Method and system for measuring blood pressure

Abstract

The method for measuring blood pressure of the present invention includes: receiving a plurality of mechanical signals provided by a force sensor disposed on the surface of the skin; identifying, based on the plurality of mechanical signals, a primary systolic pulse, a first reflection pulse, and a second reflection pulse; determining a first delay time between the primary systolic pulse and the first reflection pulse; determining a second delay time between the first reflection pulse and the second reflection pulse; determining a linear combination value of the first delay time and the second delay time, wherein a first predetermined coefficient applied to the first delay time is smaller than a second predetermined coefficient applied to the second delay time; and determining a blood pressure value based on the linear combination value.

Description

Attorney Docket No. 5199-0424PW01METHOD AND SYSTEM FOR MEASURING BLOOD PRESSURECROSS REFERENECE TO RELATED APPLICATIONSThis application claims the benefit of U. S Patent Application No. 63 / 711,611, filed on October 24, 2024, the entirety of which is incorporated by reference herein.TECHNICAL FIELD

[0001] The present invention relates to a method and a system for measuring blood pressure, and in particular to a method and system for measuring blood pressure by means of a non-invasive mechanical force sensor.BACKGROUND

[0002] Blood pressure is one of the most important physiological indicators representing the health condition of the human cardiovascular system. Variations in blood pressure directly reveal the functional state of the heart, the elasticity of blood vessels, and / or the overall performance of the circulatory system. In clinical applications, blood pressure measurements are widely used in the diagnosis and monitoring of hypertension, hypotension, and / or cardiovascular diseases, and serve as a crucial basis for evaluating treatment effectiveness and assessing health risks. Accordingly, how to accurately and promptly obtain blood pressure information has long been a significant issue in the fields of medicine and biosensing.

[0003] Conventional sphygmomanometric blood pressure measurements, such as cuff-based blood pressure monitors, estimate blood pressure by externally compressing blood vessels and detecting pulsation variations. Although these measurements provide clinically reliable accuracy, they require the use of air bladders or cuffs for pressurization. Such operation is inconvenient and unsuitable for continuous monitoring or applications for real-time measurements. These issues of theAttorney Docket No. 5199-0424PW01conventional measurements make them difficult to integrate into / with wearable devices intended for a long-term use or a portable application.

[0004] On the other hand, although recent studies have attempted to integrate blood pressure measurement functions into wearable devices, such as smartwatches or wristbands, conventional measurement approaches mostly rely on indirect estimation methods such as photoplethysmography (PPG) or pulse transit time (PTT). However, these approaches are susceptible to errors caused by posture changes, skin color, ambient light interference, and / or individual differences, resulting in unstable and inaccurate blood pressure readings.

[0005] Therefore, how to develop a blood pressure measurement technology that can be integrated into / with wearable devices without relying on conventional pressurization mechanisms, while achieving both high accuracy and real-time capability remains a major technical challenge. Addressing this issue would not only significantly enhance the convenience and accessibility of personal health monitoring but also bring substantial benefits to preventive medicine and the long-term management of chronic diseases.SUMMARY

[0006] The present invention provides a method and a system for measuring blood pressure to overcome the problems encountered in the prior art.

[0007] One objective of the present invention is to provide a wearable method and a system for measuring blood pressure which are capable of performing measurement at a single fixed point.

[0008] One objective of the present invention is to provide a method and a system for measuring blood pressure that enables linear and stable measurement results unaffected by wearing conditions.Attorney Docket No. 5199-0424PW01

[0009] In a specific embodiment, the present invention provides a method for measuring blood pressure. The method includes: receiving a plurality of mechanical signals provided by a force sensor disposed on the surface of the skin; identifying, from the plurality of mechanical signals, a primary systolic pulse, a renal reflection pulse, and an iliac reflection pulse; determining a first delay time between the primary systolic pulse and the renal reflection pulse; determining a second delay time between the renal reflection pulse and the iliac reflection pulse; determining a linear combination value of the first delay time and the second delay time, wherein the first predetermined coefficient corresponding to the first delay time is smaller than the second predetermined coefficient corresponding to the second delay time; and determining a blood pressure value according to a result of the calculation of the linear combination value.

[0010] In a specific embodiment, the present invention provides a system for measuring blood pressure. The system includes a force sensor configured to be disposed on the surface of the skin and a processing device. The processing device includes a processor and a memory, wherein the processor is configured to perform the following operations: receiving a plurality of mechanical signals provided by the force sensor disposed on the surface of the skin; measuring, based on the plurality of mechanical signals, a primary systolic pulse, a renal reflection pulse, and an iliac reflection pulse; determining a first delay time between the primary systolic pulse and the renal reflection pulse; determining a second delay time between the renal reflection pulse and the iliac reflection pulse; determining a linear combination value of the first delay time and the second delay time, wherein a first predetermined coefficient of the first delay time is smaller than a second predetermined coefficient of the second delay time; and determining a blood pressure value according to a result of the calculation of the linear combination value.Attorney Docket No. 5199-0424PW01

[0011] In one embodiment, the blood pressure value includes a systolic pressure and a diastolic pressure.

[0012] In one embodiment, the method further includes: receiving a reference blood pressure value measured by a standard device to calibrate a ratio between the first predetermined coefficient and the second predetermined coefficient.

[0013] In one embodiment, the method further includes: measuring, at predetermined times, a plurality of first delay times and a plurality of second delay times; and determining a continuous blood pressure value based on a plurality of linear combination values of the plurality of first delay times and the plurality of second delay times.

[0014] In one embodiment, a ratio between the first predetermined coefficient and the second predetermined coefficient is determined according to variances of the plurality of first delay times, variances of the plurality of second delay times, and covariances between the plurality of first delay times and the plurality of second delay times.

[0015] In one embodiment, the ratio between the first predetermined coefficient and the second predetermined coefficient is further determined based on a plurality of reference blood pressure values corresponding to the plurality of first delay times and the plurality of second delay times.

[0016] In one embodiment, the ratio between the first predetermined coefficient and the second predetermined coefficient is greater than 1 and smaller than 5.

[0017] In summary, the method and system of the present invention provide a non-invasive force sensor configured to be disposed on the skin to identify a primary systolic pulse, a first reflection pulse, and a second reflection pulse contained in pulse vibration information. By establishing a linear relationship among the delay times between the primary systolic pulse, the first reflection pulse, and the second reflection pulse, the blood pressure value can be derived.Attorney Docket No. 5199-0424PW01

[0018] Compared with conventional sphygmomanometric techniques, the present invention provides a measurement means which is able to be integrated into / with a wearable device. Moreover, the presented method, which determines blood pressure based on the time differences between reflection pulses, is less susceptible to interference caused by variations in the subject’s physiological condition or measurement environment.

[0019] On the other hand, the present invention further provides a method for determining the linear relationship coefficients, whereby different linear coefficients are applied to enhance the linear correspondence between time values and blood pressure values. Accordingly, the present invention establishes an optimized feature based on the delay times among the primary systolic pulse, the first reflection pulse, and the second reflection pulse to improve the measurement capability of the blood pressure estimation model. The method provided by the present invention not only enhances the correlation between the extracted features and the target variable but also improves the overall prediction accuracy.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are presented to help describe various aspects of the present invention. In order to simplify the accompanying drawings and highlight the contents to be presented in the accompanying drawings, conventional structures or elements in the accompanying drawings may be drawn in a simple schematic way or may be omitted. For example, a number of elements may be singular or plural. These accompanying drawings are provided merely to explain these aspects and not to limit them.

[0021] FIG. 1 illustrates a flowchart ofthe method for measuring blood pressure according to one embodiment of the present invention.Attorney Docket No. 5199-0424PW01

[0022] FIG. 2 illustrates an exemplary structural diagram for implementing the method for measuring blood pressure according to one embodiment of the present invention.

[0023] FIG. 3 illustrates a schematic diagram showing the first delay time and the second delay time according to one embodiment of the present invention.

[0024] FIGS. 4 to 10 illustrate graphs showing the correspondence between the measured blood pressure data and the linear combination values of the first delay time and the second delay time obtained according to the method for measuring blood pressure of the present invention.

[0025] FIG. 11 illustrates a flowchart of a method for repeatedly performing measurements according to an embodiment of the present invention.DETAILED DESCRIPTION

[0026] Any reference to elements using terms such as “first” and “second” herein generally does not limit the number or order of these elements. Conversely, these names are used herein as a convenient way to distinguish two or more elements or element instances. Therefore, it should be understood that the terms “first” and “second” in the request item do not necessarily correspond to the same names in the written description. Furthermore, it should be understood that references to the first element and the second element do not indicate that only two elements can be used or that the first element needs to precede the second element. Open terms such as “include”, “comprise”, “have”, “contain”, and the like used herein mean including but not limit to.

[0027] The term “coupled” is used herein to refer to direct or indirect electrical coupling between two structures. For example, in an example of indirect electrical coupling, one structure may be coupled with another structure through a passive element such as a resistor, a capacitor, or an inductor.Attorney Docket No. 5199-0424PW01

[0028] In the present invention, the terms such as “exemplary ’" or “for example” is used to represent “giving an example, instance, or description”. Any implementation or aspect described herein as “exemplary” or “for example” is not necessarily to be construed as preferred or advantageous over other aspects of the present invention. The terms “about” and “approximately” as used herein with respect to a specified value or characteristic are intended to represent within a value (for example, 10%) of the specified value or characteristic.

[0029] In one specific embodiment, the present invention provides a method for measuring blood pressure. Referring to FIG. 1, the method 100 of the present invention includes the following steps: (Step SI) receiving a plurality of mechanical signals provided by a force sensor disposed on the surface of the skin; (Step S2) identifying, based on the plurality of mechanical signals, a primary systolic pulse, a first reflection pulse, and a second reflection pulse: (Step S3) determining a first delay time between the primary systolic pulse and the first reflection pulse; (Step S4) determining a second delay time between the first reflection pulse and the second reflection pulse; (Step S5) determining a linear combination value of the first delay time and the second delay time, wherein the first predetermined coefficient corresponding to the first delay time is smaller than the second predetermined coefficient corresponding to the second delay time; and (Step S6) determining a blood pressure value according to the linear combination value.

[0030] Referring to FIG. 2, FIG. 2 illustrates a system embodiment for performing the method 100 of the present invention. As shown in FIG. 2, the method 100 of the present invention may be executed by a force sensor 230 and a processing device 200. The processing device 200 may be, for example, a computer, a smartphone, or a system-on-chip (SoC) that includes a processor 210 and a memory 220. The memory 220 is configured to store program instructions for executing the method of the present invention. The processor 210, upon accessing the program instructions ofAttorney Docket No. 5199-0424PW01the method for measuring blood pressure from the memory 220 or other storage media, is configured to execute the method 100 of the present invention. In some application embodiments, the memory 220 may also be configured to store the mechanical signals measured by the force sensor 230, which can be accessed by the processor for further analysis. In addition, the force sensor 230 and the processing device 200 may be communicatively connected through a physical wired connection or through a wireless communication (for example, via a Bluetooth module) to transmit the mechanical signals measured by the force sensor 230.

[0031] In Step SI, the force sensor may be any type of sensor capable of detecting micro-vibrations. For example, the force sensor may be a piezoelectric force sensor, a piezoresistive force sensor, a capacitive force sensor, or an electromagnetic induction sensor, all of which can be disposed on the surface of the skin and are configured to detect mechanical signals such as micro-vibrations or pressure. Preferably, the force sensor is disposed on the surface of the skin at a location near an artery. For instance, in embodiments where the sensor is arranged on the upper limb, the force sensor may be disposed on the skin above the radial artery, ulnar artery, or brachial artery. In another embodiment, where the sensor is arranged on the lower limb, the force sensor may be disposed near the femoral artery or dorsalis pedis artery. It should be noted that the force sensor may also be positioned at other locations on the body, such as the trunk, neck, or sternum, where the skin surface is relatively flat or close to an artery. The installation of the force sensor may be achieved by adhesion, suction, strapping, or by integrating the sensor into a wearable device (for example, a smartwatch or a ring) that can be worn or attached directly onto the skin.

[0032] In step S2 of measuring a plurality of mechanical signals corresponding to a primary systolic pulse, a first reflection pulse, and a second reflection pulse, the first reflection pulse and the second reflection pulse may, for example, correspond to a renal reflection pulse at a branching point of the renal artery, an iliac reflection pulse atAttorney Docket No. 5199-0424PW01a bifurcation of the common iliac artery, a femoral reflection pulse at a branching point of the femoral artery, or other possible reflections (e.g., from the aortic arch or distal lower limbs). However, the reflection pulses of the present invention are not limited to these examples. In this embodiment, the second reflection pulse is delayed relative to the first reflection pulse. For example, the first reflection pulse may be the renal reflection pulse, and the second reflection pulse may be any reflection pulse occurring after the renal reflection pulse.

[0033] In general, the “aortic pulse” and various “reflection pulses” are not distinctly separated but are instead superimposed into a composite waveform. In one embodiment, the “aortic pulse” and various “reflection pulses” can be distinguished and measured using analytical methods such as time-domain analysis, frequencydomain analysis, or signal clustering. It should be noted that the present invention is not limited to any particular technique for distinguishing the “aortic pulse” and the various “reflection pulses”. In one embodiment, the plurality of mechanical signals measured by the sensor may be referenced to an electrocardiogram (ECG) signal to determine the reception of the primary systolic pulse signal. In another embodiment, the force sensor may be combined with a processing circuit (e.g., a high-impedance amplifier) or a filtering circuit (e.g., a band-pass filter) to eliminate noise and improve the signal-to-noise ratio. It should be noted that the present invention is not limited to any specific technical means for the force sensor to measure the primary systolic pulse, the first reflection pulse, and the second reflection pulse.

[0034] In Step S3, which involves determining the first delay time between the primary’ systolic pulse and the first reflection pulse, and in Step S4, which involves determining the second delay time between the first reflection pulse and the second reflection pulse, the mechanical signals detected by the force sensor may be interpreted by the processor. For example, referring to FIG. 3, the processor may be configured to determine the peak positions of the primary' systolic pulse, the first reflection pulse, andAttorney Docket No. 5199-0424PW01the second reflection pulse from the signals measured by the force sensor, and record the corresponding times as T1 (primary systolic pulse time), T2 (first reflection pulse time), and T3 (second reflection pulse time). The processor may then determine the first delay time (T12) and the second delay time (T23) based on the differences between these peak times Tl, T2, and T3, respectively.

[0035] In Step S5, the calculation of the linear combination value of the first delay time and the second delay time may be derived through the following procedure. First, let the algebraic symbol y represent the measured blood pressure value (the unit, for example, is mmHg), xtrepresent the first delay time (T12), and x2represent the second delay time (T23) (the unit, for example, is seconds, milliseconds, or microseconds). The linear combination value of the first delay time and the second delay time is expressed as a linear equation:z = x1+ ax2where a is a weighting coefficient. The optimized correlation coefficient r(y,z) between the algebraic blood pressure value y and the linear combination value z can be expressed by the following equation:The covariance between the algebraic blood pressure value y and the linear combination value z can be expressed by the following equation:Cov(y, z) = Cov(y, x1+ ax2) = Cov(y, x1) + aCov(y, x2) The standard deviation < JZof the linear combination value z can be expressed by the following equation:σ2z= Var(z) = Var(x1+ ax2) = F’ur(x1) + a2Var x2') + 2aCov(x1,x2)By combining the above formulas, the correlation coefficient r(y, z)can be expressed as follows:Attorney Docket No. 5199-0424PW01Therefore, in order to obtain the optimal coefficient a in the linear combination of the first delay time and the second delay time, the derivative of the correlation coefficient with respect to a is set to zero. The correlation coefficient r y, z) can thus be expressed as a ratio of two functions of a, namely (a) and g (a), as follows:When applying the quotient rule to handle the correlation coefficient r(y, z) expressed as two functions of the coefficient a. namelyand g a). the derivative of r(y, z) with respect to a can be represented as:wherein:Therefore, the derivative of r(y, z) with respect to a can be expressed as:At the optimized coefficient aopt, the derivative of r(y, z) equals zero:obtained as follows:after substituting the following algebraic expressions:A = Cov(y,x2),Attorney Docket No. 5199-0424PW01B = Cov^x^),C = Var^X,D = Var^x2),E = Cov(x^,x2).the equation can be obtained as follows:_ BE - ACa°pt~ AE - BD

[0036] In the above equation, when the coefficient of the first delay time in the linear combination of the first and second delay times is set to 1 and the coefficient of the second delay time is a. the ratio between the first predetermined coefficient and the second predetermined coefficient is also a. From the above formula, it can be determined that the optimized ratio aoptof the first predetermined coefficient to the second predetermined coefficient is expressed as(BE — AC') / (AE — BD), where: = Cov(y, x2) represents the covariance between the blood pressure value and the second delay time: B = Cov(y, x ) represents the covariance between the blood pressure value and the first delay time; C = Var^x^) represents the variance of the first delay time; D = Var x2) represents the variance of the second delay time; and E = Cov x1,x2) represents the covariance between the first delay time and the second delay time. Accordingly, in one embodiment, the ratio between the first predetermined coefficient and the second predetermined coefficient is determined based on the variance of the plurality of first delay times, the variance of the plurality of second delay times, and the covariance between the plurality of first delay times and the plurality of second delay times. Furthermore, in another embodiment, the ratio between the first predetermined coefficient and the second predetermined coefficient is further determined based on a plurality of reference blood pressure values corresponding to the plurality of first delay times and the plurality of second delay times.

[0037] It should be noted that the present invention is not limited to the aforementioned formulas, which are provided solely to illustrate the correlationAttorney Docket No. 5199-0424PW01between the blood pressure value and the linear combination of the first delay time and the second delay time. The derivation process for determining the linear combination coefficients of the first and second delay times in the present invention is not restricted to the calculation procedure described above.

[0038] In Step S6, the calculation of the linear combination value is performed using the first delay time, the second delay time, and the optimized ratio aoptbetween the first and second predetermined coefficients obtained in Step S5. The measured blood pressure value can then be estimated in a linear-correspondence manner based on this linear combination value. For example, referring to FIGS. 4 and 5, FIG. 4 illustrates the data obtained from a clinical trial conducted according to the present invention. Based on the aforementioned formulas, the optimized coefficient aoptis determined to maximize the correlation between the blood pressure value (specifically, the systolic pressure) and the linear combination value z = x1+ ax2of the first delay time and the second delay time. The optimal value of aoptis 6.39, corresponding to a correlation coefficient of -0.34. Similarly, for the diastolic pressure, as shown in FIG.5, the optimized coefficient aoptis also 6.39. and the corresponding correlation coefficient is -0.30. In comparison, when only the original feature, namely, the time difference between the primary systolic pulse and the second reflection pulse, is used, the correlation coefficient with the systolic pressure is merely -0.21, and that with the diastolic pressure is only -0.18. Therefore, the use of the linear combination value of the first and second delay times provides a significantly higher correlation than using a single time-difference feature alone.

[0039] In one embodiment of the optimized coefficient aopt, referring to FIGS.6 to 10, these figures illustrate that the optimized coefficient aopCmay vary across different cases. For example, the optimized coefficient aoptmay take values such as 1.37, 1.49, 1.56, 1.85, 1.99, or 3.41. Using the optimized coefficient aopt, the linear combination value of the first delay time T12 and the second delay time T23Attorney Docket No. 5199-0424PW01demonstrates a stronger correlation and a more linear relationship with the blood pressure value than that obtained using only a single time parameter. Accordingly, by employing the linear combination of T12 and T23 together with the optimized coefficient aopt, the time-based parameters can serve as reliable indicators for blood pressure measurement. Compared with single time-based parameters or non-temporal parameters (for example, signal amplitude), this approach exhibits a higher degree of linearity with the actual blood pressure value. Furthermore, as shown in the examples of FIGS. 6 to 10, the optimized coefficient aoptis not identical in every case. In other words, within a reasonable range, any value greater than 1 may be determined as the optimized coefficient aopt. When such an optimized coefficient is applied, a better linear relationship is achieved between the blood pressure value and the linear combination of the first delay time T12 and the second delay time T23. It should be noted that the examples illustrated in FIGS. 6 to 10 are provided merely to demonstrate the possible range and variability of the optimized coefficient aopt, and are not intended to limit the specific value or range of the optimized coefficient aoptdefined by the present invention.

[0040] In one embodiment, a regression line may be established based on the linear relationship between the blood pressure value and the linear combination value of the first delay time T12 and the second delay time T23. Once the individual regression line is established, a one-to-one correspondence can be defined between the blood pressure value and the linear combination value of T12 and T23. Accordingly, the corresponding blood pressure value can be directly obtained from the linear combination value of the first delay time T12 and the second delay time T23 measured by the processor.

[0041] In one embodiment, the method for measuring blood pressure further includes: receiving a reference blood pressure value measured by a standard device to calibrate the ratio between the first predetermined coefficient and the secondAttorney Docket No. 5199-0424PW01predetermined coefficient. Specifically, from the aforementioned formulas, it can be seen that the optimized coefficient aoptis related to the covariance among the blood pressure value, the first delay time, and the second delay time. During the determination of the optimized coefficient aopt, an external standard device may be use for measuring a reference blood pressure. The standard device may be, for example, a mercury sphygmomanometer or an inflatable cuff-type blood pressure monitor recognized by medical professionals. By synchronously measuring the linear combination value of the first delay time and the second delay time along with the reference blood pressure value, the optimized coefficient aoptcan be calibrated. The reference blood pressure value may be provided to the processor through numerical input (e.g., a keyboard) or data transmission. In this embodiment, the reference blood pressure value can be used for determining the optimized coefficient aoptaccording to the aforementioned formulas. Once an appropriate and subject-specific optimized coefficient aoptis determined, the blood pressure value of the subject can thereafter be estimated solely based on the linear combination value of the first delay time and the second delay time.

[0042] In one embodiment, the method for measuring blood pressure further includes: measuring, during a predetermined period, a plurality of first delay times and a plurality of second delay times; and determining a continuous blood pressure value based on a plurality of linear combination values of the plurality of first delay times and the plurality of second delay times. Specifically, referring to FIG. 11, the method provided by the present invention may be continuously performed over a predetermined period (for example, 30 seconds), thereby collecting multiple sets of first delay times and second delay times (for example, five sets respectively). Based on the collected first and second delay times, the variance of the first delay time and / or the variance of the second delay time may be determined, thereby obtaining a more accurate and subject-specific optimized coefficient aopt. Through continuous sampling, a plurality7Attorney Docket No. 5199-0424PW01of linear combination values of the first delay time and the second delay time can be obtained. These multiple linear combination values may be processed through averaging, mean-square computation, or other statistical methods to estimate and obtain an optimal blood pressure measurement result.

[0043] In summary the method for measuring blood pressure of the present invention provides a non-invasive force sensor configured to be disposed on the skin to identify a primary systolic pulse, a first reflection pulse, and a second reflection pulse contained in pulse vibration information. By establishing a linear relationship among the delay times between the primary systolic pulse, the first reflection pulse, and the second reflection pulse, the blood pressure value can be derived. Compared with traditional sphygmomanometric methods, the present invention provides a wearable means of measurement. Moreover, the proposed method for measuring blood pressure, which utilizes time differences as the basis for estimation, is less susceptible to interference caused by variations in the subject’s condition or measurement environment. Furthermore, the present invention provides a method for determining the linear relationship coefficients, whereby different linear coefficients enhance the linear correspondence between time values and blood pressure values. Accordingly, the present invention establishes an optimized feature based on the delay times among the primary systolic pulse, the first reflection pulse, and the second reflection pulse, thereby improving the measurement capability of the blood pressure estimation model. The method for measuring blood pressure provided by the present invention not only improves the correlation between extracted features and target variables but also enhances the overall prediction accuracy of the model.

[0044] The aforementioned description of the present invention is provided to enable a person of ordinary skill in the art to make or implement the present invention. Various modifications to the present invention will be apparent to a person skilled in the art, and the general principles defined herein can be applied to other variationsAttorney Docket No. 5199-0424PW01without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the examples described herein, but is to be in accord with the widest scope consistent with the principles and novel features of the invention herein.

Claims

Attorney Docket No. 5199-0424PW01CLAIMSWhat is claimed is:

1. A method for measuring blood pressure, comprising:receiving a plurality of mechanical signals from a force sensor disposed on a surface of the skin;identifying, based on the plurality of mechanical signals, a primary systolic pulse, a first reflection pulse, and a second reflection pulse;determining a first delay time between the primary systolic pulse and the first reflection pulse;determining a second delay time between the first reflection pulse and the second reflection pulse;determining a linear combination value of the first delay time and the second delay time, wherein a first predetermined coefficient applied to the first delay time is smaller than a second predetermined coefficient applied to the second delay time; and determining a blood pressure value based on the linear combination value.

2. The method according to claim 1, wherein the blood pressure value comprises a systolic pressure and a diastolic pressure.

3. The method according to claim 1, further comprising:measuring, by a standard device, a reference blood pressure value to calibrate a ratio between the first predetermined coefficient and the second predetermined coefficient.

4. The method according to claim 1, further comprising:measuring a plurality of first delay times and a plurality of second delay times during a predetermined period; anddetermining a continuous blood pressure value based on a plurality of linearAttorney Docket No. 5199-0424PW01combination values of the plurality of first delay times and the plurality of second delay times.

5. The method according to claim 4, wherein the ratio between the first predetermined coefficient and the second predetermined coefficient is determined based on a variance of the plurality of first delay times, a variance of the plurality of second delay times, and a covariance between the plurality of first delay times and the plurality of second delay times.

6. The method according to claim 5. wherein the ratio between the first predetermined coefficient and the second predetermined coefficient is further determined based on a plurality of reference blood pressure values corresponding to the plurality of first delay times and the plurality of second delay times.

7. The method according to claim 1, wherein a ratio of the second predetermined coefficient to the first predetermined coefficient is greater than 1 and smaller than or equal to 6.39.

8. A system for measuring blood pressure, comprising:a force sensor configured to be disposed on a surface of the skin; anda processing device including a processor and a memory;wherein the processor is configured to perform the following operations:receive a plurality of mechanical signals provided by the force sensor; identify, based on the plurality of mechanical signals, a primary systolic pulse, a first reflection pulse, and a second reflection pulse;determine a first delay time between the primary systolic pulse and the first reflection pulse;Attorney Docket No. 5199-0424PW01determine a second delay time between the first reflection pulse and the second reflection pulse;determine a linear combination value of the first delay time and the second delay time, wherein a first predetermined coefficient of the first delay time is smaller than a second predetermined coefficient of the second delay time; anddetermine a blood pressure value according to the linear combination value.

9. The system according to claim 8, wherein the blood pressure value comprises a systolic pressure and a diastolic pressure.

10. The system according to claim 8, further comprising:receiving a reference blood pressure value measured by a standard device to calibrate a ratio between the first predetermined coefficient and the second predetermined coefficient.

11. The system according to claim 8, further comprising:measuring, during a predetermined period, a plurality of first delay times and a plurality of second delay times; anddetermining a continuous blood pressure value based on a plurality of linear combination values of the plurality of first delay times and the plurality of second delay times.

12. The system according to claim 11, wherein a ratio between the first predetermined coefficient and the second predetermined coefficient is determined based on a variance of the plurality of first delay times, a variance of the plurality of second delay times, and a covariance between the plurality of first delay times and the plurality of second delay times.Attorney Docket No. 5199-0424PW0113. The system according to claim 12, wherein the ratio between the first predetermined coefficient and the second predetermined coefficient is further determined based on a plurality of reference blood pressure values corresponding to the plurality of first delay times and the plurality of second delay times.

14. The system according to claim 8, wherein the ratio of the second predetermined coefficient to the first predetermined coefficient is greater than 1 and smaller than or equal to 6.39.

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