Patent ID: 12186107

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as precluding other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed.

In the following description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

Wearable Cardioverter Defibrillators (WCDs) are worn by patients at risk for sudden cardiac arrest and other potential heart conditions. Because WCDs are worn by ambulatory patients, noise on an ECG signal may be generated at the electrode-skin interface. For example, patient movement may cause movement at the electrode-skin interface to generate noise that may interfere with ECG interpretation. This noise may then interfere with obtaining accurate heartrate signals, which may result in a missed cardiac episode.

In some embodiments, a WCD device may have four monitoring electrodes that can generate six differential ECG vectors. During patient movement, some ECG vectors may be noisier than other ECG vectors. As described herein, identifying more reliable ECG vectors for ECG characteristic assessment provides greater reliability. Some of the ECG vectors may produce a relatively cleaner ECG signal and some may produce a noisier signal. To make the best ECG characteristics assessment, a WCD needs to assess which of the ECG vectors are reliable for the assessment.

For exemplary purposes only, the embodiments herein will be described in reference to a WCD system and a defibrillator. However, the methodology for determining a reliable ECG vector can be performed by a WCD or any wearable medical monitoring device that monitors a patient's ECG.

FIG.1illustrates a system100with a patient102wearing an example of a WCD system104according to embodiments described herein. In some embodiments, the WCD system104may include one or more communication devices106, a support structure110, and an external defibrillator108connected to two or more defibrillation electrodes114,116, among other components.

The support structure110may be worn by the patient102. The patient102may be ambulatory, meaning the patient102can walk around and is not necessarily bed-ridden while wearing the wearable portion of the WCD system104. While the patient102may be considered a “user” of the WCD system104, this is not a requirement. For instance, a user of the WCD system104may also be a clinician such as a doctor, nurse, emergency medical technician (EMT), or other similarly tasked individual or group of individuals. In some cases, a user may even be a bystander. The particular context of these and other related terms within this description should be interpreted accordingly.

In some embodiments, the support structure110may include a vest, shirt, series of straps, or other system enabling the patient102to carry at least a portion of the WCD system104on the patient's body. In some embodiments, the support structure110may comprise a single component. For example, the support structure110may comprise a vest or shirt that properly locates the WCD system104on a torso112of the patient102. The single component of the support structure110may additionally carry or couple to all of the various components of the WCD system104.

In other embodiments, the support structure110may comprise multiple components. For example, the support structure110may include a first component resting on a patient's shoulders. The first component may properly locate a series of defibrillation electrodes114,116on the torso112of the patient102. A second component may rest more towards a patient's hips, whereby the second component may be positioned such that the patient's hips support the heavier components of the WCD system104. In some embodiments, the heavier components of the WCD system104may be carried via a shoulder strap or may be kept close to the patient102, such as in a cart, bag, stroller, wheelchair, or another vehicle.

The external defibrillator108may be coupled to the support structure110or may be carried remotely from the patient102. The external defibrillator108may be triggered to deliver an electric shock to the patient102when patient102wears the WCD system104. For example, if certain thresholds are exceeded or met, the external defibrillator108may engage and deliver a shock to the patient102.

The defibrillation electrodes114,116can be configured to be worn by patient102in a number of ways. For instance, the defibrillator108and the defibrillation electrodes114,116can be coupled to the support structure110directly or indirectly. For example, the support structure110can be configured to be worn by the patient102to maintain at least one of the electrodes114,116on the body of the patient102, while the patient102is moving around, etc. The electrodes114,116can be thus maintained on the torso112by being attached to the skin of patient102, simply pressed against the skin directly or through garments, etc. In some embodiments, the electrodes114,116are not necessarily pressed against the skin but become biased that way upon sensing a condition that could merit intervention by the WCD system104. In addition, many of the components of defibrillator108can be considered coupled to support structure110directly or indirectly via at least one of the defibrillation electrodes114,116.

The WCD system104may defibrillate the patient102by delivering an electrical charge, pulse, or shock111to the patient102through a series of electrodes114,116positioned on the torso112. For example, when defibrillation electrodes114,116are in good electrical contact with the torso112of patient102, the defibrillator108can administer, via electrodes114,116, a brief, strong electric pulse111through the body. The pulse111is also known as shock, defibrillation shock, therapy, electrotherapy, therapy shock, etc. The pulse111is intended to go through and restart heart122in an effort to save the life of patient102. The pulse111can further include one or more pacing pulses of lesser magnitude to pace heart122if needed. The electrodes114,116may be electrically coupled to the external defibrillator108via a series of electrode leads118. The defibrillator108may administer an electric shock111to the body of the patient102when the defibrillation electrodes114,116are in good electrical contact with the torso112of patient102. In some embodiments, devices (not shown) proximate the electrodes114,116may emit a conductive fluid to encourage electrical contact between the patient102and the electrodes114,116.

In some embodiments, the WCD system104may also include either an external or internal monitoring device or some combination thereof.FIG.1displays an external monitoring device124, which may also be known as an outside monitoring device. The monitoring device124may monitor at least one local parameter. Local parameters may include a physical state of the patient102, such as ECG, movement, heart rate, pulse, temperature, and the like. Local parameters may also include a parameter of the WCD104, environmental parameters, or the like. The monitoring device124may be physically coupled to the support structure110or may be proximate to the support structure110. In either location, the monitoring device124is communicatively coupled with other components of the WCD104.

For some of these parameters, the device124may include one or more sensors or transducers. Each one of such sensors can be configured to sense a parameter of the patient102and to render an input responsive to the sensed parameter. In some embodiments, the input is quantitative, such as values of a sensed parameter; in other embodiments, the input is qualitative, such as informing whether or not a threshold is crossed. In some instances, these inputs about the patient102are also referred to herein as patient physiological inputs and patient inputs. In some embodiments, a sensor can be construed more broadly as encompassing many individual sensors. In some instances, the device124may include a blood volume sensor. According to embodiments of the present disclosure, the blood volume sensor may include communication circuitry to communicate with the WCD system so that HR and blood volume measurements can be provided to the WCD system.

In some embodiments, a communication device106may enable the patient102to interact with and garnish data from the WCD system104. The communication device106may enable a patient or third party to view patient data, dismiss a shock if the patient is still conscious, turn off an alarm, and otherwise engage with the WCD system104. In some embodiments, the communication device106may be a separable part of an external defibrillator108. For example, the communication device106may be a separate device coupled to the external defibrillator108. In some embodiments, the communication device106may be wired or wirelessly linked to the external defibrillator108and may be removable from the defibrillator108. In other embodiments, the communication device106may form an inseparable assembly and share internal components with the external defibrillator108. In some embodiments, the WCD system104may include more than one communication device106. For example, the defibrillator108may include components able to communicate to the patient, and the WCD system104may include a separate communication device106remote from the defibrillator108.

In some embodiments, the communication device106may be communicatively coupled to an alert button128. The alert button128may be removably coupled to the support structure110. The patient102may couple the alert button128to the support structure110or may couple the alert button128to an article of clothing. The alert button128may have a wired or wireless connection to the communication device106. In some embodiments, the alert button128may include a visual output, an audio output, and a user input. The visual output may include a light, such as an LED, a small screen, or some combination thereof. Likewise, the audio output may include one or more speakers. The output of the audio output may be loud enough to be heard over nominal background noise. In some embodiments, the audio output might have an adjustable volume range. In some embodiments, the alert button128may include a microphone. In still further embodiments, the alert button128may also include a haptic response.

In some embodiments, the defibrillator108may connect with one or more external devices126. For example, as shown inFIG.1, the defibrillator108may connect to various external devices126such as the cloud, a remote desktop, a laptop, a mobile device, or other external device using a network such as the Internet, local area networks, wide area networks, virtual private networks (VPN), other communication networks or channels, or any combination thereof.

In embodiments, one or more of the components of the exemplary WCD system104may be customized for the patient102. Customization may include a number of aspects including, but not limited to, fitting the support structure110to the torso112of patient102; baseline physiological parameters of patient102can be measured, such as the heart rate of patient102while resting, while walking, motion detector outputs while walking, etc. The measured values of such baseline physiological parameters can be used to customize the WCD system in order to make its diagnoses more accurate since patients' bodies differ from one another. Of course, such parameter values can be stored in a memory of the WCD system and the like. Moreover, a programming interface can be made according to embodiments, which receives such measured values of baseline physiological parameters. Such a programming interface may input automatically in the WCD system these, along with other data.

FIG.2is a diagram displaying various components of an example external defibrillator108. The external defibrillator108may be an example of the defibrillator108described with reference toFIG.1. The components shown inFIG.2may be contained within a single unit or may be separated amongst two or more units in communication with each other. The defibrillator108may include a communication device106, processor202, memory204, defibrillation port208, and ECG port210, among other components. In some embodiments, the components are contained within a housing212or casing. The housing212may comprise a hard shell around the components or may comprise a softer shell for increased patient comfort.

The communication device106, processor202, memory204(including software/firmware code (SW)214), defibrillation port208, ECG port210, communication module216, measurement circuit218, monitoring device220, and energy storage module222may communicate, directly or indirectly, with one another via one or more buses224. The one or more buses224may allow data communication between the elements and/or modules of the defibrillator108.

The memory204may include random access memory (RAM), read-only memory (ROM), flash RAM, and/or other types. The memory204may store computer-readable, computer-executable software/firmware code214, including instructions that, when executed, cause the processor202to perform various functions (e.g., determine shock criteria, determine consciousness of patient, track patient parameters, establish electrode channels, determine noise levels in electrode readings, etc.). In some embodiments, the processor202may include an intelligent hardware device, e.g., a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), etc.

In some embodiments, the memory204can contain, among other things, the Basic Input-Output system (BIOS), which may control basic hardware and/or software operations such as interactions and workings of the various components of the defibrillator108, and in some embodiments, components external to the defibrillator108. For example, the memory204may contain various modules to implement the workings of the defibrillator108and other aspects of the present disclosure.

In some embodiments, the defibrillator108may include a user interface206. The user interface206may be in addition to or part of the communication device106. The user interface206may display an ECG of the patient, a status of the defibrillator108, a status of a charge (e.g., a battery charge or an energy storage module), and the like.

In some embodiments, the defibrillator108may include a defibrillation port208. The defibrillation port208may comprise a socket, opening, or electrical connection in the housing212. In some instances, the defibrillation port208may include two or more nodes226,228. The two or more nodes226,228may accept two or more defibrillation electrodes (e.g., defibrillation electrodes114,116,FIG.1). The nodes226,228may provide an electrical connection between the defibrillation electrodes114,116and the defibrillator108. The defibrillation electrodes114,116may plug into the two or more nodes226,228via one or more leads (e.g., leads118), or, in some instances, the defibrillation electrodes114,116may be hardwired to the nodes226,228. Once an electrical connection is established between the defibrillation port208and the electrodes114,116, the defibrillator108may be able to deliver an electric shock to the patient102.

In some embodiments, the defibrillator108may include an ECG port210in the housing212. The ECG port210may accept one or more ECG electrodes230or ECG leads. In some instances, the ECG electrodes230sense a patient's ECG signal. For example, the ECG electrodes230may record electrical activity generated by heart muscle depolarization. The ECG electrodes230may utilize 4-leads to 12-leads or multichannel ECG, or the like. The ECG electrodes230may connect with the patient's skin.

In some embodiments, the defibrillator108may include a measurement circuit218. The measurement circuit218may be in communication with the ECG port210. For example, the measurement circuit218may receive physiological signals from ECG port210. The measurement circuit218may additionally or alternatively receive physiological signals via the defibrillation port208when defibrillation electrodes114,116are attached to the patient102. The measurement circuit218may determine a patient's ECG signal from a difference in voltage between the defibrillation electrodes114,116.

In some embodiments, the measurement circuit218may monitor the electrical connection between the defibrillation electrodes114,116and the skin of the patient102. For example, the measurement circuit218can detect impedance between electrodes114,116. The impedance may indicate the effective resistance of an electric circuit. An impedance calculation may determine when the electrodes114,116have a good electrical connection with the patient's body.

In some embodiments, the defibrillator108may include an internal monitoring device220within the housing212. The monitoring device220may monitor at least one local parameter. Local parameters may include the physical state of the patient, such as ECG, movement, heart rate, pulse, temperature, and the like. Local parameters may also include a parameter of the WCD system (e.g., WCD104,FIG.1), defibrillator108, environmental parameters, or the like.

In some embodiments, the WCD system104may include an internal monitoring device220and an external monitoring device (e.g., external monitoring device124). If both monitoring devices124,220are present, the monitoring devices124,220may work together to parse out specific parameters depending on position, location, and other factors. For example, the external monitoring device124may monitor environmental parameters while the internal monitoring device220may monitor patient and system parameters.

Patient parameters may include patient physiological parameters. Patient physiological parameters may include, for example and without limitation, those physiological parameters that can be of any help in detecting by the WCD system whether or not the patient is in need of a shock or other intervention or assistance. Patient physiological parameters may also optionally include the patient's medical history, event history and so on. Examples of such parameters include the patient's ECG, blood oxygen level, blood flow, blood pressure, blood perfusion, pulsatile change in light transmission or reflection properties of perfused tissue, heart sounds, heart wall motion, breathing sounds and pulse. Accordingly, monitoring devices124,220may include one or more sensors configured to acquire patient physiological signals. Examples of such sensors or transducers include one or more electrodes to detect ECG data, a perfusion sensor, a pulse oximeter, a device for detecting blood flow (e.g. a Doppler device), a sensor for detecting blood pressure (e.g. a cuff), an optical sensor, illumination detectors and sensors perhaps working together with light sources for detecting color change in tissue, a motion sensor, a device that can detect heart wall movement, a sound sensor, a device with a microphone, an SpO2 sensor, and so on. In view of this disclosure, it will be appreciated that such sensors can help detect the patient's pulse, and can therefore also be called pulse detection sensors, pulse sensors, and pulse rate sensors. In addition, a person skilled in the art may implement other ways of performing pulse detection.

In some embodiments, the local parameter is a trend that can be detected in a monitored physiological parameter of patient. A trend can be detected by comparing values of parameters at different times over short and long terms. Parameters whose detected trends can particularly help a cardiac rehabilitation program include: a) cardiac function (e.g. ejection fraction, stroke volume, cardiac output, etc.); b) heart rate variability at rest or during exercise; c) heart rate profile during exercise and measurement of activity vigor, such as from the profile of an accelerometer signal and informed from adaptive rate pacemaker technology; d) heart rate trending; e) perfusion, such as from SpO2, CO2, or other parameters such as those mentioned above, f) respiratory function, respiratory rate, etc.; g) motion, level of activity; and so on. Once a trend is detected, it can be stored and/or reported via a communication link, along perhaps with a warning if warranted. From the report, a physician monitoring the progress of patient will know about a condition that is either not improving or deteriorating.

Patient state parameters include recorded aspects of patient, such as motion, posture, whether they have spoken recently plus maybe also what they said, and so on, plus optionally the history of these parameters. In another embodiment, one of these monitoring devices could include a location sensor such as a Global Positioning System (GPS) location sensor. Such a sensor can detect the location, plus a speed can be detected as a rate of change of location over time. Many motion detectors output a motion signal that is indicative of the motion of the detector, and thus of the patient's body. Patient state parameters can be very helpful in narrowing down the determination of whether SCA is indeed taking place.

A WCD system made according to embodiments may thus include a motion detector. In embodiments, a motion detector can be implemented within monitoring device124or monitoring device220. Such a motion detector can be made in many ways as is known in the art, for example by using an accelerometer. In this example, a motion detector is implemented within one of the monitoring devices124,220. A motion detector of a WCD system according to embodiments can be configured to detect a motion event. A motion event can be defined as is convenient, for example a change in motion from a baseline motion or rest, etc. In such cases, a sensed patient parameter is motion.

System parameters of a WCD system can include system identification, battery status, system date and time, reports of self-testing, records of data entered, records of episodes and intervention, and so on. In response to the detected motion event, the motion detector may render or generate, from the detected motion event or motion, a motion detection input that can be received by a subsequent device or functionality.

Environmental parameters can include ambient temperature and pressure. Moreover, a humidity sensor may provide information as to whether or not it is likely raining. Presumed patient location could also be considered an environmental parameter. The patient location could be presumed, if monitoring device124,220includes a GPS location sensor as per the above, and if it is presumed that the patient is wearing the WCD system.

In some embodiments, the defibrillator108may include a power source232. The power source232may comprise a battery or battery pack, which may be rechargeable. In some instances, the power source232may comprise a series of different batteries to ensure the defibrillator108has power. For example, the power source232may include a series of rechargeable batteries as a prime power source and a series of non-rechargeable batteries as a secondary source. If the patient102is proximate to an AC power source, such as when sitting down, sleeping, or the like, the power source232may include an AC override wherein the power source232draws power from the AC source.

In some embodiments, the defibrillator108may include an energy storage module222. The energy storage module222may store electrical energy in preparation or anticipation of providing a sudden discharge of electrical energy to the patient. In some embodiments, the energy storage module222may have its own power source and/or battery pack. In other embodiments, the energy storage module222may pull power from the power source232. In still further embodiments, the energy storage module222may include one or more capacitors234. The one or more capacitors234may store an electrical charge, which may be administered to the patient. The processor202may be communicatively coupled to the energy storage module222to trigger the amount and timing of electrical energy to provide to the defibrillation port208and, subsequently, the patient102.

In some embodiments, the defibrillator108may include a discharge circuit236. The discharge circuit236may control the energy stored in the energy storage module222. For example, the discharge circuit236may either electrically couple or decouple the energy storage module222to the defibrillation port208. The discharge circuit236may be communicatively coupled to the processor202to control when the energy storage module222and the defibrillation port208should or should not be coupled to either administer or prevent a charge from emitting from the defibrillator108. In some embodiments, the discharge circuit236may include one or more switches238. In further embodiments, the one or more switches238may include an H-bridge.

In some embodiments, the defibrillator108may include a communication module216. The communication module216may establish one or more communication links with either local hardware and/or software to the WCD system104and defibrillator108or to remote hardwire separate from the WCD system104. In some embodiments, the communication module216may include one or more antennas, processors, and the like. The communication module216may communicate wirelessly via radio frequency, electromagnetics, local area networks (LAN), wide area networks (WAN), virtual private networks (VPN), RFID, Bluetooth, cellular networks, and the like. The communication module216may facilitate communication of data and commands such as patient data, episode information, therapy attempted, CPR performance, system data, environmental data, and so on.

In some embodiments, the communication module216may establish one or more wired or wireless communication links with other devices of other entities, such as a remote assistance center, Emergency Medical Services (EMS), and so on. The communication links can be used to transfer data and commands. The data may be patient data, event information, therapy attempted, CPR performance, system data, environmental data, and so on. For example, communication module216may transmit wirelessly, e.g. on a daily basis, heart rate, respiratory rate, and other vital signs data to a server accessible over the internet, for instance as described in US 20140043149. This data can be analyzed directly by the patient's physician and can also be analyzed automatically by algorithms designed to detect a developing illness and then notify medical personnel via text, email, phone, etc. In some embodiments, the communication module216may also include such interconnected sub-components as may be deemed necessary by a person skilled in the art, for example an antenna, portions of a processor, supporting electronics, outlet for a telephone or a network cable, etc.

In some embodiments, the processor202may execute one or more modules. For example, the processor202may execute a detection module240and/or an action module242. The detection module240may be a logic device or algorithm to determine if any or a variety of thresholds are exceeded, which may require an action from the defibrillator108. For example, the detection module240may receive and interpret all of the signals from the ECG port210, the defibrillation port208, the monitoring device220, an external monitoring device, and the like. The detection module240may process the information to ensure the patient is still conscious and healthy. If any parameter indicates the patient102may be experiencing distress or indicating a cardiac episode, the detection module240may activate the action module242.

The action module242may receive data from the detection module240and perform a series of actions. For example, an episode may merely be a loss of battery power at the power source232or the energy storage module222, or one or more electrodes (e.g., ECG electrodes, defibrillation electrodes) may have lost connection. In such instances, the action module242may trigger an alert to the patient or to an outside source of the present situation. This may include activating an alert module. If an episode is a health risk, such as a cardiac event, the action module242may begin a series of steps. This may include issuing a warning to the patient, issuing a warning to a third party, priming the energy storage module222for defibrillation, releasing one or more conductive fluids proximate defibrillation electrodes114,116, and the like.

FIG.3is a diagram of sample embodiments of components of a WCD system300according to exemplary embodiments. The WCD system300may be an example of the WCD system104described with reference toFIG.1. In some embodiments, the WCD system300may include a support structure302comprising a vest-like wearable garment. In some embodiments, the support structure302has a backside304and a frontside306that closes in front of the chest of the patient.

In some embodiments, the WCD system300may also include an external defibrillator308. The external defibrillator308may be an example of the defibrillator108described with reference toFIGS.1and2. As illustrated,FIG.3does not show any support for the external defibrillator308, but as discussed, the defibrillator308may be carried in a purse, on a belt, by a strap over the shoulder, and the like as discussed previously. One or more wires310may connect the external defibrillator308to one or more electrodes312,314,316. Of the connected electrodes, electrodes312,314are defibrillation electrodes, and electrodes316are ECG sensing electrodes.

The support structure302is worn by the patient to maintain electrodes312,314,316on a body of the patient. For example, the back-defibrillation electrodes314are maintained in pockets318. In some embodiments, the inside of pockets318may comprise loose netting so that the electrodes314can contact the back of the patient. In some instances, a conductive fluid may be deployed to increase connectivity. Additionally, in some embodiments, sensing electrodes316are maintained in positions that surround the patient's torso for sensing ECG signals and/or the impedance of the patient.

In some instances, the ECG signals in a WCD system300may comprise too much electrical noise to be useful. To ameliorate the noise problem, multiple ECG sensing electrodes316are provided for presenting many options to the processor (e.g., processor202,FIG.2). The multiple ECG sensing electrodes316provide different vectors for sensing the ECG signal of the patient.

FIG.4is a conceptual diagram illustrating how multiple electrodes of a WCD system may define a multi-vector embodiment for sensing ECG signals along different vectors according to various exemplary embodiments. A cross-section of a body of a patient422having a heart424is illustrated. InFIG.4, the patient422is viewed from the top looking down, and the plane ofFIG.4intersects patient422proximate the torso of the patient422.

In some embodiments, four ECG sensing electrodes E1, E2, E3, E4are maintained on the torso of patient482and have respective wire leads461,462,463,464. The electrodes E1, E2, E3, E4that surround the torso may be similar to the sensing electrodes316as described with reference toFIG.3.

Any pair of these four ECG sensing electrodes E1, E2, E3, E4defines a vector along which an ECG signal may be sensed and, in some instances, measured. As such, electrodes E1, E2, E3, E4define six vectors471,472,473,474,475,476.

These vectors471,472,473,474,475,476define channels A, B, C, D, E, F, respectively. ECG signals401,402,403,404,405,406may thus be sensed and/or measured from channels A, B, C, D, E, F, respectively, and in particular from the appropriate pairings of wire leads461,462,463,464for each channel.

As shown inFIG.4, electrodes E1, E2, E3, E4are drawn on the same plane for simplicity, while in actuality, the electrodes E1, E2, E3, E4may not be positioned on the same plane. Accordingly, vectors471,472,473,474,475,476are not necessarily on the same plane, either. Further, in some embodiments, the WCD system averages a value of the voltages of all four electrodes electronically and then determines the voltage of each electrode relative to the average value. Conceptually, this average value is the signal at some point in space in between the electrodes E1, E2, E3, E4. It continuously changes its virtual position based on the voltages of the electrodes E1, E2, E3, E4. In some embodiments, this virtual point is referred to herein as the M Central Terminal (MCT). Relative to the MCT, there are four resulting vectors: E1C=E1−CM, E2C=E2−CM, E3C=E3−CM and E4C=E4−CM, where CM is the average voltage value. In some embodiments, the vectors are virtually formed by selecting a pair of these signals and subtracting one from the other. For example, E1C−E2C=(E1−CM)−(E2−CM)=E1−E2+(CM−CM)=E1−E2=E12. Although six vectors are described inFIG.4, a different number of vectors may be used depending on the number of ECG electrodes present in the system and the desired number of vectors (up to the number of vectors that can be derived from the number of electrodes).

In some embodiments, to make the shock/no-shock determination as accurate as possible, a WCD system may assess the best ECG signals401,402,403,404,405,406for rhythm analysis and interpretation. For example, ECG signals with the most noise may be ignored, discarded, or not considered, leaving the remaining ECG signals as candidates for the shock/no-shock determination.

In other embodiments, the vectors may be aggregated to make a shock/no-shock decision and/or to determine the patient's heart rate and/or QRS widths. For example, in some embodiments, the aggregation can be implemented as disclosed in U.S. Pat. No. 9,757,581 issued Sep. 12, 2017, entitled “Wearable Cardioverter Defibrillator Components Making Aggregate Shock/No Shock Determination from Two or More ECG Signals,” which is incorporated herein by reference.

FIG.5is a block diagram illustrating components of one example of a defibrillator500. The defibrillator500may be an example of the defibrillator108described with reference toFIGS.1and2and defibrillator308described with reference toFIG.3. In this example, the defibrillator500has detection module502and an action module504. The detection module502may further include a reliability module506, physiological module508, and a blood volume module510.

As described previously, because the WCD is worn by an ambulatory patient, patient movement may cause changes at the electrode-skin interface, resulting in noise on any or all of the ECG signals, which may interfere with ECG interpretation. The reliability module506may analyze the ECG signals to determine which signals are reliable and usable for a rhythm analysis.

When the patient wearing the WCD is moving, some ECG electrodes may move more than others, resulting in some ECG vectors having more noise than other ECG vectors. The reliability module506may assess the ECG vectors using a variety of methods to determine if ECG vectors have similar outputs across various analysis. If the assessments for an ECG vector have similar results, then the ECG vector is deemed reliable. The ECG vectors deemed to be reliable can then be used in a rhythm analysis, resulting in a more accurate result.

In some embodiments, the reliability module506may use multiple methods to analyze each ECG vector of the patient's heart rate. If the various methods used by the reliability module506result in a similar heartrate for a specific ECG vector, the reliability module506deems that specific ECG vector reliable. By using multiple different methods to analyze an ECG signal, the reliability module506has a heightened assurance of an accurate ECG signal when the results converge.

In some embodiments, the reliability module506may use two or more methods to determine if a cardiac event is occurring. In some embodiments, the reliability module506may be used multiple predetermined methods to assess the cardiac event or the ECG signal. In other embodiments, the reliability module506may be used a variety of methods with a variety of combinations to assess the signal.

For example, in some embodiments, the reliability module506may use both a frequency domain method and a time domain method to assess the ECG signal. In the example shown inFIG.6A, the time domain method is a QRS detection method to determine the heartrate using the R-R interval between detected QRS complexes.FIG.6Ashows samples of a portion of a rectified ECG signal from a particular vector, sampled at a 1 KHz rate. There are about 391 samples on average between peaks, resulting in an average heart rate of about 153 bpm.

In the example shown inFIG.6B, the frequency domain method is an FTT method based on the same ECG portion of the same vector shown inFIG.6A. As shown inFIGS.6A and6B, the harmonics of the heart rate are about 153 bpm apart, indicating the heartrate is relatively stable at about 153 bpm. For this ECG portion vector, the QRS assessment and the frequency domain assessment closely match, and the reliability module506indicates the ECG vector is reliable.

In some embodiments, the reliability module506may use various criteria to determine whether different assessments match. The criteria may include: the difference between the values is within a predetermined range (e.g., ±5 bpm for the example shown inFIGS.6A and6B), the percentage difference is within a predetermined threshold (e.g., 3.5%), and the like. In other embodiments, the reliability module506may use different criteria for determining matching ECG vectors.

Another example of the reliability module506assessment is shown inFIGS.7A and7B.FIG.7Ashows a rectified ECG signal andFIG.7Bshows an FFT portion of an ECG signal from a separate vector. The time domain assessment based on the QRS detection results in a heartrate of about 103 bpm, whereas the frequency domain assessment based on the FFT results shows a heartrate of about 197 bpm. The reliability module506will determine the heart rates do not match and indicate to the detection module502that the ECG vector is unreliable.

Referring back toFIG.5, the reliability module506may use varies criteria in assessing the vectors. For example, the criteria may include defining ranges for the assessment that include: a criteria for matching (i.e., a reliable vector), criteria for unmatching (i.e., unreliable vector) with the range between the two criteria being indeterminate. For example, the criteria for a reliable vector may be preset as the difference between the HRs being within 5-15 beats per minute. In some embodiments, it may be within 10 beats per minute. In some embodiments, the criteria for an unreliable vector may be preset as the heart rates having a percentage difference greater than 10%. Differences in HRs between these two criteria would be indeterminate, which can be addressed by setting a default HR determining method and deciding the HR for that vector being the HR from the default HR determining method; tracking the history of that vector for being deemed reliable/unreliable and if the recent history shows the vector is unreliable for previous portions of ECG, deeming this vector unreliable for this particular portion of ECG. In other embodiments, different criteria for determining how to handle indeterminate vectors can be used.

Although in the examples above, the reliability module506uses time domain and frequency domain assessments described above, in other embodiments, the reliability module506may use different assessments. For example, methods of detecting R-R interval can include those that do not rectify the ECG signal. Other assessments can include without limitation, adaptive signal processing (including Kalman filtering), independent component analysis, principal component analysis. Further enhancements can include using adaptive learning techniques to accommodate changes in physiological signals that can vary over time.

As stated above, if the system uses only a single vector or channel, then the portions of ECG that are unreliable can be omitted from the rhythm analysis. For systems with multiple vectors or channels, if the reliability module506finds multiple channels that meet the selection criteria, the rhythm analysis is determined with a mathematical combination of the results of the reliable channels. For example, the mathematical combination could be the median value of the measurements (e.g., HR) of the reliable channels, or a mean of the measurements of the reliable channels. In some embodiments, the reliability module506may estimate a consistency for each channel and used the consistency to calculate a weighted average. The weighted average could include all available channels, or exclude channels that are deemed unreliable and indeterminate, only the channels deemed reliable, or the N most closely matched channels (e.g., where N might be 3 in a system having 4 or more channels). In some embodiments, if the reliability module506finds only one channel reliable in a multi-channel system, then the analysis would be reduced to just that channel. In some embodiments, if no channel is reliable, then the rhythm analysis may be omitted.

In some embodiments, the physiological module508may assess various physiological parameters to assist in a shockable event determination. The physiological module508may assess physiological parameters such as heartrate, blood pressure, respiratory rate, blood glucose level, sleep state, and the like. For example, heart rate can also be estimated from electroencephalography (EEG) signals, and sleep state can be estimated using brain wave signals or EEG signals. However, such physiological signals can be severely corrupted by external noise, artifact, and/or signals from other unwanted signal sources (e.g., the mother's QRS complexes when trying to detect fetal QRS complexes). The noise can be more severe when a physiological signal is collected with small, wearable, portable and non-invasive monitors.

In some embodiments, the detection module502may include a blood volume module510. The blood volume module510may receive data from a sensor capable of sensing a volume of blood in a portion of the patient's body. In one embodiment, the detection module502may couple to a device which may track blood volume, heart rate, temperature, and activity or accelerometer signals. The blood volume module510may communicate with the reliability module506to ensure the reliability of ECG signals. For example, the blood sensor may have less noise artifact in normal conditions than electrodes, and can be used for determining whether to deem a channel as unreliable if the heart rate from that channel is significantly different from that provided by the blood sensor.

Further, in some embodiments, the blood volume module510may use blood volume measurements from the blood volume sensor to improve the accuracy of shock/no shock decisions made by the detection module502. For example, when the rhythm analysis indicates a shock decision, but the blood volume data from the blood volume sensor indicates a stable blood volume, the action module504may delay or abort the shock as unnecessary. A stable blood volume may mean a blood volume measurement that indicates the patient is perfusing in a regular manner.

In some embodiments, the blood volume module510may also indicate a shockable condition when the detection module502has not found a shockable condition. If the rhythm analysis indicates a no shock decision but the blood volume module510indicates an unstable blood volume, the action module504may start the shock delivery process. In some embodiments, the blood volume module510may only indicate a shockable condition in a monitor zone. A monitor zone may include a non-shockable VT in which the patient's ECG is continuously monitored rather than a normal periodic monitoring. In some embodiments, a monitor zone may be set to a range of heart rate below the VT rate threshold. For example, if the VT rate threshold is 170 bpm, the monitor zone may be set to a range between 150 bpm and 170 bpm. However, if the blood volume module510indicates that the blood volume is stable or indeterminate, the detection module502will continue to continuously monitor the patient.

In some embodiments, the blood volume module510may receive and store the blood volume to sense and store a baseline blood volume metric as part of a set-up procedure. Once the set-up procedure is complete, the blood volume module510may have the blood sensor enter a low power mode. The blood volume module510may then activate the blood volume sensor to measure blood volume in response to the detection module502detecting an elevated heart rate. The blood volume module510may then compare the new blood volume measurements to the stored baseline and determine whether the blood is stable/unstable. If the blood volume is unstable, the action module504may take one or more actions, including issue an alert or beginning a shock sequence. By allowing the blood volume sensor to enter a sleep mode, the blood volume module510may prolong the time the blood volume sensor can operate without being recharged.

The action module504may use channels identified by the reliability module506to make a shock/no-shock decision. The action module504may analyze the heart rate and QRS data from the consistent channels to determine if the patient is having a cardiac event. In further embodiments, the action module504may also use parameters form the physiological module508and the blood volume module510to make a shock/no-shock decision.

At the same time, in some embodiments, the action module504may alert the patient of a potential electrode connectivity issue based at least in part on the inconsistent channels. For example, the consistency module506may ascertain common electrodes in inconsistent channels and pass this information on to the action module504. The action module504may then cause an alert to be issued to the patient to troubleshoot the issue.

In some embodiments, the action module504may prompt the patient to reduce activity if the number of ECG portions the reliability module506finds unsuitable exceeds a threshold. This can reduce the amount of noise generated by the patient's movement and increase the number of ECG portions that are deemed reliable.

The action module504may also use a combination of heart rate and QRS widths to make shock/no-shock decisions. The action module504may use methods similar to those disclosed in U.S. Pat. No. 10,016,614 entitled “Wearable Cardioverter Defibrillator (WCD) System Making Shock/No Shock Determinations by Aggregating Aspects of Multiple Patient Parameters” or U.S. Pat. No. 10,105,547 entitled “Wearable Cardioverter Defibrillator (WCD) Causing Patient's WRS Width to be Plotted Against the Heart Rate,” both of which are incorporated by reference herein.

FIG.8is a flow chart illustrating an example of a method800for WCD systems, in accordance with various aspects of the present disclosure. For clarity, the method800is described below with reference to aspects of one or more of the systems described herein.

At block802, the method800may receive at least one ECG signal for a predetermined period of time from a patient. The patient may be wearing a WCD system. The patient may have at least three ECG sensing electrodes attached to their skin and obtaining a signal. In some embodiments, the method800may receive multiple ECG signals. The predetermined period of time may be a snapshot in time or a continuously moving period of time.

In some embodiments, a patient may have sensing electrodes coupled to or somehow attached to them in such a way that the electrodes may sense a heart signal from the patient. The method800may obtain a signal from each of the at least three sensing electrodes. The method800may also define at least three channels between the at least three electrodes and obtain heart data for a predetermined time period from the at least three channels. The predetermined time period may be a snapshot of an ambulatory period for the patient. In some embodiments, the predetermined time period may be between five (5) seconds and two (2) minutes.

At block804, the method800may analyze the at least one ECG signal to determine a first heart rate using a first method. At block806, the method may analyze the at least one ECG signal to determine a second heart rate using a second method different from the first method. In some embodiments, the first method may be a time domain method and the second method may be a frequency domain method. In some embodiments, the first or second method may include adaptive signal processing, Kalman filtering, independent component analysis, and principal component analysis.

At block808, the method800may compare the first and second heart rates to each other. At block810, the method may classify the at least one ECG signal as reliable when a reliability threshold is satisfied. In some embodiments, the at least one ECG signal is classified as reliable when the first and second heart rates are within a predetermined number of beats. In some embodiments, the predetermined number of beats is within five to fifteen beats per minute. In some embodiments, the predetermined number of beats is within ten beats per minute. In further embodiments, the at least one ECG signal is classified as reliable when the first and second heart rates are within a predetermined percentage difference. In some embodiments, the predetermined percentage difference is less than twenty percent. In some embodiments, the predetermined percentage is approximately 10 percent.

In some embodiments, the method800may classify the at least one ECG signal as unreliable when an unreliability threshold is satisfied. The unreliability threshold may be equal to or greater than seven percent.

In some embodiments, the method800may perform a rhythm analysis using at least the first heart rate when the ECG signal is classified as reliable. In some embodiments, the method800may use an average of both the first and second heart rate or a median of the two heart rates. In further embodiments, if more than one channel is deemed reliable, the method800may perform a rhythm analysis using a mathematical combination of heart rates from the at least two ECG signals. For example, the method800may use an average, median, or other value derived from the multiple reliable heart rate calculations.

Thus, the method800may provide for determining reliable ECG channels. It should be noted that the method800is just one implementation and that the operations of the method800may be rearranged or otherwise modified such that other implementations are possible.

FIG.9is a flow chart illustrating an example of a method900for WCD systems, in accordance with various aspects of the present disclosure. For clarity, the method900is described below with reference to aspects of one or more of the systems described herein.

At block902, the method900may receive physiological data from the patient for the period of time. The physiological data may include heartrate, blood pressure, respiratory rate, blood glucose level, activity level, sleep state, and the like. For example, heart rate variability can also be estimated from electroencephalography (EEG) signals, and sleep state can be estimated using brain wave signals or EEG signals. Respiratory rate and activity level such as accelerometer data can indicate a patient is working out or moving.

At block904, the method900may analyze the physiological data for a shockable condition. In some embodiments, the method900may compare the physiological data to heart rate data. For example, the physiological data may support or contrast a shockable condition.

Thus, the method900may provide for determining reliable ECG signals. It should be noted that the method900is just one implementation and that the operations of the method900may be rearranged or otherwise modified such that other implementations are possible.

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

Some technologies or techniques described in this document may be known. Even then, however, it is not known to apply such technologies or techniques as described in this document or for the purposes described in this document.

This description includes one or more examples, but this fact does not limit how the invention may be practiced. Indeed, examples, instances, versions, or embodiments of the invention may be practiced according to what is described, or yet differently, and also in conjunction with other present or future technologies. Other such embodiments include combinations and sub-combinations of features described herein, including, for example, embodiments that are equivalent to the following: providing or applying a feature in a different order than in a described embodiment; extracting an individual feature from one embodiment and inserting such feature into another embodiment; removing one or more features from an embodiment, or both removing a feature from an embodiment and adding a feature extracted from another embodiment while providing the features incorporated in such combinations and sub-combinations.

In general, the present disclosure reflects preferred embodiments of the invention. The attentive reader will note, however, that some aspects of the disclosed embodiments extend beyond the scope of the claims. To the respect that the disclosed embodiments indeed extend beyond the scope of the claims, the disclosed embodiments are to be considered supplementary background information and do not constitute definitions of the claimed invention.

In this document, the phrases “constructed to,” “adapted to,” and/or “configured to” denote one or more actual states of construction, adaptation, and/or configuration that is fundamentally tied to physical characteristics of the element or feature preceding these phrases and, as such, reach well beyond merely describing an intended use. Any such elements or features can be implemented in a number of ways, as will be apparent to a person skilled in the art after reviewing the present disclosure, beyond any examples shown in this document.

Incorporation by reference: References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.

Parent patent applications: Any and all parent, grandparent, great-grandparent, etc. patent applications, whether mentioned in this document or in an Application Data Sheet (“ADS”) of this patent application, are hereby incorporated by reference herein as originally disclosed, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith.

Reference numerals: In this description, a single reference numeral may be used consistently to denote a single item, aspect, component, or process. Moreover, a further effort may have been made in the preparation of this description to use similar though not identical reference numerals to denote other versions or embodiments of an item, aspect, component, or process that are identical or at least similar or related. Where made, such a further effort was not required but was nevertheless made gratuitously so as to accelerate comprehension by the reader. Even where made in this document, such a further effort might not have been made completely consistently for all of the versions or embodiments that are made possible by this description. Accordingly, the description controls in defining an item, aspect, component, or process rather than its reference numeral. Any similarity in reference numerals may be used to infer a similarity in the text, but not to confuse aspects where the text or other context indicates otherwise.

The claims of this document define certain combinations and subcombinations of elements, features, and acts or operations, which are regarded as novel and non-obvious. The claims also include elements, features, and acts or operations that are equivalent to what is explicitly mentioned. Additional claims for other such combinations and subcombinations may be presented in this or a related document. These claims are intended to encompass within their scope all changes and modifications that are within the true spirit and scope of the subject matter described herein. The terms used herein, including in the claims, are generally intended as “open” terms. For example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” etc. If a specific number is ascribed to a claim recitation, this number is a minimum but not a maximum unless stated otherwise. For example, where a claim recites “a” component or “an” item, it means that the claim can have one or more of this component or this item.

In construing the claims of this document, the inventor(s) invoke 35 U.S.C. § 112(f) only when the words “means for” or “steps for” are expressly used in the claims. Accordingly, if these words are not used in a claim, then that claim is not intended to be construed by the inventor(s) in accordance with 35 U.S.C. § 112(f).