Blood pressure measurement from libraries of oscillometric curves

Abstract

Multi-use blood pressure sensor systems are capable of earning out multiple methods of blood pressure measurements, including full-length finger oscillometric curve method (FL-FOCM), short-length finger oscillometric curve method (SL-FOCM) and pulse wave analysis based on oscillometric curve (PWA-BOC) method. The short-length finger oscillometric curve (SL- FOCM) and pulse wave analysis based on oscillometric curve (PWA-BOC) methods rely on oscillometric curves previously obtained from the full-length finger oscillometric curve method (FL-FOCM) and stored in a library of curves and / or converted into a predictive curve model.

Description

BLOOD PRESSURE MEASUREMENT FROM LIBRARIES OF OSCILLOMETRIC CURVESRELATED APPLICATIONS

[0001] This present application claims the benefit of United States Provisional Patent Application Serial No 63 / 674,257 filed July 22, 2024 and entitled, “Multi-Use Blood Pressure Sensor Systems," the disclosure of which is herein incorporated by reference.FIELD OF THE INVENTION

[0002] This invention generally relates to measuring blood pressure and, more particularly, but not by way of limitation, to a sensor package that permits multiple methods of obtaining blood pressure measurements.BACKGROUND OF THE INVENTION

[0003] There is a growing recognition of the importance of enabling people to take greater control of their health. Notwithstanding this growth of emphasis on personal health management, there is a shortage of physiological measurement devices that are accurate, affordable, easy to use, and readily available to the public. Integrating the functionality for physiological measurement and monitoring into a portable and widely available product, such as a key fob or cellphone, would greatly enhance the ability of people to manage their health.

[0004] Blood pressure, for example, is a fundamental diagnostic parameter that is used throughout the world to assess health. The basic measurements for this vital sign are diastolic blood pressure, the lowest pressure observed during the pulse cycle, and systolic blood pressure, the highest pressure observed during the pulse cycle. At least three methods have been established for measuring absolute arterial blood pressure without inserting a measurement device into the artery: auscultatory, oscillometric and volume clamp methods. There are also relative measurement methods that detect changes or trends in blood pressure, but these methods require calibration for each user.

[0005] With reference to traditional oscillometric methods for blood pressure measurement, automatic sphygmomanometers such as an inflatable cuff are often used to occlude blood flow in an artery', usually the brachial (arm) or radial (wrist) artery'. The cuff is then deflated to allow blood to begin to floyv again. During deflation, the flow is detected by observing small pressure fluctuations introduced into the cuff by the pulse.

[0006] To enhance user functionality, alternatives to the traditional cuff have been developed to determine blood pressure by measuring photoplethysmography (PPG) signals from a body part (e.g., a finger) until arterial occlusion is achieved. These alternative devices differ from automatic blood pressure cuffs, yvhich rely on Korotkoff sounds (auscultatory') or cuff pressure fluctuations representative of volume changes (oscillometry) rather than PPG signals to estimate blood pressure. In most PPG-based measuring systems, one or more light emitting diodes (LEDs) or other photoemitters emit light into a vascular structure while one or more photoreceptors (e.g., photodiodes) measure the resultant reflection from or transmission through tissue of light produced by the photoemitter. To successfully estimate blood pressure using a PPG approach, it is crucial to obtain a high-quality' PPG signal from the user. The user’s pulse can be evaluated by measuring the alternating current (AC) signal attributable to the cyclical pulse, while limiting the impact of the less-cyclical direct current (DC) signal attributable to baseline blood flow and tissues within the target vascular structure.

[0007] Some blood pressure measurement systems combine a PPG sensor with a pressure sensor. The PPG sensor is configured to measure changes in blood flow volume as part of an oscillometric measurement, while the pressure determines how much force is being applied to the subject’s artery. For example, United States Patent Nos. 10,342,493 and 11.129,575 (both incorporated by reference) disclose sensor packages for measuring blood pressure that include a combination of a PPG sensor and a pressure sensor.

[0008] Although the use of these sensor packages for measuring blood pressure is well documented, these systems suffer from several deficiencies. In particular, pressure-PPG sensor packages require a lengthy test protocol for measuring blood pressure that involves detecting PPG signals over a wide range of pressures applied by, or to, the pressure-PPG sensor package. In addition to taking a long time to obtain a single discrete measurement of the user’s blood pressure, these pressure-PPG sensor packages are also unable to passively monitor the user’s blood pressure over an extended period. A need exists, therefore, for systems and methods for improving blood pressure determination using pressure-PPG sensor packages. The present disclosure is directed to these and other deficiencies in the prior art.SUMMARY OF THE INVENTION

[0009] In some embodiments, the present disclosure is directed to a method for measuring a user's blood pressure with a physiological monitoring device that includes a sensor assembly with a PPG module and a pressure sensor module. The method includes the steps of retrieving one or more reference pressures from an existing library of curves for one or more subsequent measurements by the user, instructing the user to perform the one or more subsequent measurements by applying the one or more reference pressures to the pressure sensor module, obtaining PPG data for each of the one or more subsequent measurements made by the user at the corresponding one or more reference pressures, retrieving an oscillometric curve from the plurality of oscillometric curves stored in the library of curves based on the PPG data obtained during the one or more subsequent measurements at the corresponding one or more reference pressures, and using the retrieved oscillometric curve to determine the user's blood pressure.

[0010] In yet other embodiments, the present disclosure is directed to a method for measuring a user's blood pressure with a physiological monitoring device that includes a sensorassembly with a PPG module and a pressure sensor module. The method includes the steps of retrieving one or more reference pressures from an existing library of curves for one or more subsequent measurements by the user, instructing the user to perform the one or more subsequent measurements by applying the one or more reference pressures to the pressure sensor module, obtaining PPG data for each of the one or more subsequent measurements made by the user at the corresponding one or more reference pressures, predicting a theoretical oscillometric curve from the PPG data obtained during the one or more subsequent measurements at the corresponding one or more reference pressures, and using the theoretical oscillometric curve to determine the user's blood pressure.

[0011] In yet other embodiments, the present disclosure is directed to a method for measuring a user's trending blood pressure for a measurement period with a physiological monitoring device that includes a sensor assembly with a PPG module and a pressure sensor module. The method includes the steps of placing a body part on the physiological monitoring device such that the body part is in persistent contact with the sensor assembly during the measurement period, passively obtaining coordinated PPG and pressure sensor data on a periodic basis during the measurement period, determining a predictive oscillometric curve by correlating the PPG and pressure sensor data against a library of preexisting oscillometric curves, and using the predictive oscillometric curve to determine the user's blood pressure.

[0012] In other embodiments, the present disclosure is directed to a system for measuring a user's trending blood pressure over a measurement period. The system includes a computing device that includes a program for providing blood pressure measurement instructions and blood pressure measurement results to the user during the measurement period, where the computing device has access to a library of oscillometric curves that can be used to derive a blood pressure measurement. The system further includes a firstphysiological monitoring device in data communication with the computing device and configured to be held by the user. The first physiological monitoring device includes a first pressure sensor module configured to produce an active pressure sensor signal when the user presses against the first pressure sensor module in response to an instruction from the computing device, a first PPG module configured to produce an active PPG signal when the user applies pressure to the first PPG module in response to the instruction from the computing device, and a first processor programmed to transmit the active pressure sensor signals and the active PPG signals to the computing device. The active pressure sensor signals and the active PPG signals produce a new oscillometric curve that is stored in the library of oscillometric curv es.

[0013] The system further includes a second physiological monitoring device in data communication with the computing device, where the second physiological monitoring device is configured to be worn by the user. The second physiological device includes a second pressure sensor module configured to produce a passive contact pressure signal produced by the second physiological monitoring device while worn by the user, a second PPG module configured to measure a passive PPG signal indicative of a blood volume pulse waveform of the user while wearing the second physiological monitoring device, and a second processor programmed to transmit the passive contact pressure signal and the passive PPG signal to the computing device. The passive contact pressure signal and passive PPG signal can be used to identify a matching oscillometric curve from the library of oscillometric curves. The computing device can determine the user's blood pressure from the matching oscillometric curve.

[0014] In yet other embodiments, the present disclosure is directed at a system for measuring a user's trending blood pressure over a measurement period. The system includes a computing device that includes a program for providing blood pressure measurementinstructions and blood pressure measurement results to the user during the measurement period. The computing device has access to a library7of oscillometric curves that can be used to determine a blood pressure measurement. The system further includes a physiological monitoring device in data communication with the computing device. The physiological monitoring device has a pressure sensor module configured to produce: (i) an active pressure sensor signal when the user presses against the first pressure sensor module in response to an instruction from the computing device; and (ii) a passive pressure sensor signal when the pressure sensor module in persistent contact with the user, but without the user actively pressing on, or otherwise applying force to, the pressure sensor module. The physiological monitoring device also includes a PPG module configured to: (i) produce an active PPG signal when the user applies pressure to the first PPG module in response to the instruction from the computing device; and (ii) a passive PPG signal when the PPG module is in persistent contact with the user, but without the user actively7pressing on, or otherw ise applying for to, the PPG module.

[0015] The physiological monitoring device further includes a processor programmed to transmit the active pressure sensor signals and the active PPG signals to the computing device, where the active pressure sensor signals and the active PPG signals produce a new oscillometric curve that is stored in the library of oscillometric curves. The processor is also programmed to transmit the passive contact pressure signals and the passive PPG signals to the computing device, where the passive contact pressure signals and passive PPG signals can be used as references to select a matching oscillometric curve from the library of oscillometric curves. The computing device is configured to determine the user's blood pressure from the matching oscillometric curve.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGS. 1A-1B are side perspective views of various embodiments of a PPG-based physiological monitoring device configured for engagement by a finger and connection to a mobile computing device.

[0017] FIG. 2 is a top view of the physiological monitoring device of FIG. 1.

[0018] FIG. 3 is a side cross-sectional view of the sensor assembly of the physiological monitoring device of FIGS. 1 and 2.

[0019] FIG. 4 depicts an oscillometric curve resulting from data obtained by the physiological monitoring device of FIGS. 1 and 2 using a full-length finger oscillometric curve method (FL-FOCM).

[0020] FIG. 5 is a process flow diagram for a method for obtaining a blood pressure measurement.

[0021] FIG. 6 is a process flow diagram for a method of developing a predictive curve model based on a library of oscillometric curves.

[0022] FIG. 7 shows an oscillometric curve with discrete reference pressures selected from a PPG Data Region of the oscillometric curve of FIG. 4.

[0023] FIG. 8 is a process flow diagram for a short-length finger oscillometric curve method (SL-FOCM) based on the reference pressures obtained in FIG. 7.

[0024] FIG. 9 is a process flow diagram for a method of measuring blood pressure on a continuous or trending basis using pulse wave analysis based on the oscillometric method (PWA-BOM).

[0025] FIGS. 10A-10B present side perspective and cross-sectional perspective views of a handheld physiological monitoring device.DETAILED DESCRIPTION

[0026] Turning to FIGS. 1-3, shown therein is a physiological monitoring device 100, which is well-suited for measuring blood pressure, pulse, blood oxygenation, or other physiological parameters. In the embodiment depicted in FIG. 1A, the physiological monitoring device 100 is a wristwatch that includes a body 102 and a strap 104. In this embodiment, the physiological monitoring device 100 includes a sensor assembly 106 located on the back of the body 102 (opposite the watch face). When the physiological monitoring device 100 is worn on the user’s wrist with the strap 104 secured, the sensor assembly 106 is located on the top of, and in contact with, the user’s arm. If the physiological monitoring device 100 is rotated, the sensor assembly 106 can be positioned on the underside of the user’s wrist. It will be appreciated that the physiological monitoring device 100 can include buttons and features that permit the user to access the various features of the wearable physiological monitoring device 100. The wearable physiological monitoring device 100 can be paired with a mobile computing device 200 through a wired or wireless data connection (e.g.. Bluetooth. Wi-Fi, etc.). It will be appreciated that the physiological monitoring device 100 can also take the form of other wearable devices, such as rings, chest straps, and wearable cuffs. Together, the physiological monitoring device 100 and computing device 200 form a “system” for determining a user’s blood pressure.

[0027] In FIG. IB. the physiological monitoring device 100 is not incorporated into a wristwatch, but is instead presented as a handheld device with a puck-shaped body 102. The sensor assembly 106 is located on one side of the puck-shaped body 102. The body 102 is puck-shaped to facilitate the placement of the user’s thumb on the bottom of the body 102 so the user can comfortably exert a compressive force on the sensor assembly106 with the user’s finger by squeezing the physiological monitoring device 100 between the thumb and finger.

[0028] The sensor assembly 106 includes one or more photoemitters 108, one or more photoreceptors 110 and a pressure sensor module 112. The photoemitters 108 and photoreceptors 110 together present a PPG module 114. In exemplary embodiments, the photoemitters 108 are light emitting diodes (LEDs) configured to output light (e.g., green, red, infrared) at a selected and controllable intensity (amplitude) based on a command signal from control circuits 124. In the same exemplary7embodiments, the photoreceptors 110 are photodiodes configured to output a voltage signal to the control circuits 124 in response to the detection of light. The strength of the signal produced by the photoreceptors 110 can be tuned or adjusted to increase or decrease the sensitivity and output of the photoreceptors 110.

[0029] The PPG module 114 can be configured or adapted to operate in a reflectance mode in which light emitted by the photoemitters 108 is reflected by the user’s fingertip back to the photoreceptors 110. The PPG module 1 14 can also be configured or adapted to operate in a transmissive mode in which light emitted by the photoemitters 108 is measured by the photoreceptors 110 after the light has passed through the user’s fingertip. Any number and arrangement of the photoemitters 108 and photoreceptors 110 is contemplated as falling within the scope of the embodiments disclosed herein.

[0030] The pressure sensor module 112 is configured to measure the force applied by the fingertip to the physiological monitoring device 100. In the depicted embodiment, the pressure sensor module 112 is centrally located between the photoemitters 108 and photoreceptors 110. FIG. 3 depicts a cross-sectional side view of the sensor assembly 106, with one photoemitter 108. one photoreceptor 110 and the pressure sensor module112 visible within a common sensor housing 116. In other embodiments, the pressuresensor module 112 and PPG module 114 are located in one or more separate housings. The pressure sensor module 112 includes a well 118 filled with a pressure transmitting medium 120. such as a flexible epoxy, silicone, or elastomer, that covers a force detector 122. The pressure transmitting medium 120 is filled to the upper surface of the well 118 of the sensor assembly 106. A profilometer can be used to ensure that the pressure transmitting medium 120 is flat and flush with the upper surface of the well 118, as depicted in FIG. 3. The pressure sensor module 112 is configured for direct engagement w ith the user’s fingertip such that the application of force by the user’s fingertip on the surface of the sensor assembly 106 is transferred to the force detector 122 through the pressure transmitting medium 120. The pressure sensor module 112 and PPG module 114 are connected to control circuits 124 located in the housing 116 or on a printed circuit board (PCB) 126. The control circuits 124 interface with the onboard electronics 130 to adjust the operation of the PPG module 114 and receive data from the PPG module 114 and pressure sensor module 1 12. It will be understood that the signals produced by the PPG module 114 and the pressure sensor module 112 can be digital or analog, and converted between digital and analog forms. In some embodiments, the control circuits 124 and onboard electronics 130 each include or are connected to memory for storing computer programs or instructions, and processors configured to execute those programs or instructions. In some embodiments, the control circuits 124 and onboard electronics 130 are integrated together as single processing unit.

[0031] The physiological monitoring device 100 also includes a battery 128 and onboard electronics 130 for processing signals generated by the sensor assembly 106 and exchanging data with a computing device 200 (e.g., a smartphone, tablet, laptop or desktop computer) through a wired or wireless (e.g., Bluetooth or Wi-Fi) connection.The computing device 200 provides visual or audio instructions to the user. Theseinstructions may include, but are not limited to, directions to adjust the position of the user’s fingertip on the sensor assembly 106, to increase the force applied by the user’s fingertip on the pressure sensor 106, to decrease the force applied by the user’s fingertip on the pressure sensor 106, to warm the user' s fingertip, or to increase circulation through the user’s fingertip. The computing device 200 is also adapted to display the results of the measurements made by the physiological monitoring device 100 and to store or transfer those results to other computers systems.

[0032] In some embodiments, the instructions and results can be provided directly from the physiological monitoring device 100. For example, the watch 100 can provide the instructions and results to the user by displaying the appropriate information on the watch face or through audible instructions provided through speakers located on the watch 100.

[0033] The measurements made by the sensor assembly 106 can be used to generate an oscillometric plot or graph, as depicted in FIG. 4. The pulsative signals produced by the PPG module 114 can be plotted on the y-axis as a function of pressure signals received by the pressure sensor module 112 on the x-axis. The pressure signals can be increased and decreased as the user follows instructions provided by the computing device 200 to modulate the force applied by the user’s fingertip to the pressure sensor module 1 12. The oscillometric graph can be analyzed and processed with suitable algorithms by the physiological monitoring device 100 or computing device 200 to determine the user’s blood diastolic and systolic pressure. Methods for determining blood pressure measurements, blood oxygenation, or other physiological measurements from a combination of PPG and pressure signals are disclosed in United States Patent Nos. 10.265,002, 10,342.493. 11,129,575, 11.363.973, 11,412,987. and 11,517,265. and inUnited States Patent Application Publication Nos. 2015 / 0374249, 2021 / 0236013, and2023 / 0034358. the disclosures of which are herein incorporated by reference as if fully set forth in this disclosure.

[0034] Turning to FIG. 5. shown therein is a method 300 for carry ing out a full-length blood pressure measurement with the physiological monitoring device 100. At step 302, the user is instructed to press the user’s finger against the pressure sensor module 112 at various levels of force to achieve the application of force across a range of pressures (as depicted in FIG. 4). For example, the method 300 requests the user apply force sufficient to register pressures between a minimum value (e.g., 30 mmHg) to a maximum value (e.g., 200 mmHg). As the range of pressures are applied by the user, the PPG module 114 detects changes in the blood flow through the user’s finger. Generally, the PPG signal increases in amplitude as the force applied by the finger against the pressure sensor module 112 approaches equilibrium with the internal blood pressure within the target artery. A strong PPG signal enables the detection of pulsative features of the blood flow, which can be charted as ’‘beats” within the oscillometric curve, which can be graphed or digitally represented at step 304.

[0035] The PPG signal should increase as the transmural pressure at the wall of the target artery approaches equilibrium. As the pressure applied by the user’s finger further increases, the target artery may begin to occlude and thereby reduce blood flow through the artery. As arterial occlusion occurs with continued increases in force applied by the user’s finger, the PPG signal will decline until pulsative features of the PPG signal are no longer observed, which indicates that occlusion has stopped or nearly stopped blood flow through the artery. Once the oscillometric curve has been generated across the range of applied pressures, the method moves to step 306 and the user’s blood pressure is determined as set forth above. In many cases, the full-length finger oscillometric method300 may take 30-60 seconds to obtain a blood pressure measurement.

[0036] The oscillometric curve captures the manner in which the user's finger blood volume pulse changes with respect to externally applied pressure on the arterial wall, which is a function of the user's blood pressure and their arterial compliance. If the user’s blood pressure changes, but arterial compliance remains the same, the oscillometric curve will shift horizontally to higher or lower pressures depending on whether blood pressure increases or decreases, respectively. If the user’s blood pressure stays the same, but arterial compliance increases or decreases, the curve will either have more curvature or less, respectively. Thus, for a given user, a family of curves can be obtained capturing a range of physiological conditions. This family of curves can be used then as a basis for better interpreting the outputs obtained with the other methods described below.

[0037] Turning to FIG. 6, shown therein is a method 308 for developing a predictive curve model. The method 308 can be carried out by the computing device 200 or by the physiological monitoring device 100. At step 310, the oscillometric curve produced at step 304 is acquired and added to a library of curves at step 312 stored on the computing device 200 or physiological monitoring device 100. Each oscillometric curve can be stored as one or more computer datafiles within the library of oscillometric curves using the raw or processed data output from the pressure sensor module 112 and PPG module 114. Thus, as additional measurements are made with method 300, the curves generated at step 304 can be automatically acquired at step 310 and added to the library of curves at step 312. At step 314, the library of curves are compared and analyzed.

[0038] In some embodiments, the library of curves are stored and made available as reference curves for future use. In other embodiments, the library of curves are analyzed with machine learning or artificial intelligence to produce a predictive curve model at step 314 that is based on the actual oscillometric curves generated at step 304. In some embodiments, the library of curves includes data from multiple users and multiplephysiological monitoring devices 100. Over time a large library of curves can be established from a large cohort of users and categorized by user characteristics so that user-appropriate oscillometric curves can be retrieved. For example, user characteristics such as age, weight, blood pressure and resting heartrate, can be used to identify a one or more libraries of oscillometric curves that are most appropriate for a particular user. This may be particularly useful in initially establishing a library of oscillometric curves based on PPG and pressure sensor data produced by the user with the physiological monitoring device 100.

[0039] Turning to FIGS. 7 and 8, shown therein are an oscillometric curve and a process flow diagram for a short length finger oscillometric curve method (SL-FOCM) 316. As noted in FIGS. 4 and 7, for a given user there may be a number of applied pressures that are not useful in developing an oscillometric curve. For example, based on the oscillometric curve displayed in FIG. 4, pressures applied by the user below about 50 mmHg and above about 170 mmHg are not likely to produce a PPG signal with useful information. Accordingly, each user’s blood pressure is measurable from a PPG Data Region of the oscillometric curve that exists within a smaller range of applied pressures. Thus, if the PPG Data Region can be determined from the library of oscillometric curves for a given user, pressures falling outside the PPG Data Region can be excluded from the method 316 to produce a shorter measurement period. For example, the method 300 can start by instructing the user to apply 50 mmHg of pressure (rather than 30 mmHg of pressure) and end by instructing the user to stop applying force at about 170 mmHg (rather than 200 mmHg).

[0040] In another embodiment the method 316 relies more directly on the library of curves established at step 312. Using the library of curves, a series of reference pressures can be identified. For example, by analyzing the library of preestablished oscillometric curves,a series of discrete reference pressures can be determined that can be used as differential inputs for retrieving from the library a full oscillometric curve based on the PPG data retrieved at each reference pressure. In this way, the combination of reference pressures can be used to match an entire oscillometric curve from the library of curves, which can then be used to determine the user’s blood pressure. For example, PPG data from one or more reference pressures can be used to select an entire oscillometric curve from oscillometric curves in the library of curves based on matching PPG data from the same or similar reference pressures. Increasing the number of reference pressures improves the conformance between the actual PPG measurements and the selected oscillometric curve from the library of curves. In some embodiments, the number of reference pressures is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 references pressures. Thus, in this embodiment, the full oscillometric curve is an actual oscillometric curve previously generated by the user, stored in the library of curves, and then retrieved from the library of curves based on matching PPG data for a number of reference pressures.

[0041] In another embodiment, the PPG data at the identified reference pressures are used as inputs for the predictive curve model constructed at step 314. In this embodiment, the user’s blood pressure is determined from a theoretical curve that is constructed by the predictive curve model. At step 318, the reference pressures (e.g., 80 mmHg, 110 mmHg, and 140 mmHg) are identified based on the predictive curve model. At step 320, the user is instructed to apply force to the pressure sensor module 112 to achieve the reference pressures. Using the PPG data obtained at each of the reference pressures, a theoretical curve is constructed using the predictive curve model at step 322. The user’s blood pressure can then be determined from the constructed curve at step 324. In this way. the short-length finger oscillometric curve method 316 allows the user to obtain a blood pressure measurement from a constructed curve based on PPG data obtained from a smallnumber of reference pressures. Once the library of curves or the predictive curve model have been established from the user’s past use of the physiological monitoring device 100, the user can obtain a blood pressure measurement using only PPG data at discrete reference pressures that can be more quickly obtained than the full-length finger oscillometric method 300.

[0042] For example, if the user’s oscillometric curve obtained with the method 300 has a peak at 100 mmHg (corresponding to a mean arterial pressure, MAP, estimate of 100 mmHg), the method 316 would select at least three pressure targets for the user to rapidly select that would surround the MAP value (e.g., 80, 100, and 120 mmHg). From these at least three values, and the at least one stored oscillometric curve for that user, the algorithm then calculates the optimal horizontal shift (indicating increased or decreased blood pressure compared to the full length measurement) and curvature (indicating increased or decreased arterial compliance compared to the full length measurement) such that the outputs obtained from method 316 are fit to a full oscillometric curve for the user. This shortened measurement period allows the user to perform the method 316 more frequently, such as throughout the day, or from day to day, and the full measurement method 300 less frequently, such as once per week or month.

[0043] Turning to FIG. 9, shown there is an additional method 326 of determining the user’s blood pressure based on the user’s past use of the physiological monitoring device 100. In this method, the user’s blood pressure is determined passively by monitoring the PPG data while the physiological monitoring device 100 is worn or otherwise placed in contact with the user (without requiring the user to actively press against the pressure sensor module 112 or the PPG module 114). The method 326 can be carried out. for example, when the physiological monitoring device 100 is configured as a wristwatch, as depicted in FIG. 1 A, or other wearable device and worn by the user. The method 326 provides anoutput of the blood volume pulse waveform from the PPG module 114 (a passive PPG signal) and a measure of the contact pressure between the device 100 and the skin from the pressure sensor module 112 (a passive pressure sensor signal). These isolated passive pressure sensor and PPG measurements are not typically suitable for providing an accurate, absolute measurement of the user’s blood pressure because the PPG waveform characteristics reflect both the user’s underlying blood pressure and also their arterial compliance. Without knowing the user’s arterial compliance, for example, it may not be possible to accurately obtain an output blood pressure using the PPG signal alone. The PPG signal also is affected by the contact pressure between the PPG module 114 and the user’s body, and thus the simultaneous measurement of the contact pressure from the pressure sensor module 112 to the PPG is needed to obtain accurate blood pressure. However, the passive PPG signals (indicative of blood volume pulse waveform) and passive pressure sensor signals (persistent contact pressures) can be used alone or together as reference data to retrieve an appropriately matched oscillometric curve to estimate a blood pressure measurement for the user. In this way, the library of oscillometric curves can be used as a look-up table correlated with passive PPG and passive pressure sensor data to obtain an output blood pressure for the user.

[0044] The pulse wave analysis based on oscillometric curve (PWA-BOC) method 326 starts at steps 328 and 330, in which passive PPG data and passive pressure sensor data is obtained from the user. The user is not instructed to apply pressure to the pressure sensor module 112 during these steps. The PPG data and pressure sensor data is obtained passively while the user wears the physiological monitoring device 100, or as the user otherwise remains in contact with the physiological monitoring device 100. Based on a correlation between the passively obtained PPG and pressure data and the library of oscillometric curves, a predictive curve can be determined at step 332. The user’s bloodpressure can then be determined from the predictive curve at step 334. In some embodiments, it is not necessary to construct the predictive curve and the determination of the user's blood pressure can be more directly made by comparing the actual PPG and pressure sensor data passively obtained from the user to a previous correlation between PPG and pressure sensor data and the user’s blood pressure.

[0045] Thus, the physiological monitoring device 100 can be used to provide a blood pressure measurement based on a full-length finger oscillometric curve method 300, a short-length finger oscillometric curve method 316, or on a continuous or trending basis using the pulse wave analysis based on oscillometric method 326. For example, a user provided with a wearable physiological monitoring device 100 could first obtain a blood pressure measurement using the full-length finger oscillometric curve method 300 by removing the wearable physiological monitoring device 100 from the user and following the instructions on the computing device 200 to apply pressures to the pressure sensor module 114. As the user performs the method 300, the oscillometric curve for the user is stored on the physiological monitoring device 100 or computing device 200. The user then places the wearable physiological monitoring device 100 back on the wrist or other body part, and for a period of time (e.g., a week or month), the user’s blood pressure is measured passively via the passive method 326. If the user is interested in knowing what their blood pressure is at any given time, the user can look at the screen of the computing device 200 or watch 100. The trend of blood pressure over time is captured for the user. After a certain period of time (e.g.. a week or a month), the user is prompted to take another full-length finger oscillometric method measurement 300. The user then takes the wearable physiological monitoring device 100 off of the wrist or other body part, and performs this measurement using guidance again from the computing device 200. The new oscillometric curve is again saved, and the previous and future blood pressuremeasurements based on PWA-BOC 326 can be adaptively improved based on the newly obtained curve. As more and more FL-FOCM measurements are taken, more and more oscillometric curves are obtained for the user, and this combination of curves is used to further improve the blood pressure determination using the PWA-BOC 326 approach.

[0046] Another example embodiment involves a handheld device, such as a handheld device 400 depicted in FIG. 10A and 10B, that is wirelessly connected to the computing device 200 and contains a combination of a pressure sensor module 112 and a PPG module 114. The handheld device 400 can be used by the user to obtain a blood pressure output using the FL-FOCM technique 300 based on guidance provided by an application running on the smartphone or other computing device 200. As the method 300 is used, the oscillometric curve resulting from the measurement is stored on the computing device 200. The user can then place the handheld device 400 back in their pocket, or leave the device at home. For the next period of time (e.g., for a week or a month), the user is then instructed by the application to perform shorter, more convenient blood pressure measurements with the SL-FOCM method 316. As this technique only provides a few data points on the oscillometric curve rather than the full curve (as obtained with FL- FOCM), the other oscillometric curve(s) previously obtained with the FL-FOCM method for that user are leveraged by the algorithm to still provide an accurate blood pressure measurement for the SL-FOCM approach. The application can instruct the user when another FL-FOCM measurement is needed, and with this can store more oscillometric curves for the user, providing a means of further improving subsequent SL-FOCM measurements by fitting to multiple curves and determining which curve is most representative of the current physiological state of the user.

[0047] In yet other applications, the handheld device 400 can be used to populate the library of curves, which are then referenced by the wearable physiological monitoring device 100.In these embodiments, the user calibrates the library of curves by undergoing one or moreFL-FOCM measurements to populate or supplement the library of curves stored on the physiological monitoring device 100 or computing device 200. The application software running on the computing device 200 can be configured to prompt the user to recalibrate or update the library of curves with new readings from the handheld device 400 on a periodic or as-needed basis. In some embodiments, user is instructed to take a blood pressure measurement with the handheld device 400 while wearing the physiological monitoring device 100, which simultaneously obtains PPG and pressure sensor data from the physiological monitoring device 100. Obtaining an oscillometric curve from the handheld device 400 at the same time PPG and pressure sensor data are acquired from the physiological monitoring device 100 can facilitate and improve the correlation between the passive PPG and pressure sensor data produced by the physiological monitoring device 100 and the oscillometric curves produced by the handheld device 400.

[0048] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, different photoemitters, initial pressures, pressure targets, physiological monitoring devices, optical sensors, and electronic circuits not specifically identified or described in this disclosure or not evaluated in a particular embodiment are still expected to be within the scope of this invention.

[0049] The present invention may suitably comprise, consist of, or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Asused herein, the singular forms “a,” “an,"’ and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter). As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

Claims

It is claimed:

1. A method for measuring a user’s blood pressure with a physiological monitoring device that includes a sensor assembly with a PPG module and a pressure sensor module, the method comprising the steps of: retrieving one or more reference pressures from an existing library' of curves for one or more subsequent measurements by the user; instructing the user to perform the one or more subsequent measurements by applying the one or more reference pressures to the pressure sensor module; obtaining PPG data for each of the one or more subsequent measurements made by the user at the corresponding one or more reference pressures; retrieving an oscillometric curve from the plurality of oscillometric curves stored in the library of curves based on the PPG data obtained during the one or more subsequent measurements at the corresponding one or more reference pressures; and using the retrieved oscillometric curve to determine the user’s blood pressure.

2. The method of claim 1. wherein the library of curves is established by: placing a body part on the physiological monitoring device such that the body part is in contact with the sensor assembly; instructing the user to perform an initial full-length finger oscillometric curve method of measuring blood pressure by applying a full range of pressures to the pressure sensor module to occlude the user's artery while obtaining pressure sensor data while the PPG module obtains PPG data; creating an oscillometric curve based on the PPG data and pressure sensor data; andstoring the oscillometric curve generated from the full-length finger oscillometric curve method in a I i bran- of curves that includes a plurality of oscillometric curves;3. The method of claim 2, wherein the library of curves is populated with data from multiple users.

4. The method of claim 1. wherein the one or more reference pressures comprise a number of reference pressures selected from the group consisting of 2, 3, 4, 5, 6, 7. 8 and 9 reference pressures.

5. The method of claim 1 , wherein the step of instructing the user to perform the one or more subsequent measurements by applying the one or more reference pressures to the pressure sensor module further comprises displaying instructions for the user on a mobile computing device that is connected through a data connection to the physiological monitoring device.

6. The method of claim 5, further comprising the step of displaying the user’s blood pressure on the mobile computing device.

7. A method for measuring a user’s blood pressure with a physiological monitoring device that includes a sensor assembly with a PPG module and a pressure sensor module, the method comprising the steps of: retrieving one or more reference pressures from an existing library of curves for one or more subsequent measurements by the user;instructing the user to perform the one or more subsequent measurements by applying the one or more reference pressures to the pressure sensor module; obtaining PPG data for each of the one or more subsequent measurements made by the user at the corresponding one or more reference pressures; predicting a theoretical oscillometric curve from the PPG data obtained during the one or more subsequent measurements at the corresponding one or more reference pressures; and using the theoretical oscillometric curve to determine the user’s blood pressure.

8. The method of claim 7, further comprising the step of establishing the library of curves by: placing a body part on the physiological monitoring device such that the body part is in contact with the sensor assembly; instructing the user to perform an initial full-length finger oscillometric curve method of measuring blood pressure by applying a full range of pressures to the pressure sensor module to occlude the user's artery while obtaining pressure sensor data while the PPG module obtains PPG data; creating an oscillometric curve based on the PPG data and pressure sensor data; and storing the oscillometric curve generated from the full-length finger oscillometric curve method in a library' of curves that includes a plurality of oscillometric curves.

9. The method of claim 8, wherein the library of curves is populated with data from multiple users.

10. The method of claim 7, wherein the one or more reference pressures comprise a number of reference pressures selected from the group consisting of 2, 3, 4, 5, 6, 7. 8 and 9 reference pressures.

11. A method for measuring a user’s trending blood pressure for a measurement period with a physiological monitoring device that includes a sensor assembly with a PPG module and a pressure sensor module, the method comprising the steps of: placing a body part on the physiological monitoring device such that the body part is in persistent contact with the sensor assembly during the measurement penod; passively obtaining coordinated PPG and pressure sensor data on a periodic basis during the measurement period; determining a predictive oscillometric curve by correlating the PPG and pressure sensor data against a library of preexisting oscillometric curves; and using the predictive oscillometric curve to determine the user’s blood pressure.

12. The method of claim 11, wherein the physiological monitoring device is a wearable device and the step of passively obtaining coordinated PPG and pressure sensor data is carried out while the physiological monitoring device is worn by the user.

13. The method of claim 11 , wherein the library’ of preexisting curves is established by: placing a body part on the physiological monitoring device such that the body part is in contact with the sensor assembly; instructing the user to perform an initial full-length finger oscillometric curve method of measuring blood pressure by applying a full range of pressures to thepressure sensor module to occlude the user's artery while obtaining pressure sensor data while the PPG module obtains PPG data; creating an oscillometric curve based on the PPG data and pressure sensor data; and storing the oscillometric curve generated from the full-length finger oscillometric curve method in the library' of preexisting curves.

14. The method of claim 12, wherein the library of curves is populated with data from multiple users using different physiological monitoring devices.

15. The method of claim 11 , wherein the library' of preexisting curves is established by: providing the user with a second physiological monitoring device that includes a second pressure sensor and a second PPG module; instructing the user to perform a full-length finger oscillometric curve method of measuring blood pressure with the second physiological monitoring device by applying a full range of pressures to the second pressure sensor module to occlude the user’s artery while obtaining pressure sensor data while the second PPG module obtains PPG data; creating an oscillometric curve based on the PPG data and pressure sensor data obtained from the second physiological monitoring device; and storing the oscillometric curve generated from the full-length finger oscillometric curve method in the library of preexisting curves.

16. A system for measuring a user’s trending blood pressure over a measurement period, the system comprising:a computing device that includes a program for providing blood pressure measurement instructions and blood pressure measurement results to the user during the measurement period, wherein the computing device has access to a library of oscillometric curves that can be used to derive a blood pressure measurement; a first physiological monitoring device in data communication with the computing device and configured to be held by the user, wherein the first physiological monitoring device comprises: a first pressure sensor module, wherein the first pressure sensor module is configured to produce an active pressure sensor signal when the user presses against the first pressure sensor module in response to an instruction from the computing device; a first PPG module, wherein the first PPG module is configured to produce an active PPG signal when the user applies pressure to the first PPG module in response to the instruction from the computing device; and a first processor programmed to transmit the active pressure sensor signals and the active PPG signals to the computing device, where the active pressure sensor signals the active PPG signals produce a new oscillometric curve that is stored in the library of oscillometric curves; and a second physiological monitonng device in data communication with the computing device and configured to be w'om by the user, w herein the second physiological device comprises: a second pressure sensor module configured to produce a passive contact pressure signal produced by the second physiological monitoring device while worn by the user;a second PPG module configured to measure a passive PPG signal indicative of a blood volume pulse waveform of the user while wearing the second physiological monitoring device; and a second processor programmed to transmit the passive contact pressure signal and the passive PPG signal to the computing device, where the passive contact pressure signal and passive PPG signal can be used to identify a matching oscillometric curve from the library of oscillometric curves; and wherein the computing device can determine the user’s blood pressure from the matching oscillometric curve.

17. A system for measuring a user’s trending blood pressure over a measurement period, the system comprising: a computing device that includes a program for providing blood pressure measurement instructions and blood pressure measurement results to the user during the measurement period, wherein the computing device has access to a library of oscillometric curves that can be used to determine a blood pressure measurement; a physiological monitoring device in data communication with the computing device, wherein the physiological monitoring device comprises: a pressure sensor module, wherein the pressure sensor module is configured to produce an active pressure sensor signal when the user presses against the first pressure sensor module in response to an instruction from the computing device, and a passive pressure sensor signal when the pressure sensor module in persistent contact with the user;a PPG module, wherein the first PPG module is configured to produce an activePPG signal when the user applies pressure to the first PPG module in response to the instruction from the computing device, and a passive PPG signal with the PPG module is in persistent contact with the user; and a processor programmed to transmit the active pressure sensor signals and the active PPG signals to the computing device, wherein the active pressure sensor signals the active PPG signals produce a new oscillometric curve that is stored in the library' of oscillometric curves, and wherein the processor is programmed to transmit the passive contact pressure signals and the passive PPG signals to the computing device, where the passive contact pressure signals and passive PPG signals can be used as references to select a matching oscillometric curve from the library of oscillometric curves; and wherein the computing device can determine the user’s blood pressure from the matching oscillometric curve.

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