Method of taking blood pressure with staged pressures

Abstract

A method for measuring blood pressure the steps of placing a body part on the biometric monitoring device such that the body part is covering the PPG module and the pressure sensor, instructing the user to adjust the force applied by the body part to the pressure sensor to reach a series of discrete stage target pressures, instructing the user to hold the pressure applied to the pressure sensor at each of the discrete stage target pressures for a corresponding measurement period, and taking a blood pressure measurement during one or more of the measurement periods. The biometric monitoring device can include a multiwavelength PPG module and a pressure sensor. The biometric monitoring device is connected to a mobile computing device that carries out an application program for controlling the biometric monitoring device.

Description

METHOD OF TAKING BLOOD PRESSURE WITH STAGED PRESSURESRELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Patent Application Serial No. 63 / 521,844 filed June 19, 2023 and entitled, ‘'Method of Taking Blood Pressure with Staged Pressures,” 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 methods for improving the quality of the biosignals for a blood pressure measurement.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 biometric measurement devices that are accurate, affordable, easy to use, and readily available to the public. Integrating the functionality for biometric 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 or radial (wrist) artery7. The cuff is then more slowly deflated to allow blood to begin to flow 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. The pressure at which the target artery is occluded is representative of the blood pressure and the pulsatile arterial blood volume waveforms can be used to calculate blood pressure, among other biometrics. These alternative devices differ from automatic blood pressure cuffs, which rely on Korotkoff sounds rather than PPG signals to estimate blood pressure.

[0007] 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) measures the reflective or transmissive 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.

[0008] In the past, the determination of blood pressure using a PPG signal required the user to steadily increase the amount of pressure applied by the user’s body part (e.g., fingertip) until the pressure applied by the user occluded the artery producing the PPG signal. FIG. 1 is a graph illustrating a PRIOR ART testing protocol in which the user isinstructed to gradually and consistently increase the pressure applied by the fingertip to the biometric monitoring device until the target artery begins to occlude. In many cases, this process takes a relatively long time (e.g., 30 seconds) and requires the user to focus on gradually increasing the pressure applied by the body part to the signal acquisition device. If the user becomes distracted or lacks the strength or muscle control to gradually increase the pressure applied by the body party, the entire testing protocol must be restarted. A need exists, therefore, for systems and methods for an improved testing protocol for the use of PPG blood pressure monitoring devices.SUMMARY OF THE INVENTION

[0009] In some embodiments, the present disclosure is directed to a method for measuring blood pressure with a biometric monitoring device that includes a PPG module and a pressure sensor, where the biometric monitoring device is connected to a mobile computing device that carries out an application program for controlling the biometric monitoring device. The method includes the steps of placing a body part on the biometric monitoring device such that the body part is covering the PPG module and the pressure sensor, instructing the user to adjust the force applied by the body part to the pressure sensor to reach an initial stage target pressure, and instructing the user to hold the pressure applied to the pressure sensor at the initial stage target pressure for an initial measurement period.

[0010] In these embodiments, the method continues with the steps of instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stage target pressures, wherein each of the one or more successive stage target pressures is greater than the previous stage target pressure, instructing the user to hold the pressure applied to the pressure sensor at each successive stage target pressurefor a successive measurement period, and taking a blood pressure measurement during one of the successive measurement periods.

[0011] In other embodiments, the present disclosure is directed at a method for measuring blood pressure with a biometric monitoring device that includes a PPG module and a pressure sensor, where the biometric monitoring device is connected to a mobile computing device that carries out an application program for controlling the biometric monitoring device. In these embodiments, the method includes the steps of placing a body part on the biometric monitoring device such that the body part is covering the PPG module and the pressure sensor, instructing the user to adjust the force applied by the body part to the pressure sensor to reach a series of discrete stage target pressures, instructing the user to hold the pressure applied to the pressure sensor at each of the discrete stage target pressures for a corresponding measurement period, and taking a blood pressure measurement during one or more of the measurement periods. The method may also include automatically determining the series of discrete stage target pressures based on results from past use of the biometric monitoring device by the user, demographic information for the user, or the user’s accuracy in achieving earlier discrete stage target pressures.

[0012] In yet other embodiments, the present disclosure is directed at a system for obtaining one or more biometric measurements from a user. The system includes a biometric monitoring device connected to a mobile computing device through a data connection. The biometric monitoring device includes a PPG module and a pressure sensor adapted to measure force applied by the user to the biometric monitoring device. The mobile computing device is configured to execute an application program that instructs the user to apply pressure to the pressure sensor according to a staged pressure protocol. In somecases, the application program is configured to automatically adapt the staged pressure protocol based on past use of the biometric monitoring device by the user.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a graph depicting a PRIOR ART protocol for measuring blood pressure using a PPG-based biometric monitoring device.

[0014] FIG. 2 depicts a PPG-based biometric monitoring device suitable for taking blood pressure measurements.

[0015] FIG. 3 is a process flow chart for a method of taking a blood pressure measurement using staged pressures.

[0016] FIG. 4 is a graph depicting a staged pressure protocol carried out in accordance with exemplary embodiments for measuring blood pressure.

[0017] FIG. 5 is a process flow chart for an alternate method of taking a blood pressure measurement using staged pressures.DETAILED DESCRIPTION

[0018] Turning to FIG. 2, shown therein is a biometric monitoring device 100. which is well- suited for measuring a physiological parameter such as blood pressure, pulse, blood oxygenation, or other biometrics. As used herein and unless otherwise limited, the term “biometrics” refers to a measurable physiological parameter. The biometric monitoring device 100 includes a body 102 and a finger trough 104 configured to locate the user’s fingertip onto the biometric monitoring device 100. The biometric monitoring device 100 further includes one or more photoemitters 106, one or more photoreceptors 108 and one or more control circuits 110 which is electrically connected to the photoemitters 106 and photoreceptors 108. The photoemitters 106, photoreceptors 108 and control circuits 110 together present a PPG module 112. The biometric monitoring device 100 may also include a pressure sensor 114 configured to measure the force applied by thefingertip to the biometric monitoring device 100. The pressure sensor 114 is also connected to the control circuits 110. Although the biometric monitoring device 100 in FIG. 2 is designed for use with the user’s fingertip, it will be appreciated that the biometric monitoring device 100 can also be configured for use with other vascular body parts, including toes, wrists, ears, arm, and neck.

[0019] In exemplary' embodiments, the photoemitters 106 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 the control circuits 110. In the same exemplary embodiments, the photoreceptors 108 are photodiodes configured to output a voltage signal to the control circuits 110 in response to the detection of light. The strength of the signal produced by the photoreceptors 108 can be tuned or adjusted to increase or decrease the sensitivity and output of the photoreceptors 108. The PPG module 112 can be configured to emit and detect light at multiple wavelengths or a single wavelength. Although the control circuits 110, photoemitters 106 and photoreceptors 108 are depicted as separate, interconnected components in FIG. 2, it will be appreciated that these components can also be presented on a common circuit board with integrated connectivity.

[0020] The biometric monitoring device 100 is configured for connection with a mobile computing device 116, which can be a smart phone, tablet, watch or personal computer. The biometric monitoring device 100 can be connected to the mobile computing device 116 through a wired or wireless (e.g., Bluetooth) connection. In some cases, the biometric monitoring device 100 and mobile computing device 116 are integrated together as a unitary mobile monitoring device. Together, the biometric monitoring device 100 and mobile computing device 116 present a biometric monitoring system.

[0021] The mobile computing device 116 provides instructions to the user through an application program 118. The application program 118 guides the user through the process of obtaining a blood pressure measurement with the biometric monitoring device 100. The application program 118 can include visual references 120 that sen e as guides or limits for the application of pressure. In FIG. 2, the visual references 120 are displayed on either side of a line 122 depicting the actual force applied by the user’s finger on the pressure sensor 114. The application program 118 can move the visual references 120 up or down to instruct the user to increase or decrease the amount of pressure applied by the user’s finger on the pressure sensor 114. It will be appreciated that the mobile computing device 116 and the biometric monitoring device 100 are not drawn to scale in FIG. 2. The application program 118 can be stored on the mobile computing device 116 or the biometric monitoring device 100.

[0022] Turning to FIG. 3, shown therein is a process flow diagram for a method of carrying out a biometric measurement using a staged pressure protocol or method 200. The protocol 200 can be stored within the application program 118 and carried out by the mobile computing device 116. The method begins at step 202 when the application program 118 instructs the user to place a body part (e.g., the user’s fingertip) on the pressure sensor 1 14 and apply a force to match a first stage target pressure. At step 206, the protocol determines whether the user has achieved the first stage target pressure. If the first stage target pressure was not achieved, the method 200 returns to step 202. If the first stage target pressure was successfully achieved, the method 200 proceeds to step 206 where a determination is made whether the user’s pulse can be detected by the PPG module 112 while the user is applying force to the pressure sensor 114 at the first stage target pressure. If the pulse is detected, the method 200 can proceed to step 208where a measurement is taken by the biometric monitoring device 100 using the pulsative features detected by the PPG module 112.

[0023] If the user’s pulse is not detected at step 206, or if additional measurements are needed, the method 200 proceeds to step 210 where the user is instructed to apply force to the pressure sensor 114 to match a successive stage target pressure. The method 200 moves through step 212 until the successive stage target pressure is achieved, or the testing protocol times out. Once the successive stage target pressure has been achieved, the method 200 proceeds to step 214 where a determination is made whether the user’s pulse can be detected by the PPG module 112 while the user is applying force to the pressure sensor 114 at the successive stage target pressure. If the pulse is detected, the method 200 can proceed to step 216 where a measurement is taken by the biometric monitoring device 100 using the pulsative (AC) features detected by the PPG module 112. The method 200 can loop through steps 210-216 until a sufficient number of measurements have been made based on the PPG signals produced by the PPG module 112 to calculate the user’s blood pressure or other desired biometric parameter.

[0024] FIG. 4 is a graph plotting pressure over time for the method 200. As noted in the graph in FIG. 4, the pressure is initially increased to a first stage target pressure 218. The user can then be instructed to adjust the pressure to match successive stage target pressures 220, 222 and 224. Between each discrete stage target pressure 218, 220, 222, and 224, the user may reduce or increase the pressure applied to the pressure sensor 114. The user can be instructed to hold the force applied at one or more of the discrete stage target pressures 218-224 for a measurement period 226 to obtain PPG signals from the PPG module 212 at each target pressure. As indicated in FIG. 4, each of the discrete stage target pressures 218. 220, 222 and 224 is discontinuous from the other discrete stage target pressures.

[0025] In some embodiments, the method 200 includes the optional step of instructing the user to decrease the force applied by the body part to the pressure sensor to an intermediate stage target pressure 228 after the step of instructing the user to adjust the force applied by the body part to the pressure sensor 114 to reach the initial stage target pressure 218. In this case, the intermediate stage target pressure 228 is less than the initial stage target pressure 218. Thus, in exemplary embodiments, the method 200 includes instructing the user to adjust the force applied by the body part to the pressure sensor 114 to reach a series of discrete stage target pressures, instructing the user to hold the pressure applied to the pressure sensor 114 at each of the discrete stage target pressures for a corresponding measurement period, and then taking a blood pressure measurement during one or more of the measurement periods. This is a significant departure from the prior art methodology of requiring the user to gradually and continuously increase the force applied by the user to the blood flow occlusion device.

[0026] Turning to FIG. 5, shown therein is a process flow diagram for an alternate embodiment of a staged pressure testing protocol 300 for determining blood pressure using the biometric monitoring device 100 and mobile computing device 1 16. At step 302, the application program 118 instructs the user to apply a first stage pressure to the biometric monitoring device 100. The method 300 waits until the first stage pressure has been achieved at step 306. If the first stage pressure is not achieved after a predetermined period, the method 300 may terminate or restart.

[0027] Once the first stage pressure has been achieved, the method 300 proceeds to step 306 where the method determines whether arterial occlusion has occurred. If arterial occlusion has occurred, the method 300 proceeds to step 308 where the blood pressure and other biometric measurements are taken. If the first stage pressure does not produce arterial occlusion, the method continues to step 310 where the user is instructed totemporarily relax and reduce the force applied by the user’s finger to the pressure sensor114.

[0028] Once the relax period has expired, the method moves to step 312 and the application program 118 instructs the user to apply a force on the pressure sensor 114 to match a subsequent pressure stage. Once the next pressure stage is reached at step 314, the method 300 proceeds to step 316 when a determination is made about whether arterial occlusion has occurred. If arterial occlusion has occurred at the new pressure stage, the method 300 moves to step 308 and the blood pressure measurements are taken. If arterial occlusion has not occurred at step 316, the method 300 iteratively loops through steps 310-316 for each pressure stage until arterial occlusion is reached.

[0029] In some embodiments, the steps used for staged pressure measurements are automatically adapted and optimized for a specific user based on their prior use of the biometric monitoring device 100 for obtaining blood pressure or other biometric measurements. For example, if the biometric monitoring device 100 has previously obtained blood pressure measurements for a subject ranging from 110 - 140 mmHg for systolic pressure, the biometric monitoring device 100 can be configured to automatically adjust the testing protocol so the subject is instructed to follow a series of pressures that are likely to produce useful measurements given the subject’s previous blood pressure measurements, while excluding some or all of the pressures that are unlikely to produce useful measurements. The adaptive testing protocols can decrease the time and number of measurements needed to obtain an accurate blood pressure measurement for the subject.

[0030] In some embodiments, the biometric monitoring device 100 the steps are automatically adapted for a particular user based on demographic characteristics of the user. For example, for users who have higher a body mass index (BMI), higher values ofpressures can be used for the stages because subjects with higher BMI statistically have higher blood pressures.

[0031] In some embodiments, the biometric monitoring device 100 is configured to automatically adjust the number of steps and / or the size of each step based on the user’s ability to accurately apply the specified amount of pressure to the biometric monitoring device 100. If the application program 118 detects that the user has more pressure tracking error in the way that the user responds to the instructed pressures, then additional steps may be needed to obtain an accurate measurement. If the user is capable of accurately applying the specified pressures with the finger to the biometric monitoring device 100, then the application program can be configured to automatically instruct fewer steps to obtain a reliable blood pressure measurement. In this way, the protocol 200 can include the automatically adaptive determination of the number of steps, the pressure levels used for the steps, and the duration that the user must dwell on each step can be determined based on a number of factors, including the user’s own prior data, the user’s demographics, and historical data from other users.

[0032] Thus, the application program 1 18 can be configured to automatically optimize the protocol 200 to more quickly obtain an accurate blood pressure measurement from the subject based on the subject’s physiological data and experience with the biometric monitoring device 100. The application program 118 includes a self-training aspect that allows the biometric monitoring device 100 to more quickly evaluate a subject’s blood pressure with additional physiological information and experience using the biometric monitoring device 100.

[0033] 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 theinvention 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 biometric monitoring devices, PPG modules, pressure sensors, mobile computing devices, application programs, target pressures, and measurement periods 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.

[0034] 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. As used 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 blood pressure with a biometric monitoring device that includes a PPG module and a pressure sensor, wherein the biometric monitoring device is connected to a mobile computing device that carries out an application program for controlling the biometric monitoring device, the method comprising the steps of: placing a body part on the biometric monitoring device such that the body part is covering the PPG module and the pressure sensor; instructing the user to adjust the force applied by the body part to the pressure sensor to reach an initial stage target pressure; instructing the user to hold the pressure applied to the pressure sensor at the initial stage target pressure for an initial measurement period; instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stage target pressures, wherein each of the one or more successive stage target pressures is greater than the previous stage target pressure; instructing the user to hold the pressure applied to the pressure sensor at each successive stage target pressure for a successive measurement period; and taking a blood pressure measurement during one of the successive measurement periods.

2. The method of claim 1, further comprising the step of instructing the user to decrease the force applied by the body part to the pressure sensor to an intermediate stage target pressure after the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach the initial stage target pressure, wherein the intermediate stage target pressure is less than the initial stage target pressure.

3. The method of claim 1 , further comprising the step of determining whether the user’s pulse can be detected with the PPG module during the initial measurement period.

4. The method of claim 3, further comprising the step of obtaining a biometric measurement from the user if the user’s pulse can be detected with the PPG module during the initial measurement period.

5. The method of claim 4, wherein the step of obtaining the biometric measurement from the user during the initial measurement period comprises obtaining a pulse rate measurement or an oxygen saturation measurement.

6. The method of claim 3, further comprising the step of whether the user’s pulse can be detected with the PPG module at each of the successive measurement periods.

7. The method of claim 1 , further comprising the step of determining whether the user applied sufficient force to the pressure sensor to reach the initial stage target pressure before the step of instructing the user to hold the pressure applied to the pressure sensor at the initial stage target pressure for the initial measurement period.

8. The method of claim 7, further comprising the step of repeating the instruction to the user to apply sufficient force to the pressure sensor to reach the initial stage target pressure if the user was not successful at reaching the initial stage target pressure during an initial attempt.

9. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stagetarget pressures further comprises determining the one or more successive stage target pressures based on the user’s ability to reach the initial stage target pressure.

10. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stage target pressures further comprises determining the one or more successive stage target pressures based on results from past use of the biometric monitoring device by the user.

11. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stage target pressures further comprises determining the one or more successive stage target pressures based on demographic information about the user.

12. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach one or more successive stage target pressures further comprises determining the one or more successive stage target pressures based on the user’s body mass index (BMI).

13. A method for measuring blood pressure with a biometric monitoring device that includes a PPG module and a pressure sensor, wherein the biometric monitoring device is connected to a mobile computing device that carries out an application program for controlling the biometric monitoring device, the method comprising the steps of: placing a body part on the biometric monitoring device such that the body part is covering the PPG module and the pressure sensor; instructing the user to adjust the force applied by the body part to the pressure sensor to reach a series of discrete stage target pressures;instructing the user to hold the pressure applied to the pressure sensor at each of the discrete stage target pressures for a corresponding measurement period; and taking a blood pressure measurement during one or more of the measurement periods.

14. The method of claim 13, further comprising the step of obtaining a biometric measurement from the user if the user’s pulse can be detected with the PPG module during any one of the measurement periods.

15. The method of claim 13, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach the series of discrete stage target pressures further comprises automatically determining the series of discrete stage target pressures based on results from past use of the biometric monitoring device by the user.

16. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach the series of discrete stage target pressures further comprises automatically determining the series of discrete stage target pressures based on demographic information about the user.

17. The method of claim 1, wherein the step of instructing the user to adjust the force applied by the body part to the pressure sensor to reach the series of discrete stage target pressures further comprises automatically determining the series of discrete stage target pressures based on based on the user’s body mass index (BMI).

18. A system for obtaining one or more biometric measurements from a user, the system comprising: a biometric monitoring device, wherein the biometric monitoring device comprises:a PPG module; and a pressure sensor adapted to measure force applied by the user to the biometric monitoring device; and a mobile computing device connected to the biometric monitoring device, wherein the mobile computing device is configured to execute an application program that instructs the user to apply pressure to the pressure sensor according to a staged pressure protocol.

19. The system of claim 18, wherein the staged pressure protocol instructs the user to apply a series of pressures to the pressure sensor to meet a series of discrete target pressures, wherein each of the discrete target pressures is discontinuous from one another.

20. The system of claim 18, wherein the application program is configured to automatically adapt the staged pressure protocol based on past use of the biometric monitoring device by the user.

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