Expolation method for blood pressure measurement
By terminating the measurement of pressure and optical data before the measurement endpoint and generating an extrapolation curve using an extrapolation method, the problem of long blood pressure measurement time and user discomfort in the prior art is solved, achieving faster and more accurate blood pressure measurement.
Patent Information
- Application Number
- CN202480040477.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-06-19
- Filing Date
- 2024-06-19
- Publication Date
- 2026-01-20
AI Technical Summary
In existing technologies, blood pressure measurement methods based on PPG signals require the application of external pressure higher than the systolic pressure, which causes user discomfort and long measurement time, affecting the accuracy of the measurement and user compliance.
By terminating the measurement of pressure and optical data before the measurement endpoint, an extrapolation curve is generated using the extrapolation method to estimate the user's blood pressure, reducing pressure on body parts and measurement time.
It shortens blood pressure measurement time, improves measurement accuracy and user comfort, reduces signal distortion, and enhances user compliance.
Smart Images
Figure CN121368451A_ABST
Abstract
Description
Cross Reference to Related Applications
[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 521,840, filed June 19, 2023, entitled “Extrapolation Methods for Blood Pressure Measurement,” the disclosure of which is incorporated herein by reference. TECHNICAL FIELD
[0002] The present invention relates generally to measuring blood pressure, and more particularly, but not exclusively, to methods for shortening user blood pressure measurement time through data extrapolation. BACKGROUND
[0003] There is an increasing recognition of the importance of empowering individuals to better manage their own health. Despite the growing emphasis on personal health management, there is still a shortage of accurate, affordable, easy-to-use, and publicly accessible biometric measurement devices. Integrating biometric measurement and monitoring functions into portable and widely used products such as key fobs or cell phones would greatly enhance people’s ability to manage their own health.
[0004] For example, blood pressure is a fundamental diagnostic parameter used to assess health status worldwide. The basic measurements of this vital sign include diastolic pressure (the lowest pressure observed during a pulse cycle) and systolic pressure (the highest pressure observed during a pulse cycle). There are currently at least three methods for measuring absolute arterial blood pressure without inserting a measurement device into an artery: auscultatory, oscillometric, and volumetric cuff. There are also relative measurement methods that detect changes or trends in blood pressure, but these methods require calibration for each user.
[0005] Referring to the traditional oscillometric method of measuring blood pressure, an automated blood pressure cuff (e.g., an inflatable cuff) is typically used to occlude blood flow in an artery, usually the brachial or radial (wrist) artery. The cuff is then deflated more slowly to allow blood flow to resume. During deflation, flow is detected by observing the small pressure fluctuations introduced into the cuff by the pulse.
[0006] To enhance user functionality, alternatives to the traditional cuff have been developed that determine blood pressure by measuring a photoplethysmography (PPG) signal at a body site (e.g., a finger) until an artery is occluded. The pressure at which the target artery is occluded is representative of blood pressure, and the pulsatile arterial blood volume waveform can be used to calculate blood pressure as well as other biometrics. These alternative devices differ from automated blood pressure cuffs that rely on Korotkoff sounds rather than PPG signals to estimate blood pressure.
[0007] In most PPG-based measurement systems, one or more light-emitting diodes (LEDs) or other photoelectric emitters emit light into a vascular structure while one or more light receivers (e.g., photodiodes) measure reflected or transmitted light produced by the photoelectric emitters. In order to successfully estimate blood pressure using the PPG method, it is essential to acquire high-quality user PPG signals. The user’s pulse can be evaluated by measuring the alternating current (AC) signals caused by the periodic pulse while limiting the influence of the non-periodic direct current (DC) signals caused by the tissue within the target vascular structure and the baseline blood flow.
[0008] In order to successfully estimate blood pressure using the PPG method, an external pressure higher than the systolic pressure must be applied by or to the body part wearing the PPG sensor. The body part applying such a high external pressure to the sensor can be uncomfortable. Furthermore, it can take a long time for the pressure applied by the body part to increase to a sufficient degree to exceed the systolic pressure. For devices that rely on users to apply external pressure, the users’ compliance can decrease as the measurement time extends. For example, users can feel tired and inattentive later in the measurement and thus can interfere with the measurement quality by failing to continuously apply pressure, walking around, speaking, or changing the position of the body part on the measurement device (only a few examples are listed above). In addition to the usability issues, the PPG signals obtained under high pressure can also be unreliable due to distortions caused by harmonic interference and the like. Any of these limitations can negatively affect the quality of the obtained PPG signals, thereby reducing the accuracy of blood pressure measurements.
[0009] Therefore, there is a need for systems and methods that can obtain accurate blood pressure measurements from biological signals (e.g., PPG signals) while avoiding signal distortions that occur when a large external pressure is applied to a body part and / or when blood pressure measurements are performed for a long time. SUMMARY
[0010] In some embodiments, a method for shortening a user blood pressure measurement period is disclosed. The method can include the steps of measuring pressure data and optical data over a measurement period using a biometric monitoring device; terminating the measurement period at an end-of-measurement point; and obtaining extrapolated pressure values and extrapolated optical values reflecting an extrapolation period after the end-of-measurement point. The pressure data can reflect pressure applied by a user’s finger to the biometric monitoring device, and the optical data can reflect blood flow through the finger detected by the biometric monitoring device. The method can further include the steps of generating an extrapolation curve using the pressure data, the optical data, the extrapolated pressure values, and the extrapolated optical values; and estimating a user blood pressure using the extrapolation curve.
[0011] In other embodiments, a method for measuring blood pressure of a user is disclosed. The method can include the step of measuring pressure data and optical data over a measurement period using a biometric monitoring device, where the pressure data reflects pressure applied to the biometric monitoring device by a user's finger, and where the optical data reflects blood flow through the finger detected by the biometric monitoring device. The method can also include the step of terminating the measurement period at an end of measurement and generating an initial curve using the optical data and the pressure data. Other steps of the method can include obtaining extrapolated pressure values and extrapolated optical values reflecting an extrapolation period after the end of measurement, modifying the initial curve to include the extrapolated pressure values and the extrapolated optical values, and estimating the blood pressure of the user using the resulting extrapolated curve. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 A PPG-based biometric monitoring device suitable for taking blood pressure measurements is depicted in accordance with example embodiments.
[0013] Figure 2 is a diagram depicting the application of the extrapolation processing method disclosed herein in accordance with example embodiments.
[0014] Figure 3 is a diagram depicting a method of shortening a user blood pressure measurement period in accordance with example embodiments.
[0015] Figure 4 is a diagram depicting a method of shortening a user blood pressure measurement period in accordance with another example embodiment. DETAILED DESCRIPTION
[0016] It has been discovered that accurate blood pressure measurements can be obtained from data collected prior to the arterial occlusion point using extrapolation methods. Such extrapolation methods use measured pressure data and optical data to predict additional pressure values and optical values that can be used along with the measured data to estimate blood pressure using prediction techniques or analytical models. Advantages of these extrapolation methods over prior systems include reduced measurement time and improved usability. For example, in certain embodiments, these extrapolation methods can reduce measurement time by half or more compared to the time required to take the same blood pressure measurement without using an extrapolation method.
[0017] Turning to Figure 1, shown in FIG. 1, is a biometric monitoring device 100 that is well suited for measuring blood pressure, pulse, blood oxygen, or other biometric characteristics. The biometric monitoring device 100 includes a main body 102 and a finger slot 104 configured to position a user's fingertip onto the biometric monitoring device 100. The biometric monitoring device 100 also includes one or more light emitters 106, one or more light receivers 108, and one or more control circuits 110 that are electrically connected to the light emitters 106 and the light receivers 108. The light emitters 106, the light receivers 108, and the control circuits 110 collectively comprise a PPG module 112. The biometric monitoring device 100 can also include a pressure sensor 114 configured to measure the force exerted by the fingertip on the biometric monitoring device 100. The pressure sensor 114 is also connected to the control circuits 110. Although Figure 1 The biometric monitoring device 100 in FIG. 1 is designed for a user's fingertip, but it is understood that the biometric monitoring device 100 can also be configured for other vascular body parts, including the toes, the wrist, the ear, the arm, and the neck.
[0018] In an example embodiment, the photoelectric emitters 106 are light emitting diodes (LEDs) configured to output light (e.g., green light, red light, infrared light) at a selected, controllable intensity (amplitude) according to a command signal from the control circuits 110. In the same example embodiment, the light receivers 108 are photodiodes configured to output a voltage signal to the control circuits 110 in response to detecting light. The signal intensity produced by the light receivers 108 can be tuned or adjusted to increase or decrease the sensitivity and output of the light receivers 108. Although in FIG. 1 the control circuits 110, the photoelectric emitters 106, and the light receivers 108 are depicted as separate, interconnected components, it is understood that these components can also be placed on the same circuit board with integrated connectivity. Figure 1
[0019] The biometric monitoring device 100 is configured to connect with a mobile computing device 116, which can be a smartphone, a tablet computer, a watch, or a personal computer. The biometric monitoring device 100 can connect with the mobile computing device 116 through a wired or wireless (e.g., Bluetooth) connection. In some cases, the biometric monitoring device 100 and the mobile computing device 116 are integrated together, constituting a monolithic mobile monitoring device.
[0020] The mobile computing device 116 provides instructions to the user through an application 118. The application 118 guides the user through a blood pressure measurement using the biometric monitoring device 100. The application 118 can include visual references 120 that serve as a guide or a limit for applying pressure. In Figure 1 In some embodiments, the visual reference 120 is displayed on both sides of a line 122, which represents the actual force exerted by the user's finger on the pressure sensor 114. The application 118 can move the visual reference 120 up or down to indicate to the user to increase or decrease the amount of pressure exerted by the user's finger on the pressure sensor 114. It will be understood that in some embodiments, the visual reference 120 is displayed on only one side of the line 122. Figure 1 In some embodiments, the mobile computing device 116 and the biometric monitoring device 100 are not drawn to scale.
[0021] In one embodiment, a method 200 is disclosed for using the biometric monitoring device 100 to shorten a measurement period 124 for a user's blood pressure. In this embodiment, the method includes a step 202 of using the biometric monitoring device 100 to measure pressure data and optical (PPG) data over the measurement period 124. The pressure data, which can be measured using the pressure sensor 114, reflects the pressure exerted by the user's finger on the biometric monitoring device 100. The optical data reflects the blood flow through the user's finger, which is detected by the PPG module 112 of the biometric monitoring device 100. More specifically, the optical data reflects the blood flow through the user's arterial arch, preferably the transverse palmar arch.
[0022] The method 200 also includes a step 204 of terminating the measurement period 124. As shown in Figure 2 The measurement period 124 for measuring the pressure data and the optical data can be terminated at a measurement endpoint 126. Ending the measurement at the measurement endpoint 126 can involve detecting a point at which the pressure data indicates that the pressure exerted by the user's finger on the biometric monitoring device 100 is above the mean arterial pressure 128. Any pressure measurements taken prior to the measurement endpoint 126 need not be significantly above the mean arterial pressure 128. In an exemplary embodiment, the measurement endpoint 126 occurs when the pressure exerted by the user's finger is slightly above the mean arterial pressure 128. It will be understood that the term "slightly" can refer to a pressure differential of about 1% to about 5% above the mean arterial pressure 128. The termination of the measurement period 124 can be based in whole or in part on detecting a pressure above the mean arterial pressure 128.
[0023] In some embodiments, the measurement period 124 is terminated by providing an indicator to the user on the mobile computing device 116 to remove the user's finger from the biometric monitoring device 100. The indicator can include a visual indicator, an audible indicator, or a tactile indicator, or a combination thereof.
[0024] As shown in Figure 3As shown, method 200 includes a further step 206, namely, obtaining extrapolated pressure values and extrapolated optical values reflecting an extrapolated time period 130 following the measurement endpoint 126. In some exemplary embodiments, these extrapolated pressure values and extrapolated optical values are obtained by applying algorithms, machine learning, artificial intelligence, or physiologically guided theoretical models to pressure and optical data collected from the user. These algorithms and models may be applied to all measured pressure and optical data or only to a portion of the data.
[0025] Similarly, algorithms and models can be used to extrapolate pressure and PPG values from collected pressure and optical data. This is done by identifying a correlation or other relationship between the pressure applied by the user and a corresponding decrease or increase in blood flow, such as a PPG signal, to estimate a point 132 at which applied pressure would cause arterial occlusion in the user's finger (assuming measurement period 124 continues until arterial occlusion). Figure 2 As shown, the arterial occlusion point 132 occurs later than the measurement endpoint 126, and the pressure at this point is higher than the mean arterial pressure 128. The estimated pressure value up to the arterial occlusion point 132 and the applied pressure value at that point is the extrapolated pressure value. By applying the same correlation or other relationship identified between the pressure data and the optical data, the extrapolated pressure value can be used to determine the extrapolated optical value. The mobile computing device 116 can perform the step of extrapolating the PPG signal to the expected pressure reading.
[0026] By combining the pressure and optical data obtained before the measurement endpoint 126, and the extrapolated pressure and extrapolated PPG values obtained after the measurement endpoint 126, an extrapolation curve can be generated (step 208) and used to estimate the user's blood pressure (step 210). In some non-limiting exemplary embodiments, the process of generating the extrapolation curve may include the following steps: associating optical data with corresponding pressure data; associating extrapolated optical values with corresponding extrapolated pressure values; and plotting the optical data and extrapolated optical values on the corresponding pressure data and the corresponding extrapolated pressure values to generate the extrapolation curve.
[0027] On the other hand, the method 300 for measuring a user's blood pressure includes: acquiring pressure data and optical data using a biometric monitoring device 100 during a measurement period 124 (step 302); terminating the measurement period 124 (step 304); and generating an initial curve using the pressure data and optical data acquired up to the measurement endpoint 126 (step 306). During an extrapolation period 130 following the measurement endpoint 126, extrapolated pressure values and extrapolated optical values are acquired (step 308). Although... Figure 4The extrapolation step 308 is shown as occurring after step 306, but it will be appreciated that the extrapolated pressure values and the extrapolated optical values can be obtained before or after the initial curve is generated. In some embodiments, if the extrapolation is performed after step 306, the initial curve of pressure data and optical data is used to estimate the extrapolated optical values and the extrapolated pressure values. After the initial curve is generated and the extrapolated values are obtained, the initial curve is modified (step 310) to include the extrapolated pressure values and optical values, thereby generating an extrapolated curve that is used to estimate the user's blood pressure in step 312.
[0028] In some cases, all of the measured pressure data and optical data are used to generate the initial curve, the extrapolated curve, or both. In other cases, only a subset of the pressure data and optical data is used for this purpose. In the latter case, the method can further include a step of identifying the subset of pressure data and optical data that is used to generate the initial curve and / or the extrapolated curve.
[0029] It will be appreciated that various methods and / or algorithms can be used to estimate the user's blood pressure using the extrapolated curve. In an exemplary embodiment, the extrapolated curve can be used to estimate the user's systolic pressure, diastolic pressure, or both.
[0030] In the foregoing specification, the application has been described with reference to specific embodiments thereof. It is evident, however, that various modifications and changes can be made thereto without departing from the broader spirit and scope of the application as set forth in the appended claims. The Specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. For example, different measurement periods, biometric monitoring devices, body parts, arteries, curves, theoretical models, and algorithms not specifically identified or described in the present disclosure, or not evaluated in a particular embodiment, are still intended to be encompassed within the scope of the present application.
[0031] The application can suitably include, be implemented by, or consist of, the inventive features as described herein, and can be practiced in conjunction with the disclosure as set forth in the appended claims. 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 degree of error associated with measurement of the given parameter (e.g., it includes the degree of error that would be expected from measurement of the given parameter by a skilled artisan). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.
Claims
1. A method for shortening a user blood pressure measurement period, comprising: measuring pressure data and optical data over the measurement period using a biometric monitoring device, wherein the pressure data reflects pressure applied to the biometric monitoring device by a user's finger, and wherein the optical data reflects blood flow through the finger as detected by the biometric monitoring device; terminating the measurement period at an end of measurement; obtaining an extrapolated pressure value and an extrapolated optical value reflecting an extrapolation period after the end of measurement; generating an extrapolated curve using the pressure data, the optical data, the extrapolated pressure value, and the extrapolated optical value; and estimating user blood pressure using the extrapolated curve.
2. The method of claim 1, wherein the step of measuring the pressure data and the optical data over the measurement period further comprises: measuring the pressure data using a pressure sensor on the biometric monitoring device; and measuring the optical data using a photoplethysmography sensor on the biometric monitoring device.
3. The method of claim 1, wherein the step of terminating the measurement period at the end of measurement further comprises: detecting when the pressure data indicates pressure above mean arterial pressure; and initiating termination of the measurement period based on detecting pressure above mean arterial pressure.
4. The method of claim 1, wherein the step of terminating the measurement period further comprises providing an indicator to the user to remove the finger from the biometric monitoring device.
5. The method of claim 4, wherein the step of providing an indicator to the user to remove the finger from the biometric monitoring device further comprises providing a visual indicator, an audible indicator, a tactile indicator, or a combination thereof to the user.
6. The method of claim 1, wherein the step of obtaining the extrapolated pressure value and the extrapolated optical value further comprises applying a physiologically guided model to the pressure data and the optical data.
7. The method of claim 6, wherein the step of obtaining the extrapolated pressure value and the extrapolated optical value further comprises the steps of: identifying a correlation between the pressure data and the optical data; estimating a pressure applied from the end of measurement to a point at which arterial occlusion would occur in the user's finger if the measurement period were to continue, wherein the pressure applied is the extrapolated pressure value; and determining the extrapolated optical value by applying the correlation between the pressure data and the optical data to the extrapolated pressure value.
8. The method of claim 1, further comprising the step of generating an initial curve using the pressure data and the optical data, wherein the step of generating the extrapolated curve further comprises the step of modifying the initial curve to include the extrapolated pressure value and the extrapolated optical value.
9. The method of claim 8, wherein the step of generating the initial curve using the pressure data and the optical data further comprises: identifying a subset of the pressure data and the optical data; and generating the initial curve using the subset of the pressure data and the optical data. 10. The method of claim 8, wherein the step of obtaining the extrapolated pressure values and the extrapolated optical values further comprises using initial curves of the pressure data and the optical data to estimate the extrapolated pressure values and the extrapolated optical values.
11. The method of claim 1, wherein the step of generating the extrapolated curve further comprises: associating the optical data with corresponding pressure data; associating the extrapolated optical values with corresponding extrapolated pressure values; and plotting the optical data and the extrapolated optical values on the corresponding pressure data and the corresponding extrapolated pressure values to generate the extrapolated curve.
12. The method of claim 1, wherein the step of generating the extrapolated curve using the pressure data and the optical data further comprises: identifying a subset of the pressure data and the optical data; and generating the extrapolated curve using the subset of the pressure data and the optical data.
13. The method of claim 1, wherein the step of estimating a user’s blood pressure using the extrapolated curve further comprises: estimating a systolic blood pressure of the user using the extrapolated curve; and estimating a diastolic blood pressure of the user using the extrapolated curve.