TECHNICAL FIELD

Various embodiments disclosed herein relate generally to a rapid pulse confirmation device and, more particularly but not exclusively, to a device to determine chest compression efficacy and return of spontaneous circulation (“ROSC”) during cardiopulmonary resuscitation (“CPR”). BACKGROUND

Effective chest compressions are one of the essential functions to perform for survival in CPR. In addition to performing chest compressions, pulse checks must be performed quickly and accurately in less than 10 seconds during CPR. Currently, no device exists that quickly and accurately determines ROSC and chest compression efficacy as measured by red blood cell during CPR.

An effective chest compression, as defined by the American Heart Association, is compression of approximately 1/3 the anteroposterior diameter of the chest (i.e., approximately 2 inches in an adult or approximately 1.5 inches in an infant). The limitations of a depth approach are that patients are different sizes and an absolute depth is difficult to gauge during an arrest scenario. Furthermore, there is great variability in the effectiveness between individuals performing the chest compressions and detecting ROSC.

Therefore, there is a need to create a device which can determine chest compression efficacy and ROSC during CPR.

SUMMARY

In order to improve determination of chest compression efficacy and in light of the present need to create a rapid pulse confirmation device, a brief summary of various exemplary embodiments is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, but not to limit the scope of the invention. Detailed descriptions of a preferred exemplary embodiment adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections.

Various embodiments disclosed herein relate to a wearable rapid pulse confirmation (“RPC”) device configured to be worn by a living subject, including a Doppler array; a screen, and a loud speaker. In various embodiments, the Doppler array is configured to detect a change in blood velocity, pulse rate, pulse strength, or a combination thereof in a blood vessel; and the Doppler array is configured to provide feedback through the screen and the loudspeaker.

In various embodiments, the RPC device includes a Doppler array including an array of piezoelectric ultrasonic transducers, configured to detect a change in blood velocity in the blood vessel. The RPC device may further include at least one passive piezoelectric pressure sensor, configured to detect a change in blood pressure or pulse rate in the blood vessel, and/ or a pulse oximeter, configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin in the blood vessel. The piezoelectric pressure sensor may be included in the Doppler array of ultrasonic transducers, or the pressure sensor may be separate from the Doppler array. In various embodiments, the pulse oximeter is an infrared sensor, configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin, based on a first IR absorbance value or a first IR reflectance value at about 970 ± 30 nm and a second IR absorbance or reflectance value at about 670 ± 30 nm.

The wearable RPC device may include a pulse oximeter including a first infrared sensor configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin, and a second infrared sensor configured to determine pulse rate. The second infrared sensor determines pulse rate based on time-dependent changes in reflection of infrared light from a tissue of a living subject. In various embodiments, the wearable RPC device further includes a band configured to hold the wearable RPC device in proximity to a body surface of a living subject, where the body surface may be a wrist, an arm, a leg, a neck, or a torso of the living subject. In various embodiments, the wearable RPC device includes a sensor configured to detect a diameter of the band after it is secured to the body portion. The wearable RPC device may further include a central processing unit configured to calculate a diameter or circumference of a body portion to which the RPC is attached, based on a change in elongation or strain of the elastic band upon attachment to the body portion. In various embodiments, the band may be used to position the wearable RPC device in proximity to an artery selected from the group consisting of a radial artery, an ulnar artery, a carotid artery, a femoral artery, and/ or a combination thereof. The diameter of the band corresponds to a diameter of the body portion to which the wearable RPC device is attached. The diameter of the band may be used to estimate blood vessel depth within the body portion, and thus the amount of tissue which must be traversed by sound waves from the Doppler array to reach the blood vessel. Also, the diameter of the band may be used to estimate body composition, i.e., percentage of muscle and percentage of fate. As sound waves travel more slowly through fat than muscle, an estimation of body composition may be used to increase the accuracy of data from the Doppler array.

In various embodiments, the wearable RPC device is attached to a band with a first end and a second end, where the band includes a plurality of evenly spaced teeth on the first end, and a latch including a pawl or a tooth on the second end. The teeth on the first end engage the pawl or tooth on the second end as the first end of the band enters the latch. Once the first end of the band has entered the latch, the pawl or tooth on the second end of the band engages at least one tooth on the first end to prevent the first end of the band from being disengaged from the latch during use. The latch may include a tab or other means to disengage the pawl or tooth on the second end of the band from the teeth on the first end of the band, allowing the first end of the band to be disengaged from the latch after use to determine chest compression efficacy. The band is configured to be wrapped around a body surface, e.g., a wrist, an arm, a leg, or a neck of a living subject.

In various embodiments, the wearable RPC device is attached to a band with a plurality of evenly spaced teeth on a first end, and a click counter and a latch including a pawl or a tooth on the second end. The click counter is configured to record the number of teeth which enter the latch on the second end, based on the number of teeth which pass the pawl or tooth in the second end of the band. The click counter sends a signal providing the recorded number of teeth to a CPU, which is configured to calculate a diameter or circumference of the band after insertion of the first end into the latch. The band may be used to position the wearable RPC device in proximity to a blood vessel, which may be an artery or a vein.

The wearable RPC device may include an elastic band, and a sensor configured to detect a change in elongation or strain on the band and calculate a change in band diameter based on changes in elongation or strain.

In various embodiments, the wearable RPC device further includes a hydrogel layer positioned under the Doppler array, where the hydrogel layer is configured to conduct ultrasound waves from the Doppler array to a blood vessel. The hydrogel layer may be an adhesive layer configured to hold the wearable RPC device in proximity to a body surface of a living subject, the body surface being a wrist, an arm, a leg, or a neck of the living subject. The adhesive layer may be used in combination with a band, or instead of a band. The adhesive layer may be an adhesive polymeric hydrogel. The adhesive layer should conduct ultrasonic energy, and may be transparent to infrared light. A protective release layer may be positioned on the hydrogel layer. The release layer is removed prior to placing the hydrogel layer on a body surface.

In various embodiments, the Doppler array is configured to record a Doppler shift from moving blood vessels. The pulse oximeter is configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin. A passive piezoelectric sensor may be used to determine time-dependent pressure changes in a blood vessel. An IR sensor may be used to detect reflection or refraction of blood at a tissue surface. In various embodiments, the data collected by the various sensors the wearable RPC device is sent to a CPU, is configured to calculate at least one of blood oxygenation, beats per minute, blood pressure, and relative blood velocity based on the recorded data. In various embodiments, the wearable RPC device includes a screen providing visual feedback including at least one of blood oxygenation, beats per minute, blood pressure, and relative blood velocity, based on results obtained from the CPU.

In various embodiments, the wearable RPC device includes a loudspeaker providing audible feedback regarding the efficacy of chest compressions. The loud speaker may provide audible feedback in the form of vascular sounds. Such vascular sounds may include audio feedback in the form of sound generated by blood flow. The audible feedback may be configured with a limiting mechanism, which prevents audible feedback of vascular sounds unless blood velocity or pulse rate reach a minimum threshold value. The loud speaker may provide audible feedback in the form of alarms or prerecorded messages warning that the magnitude of chest compressions is insufficient or excessive.

In various embodiments, a wearable RPC device may include a wearable sensor, and an automated external defibrillator. The wearable sensor includes a Doppler array, and may additionally include a passive piezoelectric pressure sensor, configured to detect a change in blood pressure or pulse rate in the blood vessel, and/ or a pulse oximeter. A screen and a loud speaker are provided on an automated external defibrillator. The Doppler array is configured to detect a change in blood velocity, pulse rate, pulse strength, or a combination thereof in a blood vessel; and the screen and the loudspeaker on the automated external defibrillator are configured to provide feedback based on data from the Doppler array.

Various embodiments described herein relate to an RPC device, including a Doppler array, a screen, and a loud speaker, wherein the Doppler array detects a change in blood velocity in an artery through the Doppler array and provides feedback through the screen and the loudspeaker.

Various embodiments described herein relate to a RPC device, including an automated external defibrillator (“AED”) connected to a wearable sensor, the AED device including a screen, and a loud speaker, the AED connected to the wearable sensor, the wearable sensor including a Doppler array, wherein the Doppler array detects a change in blood velocity in an artery through the Doppler array and provides feedback through the screen and the loudspeaker.

[0018] In various embodiments, the Rapid Pulse Confirmation (“RPC”) device is a wearable device designed to accurately determine chest compression efficacy and ROSC during CPR using Doppler shift measurements. The RPC device in the present embodiment may be a self-contained and standalone wearable device with an array of multiple Doppler piezoelectric crystals to evaluate compression efficacy and to use during a pulse check period.

[0019] In an alternative embodiment, the wearable portion of the RPC device which may contain the Doppler and sensor array may be attached by a cable to an Automated External Defibrillator (“AED”) that may be modified to include a power source, speaker, screen for information feedback and processor for the RPC device. The RPC device includes an array of piezoelectric crystals and/ or infrared sensors which are configured to detect the Doppler shift of moving red blood cells through the radial, ulnar, carotid or femoral arteries. The Doppler array of piezoelectric crystals may be embedded into a wearable device attached to a strap for quick application to an arresting patient.

[0020] The signal from the wearable device would be routed into a speaker and liquid crystal display (“LCD”) screen to produce audible and visual feedback to the rescuer during compressions and pulse checks. In an alternative embodiment, the signal may be routed through a central processor to apply algorithms designed for signal noise filtration and aid in determination or successful compression of ROSC. The RPC device could also be programmed with basic and advance lifesaving algorithms for guidance. The band of the wearable device would have a ratcheting device attached that would serve to track wrist, leg or neck diameter and make automatic depth adjustments needed to accurately detect a pulse. The input from the ratcheting device may be input to the central processor to make various adjustments in signal processing and Doppler function.

[0021] The sensors of the Doppler array may be organized and be configured to detect specific frequencies specified for pulse detection on the wrist, neck, or leg. The speaker would be specifically tuned for reproduction of vascular tones to minimize artifact noise. The LCD screen may be fitted to the RPC device for displaying easy to read signals for compression efficacy and pulse checks, with a band, which may be an elastic or ratcheting band. The ratcheting band may automatically detect patient size, which may be used to adjust various operational parameters.

[0022] The RPC device may be a disposable, battery powered device, configured to provide clear audio and visual feedback to a user. The RPC device may be configured to measure blood velocity and/ or pulse rate at the radial and ulnar arteries, but may also be designed to measure at the carotid, femoral and brachial arteries. The RPC device outputs visual and audio feedback to a user via a light bar indicator such as an LED array, a speaker, and/or a graphic display. The output visual and auditable feedback may be based on compression efficacy and pulse strength, derived from measured values of blood velocity and pulse rate.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various embodiments, reference is made to the accompanying drawings, wherein:

FIG. 1 illustrates a first embodiment of a wearable RPC device;

FIG. 2 illustrates a cross section view of a second embodiment of a wearable RPC device;

FIG. 3 illustrates a housing with feedback devices for use with an RPC device; FIG. 4 illustrates a sensor array for use with an RPC device;

FIG. 5 illustrates a third embodiment of a wearable RPC device, positioned on the wrist of a patient;

FIG. 6 illustrates a fourth embodiment of an RPC device, including an automated external defibrillator and a wrist-mounted sensor;

To facilitate understanding, identical reference numerals have been used to designate elements having substantially the same or similar structure or substantially the same or similar function. DETAILED DESCRIPTION OF THE INVENTION

The description and drawings presented herein illustrate various principles. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody these principles and are included within the scope of this disclosure. As used herein, the term,“or” refers to a non-exclusive or (i.e., and/or), unless otherwise indicated (e.g., “or else” or “or in the alternative”). Additionally, the various embodiments described herein are not necessarily mutually exclusive and may be combined to produce additional embodiments that incorporate the principles described herein.

FIG. 1 illustrates a first embodiment of the wearable RPC device 1. The wearable RPC device 1 includes a housing 9 with a power button 5; a screen 6, e.g., an LCD screen; an LED array 7; and a loud speaker 8. A cable 4 connects RPC device 1 to a sensor array 2. RPC device 1 may be held to the patient’s wrist by a band or strap encircling the wrist (not shown in FIG. 1). Sensor array 2 is a Doppler array, and may be held in place by a second band or strap. In various embodiments, sensor array 2 may be held in position on the wrist by an adhesive strip 3, where the adhesive strip is a hydrogel adhesive which transmits sound waves. The Doppler array is configured to transmit ultrasound waves at a first reference frequency fii, and receive ultrasound waves at a second frequency fm-fio, where £D is the Doppler shift frequency. The frequency £D is directly proportional to blood velocity v, by the equation:

£D = 2fRv(cos Q)/ c,

where Q is the angle between the path of an ultrasound beam and the path of blood flow, and c is the velocity of sound in soft tissue. The Doppler array may also be used to determine pulse rate (beats per minute, or“BPM”) of a patient, or chest compression rate for a patient undergoing CPR, based on recording time-dependent changes in blood velocity, where a heart contraction or chest compression leads to an increase in blood velocity.

The screen 6 in FIG. 1 may provide feedback for a person administering

CPR to a patient. Such feedback may include textual or graphical data reporting instantaneous blood velocity or blood velocity as a function of time. The feedback may also provide data on pulse rate in BPM and/ or a relative blood velocity meter to ensure that the rescuer is performing the CPR correctly. The screen may provide textual or graphical alerts if blood velocity or pulse rate is insufficient or too high, allowing the user to adjust the frequency and/ or strength of chest compressions as needed. The loud speaker 8 in FIG. 1 may provide audible feedback to ensure that the rescuer is performing the CPR correctly. Such feedback may include playing audio corresponding to Doppler-shifted sound waves received by the Doppler array. The loudspeaker may also provide audible alerts if blood velocity or pulse rate fall outside a defined range (too low or too high.

The LED array 7 in FIG. 1 includes a sequence of LED lights. The lights in the LED array may light up sequentially from left to right, based on data regarding one of pulse rate in BPM or blood velocity received from the CPU. The number of lights lighting up may be proportional to the value of pulse rate or blood velocity. If pulse rate or blood velocity is insufficient, no lights in the LED array may light up. Alternatively, if pulse rate or blood velocity is insufficient, a red alert light at the left end of the LED array may light up, advising a person administering CPR that more vigorous or more frequent chest compressions are required. If pulse rate or blood velocity is too high, all lights including a red alert light at the right end of the LED array may light up, advising a person administering CPR that less frequent chest compressions should be used. If pulse rate or blood velocity is too high, about 30% to about 70% of the lights in the LED array may light up, including a series of green lights in the center of the LED array 7.

The RPC device of FIG. 1 may be reusable or disposable. The RPC device may be used when providing chest compressions or other life-saving treatment to a patient, e.g., during CPR. Screen 6 and or loudspeaker 8 may be used to provide alert messages if data on pulse rate or blood velocity indicates that the pulse or blood velocity is either too low or too high, allowing the user to increase the rate or depth of chest compressions. The screen 6 may provide graphical or textual reminders between CPR attempts, e.g., chest compressions, where such reminders may be administered at intervals of about 8 seconds. The screen may display textual or graphical instructions on proper CPR methods. The RPC device may detect pulse rate in terms of beats per minute (“BPM”) upon the return of spontaneous circulation, and display pulse rate or blood velocity on screen 6, or using a sequence of lights in LED array 7, based on pulse/ signal strength.

FIG. 2 illustrates a second embodiment of the wearable RPC device 1 , in which the RPC device 1 and the sensor array are incorporated into a single housing 9. The LED array 7 and/ or an LCD screen (not shown in FIG. 2), together with the loud speaker 8, are positioned on the top portion of the housing 9 of RPC device 1. In the current embodiment, under the LED array 7 and the loud speaker 8, a Doppler array 27 is positioned on a bottom surface of housing 9. The Doppler array 27 is configured to emit continuous or pulsed ultrasonic waves 29 in the direction of a blood vessel 28. The Doppler array 27 is positioned to cover the surface of the wrist of the patient (or other surface where a pulse may be detected) and includes passive piezoelectric sensors which measure velocity of red blood cells in the target artery. Under the Doppler array 27 is a thin layer of a sound-transmitting hydrogel adhesive 30, positioned along the length of the Doppler array 27. The hydrogel adhesive layer 30 is optionally covered by a release material, such as silicone coated paper or polyester, which does not bond to the adhesive layer. When the wearable RPC device 1 is positioned on a patient, the rescuer may remove the release material to expose the adhesive layer 30 to make contact with the patient’s skin, which is required for the operation of the Doppler array 27. In embodiments where a strap is used to hold RPC device 1 in position on the patient’s skin, adhesive layer 30 may be replaced with a non-adhesive hydrogel. Doppler array 27 on wearable RPC device 1 is positioned in proximity to a blood vessel 28 (shown as a radial or ulnar artery in FIG. 2, although other blood vessels in the arm, leg, or neck, for example, may be used).

The wearable RPC device 1 of FIG. 2 further includes a ratcheting band having a first end 21 and a second end 22 connected to housing 9. The first end of the band 21 has a plurality of evenly spaced teeth 23, and the second end of the band 22 includes a latch 24, with an opening 25 configured to receive the first end of the wrist band 21 until the band fits a patient’s wrist or other body part. A tooth or pawl 26 in latch 24 engages teeth 23 as the first end of band 21 enters latch 24, preventing accidental disengagement of the band. When strap 21 is inserted into latch 24 past pawl or tooth 26, a sensor, or click counter, detects the number of teeth 23 which pass pawl or tooth 26, as the wrist band is adjusted to fit the wrist of the patient. Information on the number of teeth 23 entering latch 24 is passed to a CPU in housing 9, which calculates the diameter and/ or circumference of the wrist or other body part of the patient. This wrist band construction ensures that the wearable RPC device 1 is positioned tightly on the patient, and provides measurements to the CPU, allowing the CPU to calculate the size of the patient. The CPU may be configured to receive input from a user, providing data on age, height, and weight of the patient, as well as data identifying a body part to which the RPC device 1 is attached, e.g., wrist, leg, neck, torso, etc.

Based on data regarding the patient and the diameter of the body part, the CPU may provide an estimate as to the depth of a blood vessel 28, allowing the Doppler results to be corrected to account for the distance that sound waves 29 must travel through soft tissue to reach blood vessel 29. Also, as is known in the art, the Doppler shift frequency is directly proportional to blood velocity, and inversely proportional to the speed of sound in tissue. The speed of sound in soft tissue, e.g., muscle, is 1,540 m/s, while the speed of sound in fat is 1,450 m/s. Based on data on the size of the body part, as well as the height, weight, and age of the patient, the CPU may provide an estimate of body composition, e.g., percentage of fat in the body part. This allows an estimate of the mean velocity of sound through tissue in the body part, based on percentages of fat and soft tissue. Such an estimate of mean sound velocity may improve the accuracy of Doppler shift frequencies calculated by the CPU.

FIG. 3 illustrates a perspective view of an automated external defibrillator (“AED”) device 31 for use with an alternative embodiment of the wearable RPC device including a wearable sensor. The wearable sensor may be connected to the AED device 31 using a cable, generally corresponding to cable 4 of FIG. 1, where port 32 receives the cable from the wearable sensor. The AED device may be attached to a body part with a strap, or used as a freestanding device. The AED device includes a power button 5, an LCD screen 6, an array of LED lights 7, and a loudspeaker 8, all of which function generally as described for the embodiment of FIG. 1 to provide audible and visual feedback to a person administering CPR or other lifesaving treatment. The AED device 31 may include a loud speaker 8 for providing audible feedback in the form of a Doppler tone to ensure that the rescuer is performing the CPR correctly. The AED device 31 may include a screen 6 for providing visual feedback for the rescuer, which may include feedback such as BPM and/ or a relative blood velocity meter to ensure that the rescuer is performing the CPR correctly.

The wearable sensor transmits data through a cable to the AED device 31 to provide audible and visual feedback on the AED screen and speaker. Power would be supplied to the wearable sensor from the AED power supply. FIG. 4 provides a view of a sensor 40. Sensor 40 may be used with the wearable RPC device 1 of FIG. 1, where cable 4 connects the RPC device 1 to the sensor array 40. Sensor 40 may also be used with the AED device 31 of FIG. 3, where cable 4 connects the sensor 1 to the port 31 on the AED device. Alternatively, sensor 40 may be used with the wearable RPC device 1 of FIG. 2, where sensor 40 is positioned on the underside of housing 9, generally where Doppler array 27 is positioned in FIG. 2. When sensor 40 is positioned on the underside of housing 9 in the embodiment of FIG. 2, cable 4 is not required to connect the sensor to the RPC device.

As shown in FIG. 4, sensor 40 includes a sensor array 41. Sensor array 41 includes an array 27 of piezoelectric ultrasonic transmitters 27a, which transmit ultrasound waves at a first reference frequency fii, and piezoelectric ultrasonic receivers 27b, which receive ultrasound waves at a Doppler-shifted frequency fm- fio, where £D is the Doppler shift frequency. In some embodiments, the array 27 may include piezoelectric ultrasonic transceivers which are configured to both transmit and receive ultrasonic waves. Data from the ultrasonic receivers 27b is transmitted to a CPU in the RPC or AED device, which calculates blood velocity from the Doppler shift frequency. The CPU may also calculate pulse rate from time- dependent changes in Doppler shift frequency.

Sensor array 41 may also include one or more of the following:

a. A passive piezoelectric pressure sensor 42, applied to a body tissue above a blood vessel. Sensor 42 measures an instantaneous pressure change via a change in force applied to the sensor, where the pressure change corresponds to an increase in blood pressure. By recording instantaneous pressure change in a time-dependent manner, sensor 42 can accurately detect pulse rate in BPM. However, passive piezoelectric pressure sensors are influenced by outside movement and noise. Such sensors may not be suitable for emergency situations alone, but can be used to check accuracy of pulse rates calculated from Doppler shift data. b. An infrared sensor 43, which measures infrared light refracted and/or reflected from a body surface to correlate to the movement of blood, where an increase in blood volume following a heartbeat or chest compression changes the reflectance of the tissue. Time-dependent changes in reflectance can be used to determine pulse rate. Since IR reflectance is a proven method for the measurement of pulse rate, but does not accurately measure the strength of the pulse, e.g., blood velocity, IR reflectance may be combined with Doppler ultrasonic data to increase measurement capabilities.

c. A pulse oximeter 43, configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin in the blood vessel. In various embodiments, the pulse oximeter 43 is an infrared sensor, configured to determine a ratio of oxygenated hemoglobin to deoxygenated hemoglobin, based on a first IR absorbance value or a first IR reflectance value at about 970 ± 30 nm and a second IR absorbance or reflectance value at about

670 ± 30 nm.

Sensor array 41 may be attached to a body surface of a patient with a hydrogel adhesive which conducts ultrasound and IR radiation. Alternatively, sensor array 41 may be attached to a body surface of a patient with a strap, and a non- adhesive hydrogel which conducts ultrasound and IR radiation may be positioned between sensor array 41 and the body surface. When the sensor array 41 is positioned on a patient, the hydrogel makes contact with the patient’s skin, allowing proper propagation of ultrasonic waves and IR radiation. As provided to the user, a hydrogel layer and a protective release liner may be positioned on the sensor array. Prior to use, the release liner is removed to expose the hydrogel layer, and the sensor array is placed on the body surface through the hydrogel layer.

FIG. 5 shows an alternative embodiment of the wearable RPC device 1 of FIG. 2, in which the RPC device 1 and a sensor array (not shown in FIG. 5) are incorporated into a single housing 9. A power button 5, an LED array 7, and/ or an LCD screen 6 are positioned on the top portion of the housing 9 of RPC device 1. A loudspeaker, not shown in FIG. 5, may be positioned on a side or bottom surface of housing 9. Strap 51 holds the wearable RPC device on a wrist of patient 52. In the embodiment of FIG. 5, an adhesive or non-adhesive hydrogel layer 30 which conducts ultrasound and IR is positioned between a lower surface of housing 9 and the wrist of patient 52. A sensor array including at least an array of piezoelectric ultrasonic transceivers in accordance with array 27 of FIG. 2 is positioned between a bottom surface of housing 9 and the hydrogel layer 30. In various embodiments, a sensor array 41, as seen in FIG. 4, including an array 27 of piezoelectric ultrasonic transceivers in combination with a passive piezoelectric pressure sensor 42 and/ or at least one IR sensor 43 or 44, may be positioned between a bottom surface of housing 9 and the hydrogel layer 30.

FIG. 6 shows a view of the embodiment of the automated external defibrillator device 31 of FIG. 3, in which the defibrillator device 31 is connected to an external sensor 61 by means of cable 4. Sensor 61 is powered by cable 4, and transmits data to a CPU in housing 9 through cable 4, which enters device 31 through port 31 in housing 9. Device 31 includes a power button 5, an LED array 7 and/ or an LCD screen 6, and loudspeaker 8 on the top portion of the housing 9. Strap 51 holds the sensor 61 on a wrist of patient 52. An adhesive or non-adhesive hydrogel layer which conducts ultrasound and IR may be positioned between a sensor 61 and the wrist of patient 52. In various embodiments, sensor 61 includes a sensor array 41, as seen in FIG. 4, including an array 27 of piezoelectric ultrasonic transceivers, optionally in combination with a passive piezoelectric pressure sensor 42 and/ or at least one IR sensor 43 or 44. The sensor array 41 may be positioned between a bottom surface of sensor 61 and the hydrogel layer. In various embodiments, external defibrillator device 31 may be hand-held or portable, but is not strapped to a body surface. EXAMPLE

A study was conducted to assess the viability and functionality of an RPC device prototype, generally as shown in FIG. 6. Ten patients were assessed prior to a scheduled isolated open-heart valve or isolated coronary artery bypass graft surgery. Information regarding the patients is presented in Table 1.

Table 1. Patients involved in the present study.

Height Weight

Patient Sex (cm) (kg) BMI

1 male 172 80.1 27.01

2 male 182.9 83.1 24.85

3 male 175.6 123.8 39.69

4 female 177.6 93.8 29.74

5 male 168 85.5 30.29

6 female 172.7 98.9 33.15

7 female 162.6 65.5 24.79

8 female 170.2 95.6 33.01

9 male 172.9 119.4 39.9

10 male 175.3 85.5 27.82 The patients went through induction of general anesthesia, surgical exposure, initiation of cardiopulmonary bypass, and the scheduled surgical intervention. During the process of rewarming and cessation of cardioplegia after surgery, the RPC sensor 61 was applied to the patient’s wrist, with a Doppler array positioned directly above the radial and ulnar arteries on the side opposite the peripheral arterial catheter. The anesthesia monitors were monitored for pulsatile flow recorded by pulmonary artery and peripheral arterial catheter tracings. A Massimo pulse oximeter will also be applied to a finger on the same side of RPC device wrist application and would be used for further confirmation of return of pulsatile flow.

The pulse rate associated with the return of pulsatile flow following cessation of cardioplegia, and the time at which pulsatile flow was detected, was recorded based on data from arterial catheter tracings, from the pulse oximeter, and from the Doppler array in the RPC sensor. The results are reported in Table 2.

Table 2. Pulse rates determined from arterial lines, Doppler measurements with the

Rapid Pulse Confirmation (RPC) device, and a pulse oximeter.

Pulse Pulse

Arterial line Arterial RPC RPC pulse

Oximeter Oximeter

Patient detection line pulse Detection rate

detection Pulse Rate time (sec) rate (BPM) Time (sec) (BPM)

time (sec) (BPM)

1 1051 62 1052 62 1048 62

2 1424 80 1424 79 1411 63

3 938 78 941 80 927 77

4 1230 75 1234 75 1229 75

5 1523 51 1525 60 1522 49

6 1152 90 1152 74 1140 88

7 1109 77 1109 77 1107 77

8 1344 104 1344 144 1346 104

9 1152 92 1152 90 1152 86

10 1748 65 1748 67 1747 79

Average 77.4 80.8 76 St. Dev. 15.56 23.93 15.4

As seen in Table 2, the Doppler-based measurements obtained with the RPC device provided a mean pulse rate of 80.8 beats/minute (standard deviation: 24 beats/minute) for the 10 patients in the study, following cessation of cardioplegia.

This compares favorably with the mean pulse rate of 77.4 beats/ minute (standard deviation: 15.6 beats/minute) obtained with an arterial line, and 76 beats/minute (standard deviation: 15.4 beats/minute) obtained with a pulse oximeter. More importantly, Doppler measurements with the RPC device detected the return of spontaneous circulation at substantially the same time as measurements with an arterial line, demonstrating that the Doppler-based measurements with the RPC device provide a non-invasive alternative to arterial catheters for detecting the return of blood circulation. Although the various embodiments have been described in detail with particular reference to certain aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be effected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.