DIGITAL STETHOSCOPE USING MECHANO-ACOUSTIC SENSOR SUITE

A system and method for sensing acoustic data generated by a user is disclosed. The system includes a wearable sensor including an accelerometer sensor in contact with the skin of the patient to measure mechano-acoustic signals generated from a bodily function and generate an accelerometer waveform. A controller receives the accelerometer waveform from the accelerometer sensor to determine a measurement of the bodily function. The wearable sensor includes features to directly contact the skin and isolate the accelerometer sensor to produce more accurate output signals.

TECHNICAL FIELD

The present disclosure relates generally to mechano-acoustical body sensors. More particularly, aspects of this disclosure relate to using wearable mechano-acoustic sensors to measure acoustic signals from a body.

BACKGROUND

Integrated circuits (ICs) are the cornerstone of the information age and the foundation of today's information technology industries. The integrated circuit, a.k.a. “chip” or “microchip,” is a set of interconnected electronic components, such as transistors, capacitors, and resistors, which are etched or imprinted onto a semiconducting material, such as silicon or germanium. Integrated circuits take on various forms including, as some non-limiting examples, microprocessors, amplifiers, flash memories, application specific integrated circuits (ASICs), static random access memories (SRAMs), digital signal processors (DSPs), dynamic random access memories (DRAMs), erasable programmable read only memories (EPROMs), and programmable logic. Integrated circuits are used in innumerable products, including computers (e.g., personal, laptop, and tablet computers), smartphones, flat-screen televisions, medical instruments, telecommunication and networking equipment, airplanes, watercraft, and automobiles.

Advances in integrated circuit technology and microchip manufacturing have led to a steady decrease in chip size and an increase in circuit density and circuit performance. The scale of semiconductor integration has advanced to the point where a single semiconductor chip can hold tens of millions to over a billion devices in a space smaller than a U.S. penny. Moreover, the width of each conducting line in a modern microchip can be made as small as a fraction of a nanometer. The operating speed and overall performance of a semiconductor chip (e.g., clock speed and signal net switching speeds) has concomitantly increased with the level of integration. To keep pace with increases in on-chip circuit switching frequency and circuit density, semiconductor packages currently offer higher pin counts, greater power dissipation, more protection, and higher speeds than packages of just a few years ago.

The advances in integrated circuits have led to related advances within other fields. One such field is sensors for monitoring body readings such as temperature, blood pressure, heart rate, and the like. Advances in integrated circuits have allowed sensors to become smaller and more efficient, while simultaneously becoming more capable of performing complex operations. Other advances in the field of sensors and circuitry in general have led to wearable circuitry, a.k.a. “wearable devices” or “wearable systems.” Within the medical field, as an example, wearable devices have given rise to new methods of acquiring, analyzing, and diagnosing medical issues with patients, by having the patient wear a sensor that monitors specific characteristics. Related to the medical field, other wearable devices have been created within the sports and recreational fields for the purpose of monitoring physical activity and fitness. For example, a user may don a wearable device, such as a wearable running coach, to measure the distance traveled during an activity (e.g., running, walking, etc.), and measure the kinematics of the user's motion during the activity.

SUMMARY

Certain bodily functions may be monitored by analyzing sounds from the heart, lungs, and intestines. Such acoustic data may assist in diagnosis of abnormalities in the respiratory system, circulatory system, or digestion system, among others. One well-known instrument used by physicians is a manual stethoscope that a medical practitioner uses to listen to sounds generated by the respiratory system, circulatory system, or digestion system in a patient. However, a manual stethoscope is not sensitive to a full range of sounds and requires human interpretation of the sounds. Further a manual stethoscope is not capable of discerning other useful sound signals that may not be detectable by the human ear.

Recently, electrical acoustic sensors have made the functions of a traditional stethoscope possible in an electronic stethoscope that provides amplification of detected sounds so that it is easier to detect heart and lung sounds. However, traditional electronics with rigid packaging cannot measure mechanical vibrations with sufficient sensitivity due to lack of direct mechanical coupling to skin. Further, since such instruments are generally not wearable, they cannot provide continuous monitoring of a patient. To the extent that acoustical sensing has been used in a wearable device, an accelerometer sensor has been used for sensing mechano-acoustical signals. However, the internal components of such devices may impede the accurate determination of acoustic signals from a patient due to dampening. Without unique design and positioning of the accelerometer sensor in the sensor configuration, and verification with a heartbeat such as an ECG signal, useful fine signals that may be real physiological signals cannot be used.

Thus, there is a need for an accurate acoustic system to determine acoustic data from a patient. There is a further need for a wearable sensor that allows the continuous sensing of acoustic signals from a patient. There is also a need for an accurate wearable acoustic sensor where an accelerometer is configured on the sensor housing that minimizes interference.

One disclosed example is a sensor system for sensing sound associated with a bodily function of a user. The system includes a wearable sensor including a planar mechano-acoustic conductor in direct contact with the skin of the user to measure mechano-acoustic vibration signals generated from a bodily function and generate a vibration waveform. A controller receives the mechano-acoustic vibration waveform from the wearable sensor to determine a measurement of the bodily function.

Another example is a wearable sensor for detecting a mechano-accoustical signal from a user. The sensor includes a rectangular planar body composed of encapsulation material. A first island is located in the middle of the rectangular planar body. A second island includes an accelerometer. The second island is isolated from the first island using flexible interconnections to buffer vibrations. The second island is located in proximity to a corner of the rectangular planar body.

Another example is a method of detecting an acoustic signal from a user. A wearable sensor including a planar mechano-acoustic conductor is attached in direct contact with the skin of the user to measure mechano-acoustic vibration signals generated from a bodily function and generate a vibration waveform. A measurement of the bodily function is determined from the mechano-acoustic vibration waveform via a controller.

The present disclosure is susceptible to various modifications and alternative forms, and some representative embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present inventions can be embodied in many different forms. There are shown in the drawings, and will herein be described in detailed, representative embodiments with the understanding that the present disclosure is to be considered as an exemplification or illustration of the principles of the present disclosure and is not intended to limit the broad aspects of the disclosure to the embodiments illustrated. To that extent, elements and limitations that are disclosed, for example, in the Abstract, Summary, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference, or otherwise. For purposes of the present detailed description, unless specifically disclaimed: the singular includes the plural and vice versa; and the word “including” means “including without limitation.” Moreover, words of approximation, such as “about,” “almost,” “substantially,” “approximately,” and the like, can be used herein in the sense of “at, near, or nearly at,” or “within 3-5% of,” or “within acceptable manufacturing tolerances,” or any logical combination thereof, for example.

FIG. 1shows a monitoring system102that can be employed by a user100for monitoring of acoustic data such as heartbeat or blood circulation sounds. The system102can include multiple wearable sensor devices110,112,114, and116. Each of the wearable sensor devices110,112,114, and116can include an accelerometer that can detect the motion and vibrations transmitted to the skin of the user100produced by the organs of the body, such as the heart and circulatory system in this example. The wearable sensor devices110,112,114, and116may also function as a heartbeat sensor that can, for example, obtain an electro-cardiogram (ECG) signal, a seismocardiogram (SCG) waveform, or a PPG signal indicative of the heartbeat.

In this example, the sensors110,112,114, and116are attached to the skin at various locations on the body to efficiently obtain acoustic data relating to the function of the heart of the user100. Thus the wearable sensor device110is preferably positioned on the chest in the position shown inFIG. 1in proximity to the aortic valve of the heart. The wearable sensor device112is preferably positioned on the chest in the position shown inFIG. 1near the transcuspid value of the heart. The wearable sensor device114is preferably positioned on the chest in the position shown inFIG. 1near the pulmonary valve of the heart. The wearable sensor device116is preferably positioned on an area of the chest near the mitral valve of the heart. However, as will be explained below, the sensor devices such as the sensor device110can be located in any area relative to the source of desired acoustic signals, such as in proximity to the lungs to monitor respiratory functions or the intestines to monitor digestion functions. Of course less than four or more than four of wearable sensor devices such as the devices110,112,114, and116can be used depending on the desired acoustic data.

The sensor device110produces an output signal that is based on sampling of accelerometer signals indicative of mechano-acoustic motion and vibration generated by heart activity (e.g., blood flow between heart chambers) from the aortic valve. The wearable sensor device110can also produce other output signals (e.g., an ECG or similar signal) that is based on sampling ECG electrodes or other inputs. Similarly, in this example, the other sensor devices112,114, and116also produce an output signal that is based on sampling of accelerometer signals from mechano-acoustic motion and vibration generated by blood flow through their corresponding valves. Of course other acoustic data may be detected by attaching another sensor or moving one of the sensor devices110,112,114, and116to another location on the user100. For example, respiratory monitoring can be performed by the system102by sampling accelerometer signals from mechano-acoustic motion and vibration generated by airflow (e.g., expansion and contraction of the airway and sound and/or vibrations resulting from airflow passing through an airway).

The wearable sensor devices110,112,114, and116can be in communication with a smart device or hub such as a user device130. The user device130can be a computing device such as a smart phone, a tablet, a laptop or desktop computer, a personal digital assistant, or a network of computers (e.g., a cloud or a cluster). The user device130can be used to control, configure, and/or program the wearable sensor devices110,112,114, and116. For example, the user device130can configure the wearable sensor devices to sense certain audio signals related to a particular function such as heart monitoring. Identification and location information may also be set for each of the wearable sensor devices by the user device130for the particular function. Although the wearable sensor devices110,112,114, and116, as described herein, are used for non-invasive acoustic sensing for bodily functions such as respiratory and/or heart monitoring, each can have other measurement and sensing functions in relation to the user100.

The acoustic data from the wearable sensor devices110,112,114, and116representative of heart activity and, optionally, the data from the ECG sensor representative of the heartbeat signal can be uploaded to a cloud storage server140periodically (e.g., in time-stamped blocks) or continuously (e.g., streamed) and analyzed by applications running on one or more cloud application servers142from the sensor devices directly or via the user device130. The data can be processed in real time or using post-processing techniques. The user can access the data, the analysis applications or the output of the applications by accessing the cloud server142, such as through a website.

As will be explained below, any of the sensors110,112,114, and116may be used to sense and store accelerometer data representative of sensed acoustical data and ECG or other heartbeat generated data. As will be explained below, the user device130can include software that processes the sensed data in order to determine the occurrence and characterization of conditions such as abnormal heart operation, respiratory abnormalities, digestive abnormalities, etc. Alternatively, one or more cloud applications executed on the cloud application server160can process the data received from the sensors110,112,114, and116(e.g., via the user device130) to the determination of the occurrence and characterization of detected abnormalities based on the sensed acoustic data.

FIG. 2shows a diagrammatic example of a wearable sensor device200such as the sensor devices110,112,114, and116inFIG. 1in accord with aspects of the present disclosure. The wearable device200can provide conformal sensing capabilities, providing mechanically transparent close contact with a surface (such as the skin or other portion of the body) to provide measurement and/or analysis of physiological information from the user100. According to some embodiments, the wearable device200senses, measures, or otherwise quantifies the mechano-acoustic signals of at least one body part of a user upon which the wearable device200is located. Additionally, or in the alternative, according to some embodiments, the wearable device200senses, measures, or otherwise quantifies the temperature of the environment of the wearable device200, including, for example, the skin and/or body temperature at the location that the wearable device200is coupled to the body of a user. Additionally, or in the alternative, according to some embodiments, the wearable device200senses, measures, or otherwise quantifies other characteristics and/or parameters of the body (e.g., human or animal body) and/or surface of the body, including, for example, temperature, motion, electrical signals associated with cardiac activity (e.g., ECG), electrical signals associated with muscle activity (e.g., electromyography (EMG)), changes in electrical potential and impedance associated with changes to the skin (e.g., galvanic skin response), electrical signals of the brain (e.g., electroencephalogram (EEG)), bioimpedance monitoring (e.g., body-mass index, stress characterization, and sweat quantification), and optically modulated sensing (e.g., photoplethysmography (PPG) and pulse-wave velocity), and the like.

The wearable device200described herein can be formed as a patch. The patch can be flexible and stretchable, and can include stretchable and/or conformal electronics and/or conformal electrodes disposed in or on a flexible and/or stretchable substrate. Alternatively, the wearable device200can be rigid but otherwise attachable to a user. In accordance with some embodiments of the invention, the wearable device200can include portions that are stretchable and/or conformable and portions that are rigid. Thus, the wearable device200can be any device that is wearable on a user, such as coupled to the skin of the user, to provide measurement and/or analysis of physiological information of the user. For example, the wearable device can be adhered to the body by adhesive (e.g., a pressure sensitive adhesive), held in place against the body by tape or straps, or held in place against the body by clothing. The more conformal the sensing device, the more likely it is to stay in position on the skin and produce more reliable and accurate sensor data.

In general, the wearable device200ofFIG. 2can include at least one processor201connected to one or more associated memory storage modules203. The wearable device200can further include one or more sensors, such as an accelerometer205and/or a temperature sensor213and/or an optical sensor217, connected to the processor201. The wearable device200can optionally include one or more wireless transceivers, such as transceiver207, connected to processor201for communicating with other sensor devices such as the sensor devices110and112or other computing devices such as the user device130inFIG. 1. The wearable device200can also include a power source209connected to the components of the wearable device200to power the processor201, the memory203, and each of the other components of the wearable device200. In accordance with some embodiments, the wearable device200can be configured to draw power from a wireless connection or an electromagnetic field (e.g., an induction coil, an NFC reader device, microwaves, and light). The wearable device can include, for example, an induction coil and a wireless charging circuit that produces electric power when exposed to an electric or magnetic field to charge the battery and provide power to the wearable device.

The processor201can be used as a controller that is configured to control the wearable device200and components thereof based on computer program code (e.g., one or more software modules). Thus, the processor201can control the wearable device200to receive and store sensor data from one or more of the sensors205,213,217. The sensor data can be calibrated and used to determine measures indicative of temperature, motion, and/or other physiological data (e.g., ECG, EMG, EEG signals and data), and/or analyze such data indicative of temperature, motion, and/or other physiological data according to the principles described herein.

The memory storage module203can be configured to save the generated sensor data (e.g., the time when a pulse in blood flow is sensed, accelerometer205information, temperature sensor213information, or other physiological information, such as ECG, EMG, EEG signals and data) or information representative of acceleration and/or temperature and/or other physiological information derived from the sensor data. Further, according to some embodiments, the memory storage module203can be configured to store the computer program code that controls the processor201. In some implementations, the memory storage module203can include volatile and/or non-volatile memory. For example, the memory storage module203can include dynamic memory, flash memory, static memory, solid state memory, removable memory cards, or any combination thereof. In certain examples, one or more of the memory storage modules203can be removable from the wearable device200. In some implementations, one or more of the memory storage modules203can be local to the wearable device200, while in other examples one or more of the memory storage modules203can be remote from the wearable device200. For example, one or more of the memory storage modules203can include the internal memory of a smartphone such as the user device130inFIG. 1that is connected by a wired or wireless connection to the wearable device200, such as through radio frequency communication protocols including, for example, WiFi, Zigbee, Bluetooth®, medical telemetry, and near-field communication (NFC), and/or optically using, for example, infrared or non-infrared LEDs. In such an example, the wearable device200can optionally communicate (e.g., wirelessly) with the user device130via an application (e.g., program) executing on the user device130.

In some embodiments, the generated data, including the temperature information, the acceleration information, and/or the other physiological information (e.g., ECG, EMG, EEG etc.), can be stored in one or more of the memory storage modules203for processing at a later time. Thus, in some embodiments, the wearable device200can include more than one memory storage module203, such as one volatile and one non-volatile memory storage module203. In other examples, the memory storage module203can store the information indicative of motion (e.g., acceleration information), temperature information, physiological data, or analysis of such information indicative of motion, temperature, and physiological data according to the principles described herein, such as storing historical acceleration information, historical temperature information, historical extracted features, and/or historical locations. The memory storage module203can also store time and/or date information about when the information was received from the sensor. For example, each data element or block of data elements can be associated with a date and/or time at which it was created.

Although described as the processor201being configured according to computer program code in the form of software and firmware, the functionality of the wearable device200can be implemented based on hardware, software, or firmware or a combination thereof. For example, the memory storage module203can include computer program code in the form of software or firmware that can be retrieved and executed by the processor201. The processor201executes the computer program code that implements the functionality discussed below with respect to determining the on-body status of the wearable device200, the location of the wearable device200on a user, and configuring functionality of the wearable device200(e.g., based on the on-body status and sensed location). Alternatively, one or more other components of the wearable device200can be hardwired to perform some or all of the functionality.

The power source209can be any type of rechargeable (or single use) power source for an electronic device, such as, but not limited to, one or more electrochemical cells or batteries, one or more photovoltaic cells, or a combination thereof. In the case of the photovoltaic cells, the cells can charge one or more electrochemical cells and/or batteries. In accordance with some embodiments, the power source209can be a small battery or capacitor that stores enough energy for the device to power up and execute a predefined program sequence before running out of energy, for example, an NFC-based sensing device.

As discussed above, the wearable device200can include one or more sensors, such as the accelerometer205, a temperature sensor213, electrical contacts215(e.g., electrical contacts or electrodes), and/or an optical sensor217. In accordance with some embodiments, one or more of the sensors, such as accelerometer205, the optical sensor217, and/or electrical contacts215, can be separate components from the wearable device200. That is, the wearable device200can be connected (by wire or wirelessly) to each sensor (e.g., accelerometer205, temperature sensor213, electrical contacts215, and optical sensor217). This enables the wearable device200to sense conditions at one or more locations that are remote from the wearable device200. In accordance with some embodiments, the wearable device200can include one or more integral sensors in addition to one or more remote sensors.

The accelerometer205measures and/or generates acceleration information indicative of a motion and/or acceleration of the wearable device200, including information indicative of a user wearing, and/or body parts of the user wearing, the wearable device200. In accordance with one embodiment, the accelerometer205within the wearable device200can include a 3-axis accelerometer that generates acceleration information with respect to the x-axis, the y-axis, and the z-axis of the accelerometer based on the acceleration experienced by the wearable device200. Alternatively, the wearable device200can include three independent accelerometers (not shown for illustrative convenience) that each generate acceleration information with respect to a single axis, such as the x-axis, the y-axis, or the z-axis of the wearable device200. Alternatively, the wearable device200can include an inertial measurement unit (IMU) that measures the angular velocity, the orientation, and the acceleration using a combination of one or more accelerometers, gyroscopes, and magnetometers. Thus, although generally referred to herein as an accelerometer205, the accelerometer205can be any motion sensing element or combination of elements that provides acceleration information. In this example, the accelerometer may be specialized to detect mechano-acoustic vibrations. Of course other acoustic sensors such as a microelectromechanical system (MEMs) microphone may be used. A MEMs microphone will transduce the pressure waves propagating from the skin, generated by mechanical vibrations from within the body, into electrical signals that processor201can divert to memory storage module203or transceiver207.

In this example, the accelerometer205is an MPU-6500 manufactured by Invensense. According to some embodiments, the accelerometer205includes a detection range of ±2 times the force of gravity (Gs). However, the range can vary, such as being ±16 Gs or ±2 Gs. Further, the accelerometer205can have a sampling rate of 100 hertz (Hz) such that each second the accelerometer205generates 300 points of acceleration information, or 100 points within each axis. However, the sampling rate can vary, such as being 20 Hz to 500 Hz.

According to some embodiments, one or more sensors of the wearable device200, such as the accelerometer205, can include a built-in temperature sensor, such as the temperature sensor211within the accelerometer205. For example, the temperature sensor211within the accelerometer205can be used to calibrate the accelerometer205over a wide temperature range and to measure the temperature of the area of the body that the accelerometer205is coupled to. Other temperature sensors included with other device components can also be used. Other than the accelerometer205, and temperature sensor211, other subcomponents or elements of the wearable device200can include one or more microelectromechanical system (MEMS) components within the wearable device200that is designed to measure motion or orientation (e.g., angular-rate gyroscope, etc.).

In accordance with some embodiments of the invention, an accelerometer (or an acoustic sensor) such as the accelerometer205of the wearable sensor device200shown inFIG. 2can be used to detect and measure a biometric signal known as a seismocardiogram (SCG). The SCG signal can be detected and recorded by the accelerometer205of the wearable sensor device200, for example, due to the tight mechano-acoustic coupling of the wearable sensor device200to the skin (or other organ) that enables the device to sense mechano-acoustic waveforms that propagate from the internal organs of the body to the surface of the skin. These waveforms are transduced by the onboard accelerometer205of the sensor device200into electrical signals that the device can measure, record, and store and/or transmit to other devices such as the user device130inFIG. 1. In accordance with some embodiments, the SCG waveform can be more reliable than measurement of the ECG for sensors that are attached at points in the body that are relatively far from the heart or chest of the patient.

Alternatively, or in addition, the wearable device200can include a discrete temperature sensor, such as the temperature sensor213, which can be positioned in a different location from the wearable device200. The wearable device200can use the temperature information detected by the temperature sensor211and/or the temperature sensor213according to various methods and processes. For purposes of convenience, reference is made below to the temperature sensor211. However, such reference is not limited to apply only to the temperature sensor211, but applies to any one or more temperature sensors within or connected to the wearable device200.

The electrical contacts215can be formed of conductive material (e.g., copper, silver, gold, aluminum, a hydrogel, conductive polymer, etc.) and provide an interface between the wearable device200and the skin of the user100, for receiving electrical signals (e.g., ECG, EMG, etc.) from the skin. The electrical contacts215can include one or more electrical contacts215, such as two electrical contacts215, electrically connecting the skin of the user100to an amplifier circuit that can be part of an analog front end circuit216, to amplify and condition electrical signals (e.g., ECG, EMG, etc.). With two electrical contacts215, one contact can be electrically configured as a positive contact and the other contact can be electrically configured as a negative contact. However, in some aspects, there may be more than two electrical contacts, such as four electrical contacts215(e.g., two positive and two negative electrical contacts), six electrical contacts215, etc. The electrical contacts215may also be used as an acoustic contact surface for efficient transmission of acoustic signals to the accelerometer205.

The optical sensor217can measure the photoplethysmography (PPG) signal when placed on the skin's surface, allowing for the monitoring of various biometrics including, but not limited to, heart rate, respiration, and blood oxygen measurements. The optical sensor217can include one or more light emitters that can emit red, green, infrared light, or a combination thereof and one or more optical transducers (e.g., photodiode, CCD sensors). Using the one or more optical transducers, the optical sensor217can sense the wavelength of the reflected light. In this example, the optical sensor217illuminates the skin and the reflected light changes intensity based on the concentration of oxygen in a blood vessel such as an artery or a capillary bed. Thus, a pulse can be detected as a change in the amount of the reflected light due to a change in the concentration of oxygen in a blood vessel and thus the reflected light detected by the optical sensor217. The system can contain an array of optical sensors in a one-dimensional or two-dimensional grid. In this configuration, the optical sensors can measure reflected light (pulse oxygenation and pulse waveforms) at multiple locations along the vasculature, enabling measurement of time of flight and pulse wave velocity over a given distance (e.g., the separation distance between individual optical sensors.

In addition to the above-described components, the wearable device200can include one or more additional components without departing from the spirit and scope of the present disclosure. Such components can include a display (e.g., one or more light-emitting diodes (LEDs), liquid crystal display (LCD), organic light-emitting diode (OLED)), a speaker, a microphone, a vibration motor, a barometer, a light sensor, a photoelectric sensor, or any other sensor for sensing, measuring, or otherwise quantifying parameters and/or characteristics of the body. In other embodiments of the invention, the wearable device200can include components for performing one or more additional sensor modalities, such as, but not limited to, hydration level measurements, conductance measurements, and/or pressure measurements. For example, the wearable device200can be configured to, or include one or more components that, perform any combination of these different types of sensor measurements, in addition to the accelerometer205and temperature sensor211.

Referring back to the temperature sensor211, according to some embodiments, the primary purpose of the temperature sensor211is for calibrating the accelerometer205. Accordingly, the temperature sensor211does not rely on direct contact to an object to detect the temperature. By way of example, the temperature sensor211does not require direct contact to the skin of a user when coupled to the user to determine the skin temperature. For example, the skin temperature affects the temperature information generated by the wearable device200without direct contact between the temperature sensor211and the skin. Accordingly, the temperature sensor211can be fully encapsulated and, therefore, be waterproof for greater durability. The thermal conductivity of the encapsulating material can be selected to control the ability of the temperature sensor211to detect the temperature without direct contact.

The wearable device200can be constructed of a flexible and/or stretchable printed circuit (e.g., a flex printed circuit board) that can be encapsulated in an elastomer (e.g., silicone, poly urethane, PDMS) that enables the device to stretch and bend. In accordance with some embodiments of the invention, the wearable device200can be constructed to have modulus of elasticity (e.g., Young's modulus) similar to the skin of the user or subject. This construction enables the wearable device200to be tightly adhered to the skin using a pressure sensitive adhesive such that the sensors in the wearable device are able to detect the slightest motion of the skin as well as the muscles and organ under the skin in the area of the body where the wearable device200is attached. This tight coupling can be accomplished using a thin layer (e.g., less than 150 um) of pressure sensitive adhesive and a thin layer (e.g., less than 150 um) of encapsulating material (e.g., silicone). The adhesive and encapsulating materials can be selected to faithfully transmit to the sensors any vibrations or motions from the skin to which it is attached.

The form factor of the wearable device200allows positioning and repositioning of the sensor devices at different locations on the body of the user100in order to achieve the highest quality of mechano-acoustic data from the accelerometer205. In this example, the sensor devices110,112,114, and116placed on the chest of the user100inFIG. 1can each be configured in electrocardiogram (ECG) mode in order to receive the ECG signal from the user's heart. The ECG signal can be processed by the respective wearable sensor to detect the R-wave portion of the ECG signal and determine a pulse rate from the time-period measured or calculated between the R-waves (e.g., the peaks of the R-wave). Sensor devices110,112,114, and116can be a wearable sensor device200with the electrical contacts removed (or disabled) that is coupled to the skin (e.g., by an adhesive) and conforms to the body without applying pressure on the arterial wall that would alter the natural motion or flow (and impede the accuracy of the measured motion and vibration signals). This tight coupling also reduces the motion artifacts while enabling high resolution and accurate sensing.

In accordance with some embodiments of the invention, the system shown inFIG. 1can be used for detection and recording of heartbeat, respiratory, or digestion acoustic data. By designing the accelerometer and encapsulation (to be sub-1 mm and low modulus) to allow intimately coupling with the skin, very fine signals from the chest may be achieved, including coughing, wheezing, and detection of valves opening and closing. Detection of heart murmurs due to improper valve closure and opening may also be detected. The patch may be positioned at a number of locations on the user100where vibrations due to pressure waves, sound pressure, and mechano-acoustics are present.

FIGS. 3A-3Dare graphs of signal outputs from the wearable sensors110,112,114, and116inFIG. 1.FIG. 3Aincludes an ECG waveform310and an accelerometer data output signal312taken from the wearable sensor110near the aortic valve of the heart. FIG.3B includes an ECG waveform320and an accelerometer data output signal322taken from the wearable sensor112near the transcuspid valve of the heart.FIG. 3Cincludes an ECG waveform330and an accelerometer data output signal332taken from the wearable sensor114near the pulmonary valve of the heart.FIG. 3Bincludes an ECG waveform340and an accelerometer data output signal342taken from the wearable sensor116near the mitral valve of the heart. These outputs show how the system102can relate these mechanical vibrations to faster electrical markers driven by cardiac activity or muscle activity. These electrical signals help to verify whether or not the mechano-acoustic signals are physiological or due to motion artifacts. Each location may be used in aggregate with the others to form a cohesive, holistic picture of the cardiac cycle. That is, knowing the ECG and mechano-acoustic signals from each of these four locations and their relative timings can inform an end-user (e.g. physician, cardiologist, patient, etc.) whether the heart valves are operating correctly and are within timing tolerances. If they are not, the heart's pumping efficiency degrades and prevents optimal blood flow through the vasculature. For example, this reduction in efficiency occurs when any of these four valves develops stenosis, or a narrowing of the valve. This can result in the inability of the valve to close properly, promoting backflow of blood within the heart, degrading the pumping mechanics. The mechano-acoustic recording allows one to verify the correct morphology of the waveform; any aberrations from the ideal would indicate an issue with the valve.

FIG. 4Ais a top view of the internal components of the wearable sensor device110andFIG. 4Bis a bottom perspective view of internal components of the wearable sensor device110inFIG. 1. The wearable sensor device110includes a number of islands410,412,414,416, and418as well as a battery420. The islands410,412,414,416, and418, and the battery420are coupled together by flexible conductive interconnections422and are generally positioned in the same horizontal plane. In this example, the flexible conductive interconnections422are in a serpentine shape, but other shapes may be used. In this manner, the wearable sensor device110can be in conformal contact and flex with movements of a user's skin due to the flexible conductive interconnections422.

In this example, the overall shape of the sensor device110and the plane including the islands410,412,414,416, and418and the battery420is a rectangular shape. The battery420is centered relative to the rectangular shape and the islands410and412are arranged on one wing of the sensor device110relative to the battery420. The island412is further isolated at a corner of the sensor device110. Similarly islands416and418are arranged on an opposite wing of the sensor device110opposite the wing including the islands410and412. As will be explained below, the location of the islands410,412,416, and418on the wings allows better isolation from dampening effects from the other components of the sensor.

The islands410,412,414,416, and418can be used to support different components (e.g., integrated circuits) on their respective top surfaces as shown inFIG. 4A. In this example, a flash memory chip430is mounted on the island414. A heart rate sensor front end integrated circuit432is mounted on the island410. A microcontroller434is mounted on the island410. A motion sensor 6-axis internal measurement (IMU) integrated circuit436that may be used for the accelerometer205shown inFIG. 2is mounted on the island412. A power management integrated circuit438is mounted on the island414. A series of support components440are mounted on the island416. The memory chip430in this example can be a 64 MB memory chip that is part of the memory storage module203inFIG. 2. The battery420has a flat surface442that mounts an optical sensor integrated circuit444. As will be explained below, the arrangement of the accelerometer components436on the island412that are on a wing of the sensor device110are separated from the other components by the soft and flexible interconnects422that isolate the accelerometer from sound and vibration produced by or received by other islands and components of the sensor device110.

As shown inFIG. 4B, the bottom of the islands418and412can include respective electrodes450and452that are in contact with the skin when the wearable sensor110is worn by the user. The electrodes450and452can be electrically connected (e.g., either directly or through an amplifier) to the heart rate sensor integrated circuit432. Of course, the electrodes450and452can be included as parts of other islands or in other locations on the islands other than those shown inFIG. 4B. The electrodes450and452constitute the electrical contacts215inFIG. 2. In this example, the battery420and the power management integrated circuit438constitute the power source209inFIG. 2.

In this example, the microcontroller434is an onboard nRF52832 system on chip manufactured by Nordic Semiconductor that performs the functions of the processor201and transceiver207inFIG. 2. In this example, the microcontroller434is an ultra-low power multiprotocol system on chip suited for Bluetooth® low energy communication, ANT and 2.4 GHz ultra low-power wireless applications. The system on chip includes a CPU that supports DSP instructions, a Floating Point Unit (FPU), single-cycle multiply and accumulate, and hardware divide for energy-efficient process of computationally complex operations. The microcontroller434includes an embedded transceiver that supports Bluetooth low energy, ANT and proprietary 2.4 GHz protocol stack. The microcontroller also includes a multiprotocol radio that includes DMA for direct memory access during packet send and retrieve.

In this example, the heart rate sensor front end integrated circuit432is an ADS1191 chip manufactured by Texas Instruments and can be an integrated part of the processor201inFIG. 2. The front end integrated circuit432in this example is a multichannel, simultaneous sampling, 16-bit, delta-sigma analog-to-digital converter (ADCs) with a built-in programmable gain amplifier (PGA), internal reference, and an onboard oscillator. The front end integrated circuit432has a flexible input multiplexer per channel that can be independently connected to the internally-generated signals for test, temperature, and lead-off detection. The heart rate sensor front end integrated circuit432makes electrical contact with the subject's skin via electrodes450and452on the skin-facing side of the device as shown inFIG. 4B.

The optical sensor integrated circuit440is a MAX30101 chip manufactured by Maxim Integrated and serves as the optical sensor217inFIG. 2. In this example, the optical sensor integrated circuit440includes internal LEDs, photodetectors, optical elements, and low-noise electronics with ambient light rejection. The sensor includes a reflective LED based heart-rate monitor and a pulse oximeter sensor.

FIG. 4Cis a side view of the wearable sensor110showing the island412and electrode450in contact with the skin460of the user. The island412and the other internal components are encapsulated in an encapsulation material470that is flexible to allow the wearable sensor device110to conform with the distortions in the skin460. In this example, the encapsulation material470is an elastomer (e.g., silicone, poly urethane, PDMS), but any sufficiently protective and flexible material may be used. As shown inFIG. 4C, the encapsulation material470is not formed over the electrode450to allow direct contact with the skin and thus provide the most highly conductive path for transmission of the mechano-acoustic signal to the mechano-acoustic sensor (e.g., the accelerometer or IMU). Because of the direct contact with the skin provided by the electrode450, this configuration provides a highly effective, low distortion mechano-coustic path from the skin to the integrated circuit436that is part of the accelerometer.

The system102inFIG. 1functions as a digital stethoscope that uses an accelerometer with tight mechanical coupling to the user's skin. Thus, the example wearable sensor device110(as well as the other wearable sensor devices112,114, and116) shown inFIGS. 4A-4Chas salient features that allow for this high level of coupling.

The accelerometer integrated circuit436is placed on an isolated island such as the corner island412. This placement benefits from an extra horizontal column of the serpentine interconnections422, which, like a spring, decouples the mass of the corner island412from the rest of the device110. Alternatively, the flexible interconnections422around the accelerometer sensor island may be made sufficiently soft to further decouple the accelerometer sensor from the rest of the sensor device110and thus isolating the accelerometer sensor and enabling the use of a highly sensitive sensor to detect lower levels of vibrations. For example, these interconnections can be made of thinner metal trace materials relative to the other flexible interconnections and/or use a softer metal material. Trace material and physical dimensions are useful factors in minimizing stiffness and maximizing reliability. Certain materials, for example rolled-annealed copper, have mechanical properties that are amenable to bending and stretching. This is due to the structure of the molecules which align like wood grains that allows for easy bending and flexing while maintaining high mechanical reliability along the direction of the grain. Additionally, an interconnection may have an overall trace thickness and width of 12 μm and 75 μm, respectively. When these dimensions are used in serpentines, they minimize stiffness and allow islands to decouple mechanically. As a point of comparison, if the thickness were doubled to 24 μm, the bending stiffness would increase by a factor of 8 and the stretching stiffness would increase by a factor of 2. This occurs since the bending and stretching area moments of inertia for a trace is related by the equation bh3/12 for the former and hb3/12 for the latter, where b and h are trace width and thickness, respectively. These moments of inertia are directly proportional to stiffness. With a high area moment of inertia, a trace will have a high amount of stiffness. Thinner trace dimensions help ensure less stiffness and a softer serpentine. Both the features of an additional horizontal column and a softer serpentine can be combined. This ensures that any vibration picked up by the accelerometer integrated circuit436at the skin surface comes from an internal organ of the body and not from the mechanical movements of the other islands410and414, (i.e., motion artifacts). In this example, the electrode450is in direct contact with the skin460and therefore directly transmits the mechano-acoustic signals received from the surface of the skin to the accelerometer integrated circuit436.

The design on the wearable device110having the battery centrally located with the acoustic sensor isolated on the wings prevents lift-off of the device on the skin. Since the battery420is the most massive component in the device, it could cause the device to peel if positioned on an edge of the device. By being in the middle of the device, the battery420has less effect on overall device lift-off, mitigating any unintended mechanical movements of the device relative to the skin that may transmit motion or acoustic artifacts to the accelerometer integrated circuit436. The location of the island412in a corner of the rectangular plane relative to the middle position of the battery420thus isolates the island412from mechano-acoustic signals of the other islands410,414,416, and418.

With the onboard heart rate sensor integrated circuit432, the wearable sensor device110can reduce false-positives in the stethoscope recording function of the system102by correlating mechano-acoustic signals from the accelerometer integrated circuit436with their corresponding electrical signal from the heart rate sensor integrated circuit432. A heartbeat can be successfully identified via the accelerometer integrated circuit436if there is a valid ECG signal that precedes it since bioelectrical signals are present before the accompanying mechanical one. This may be accomplished by the use of algorithms that can appropriately detect the R-wave component of an ECG, signifying to the user that an ECG pulse is present. The ECG pulse verifies that a valid cardiac cycle has taken place. Given this event in normal subjects, an accompanying mechano-acoustic signal must be generated, since a valid cardiac-electrical cycle cannot occur without cardiac-mechanical activity. Once this determination is made, any mechano-acoustic waveform that matches one of the signal morphologies shown inFIGS. 3A-3Dmay be classified as valid. The waveform morphology may be matched by a correlation filter in either the time or frequency domains. By combining the signals of two or more sensors, the digital stethoscope function of the system102can reduce sensitivity to noise and motion artifacts, increasing the overall signal quality (e.g., signal-to-noise ratio for the mechano-acoustic signals of interest).

The thin encapsulation layer470promotes tight mechanical coupling between the accelerometer integrated circuit436and the user's skin. This ultimately allows for efficient transduction of mechano-acoustic energy (induced by physiological processes) to the accelerometer integrated circuit436.

FIG. 5is a flow diagram of the process of collecting mechano-acoustic data and determining an abnormal heart function in the system102shown inFIG. 1. Handshaking is performed between the user device130and the sensor devices110,112,114, and116(500). The handshaking involves sending identification information for the sensor devices110,112,114, and116and respective MAC addresses to the user device130. The user device130sets initial configuration data such as the location of the sensor devices110,112,114, and116on the body, the sampling rate and applicable storage parameters (502).

The sensor devices110,112,114, and116continuously (or periodically) send an output accelerometer signal to the user device130that can include one or more samples (e.g., 2, 3, 4, 5, 10, 20, or more samples) associated with a particular timestamp (504). As explained above, each of the sensor devices110,112,114, and116gathers acoustic data from different valves in the heart reflecting circulation of blood in the circulatory system. In this example, the sensor devices110,112,114, and116can continuously (or periodically) send the output of the ECG signal received from the electrical contacts215inFIG. 2to the user device130in order to confirm the data relating to circulation of blood from the heartbeat (506). The output of the ECG signal can include one or more samples (e.g., 2, 3, 4, 5, 10, 20, or more samples) associated with a particular timestamp. The ECG signal is optional for the application relating to heartbeat data. For other mechano-acoustic measurements, the ECG signal gathering step may be eliminated or other types of data may be sensed to assist in confirming the mechano-acoustic measurements. For example, a system may use the optical sensor217to determine if a mechano-acoustic event is valid. This can be accomplished by time-aligning an appropriate optical sensor waveform (PPG) event with a corresponding mechano-acoustic event. Using this sensor, the PPG waveform can be correlated to the mechano-acoustic waveform in a process similar to that described above.

The user device130receives the accelerometer output waveform signal and the ECG output waveform signals from each of the sensor devices110,112,114, and116(508). The user device130determines whether there is an abnormal event such as an irregular heartbeat based on the analysis of the received data (510). Since each sensor110,112,114, and116is monitoring a different part of the heart, the source of the abnormal event may be isolated. If there is no abnormal event, the user device130returns to receiving the output signals (508). If an interruption is detected, the user device130stores the data from the waveform signals in memory (512). As explained above, the stored data may be used as part of an input to an LVAD implantable device or pump that changes its routine based on the mechanoacoustic input signals.

Alternatively, the timestamp data and respective signals may be transmitted to the cloud server142and some or all of the above operations may be performed by the cloud server142. Alternatively, the sensor device110or the sensor device112may store the waveform data and transmit the stored data periodically to the user device130for analysis of sleep interruption or abnormal patterns at a delayed time.

Thus, a single device such as the wearable sensor device110constitutes an epidermal device that can capture both ECG and mechano-acoustic vibrations of the chest in a way that allows proper characterization of electrical and mechanical waves propagating through the soft tissues of the human body for heart-based monitoring. As explained above, the wearable sensor has an accelerometer very closely coupled to skin surface. Of course, using multiple sensors will allow further isolation of events on different parts monitored by the corresponding sensors. As shown inFIGS. 4A-4C, the accelerometer is encapsulated with very soft, thin layer of silicone, which allows for direct coupling of mechanical vibrations and wave propagation along the chest cavity to the accelerometer sensor. This direct coupling allows the epidermal accelerometer in the wearable sensor device110to become a wearable electronic stethoscope. There are design variants to optimize coupling of the accelerometer with skin even further to enhance signal quality even further. For example, the accelerometer could be mounted on the undersurface of the wearable sensor device (facing the skin surface). This design variant would in turn couple the accelerometer directly with the surface of skin (without having the flexboard barrier).

The digital stethoscope function of the system102may have numerous uses as explained above in relation to heart, respiratory, and digestive monitoring. For example, heart murmurs may be detected from wearable sensors such as the sensors110,112,114, and116that are attached in proximity to the heart of the user. A heart murmur is detected by blood rushing quickly through the valves that creates a unique acoustic signal. Another example is detection of a ventricular defect that is detected via the presence of a third heart sound (S3 or ventricular gallop) that is like a low frequency vibration.

As explained above, some or all of the wearable sensors110,112,114, and116may be used for respiratory monitoring. In such monitoring, sensors would be attached on the user100at the lower part of the neck, where the clavicles and lower neck meet. In addition, any location on the chest would suffice for detecting respiration. The user device130would be configured to detect data relating to respiration. Such data may include bronchial breath sounds detected from within the tracheobronchial tree or vesicular breath sounds heard over the lung tissue.

Abnormal breath sounds include wheezing, stridor, rhonchi, and rales sounds. Further, the absence of breathing sounds may indicate air or fluid around the lungs, thickness around the chest wall, or airflow that is slowed down or over inflation to the lungs. Wheezing sounds like a high pitched sound when the person exhales, and sometimes when they inhale may indicate asthma. Stridor sounds like high-pitched musical breathing, similar to wheezing, heard most often when the patient inhales. Stridor is caused by a blockage in the back of the throat. Rhonchi sounds like snoring and is a result of the air following a “rough” path through the lungs or because airflow is blocked. Rales sounds like popping bubble wrap or rattling in the lungs and may indicate respiratory disease.

The system102can also be used to monitor digestive functions. In such monitoring, sensors would be attached on the user100at lower trunk area where the stomach and intestines are located. The user device130would be configured to detect data relating to digestion. Bowel sounds may be compared to normal functioning bowel sounds to determine the presence of abnormalities. The absence of any bowel sounds may indicate something is blocked in the patient's stomach or constipation. Over the course of monitoring the digestive system over a period of time, if the patient has hyperactive bowel sounds followed by a lack of bowel sounds, a rupture or necrosis of the bowel tissue could be detected. Very high-pitched bowel sounds, can indicate that there is an obstruction in the patient's bowels. Slow bowel sounds may be caused by prescription drugs, spinal anesthesia, infection, trauma, abdominal surgery, or overexpansion of the bowel. Fast or hyperactive bowel sounds can be caused by Crohn's disease, a gastrointestinal bleed, food allergies, diarrhea, infection, and ulcerative colitis.

The blood flow in other parts of a patient's body may be monitored by taking mechano-acoustic data. For example, a bruit may be detected in the renal arteries, iliac arteries, and the femoral arties by detecting a whooshing sound that indicates that the artery is narrowed.

There are several commercial applications ranging from in-home wearable stethoscopes for monitoring valve opening and closure post- or pre-operatively. If patients are experiencing heart murmurs, a wearable stethoscope system could help detect murmurs during sleep or during rest. This monitoring system could be a companion device with artificial valve implants to monitor performance over time post-procedure. Ventricular assist devices (VAD) could benefit from having these non-invasive wearables, which could track vibrations caused by the VAD pump. These vibrations could indicate potential failure modes where blood flow through the VAD may be reduced or obstructed due to a latent pathology. Once detected by the digital stethoscope, these vibrations could motivate a clinician to run a more complete battery of tests to determine the efficacy of the VAD and/or overall heart health.

In some embodiments, the aforementioned methods include at least those steps enumerated above. It is also within the scope and spirit of the present disclosure to omit steps, include additional steps, and/or modify the order of steps presented herein. It should be further noted that each of the foregoing methods can be representative of a single sequence of related steps; however, it is expected that each of these methods will be practiced in a systematic and repetitive manner.