Wearable Health Monitoring Devices

Abstract

Providing a wearable health monitoring device with a blood pressure estimator A health monitoring device for detecting blood pressure has a blood pressure sensor including a first fiber Bragg grating (FBG) having a refractive index configured to be placed in contact with a user's skin near an artery or vein. A baseline sensor including a second fiber Bragg grating (FBG) having a similar refractive index is placed in contact with the user's skin away from the artery or vein and configured to provide a baseline refractive index. The device pulses light waves through the FBG and provides a reading of the refractive index from the FBG to a processor. Based on the effective shift in the Bragg wavelength due to axial strain on the FBG, a blood pressure estimator estimates systolic and diastolic blood pressure based on a calibration curve that compares pressure to strain.

Description

[Technical Field]

[0001] (Related Applications) This application is a continuation of U.S. Application No. 16 / 723,078, filed December 20, 2019, the entire teachings of which are incorporated herein by reference. [Background technology]

[0002] A person's health is often assessed in light of certain vital signs, including blood pressure, respiratory rate, heart rate, blood oxygen saturation, and body temperature. Blood pressure refers to the pressure of circulating blood against the walls of blood vessels as the heart pumps blood through the circulatory system. Blood pressure is typically expressed as systolic pressure (maximum value over one heartbeat) / diastolic pressure (minimum value between two heartbeats) above the surrounding atmospheric pressure and is measured in millimeters of mercury (mmHg).

[0003] Normal resting blood pressure for the average adult is approximately 120 mmHG systolic and 80 mmHG diastolic (120 / 80). Consistently high blood pressure is called hypertension, and consistently low blood pressure is called hypotension. Long-term hypertension is a risk factor for many diseases, including heart disease, stroke, and kidney failure.

[0004] Blood pressure is commonly measured using a sphygmomanometer, which generally consists of an inflatable cuff, a measuring unit (e.g., a mercury manometer or aneroid manometer), and an inflation mechanism, which can be a manually operated valve and valve or an electrically operated pump. The inflatable cuff is placed around the upper arm (or wrist in some cases) and inflated, constricting the arm and blood vessel within the cuff. By auscultating the brachial artery near the elbow with a stethoscope, the examiner slowly releases the cuff pressure. As the cuff pressure decreases, a whooshing or tapping sound is heard as blood begins to flow again within the artery. The pressure at which this sound begins to be heard is recorded as the systolic blood pressure. Further release of the cuff pressure is continued until the sound ceases to be heard. This is recorded as the diastolic blood pressure. Digital devices use a cuff that can be placed around the upper arm, wrist, or finger, depending on the device, in all cases elevated to heart level. Automated devices measure blood pressure using oscillometry, which involves inflating a cuff and gradually reducing the pressure in the same manner as a manual sphygmomanometer, and measuring blood pressure-induced oscillations in the cuff pressure.

[0005] More recently, methods and systems for measuring blood pressure without applying pressure (or by applying very minimal pressure) to a patient's body have been developed. One method estimates blood pressure from the time difference (propagation velocity) between pulse waves measured by fiber Bragg grating sensors (hereinafter referred to as "FBG sensors") attached to multiple locations on a subject. Another method estimates blood pressure using a calibration model that represents the correlation between the waveform data of acceleration pulse waves measured by the FBG and blood pressure values measured at each measurement time point of the measured waveform data. The calibration model is used to estimate the subject's blood pressure value at the time of acceleration pulse wave measurement from the waveform data of the acceleration pulse wave measured from the subject. Summary of the Invention

[0006] Embodiments of the present invention provide a wearable health monitoring device for detecting blood pressure. In one embodiment consistent with the principles of the present invention, a first fiber Bragg grating (FBG) is configured to be placed in contact with a user's skin proximal to an artery or vein. A second fiber Bragg grating (FBG) is configured to be placed in contact with a user's skin distal to the artery or vein to provide a baseline. The device includes an optical emitter that emits pulses of light waves through the FBG and an optical sensor that receives the pulsed light waves, and detects an effective Bragg wavelength (λ) of the FBG. eff ) to a processor. The data acquisition module receives the peak wavelength of the optical sensor reflected by the FBG. The comparator determines the effective shift in the Bragg wavelength due to axial strain on the FBG, resulting in a complete measurement of the blood pressure pulse. The blood pressure estimator is configured to calculate the total blood pressure pulse along with the effective shift in the Bragg wavelength of the first FBG and the second FBG, and estimate the systolic and diastolic blood pressure based on a calibration curve that compares pressure to strain. The device provides the estimated systolic and diastolic blood pressure using a display.

[0007] Another embodiment consistent with the principles of the present invention includes a heart rate monitor configured to detect periodic changes in surface deformation associated with heart rate.

[0008] In addition to monitoring blood pressure using FBG, some embodiments of a wearable health monitor may include various physiological attribute or wellness monitors, such as a blood oxygen saturation sensor, a blood glucose sensor, or a temperature sensor. For example, an optical sensor or a skin temperature sensor may be included in the device.

[0009] Embodiments of the device may also include a transmitter that provides blood pressure pulse and estimated systolic and diastolic blood pressure information for display on a remote device, which may be transmitted to a remote device for monitoring purposes and for data analysis to derive health indicators.

[0010] Yet another embodiment of the present invention may include a plurality of fiber Bragg gratings (FBGs) configured to be placed in contact with a user's skin proximate an artery or vein, each FBG being displaced from one another by a predetermined amount. [Brief explanation of the drawings]

[0011] The foregoing will become apparent from the following more particular description of exemplary embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the embodiments.

[0012] [Figure 1] 1 shows a representative FBG in a fiber core. [Figure 2] FIG. 1 illustrates an exemplary wearable health monitoring device consistent with the principles of the present invention. [Figure 3A] FIG. 1 shows a representative example of a string of fibers with FBGs disposed therein. [Figure 3B] 3B illustrates an exemplary wearable health monitoring device consistent with the principles of the present invention that implements the series of fibers shown in FIG. 3A. [Figure 4] FIG. 1 illustrates an exemplary wearable health monitoring device consistent with the principles of the present invention. [Figure 5] 1 is a flowchart illustrating a method for estimating blood pressure using FBG measurements consistent with the principles of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] A description of an exemplary embodiment follows.

[0014] TIFF0007723421000001.tif30170

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[0015]

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[0016] By embedding one or more optical fibers with one or more FBGs into a wearable material that can be wrapped around an anatomically relevant portion of the human body, the wearable material can be used to sense surface deformation of that portion resulting from physiological processes such as heartbeat and changes between systolic and diastolic blood pressure. As shown in FIG. 2 , a band 200 may be provided that wraps around an appendage, such as a user's wrist A. A blood pressure sensor 230 including an FBG may be positioned within the band and configured to detect subtle changes in the user's skin, particularly near an artery such as the radial artery B. By measuring the surface deformation of the skin, the device 200 can detect and track periodic movements due to the user's pulse (e.g., radial artery pulsation) resulting from pressure waves due to changes in arterial pressure as the pulsating heart pumps oxygen-rich blood through the body. By counting the number of blood pressure signal pulses in a given time period as well as the time interval between pulses, the system can be used to detect pulse / heart rate and any heart rate variability.

[0017] Additionally, the device can measure the user's blood pressure by using a calibration curve that correlates the change in Bragg wavelength (and therefore induced strain) caused by the deformation of the FBG by the pulse with the pressure required to induce that change. Another sensor acts as a baseline sensor 270, comprising an optical fiber with an embedded FBG located away from the artery B, and can provide real-time baseline measurements. Based on the calibration curve that compares pressure to strain or wavelength, both systolic and diastolic blood pressure can be detected, along with the strain data from these two sets of sensors. Additionally, the effective Bragg wavelength (λ) of the FBG can be measured. eff ) is also known to be a function of temperature. The second FBG may also provide a way to measure temperature by measuring a baseline that may vary with temperature or other variables. The second FBG may measure the time-varying λ due to the blood pressure pulse of the first FBG in contact with the artery. eff may be used to correct for shifts in

[0018] Before an embedded FBG can be used as a strain gauge, its response function and linearity as a function of load must be characterized. To characterize the response function and linearity of the FBG, an electrical strain gauge can be used to calibrate the FBG so that an applied tensile load approximates the reading of a user's skin displacement due to blood flow. Once calibrated, the response of the FBG can be reliably used as an embedded strain gauge to detect surface deformation of an object.

[0019] For an FBG to function reliably as a strain gauge, the change in reflected wavelength as the FBG is stretched under tensile load must linearly track the electrical strain gauge data. The Bragg wavelength shift of an embedded FBG under tensile load has been shown to be linearly correlated with the induced strain when measured using an electrical strain gauge within its elastic limit. Furthermore, at low strains, as is the case in this application, stress, defined as the tensile load divided by the cross-sectional area (in units of pressure), is known to be linearly correlated with the induced strain, with the proportionality constant being the elastic modulus. This is the classic definition of Hooke's Law. Based on these two linear relationships, it can be inferred that stress is linearly correlated with the Bragg wavelength. This proportionality can be used to infer blood pressure from the Bragg wavelength shift of the embedded FBG. This can also be used to detect the degree to which an object's surface is displaced for the purpose of detecting blood pressure readings, within reasonable limits of the gauge's elasticity.

[0020] Referring again to device 200, the FBG sensor is typically embedded longitudinally along band 200, which extends in a direction perpendicular to the blood flow of a major artery or vein B. Band 200 may have a laser or light source input 225 transmitted through FBG 230. FBG 230 is connected to an optical sensor 220, which receives light wave pulses emitted from light source 225. The optical sensor is connected to a processor 210 configured to analyze data regarding the light transmittance through FBG 230. Processor 210 identifies changes in the refractive index of FBG 230 and calculates the user's blood pressure based on these readings. In addition to reading blood pressure, the FBG sensor can also be used to measure pulse rate by detecting periodic changes in surface deformation resulting from pumping blood through the user's circulatory system.

[0021] In the embodiment shown in device 200, blood pressure calculations and / or pulse rate can be transmitted by transmitter 240 to an application on an external device (not shown), such as a cell phone or handheld reader. The band may be designed to communicate wirelessly via Bluetooth, cellular data, local WiFi, or some other wireless transmission. The embodiment shown in device 200 also provides a localized display 250, allowing real-time reading of the user's blood pressure and other readings without the use of an external device reader. Circuitry within the band may include other known elements known to those skilled in the art, such as wireless communication circuitry, an energy reservoir, and other processors not shown.

[0022] Thus, the band 200 may use one or more embedded FBG sensors to provide blood pressure and pulse rate as a stand-alone blood pressure monitor that does not include physically moving parts such as pumps used in current versions of blood pressure monitors, which are robust to environmental conditions and more cost-effective to manufacture. Wearable blood pressure monitors (commonly known as health monitors) that do not have wired connections and cumbersome devices (such as pumps and inflatable cuffs) that have a display for the user and / or can transmit health data remotely for display or monitoring may be used in both hospital or medical settings.

[0023] While such devices may be particularly useful in situations requiring patient monitoring, personal health monitoring devices are becoming increasingly common, allowing individuals with less critical needs to track their own health. Tracking vital signs such as blood pressure, blood oxygen, and blood glucose levels could lead to early detection of many conditions, such as sleep apnea through blood oxygen monitoring, and cardiac conditions such as patent foramen ovale (PFO) and atrial septal aneurysm (ASA) through blood pressure and blood oxygen monitoring. Furthermore, complete, detailed, real-time measurement of blood pressure pulse waveforms could open up new ways to assess pulmonary function and, through measurement of the dicrotic notch, identify signs of septic or neurogenic shock. With the advent of big data analytics and artificial intelligence, comprehensive vital data from individuals and populations can be mined to detect and predict conditions not possible today. Health monitors consistent with the principles of the present invention could extend far beyond health and activity monitoring and become powerful tools in preventive medicine.

[0024] The wearable band 200 should be constructed from a thin elastic or otherwise flexible material (such as a stretchy fabric) that allows some movement of the material on the user's skin, as the band is configured to fit around a body part of the user. The band may be constructed to hold the FBG 230 against the body part where surface deformation is to be detected. The band material should be sufficiently elastic so that the stiffness of the band material does not interfere with the bending of the optical fiber and FBG embedded therein.

[0025] Other embodiments consistent with the principles of the present invention may use multiple FBGs embedded in the band to obtain multiple different readings that can be cross-checked to provide a more accurate blood pressure calculation. Figures 3A and 3B illustrate another embodiment consistent with the principles of the present invention. Figure 3A shows a sensor strip 310 having a series of optical fibers 320, 330, 340, and 350 with embedded FBGs 325a-n, 335a-n, 345a-n, and 355a-n that are slightly displaced from one another. In Figure 3B, a wearable band 300 includes a blood pressure sensor 310 that includes multiple optical fibers as shown in Figure 3A. The optical fibers of the sensor strip 310 may span an area directly over the radial artery B and, by way of example, may measure pulse shape. Another embedded optical fiber 370 with an embedded FBG is located away from the artery to provide real-time baseline measurements. Each of the optical fibers 320, 330, 340, 350, and 370 uses both a light source and a light sensor (not shown) to provide pulsed light wave data to a processor 380. The band 300 shown in Figure 3B also has a transmitter 385 that allows the band 300 to transmit data to an application on an external device (not shown), such as a cell phone or handheld reader. Additionally, the band 300 also provides a localized display 390.

[0026] Similarly, while the optical fibers and FBGs shown in Figures 2 and 3B are embedded longitudinally along the band 200, in alternative embodiments, data may be acquired with one or more FBGs embedded perpendicular to the length of the band, and the processor would analyze the deformation accordingly.

[0027] Additionally, in other embodiments consistent with the principles of the present invention, the blood pressure monitor described above may be combined with other miniaturized physiological monitors (such as blood oxygen saturation, body temperature, and blood glucose measurements using known contact temperature sensors and optical methods) to create a comprehensive wearable health monitor. These other miniaturized physiological monitors may be integral parts of a single device or may be integral parts of some embodiments, employed in separate standalone devices that communicate with the health monitor via wireless transmission (e.g., Bluetooth or near-field communication). For example, a blood oxygen saturation sensor may be in the form of a finger ring that communicates with the health monitor.

[0028] In other embodiments, a single optical fiber having multiple FBGs imprinted along its length with each FBG having a unique Bragg wavelength and separated from one another by a predetermined distance may be configured so that some FBGs are above an artery (e.g., the radial artery) and others are away from the artery. Such a fiber may be probed using a single light source and optical sensor. In this configuration, the pulsatile component of the Bragg wavelength shift of the FBGs overlapping the artery may be used to measure the BP waveform, and the non-pulsatile wavelength shift of the FBGs not overlapping the artery may be used to correct for baseline shifts in the blood pressure waveform and for temperature sensing.

[0029] FIG. 4 illustrates yet another embodiment consistent with the principles of the present invention. In FIG. 4, a wearable blood pressure monitoring system 400 comprises a blood pressure processing unit 450 and a removable band 440. The removable band 440 includes at least one blood pressure sensing optical fiber 410 with an FBG and a baseline optical fiber 460 with an FBG. The blood pressure processing unit 450 includes internal electronics (not shown) that enable laser or light pulsing through the optical fibers 410 and 460 of the band 440, sensing the refractive index through the fiber, and processing the index to determine the blood pressure of wearer A. The band 440 is removably connected to the blood pressure processing unit 450 such that, upon connection, the unit 450 can emit pulses of laser or light through the band 440. As a wearable device, the band 440 can become dirty or damaged. However, as a removable component of the device, the band 440 can be easily replaced with minimal expense.

[0030] 5 is a flowchart illustrating a method 500 for detecting blood pressure using a wearable item embedded with a fiber Bragg grating (FBG). Blood pressure detection may be initiated by the user, or blood pressure may be detected and monitored periodically. Once initiated, peak wavelength data is acquired in step 510 from at least one FBG positioned along the wearable item. Data is continuously acquired, and the user's skin is monitored in step 520 for an effective shift in the Bragg wavelength of the FBG caused by surface deformation. Once a shift is detected 530, the data is processed to calculate 540 estimated systolic and diastolic blood pressure. The estimated systolic and diastolic blood pressures are then presented in step 550.

[0031] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[0032] While exemplary embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the appended claims.

[0033] It should be understood that the exemplary embodiments described above can be implemented in many different ways. In some examples, the various methods and machines described herein may each be implemented by a physical, virtual, or hybrid general-purpose computer having a central processor, memory, disks or other mass storage devices, communication interface(s), input / output (I / O) device(s), and other peripherals. A general-purpose computer is converted into a machine that performs the methods described above, for example, by loading software instructions into a data processor and then causing execution of the instructions to perform the functions described herein.

[0034] As is well known in the art, such computers may include a system bus, where a bus is a series of hardware lines used to transfer data between components of a computer or processing system. The bus(es) is essentially a shared conduit connecting different elements of a computer system, such as the processor, disk storage, memory, input / output ports, network ports, etc., allowing information to be transferred between the elements. One or more central processor units are attached to the system bus and provide for the execution of computer instructions. The system bus also typically includes an I / O device interface for connecting various input and output devices, such as a keyboard, mouse, display, printer, speakers, etc., to the computer. The network interface(s) allow the computer to connect to various other devices connected to a network. The memory provides volatile storage for computer software instructions and data used to implement embodiments. The disk or other mass storage provides non-volatile storage for computer software instructions and data, for example, used to perform the various procedures described herein.

[0035] Thus, embodiments may typically be implemented in hardware, firmware, software, or any combination thereof.

[0036] In certain embodiments, the procedures, apparatus, and processes described herein constitute a computer program product that includes a non-transitory computer-readable medium, e.g., one or more removable storage media, such as DVD-ROMs, CD-ROMs, diskettes, tapes, etc., that provide at least a portion of the software instructions for the system. Such a computer program product may be installed by any suitable software installation procedure known in the art. In other embodiments, at least a portion of the software instructions may be downloaded via a cable, communication, and / or wireless connection.

[0037] Furthermore, firmware, software, routines, or instructions may be described herein as performing certain operations and / or functions of a data processor, but it will be understood that such description herein is merely for convenience and that such operations actually result from a computing device, processor, controller, or other device that executes the firmware, software, routines, instructions, etc.

[0038] It should be understood that the flow diagrams, block diagrams, and network diagrams may include more or fewer elements, may be arranged differently, or may be represented differently, but it should be further understood that particular implementations may be affected by the number of block diagrams and network diagrams, and that execution of embodiments may be implemented in particular ways.

[0039] Accordingly, further embodiments may also be implemented with various computer architectures, physical computers, virtual computers, cloud computers, and / or some combination thereof, and therefore the data processors described herein are for illustrative purposes only and are not limiting of embodiments.

[0040] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined in the appended claims.

Claims

1. 1. A health monitoring device, comprising: a blood pressure sensor positioned in contact with the user's skin proximate an artery or vein, the blood pressure sensor including a first fiber Bragg grating (FBG) configured to have a first Bragg wavelength; a baseline sensor positioned in contact with the user's skin remote from the artery or vein, the baseline sensor including a second fiber Bragg grating (FBG) having a second Bragg wavelength and configured to provide a baseline signal measurement; an optical emitter configured to emit pulses of light waves through the FBG; a light sensor configured to receive pulsed light waves; 1. A processor, comprising: a data acquisition module configured to receive data from an optical sensor related to a peak wavelength of the pulsed light wave reflected by the FBG; a comparator configured to determine an effective shift of the first Bragg wavelength over time and an effective shift of the second Bragg wavelength over time; 1) the effective shift of the first Bragg wavelength corrected for drift of the baseline signal based on the effective shift of the second Bragg wavelength; and 2) a calibration curve relating blood pressure to the Bragg wavelength of the pulsed light wave reflected by the FBG; and a blood pressure estimator configured to estimate systolic and diastolic blood pressure based on the calibration curve relating blood pressure to the Bragg wavelength of the pulsed light wave reflected by the FBG. and a processor including a display that provides an estimated systolic blood pressure and an estimated diastolic blood pressure.

2. The device of claim 1 , wherein the processor further comprises a heart rate monitor configured to detect periodic changes in surface deformation associated with heart rate.

3. The device of claim 1 further comprising a physiological attribute monitor.

4. The device of claim 3 , wherein the physiological attribute monitor measures one of blood oxygen saturation, body temperature, and blood glucose measurements.

5. The device of claim 1 , wherein the display is located on a remote device, and further comprising a transmitter configured to transmit the estimated systolic blood pressure and the estimated diastolic blood pressure to the display.

6. 10. The device of claim 1, wherein the blood pressure sensor is positioned in contact with a user's skin proximate an artery or vein and further comprises a plurality of FBGs configured to have Bragg wavelengths, each FBG displaced from one another by a predetermined amount.

7. 1. A health monitoring device, comprising: A processing unit comprising: i) an optical emitter configured to emit pulses of light waves; ii) a light sensor configured to receive pulsed light waves; and iii) a data acquisition module configured to receive data from the optical sensor relating to a peak wavelength of the pulsed light wave reflected by a fiber Bragg grating (FBG); and iv) a comparator configured to determine an effective shift of the first Bragg wavelength over time and an effective shift of the second Bragg wavelength over time; v) 1) the effective shift of the first Bragg wavelength corrected for baseline signal drift based on the effective shift of the second Bragg wavelength; and 2) a calibration curve relating blood pressure to the Bragg wavelength of the pulsed light wave reflected by a fiber Bragg grating (FBG), a blood pressure estimator configured to estimate systolic and diastolic blood pressure; vi) a display for providing an estimated systolic blood pressure and an estimated diastolic blood pressure; a flexible band removably connected to the processing unit, i) a blood pressure sensor including a first fiber Bragg grating (FBG) configured to receive pulsed light waves from the light emitter in the processing unit and positioned in contact with a user's skin near an artery or vein, the first fiber Bragg grating (FBG) configured to have the first Bragg wavelength; ii) a flexible band including a baseline sensor configured to receive pulsed light waves from the light emitter in the processing unit and positioned in contact with the user's skin away from the artery or vein, the baseline sensor including a second fiber Bragg grating (FBG) having the second Bragg wavelength and providing a measurement of the baseline signal.

8. 8. The device of claim 7, wherein the blood pressure sensor further comprises a plurality of fiber Bragg gratings (FBGs) positioned in contact with the user's skin proximate an artery or vein and configured to have Bragg wavelengths, each FBG displaced from one another by a predetermined amount.

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