Device, system, and method to control activation and configuration of pulse detection and pulse oximetry measurements during CPR

A device, system, and method to control activation of oxygen saturation (SpO2) measurements in a cardio-pulmonary resuscitation (CPR) procedure. When compressions are present, only a PPG-based pulse detection algorithm is performed. When a spontaneous pulse has been detected and compressions are not detected during a predetermined time period, both a PPG-based pulse detection algorithm and an SpO2 measurement algorithm are performed. Depending on whether a chest compression is delivered manually or automatically, parameter selections for the compression detection algorithm, the PPG-based pulse detection algorithm, and the SpO2 measurement algorithm are adjusted accordingly.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2020/069044, filed on Jul. 7, 2020, which claims the benefit of European Patent Application No. 19186879.3, filed on Jul. 18, 2019. These applications are hereby incorporated by reference herein.

FIELD OF THE INVENTION

The inventive subject matter relates to devices, systems and methods to control activation and configuration of pulse detection and pulse oximetry (SpO2) measurements during a cardiopulmonary resuscitation (CPR) procedure.

BACKGROUND OF THE INVENTION

CPR is an emergency procedure for people suffering from a cardiac arrest. During CPR, chest compressions are delivered to artificially generate circulation of blood, and ventilations are given to supply blood with oxygen. The goal of CPR is to achieve return of spontaneous circulation (ROSC). When ROSC has been achieved, the heart of the patient has resumed beating and generates a spontaneous circulation which is life-sustaining. CPR can be stopped after achieving ROSC.

Detecting ROSC during CPR is challenging and time consuming. Determining whether a patient has achieved ROSC involves checking whether the patient has a spontaneous circulatory pulse, i.e., whether the heart is beating and is generating output. Typically, ROSC detection involves manual palpation for an arterial pulse, which requires interrupting the chest compressions. CPR procedures generally benefit from improved monitoring and feedback during the procedure. For example, EP 2502560 A1 describes a CPR monitoring apparatus to obtain an oxygen saturation value during ongoing compressions in order to assess and improve the quality of the chest compressions. Additionally, after a spontaneous pulse has returned and chest compressions have stopped, clinicians want to know the patient's oxygen saturation to further monitor the patient and tailor the patient's treatment.

Hence, there is an ongoing need to improve the CPR work-flow aspects of pulse detection and SpO2 measurements in cardiac monitoring devices and to minimize disadvantages associated with interruptions of the chest compression sequence being performed on a patient.

SUMMARY OF THE INVENTION

The disclosed subject matter relates to usability aspects of the combination of pulse detection and SpO2 measurements throughout a CPR procedure.

Pulse detection during CPR can be performed by using photoplethysmography (PPG), for example as described in R. W. C. G. R. Wijshoff, et al: “Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model,” Resuscitation, vol. 84, no. 11, pp. 1625-32, November 2013, which is hereby incorporated by reference in its entirety, disclosing an investigation of the potential of PPG signals to detect the presence and rate of a spontaneous cardiac pulse during CPR, by retrospectively analyzing PPG and arterial blood pressure signals simultaneously recorded in pigs undergoing automated CPR.

The use of PPG signals to support detection of ROSC during CPR has been described, for example in WO2015121114 (A1) “Method and apparatus for minimizing detrimental interruptions in the chest compression sequence during cardiopulmonary resuscitation”, which is hereby incorporated by reference in its entirety, and WO2017211814 “System and methods for photoplethysmography-based pulse detection support during interruptions in chest compressions”, which is hereby incorporated by reference in its entirety.

Algorithms based on PPG signals to detect ROSC may be found, for example, R. W. C. G. R. Wijshoff, et al: “Photoplethysmography-Based Algorithm for Detection of Cardiogenic Output During Cardiopulmonary Resuscitation,” IEEE Trans. Biomed. Eng., vol. 62, no. 3, pp. 909-921, 2015, which is hereby incorporated by reference in its entirety, describes a PPG-based algorithm that supports ROSC detection by combining the compression-free PPG signal with an indicator based on the detected perfusing rhythm and redistribution of blood volume. Further examples of algorithms used to analyze PPG signal content to support detection of ROSC may be found in US 2016/0157739 or WO 2017/072055.

According to the inventive subject matter, oxygen saturation measurements are activated in absence of chest compressions and when a spontaneous pulse has returned. Since the PPG signals for pulse rate (PR) and SpO2 measurements can be collected by the same pulse oximetry hardware and optimal settings of the pulse oximetry hardware differ for PR only measurements and for PR and SpO2 measurements, the settings of the pulse oximetry hardware are automatically adjusted to PR only measurement and to PR and SpO2 measurements, to provide optimal performance in each scenario. The SpO2 algorithm can be activated by a manual mode to switch on SpO2 measurement or by an automatic mode to switch on SpO2 measurements. Additionally, the pulse detection algorithm has different optimal settings for manual and automated chest compression delivery. The optimal settings for the pulse detection algorithm are automatically determined by the monitor-defibrillator device, for example by analysis of an impedance signal or another compression reference signal. Pulse oximetry hardware can perform this type of analysis during compressions, thereby minimizing interruptions to the chest compression sequence, and extend the analysis with an SpO2 measurement when compressions have stopped and a spontaneous pulse has returned.

One advantage of the inventive subject matter described herein is that it provides for convenient automatic activation of SpO2 measurements and convenient automatic optimal configuration of the pulse oximetry hardware and pulse detection algorithm, without specific user intervention other than normally performed clinically.

This Summary is not intended to limit the scope or meaning of the disclosed subject matter. Further, the Summary is not intended to identify key features or essential features of the disclosed subject matter, nor is it intended to be used as an aid in determining the scope of the disclosed subject matter.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosed subject matter will become better understood through review of the following detailed description in conjunction with the figures. The detailed description and figures provide example embodiments of the invention described herein. Those skilled in the art will understand that the disclosed examples may be varied, modified, and altered without departing from the scope of the invention described herein.

Throughout the following detailed description, various examples of devices, systems and methods to control activation and configuration of pulse detection and SpO2 measurements during the CPR procedure are provided. Related features in the examples may be identical, similar, or dissimilar in different examples. Related features will not be redundantly explained in each example. Instead, the use of related feature names will cue the reader that the feature with a related feature name may be similar to the related feature in an example explained previously. Features specific to a given example will be described in that particular example. The reader should understand that a given feature need not be the same or similar to the specific portrayal of a related feature or example. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the inventive subject matter.

The present disclosure focusses on the work-flow aspects of a CPR procedure, in particular on how to conveniently activate the pulse detection and SpO2 algorithms in CPR related devices while minimizing interruptions to the procedure. As such, the inventive subject matter allows for activation of the SpO2 measurement when it is required and reliable, i.e., the SpO2 measurement algorithm is deactivated when compressions are present, and the SpO2 measurement algorithm is activated when a spontaneous pulse has been detected and compressions are not detected during a predetermined time period. Additionally, the inventive subject matter allows automatic optimization of the pulse oximetry hardware settings depending on whether PR only or PR and SpO2 need to be measured, and automatic configuration of the pulse detection algorithm for optimal performance. In some embodiments, user intervention may be as standard in clinical practice such as changing device mode. In other embodiments, there is no user intervention at all.

FIG. 1illustrates a first embodiment wherein a system100and device10include a manual mode to activate the SpO2 algorithm. Device10, for example a monitor-defibrillator or advanced automated external defibrillator (AED), includes a compression detection module12and a pulse oximetry module14. Compression detection module12receives a compression signal from a compression sensor16and provides compression presence data and compression rate data. Pulse oximetry module14receives one or more PPG signals from an SpO2/PPG sensor18and provides PPG data. During a CPR procedure, device10runs the PPG-based pulse detection algorithm and the activation of the SpO2 measurement is linked to a mode selection of a user input switch44.

The device10contains a signal processing unit20with access to or including one or more predetermined algorithms. Signal processing unit20receives PPG signals and compression signals via suitable input ports of device10. In this embodiment, signal processing unit20is adapted to perform a pulse detection algorithm with the retrieved compression presence and rate data to determine whether a pulse is present. For example, compression detection module12is configured to determine a compression condition of “compression”, “no compressions”, or “artifact” from the signal input data as well as the compression rate when compressions are being delivered. Signal processing unit20is also adapted to perform a PPG-based pulse detection algorithm and an SpO2 measurement algorithm based on the received PPG data to provide pulse detection and SpO2 measurements. Here, the PPG-based pulsed detection algorithm may make use of the information provided by the compression detection, e.g., to distinguish between compression-related and spontaneous pulse related components in a PPG signal. In some embodiments, system100may include other physiological sensors and perform related algorithms in addition to the ones described herein.

As used herein, the term “signal processing unit” describes various apparatus relating to the operation of the medical device, system, and method. The processing unit can be implemented in numerous ways to perform the various functions described herein. For example, the signal processing unit can include a combination of dedicated hardware to perform some functions and a processor, such as one or more microprocessors that may be programmed using software to perform various functions discussed herein. “Signals”, “inputs”, and “outputs” may be understood to be electrical or optical energy impulses which represent a particular detection of processing result. In various implementations, the processing unit may be associated with one or more computer storage media, for example volatile and non-volatile computer memory, and may be fixed within a processor or controller or may be transportable.

Signal processing unit20is configured to analyze the chest compression signal to discriminate a pause in compressions from ongoing compressions. If the compression signal is determined to indicate a compression rate below a predefined threshold or is determined not to contain compression-related characteristics, signal processing unit20assesses that there are no chest compressions being delivered to the patient, i.e. that there is a pause in compressions. Identifying a pause in compressions based on the compression signal can be used to obtain an alternative detection of presence or absence of the spontaneous cardiac component and the spontaneous pulse rate in the PPG signal. If the compression signal is determined to indicate a compression rate within a specified range of compression rates, signal processing unit20assesses that there are chest compressions being delivered to the patient. In this case, the compression rate can also be provided by the compression detection12to the pulse detection and this information can be taken into account by the pulse detection to discriminate between compression components and spontaneous pulse components and identify the spontaneous pulse component and the spontaneous pulse rate. Signal processing unit20executes computer program instructions and algorithmic functions related to CPR compressions and processes the SpO2 signal and PPG signal, for example as described in WO2017/211814.

FIG. 2illustrates an exemplary implementation of system100. The main goal of CPR is to achieve ROSC, in which situation the patient's heart has resumed beating. To determine whether ROSC has been achieved, pulse detection is typically performed throughout the CPR procedure. For example, device10can include pulse oximetry module14as illustrated inFIG. 1and can be used for PPG-based pulse detection and SpO2 measurements. Pulse detection can be obtained by analyzing a PPG signal obtained from an SpO2/PPG sensor18, for example arranged in a finger cuff. In other embodiments, the PPG measurement could be obtained using a PPG sensor applied to the forehead, the nasal septum, the alar wing, the earlobe, the concha of the ear, or any other suitable location on the patient.

Once the heart of the patient has resumed beating, clinically it is desirable to know the patient's SpO2 levels. PPG signals can be measured during CPR using standard SpO2 sensors and hardware. For example, SpO2 can be determined from a red and an infrared PPG signal, as measured with a standard SpO2 sensor. Thus, allowing a single SpO2 probe to be used for both pulse detection and SpO2 measurements. However, during cardiac arrest SpO2 measurements are not feasible, and during chest compressions SpO2 measurements are not reliable. Basic hemodynamic features may disappear with a cardiac arrest, in which case the sampled signal may look like a noise line. Therefore, only when there is pulse present and there are no compressions, the SpO2 algorithm should be activated.

Output of signal processing unit20can be displayed on a user interface22having one or more displays, buttons, touchscreens, keyboards or other human machine interface means. In the illustrated example, a first user interface24and a second user interface26function as a patient monitor. The first and second user interface may consist of separate units formed as a single unit, for example a single user interface configured to obtain user information and to provide ROSC information.

Compression detection module12detects a signal of a timing of a chest compression during a CPR procedure. The signal may be obtained from a compression sensor16, for example a displacement sensor, a speed sensor, an acceleration sensor, a force sensor or a pressure sensor or other suitable compression signal sensor attached to the patient's chest and subject to compression. Compression detection module12can be based on pad impedance, compression depth, compression velocity, compression acceleration or compression force. In some embodiments, an accelerometer can provide information regarding CPR compression frequency, phase, and acceleration, velocity and depth as well as compression pauses. A PPG signal can be measured during a pause in compressions, wherein the pause in chest compressions can be detected with a compression signal being delivered via a chest compression cable32from the chest compression sensor16to device10. Chest compressions can be delivered either manually by a clinician28, for example, or with an automated mechanical device30.

The system100may include other physiological sensors, such as a blood pressure sensor34arranged in an inflatable arm cuff and coupled to device10via cable46, and ECG sensors38,40attached to the patient's chest and both coupled to device10via cable42. The device can also be connected to a set of defibrillator pads. This allows the algorithm to know when the shock is given and to obtain information on the chest compressions, for example with a transthoracic impedance measurement.

The PPG signal can be delivered via a PPG cable36from SpO2/PPG sensor18in the finger cuff to device10and is analyzed by a signal processing unit of device10for presence of a spontaneous pulse. To support such analysis ECG signals measured by the ECG sensors38,40, and provided to the device10via an ECG cable42, may be used. Furthermore, system100may also measure and analyze PPG signals for pulse presence during ongoing compressions. A blood pressure measurement can be performed during a pause in compressions, either automatically or after a confirmation from the user via user interface24. If compressions are delivered in cycles of two minutes, for instance, as is customary in CPR, a blood pressure measurement can be scheduled for the short pause directly following the two-minute cycle of compressions. Alternatively, the system can prompt to the clinician28that a spontaneous pulse has been detected and suggest starting the blood pressure measurement directly after pressing a button of the first user interface24. In the latter case the clinician28has the option not to wait for the next pause in the protocol but deviate from the standard protocol to personalize the treatment to a patient.

In this first embodiment, activation of the SpO2 measurement algorithm is linked to a mode-selection of device10. Here, device10has four operating modes: monitor mode, pacer mode, manual defib mode and AED mode. The basic assumption is that pacer/manual defib mode/AED mode are used during CPR and that the device is switched to monitor-mode once ROSC has been achieved.

If device10is in pacer/manual defib/AED mode, only the PPG-based CPR pulse-detection algorithm is activated. The pulse detection algorithm can indicate pulse presence only or can provide the PR in addition.

If device10is in monitor mode, the pulse detection algorithm and the SpO2 algorithm are both activated. The SpO2 measurement can, for example, be activated only in monitor-mode and not in pacer/manual defib/AED mode. In the monitor mode, the pulse detection algorithm may be different than in the pacer/manual defib/AED mode, as now one may assume that chest compressions are no longer delivered so the algorithm need not be specifically designed to handle chest compressions. That is, in the monitor mode, a “standard motion robust” PR and SpO2 algorithm can be used.

In one embodiment, device10has a user input switch44, such as a knob, to indicate the elected mode setting of device10. User interface24can show the position of the knob or otherwise indicate the operating mode of the monitor-defibrillator. In other embodiments, the user input switch44can be a software-based button on a touch-screen user interface, such as on interface22.

Pulse oximetry module14receives one or more PPG signals of a patient from SpO2/PPG sensor18and generates a PPG waveform to determine whether a pulse is present. If a pulse is detected but the associated pulse rate is below a predetermined threshold, the signal processing unit assumes that no pulse is present and there is no ROSC. PPG-based pulse detection can be carried out using pulse oximetry hardware and sensors commonly used in clinical practice. The PPG signals for pulse detection and SpO2 measurement can be collected by the same pulse oximetry module and sensor. However, optimal settings of the pulse oximetry hardware are different for PR only measurements than for PR and SpO2 measurements. The pulse oximeter module can be a stand-alone device or may be incorporated as a module or built-in portion of a multiparameter patient monitoring system. Typically, the pulse oximeter provides numerical information of the oxygen saturation of the patient, numerical information of pulse rate, an audible indicator or a “beep” generated at each pulse and a filtered PPG signal waveform.

FIG. 3is a simplified flowchart illustrating a method of operation of system100executed according to the first embodiment. The operation of the algorithm depends on the mode selection of user input switch44. If user input switch44indicates “pacer/manual defib/AED mode” (302), only the PPG-based pulse detection is run. After the CPR procedure is started, compression detection module14determines whether a chest compression is present or not based on a signal received from compression sensor16(304). If a chest compression is present, the PPG-based pulse detection algorithm is activated in a mode that takes into account the chest compression rate (306). If a chest compression is not present, the PPG-based pulse detection algorithm is activated in a mode that does not take into account the chest compression rate (308). The process can be repeated as needed. If the user input switch44indicates “monitor mode”, it is assumed that no chest compressions are being delivered when the user sets the device in this mode (310). In this mode, the PPG-based pulse detection and the SpO2 measurement are run simultaneously (312). Operation of system100may be affected by input of other physiological sensors.

A second embodiment is described with reference toFIGS. 4 and 5. In this embodiment, the SpO2 measurement can be automatically activated and deactivated in any operating mode of the device by using the output of the pulse detection algorithm and the output of the compression detection algorithm. System200includes device210, an SpO2/PPG sensor218providing a PPG signal to pulse oximetry module214, and a compression sensor216providing a compression signal to compression detection module212. Device210further includes a status determination unit222allowing for the SpO2 measurement to be automatically activated once the pulse detection algorithm detects presence of a spontaneous pulse and the compression detection algorithm detects absence of compression.

When the CPR procedure starts, and device210is switched on, signal processing unit220activates both the PPG-based CPR pulse-detection algorithm and the SpO2 algorithm. This is independent of the selected mode of device210. When chest compressions start on the patient, as detected from the analysis of the compression signal, the SpO2 algorithm is deactivated. During chest compressions, SpO2 measurements will become unreliable due to the chest compression artifacts, but the pulse detection algorithm remains active. When loss of a spontaneous pulse has been detected by the pulse detection algorithm during periods without compressions, the SpO2 algorithm is deactivated as a cardiac pulse is required to measure SpO2. When compressions have not occurred during a predetermined time period, for example 10 seconds, and a pulse has been detected, the SpO2 algorithm is activated. Now, a cardiac pulse is present which is required to measure SpO2 and no compression artifacts are present which could have corrupted the SpO2 measurement.

Furthermore, when a pulse has returned it may be clinically desirable to know the patient's oxygen saturation levels to further monitor the patient's status and tailor the therapy. At this point in time a buffer of red and infrared PPG data is available which indicate a cardiac pulse and no compressions. Upon activation of the SpO2 measurement, the algorithm analyzes the buffer of data to directly provide an SpO2 value. This requires that both the red and infrared light emitting diodes are kept on during the mode of pulse detection only.

Thus, activation of the SpO2 algorithm is automatically determined from the output of the pulse detection algorithm and the output of the compression detection algorithm. The PPG-based pulse detection algorithm is tailored to detecting pulse presence and reporting a PR if the heart is beating sufficiently stable to report a PR.

FIG. 5illustrates operation of system200. When the device is turned on, both the PPG-based pulse detection algorithm and the SpO2 algorithm are activated (502). The presence of a chest compression is determined (504). If a chest compression is present, the SpO2 algorithm is deactivated, and the PPG-based pulse detection algorithm remains active (506). If a chest compression is not present, both the PPG-based pulse detection algorithm and the SpO2 algorithm remain active (508). The presence of a pulse is verified (510). When there is no pulse detected, the SpO2 algorithm is deactivated (506). If a pulse is present, and a chest compression is present, the PPG-based pulse detection algorithm is activated and the SpO2 algorithm is deactivated (506). The process can be repeated until ROSC is achieved.

According to a third embodiment, the system allows for automatic configuration of the pulse oximetry hardware. Since the PPG signals for PR and SpO2 measurements are collected by the same pulse oximetry module and sensor, the optimal configuration of the pulse oximetry hardware can be adjusted depending on whether PR only or PR and SpO2 measurements need to be performed. This embodiment can be combined with the first or second embodiments described above and/or with a fourth embodiment described below.

FIG. 6illustrates a simplified component600of a system and device according to the third embodiment wherein the pulse oximetry module614has different optimal configurations for detecting PR only and for providing both PR detection and SpO2 measurement. When a measurement of the PPG signals is used for pulse rate detection only, an SpO2/PPG sensor618can provide a measurement at one wavelength. When a measurement of PPG signals is used for pulse rate detection and SpO2 measurement, SpO2/PPG sensor618can provide a measurement at two wavelengths. For example, one light emitting diode can be switched off during the PR detection only mode or the light intensity can be increased in the PR detection only mode. Additionally, the algorithm that prevents saturation can be different for PR only mode.

When detecting PR only, only one wavelength may be relevant, for example only infrared is used, and the hardware settings can be optimized to have a maximum signal-to-noise-ratio (SNR) in the infrared PPG signal. For example, the infrared signal level on the analog digital converter (ADC) can be maximized in this setting. The other PPG signal, for example red, may be completely deactivated in this setting at the expense of an additional delay of the SpO2 measurement once this is required. Alternatively, the other PPG signal may be kept on in this setting to have a rapid SpO2 measurement available once this is required.

Furthermore, in this situation the algorithm that prevents saturation of the ADC can have a more aggressive setting. During CPR, motion artifacts can be very large and probe-skin motion is more likely to occur which can have significant effects on the signal level on the ADC, i.e., saturation of the ADC input is more likely to occur. Detection of saturation can be achieved using a low-pass filtered signal. During CPR, the bandwidth of this filter can be set wider than during non-CPR. Alternatively, the allowed margin of the low-pass filtered signal to the maximum input of the ADC can be set larger during CPR than during non-CPR to prevent saturation.

When both PR and SpO2 need to be measured, two PPG signals will be measured, for example red and infrared, and the hardware settings are optimized to have good SNR in both PPG signals and have the signals balanced, i.e., with comparable average level on the ADC.

According to a fourth embodiment, the system allows automatic configuration of the device and related hardware to provide optimal pulse detection. The optimal configuration of the pulse detection algorithm depends on whether chest compressions are being delivered manually or by an automated device. Analysis of the chest compression signal indicates whether chest compressions are being delivered manually or by an automated device and the pulse detection algorithm parameters are adjusted accordingly to assure optimal performance. The PPG-based pulse detection algorithm has different optimal parameter settings for manual and automated chest compression delivery. Parameter settings of the pulse detection algorithm can be adjusted based on analysis of measured compression signals and a compression reference signal. Alternatively, parameter settings of the pulse detection algorithm can be adjusted based on communication between system100and the automatic chest compression delivery system or between system200and the automatic chest compression delivery system. Communication between system100and the automatic chest compression delivery system or between system200and the automatic chest compression delivery system can occur via wired or wireless means.

The optimal settings for the pulse detection algorithm are automatically determined by the monitor-defibrillator device, for example by analysis of the impedance signal or another compression reference signal. A compression reference signal can be any of pad impedance, compression depth, compression velocity, compression acceleration or compression force. The analysis of the compression signal can, for example, be determined by the standard deviation of the compression rate, which is expected to be smaller for automated compressions than for manual compressions. An algorithm parameter which depends on the compression method is for instance the predefined bandwidth around the compression rate and its harmonics which is excluded for finding pulse rates. This bandwidth can be, for example [−5 BPM, +5 BPM] for automated compressions, and, for example [−10 BPM, +10 BPM] for manual compressions. In this embodiment, optimal pulse detection can be automatically configured without any user intervention. This embodiment can be combined with any of the embodiments described above.

The inventive subject matter further contemplates a method to control activation of SpO2 measurements in a CPR procedure. Compression presence data and compression rate data can be obtained from a compression sensor, and PPG data are obtained from a pulse oximetry sensor. The compression presence data and compression rate data are processed with a compression detection algorithm to determine whether a chest compression is present. A PPG-based pulse detection algorithm is performed only when compressions are present. Both the PPG-based pulse detection algorithm and an SpO2 measurement algorithm are performed when a spontaneous pulse has been detected and compressions are not detected during a predetermined time period. Different types of algorithms for PPG-based pulse detection can run during absence of compressions and during presence of compressions.

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to.