodiments may be incorporated into each of the other species to obtain the benefits of those elements in combination with such other species, and the various beneficial features may be employed in embodiments alone or in combination with each other. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.