Blood pressure measurement system and method

Abstract

The blood pressure measurement system and method includes detecting a first wave signal from a blood vessel using a bioinformation measurement device during a first pressing period of the wearable pressing unit, the wearable pressing unit applying pressure to an upstream blood vessel relative to the blood vessel, and generating an envelope signal of the first wave signal in response to the first wave signal. During a second pressing period of the wearable pressing unit, detecting a second wave signal from the blood vessel using the bioinformation measurement device, determining a first time point at which the waveform of the second wave signal intersects with the waveform of the envelope signal, outputting the pressure value exerted by the wearable pressing unit on the upstream blood vessel at the first time point as a systolic blood pressure value. Determining a second time point at which the envelope signal has a predetermined amplitude, and outputting the pressure value exerted by the wearable pressing unit on the upstream blood vessel as a diastolic blood pressure value at the second time point.

Description

[Technical Field]

[0001] This patent specification is in the field of blood pressure measurement methods and devices, and more particularly, to methods and devices for reducing errors in blood pressure measurements. [Background technology]

[0002] Cardiovascular disease (CVD) accounts for a significant number of deaths worldwide. CVD includes coronary heart disease, which accounts for the majority of CVD deaths, as well as stroke and heart failure. CVD is closely related to pathogenic factors and lifestyle habits. In addition to maintaining a healthy lifestyle, frequent monitoring of blood pressure, blood glucose, and cholesterol also plays an important role in preventing CVD. To meet the demand for CVD prevention and control, many portable vital signs monitoring devices have emerged that allow users to measure their own heart rate, blood pressure, blood glucose, etc.

[0003] Arterial pressure is typically measured with a sphygmomanometer. Traditionally, when a patient's blood pressure is monitored, the blood pressure varies between systolic and diastolic pressure during each heartbeat. Systolic pressure is the peak pressure in the arteries, which occurs near the end of the cardiac cycle or contraction. Diastolic pressure is the lowest pressure in the arteries, which occurs near the beginning of the cardiac cycle as the heart fills with blood. Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional portable blood pressure monitoring devices typically measure mean blood pressure and then estimate the systolic and diastolic blood pressures based on the statistical relationship between the measured mean blood pressure and the systolic and diastolic blood pressures. However, the relationship between systolic, diastolic, and mean blood pressures can vary depending on various variables within a particular patient, such as age, personal physiology, or living environment. This inevitably results in measurement errors in conventional blood pressure monitoring devices. In some variations, portable blood pressure monitoring devices combine a conventional blood pressure cuff with a finger clip sensor. These devices measure systolic blood pressure by applying compressive pressure to the artery to stop blood flow and then releasing the pressure. However, this method still suffers from measurement errors due to motion artifacts and changes in the subject's breathing. Therefore, there is a need for an improved blood pressure measurement device that can reduce errors and improve the accuracy of measuring actual blood pressure.

[0005] In this regard, the systems and methods described herein include a blood pressure measurement system that produces accurate blood pressure measurements. One aspect of the system is that it directly measures blood pressure in a portable device configuration, while effectively reducing errors due to motion artifacts and blood pressure variations caused by breathing. [Means for solving the problem]

[0006] In a first embodiment, the system enables blood pressure measurement of a human, and includes a control unit coupled to a pressing unit and a biological information measurement device, the control unit being configured to gradually increase pressure applied to a body part of the human by the pressing unit during a first pressing period to compress the body part and affect blood flow in an upstream blood vessel within the body part, and the biological information measurement device being configured to generate a first wave signal indicative of blood activity from a downstream blood vessel during the first pressing period and transmit the first wave signal to the control unit; The control unit is configured to generate an envelope signal using the first wave signal, and to establish a second pressing period by determining that the bioinformation measuring device has not detected blood activity, the bioinformation measuring device is configured to generate a second wave signal of the blood vessel using the bioinformation measuring device during the second pressing period, the control unit determines a first time point at which the waveform of the second wave signal intersects with the waveform of the envelope signal, and establishes a systolic blood pressure value using a first pressure value applied by the pressing unit to the upstream blood vessel at the first time point, and the control unit further determines a second time point at which the envelope signal has a predetermined amplitude, and establishes a diastolic blood pressure value using a second pressure value applied by the pressing unit to the upstream blood vessel at the second time point.

[0007] Variations of the systems described herein may include systems that include only a controller configured to interface with a separate vital sign device and / or pressure unit. For example, such a blood pressure measurement system may include a controller configured for use in combination with a vital sign measurement device and pressure unit, where the controller is configured to electronically communicate with the pressure unit and vital sign measurement device to perform the functions described herein.

[0008] In one embodiment, the system includes a first wave signal having a plurality of periodic waves, and the system for generating an envelope signal further includes calculating an average value of each periodic wave of the first wave signal, obtaining a first modified wave signal by subtracting the average value from the amplitude of each corresponding periodic wave, and obtaining the envelope signal by connecting a plurality of peaks of the first modified wave signal and a plurality of valleys of the first modified wave signal.

[0009] In another variation, the first wave signal has a plurality of periodic waves, and the control unit generates the envelope signal by connecting the peaks and valleys of each periodic wave.

[0010] In another example, the system detects a third wave signal from a blood vessel using a bioinformation measuring device during a non-pressing period of the wearable pressing unit, the third wave signal being a continuous wave, and includes a control unit further configured to output a systolic blood pressure value as the first peak value of a peak in the third wave signal, output a diastolic blood pressure value as the first valley value of a valley in the third wave signal that is temporally adjacent to the peak in the third wave signal, and calculate multiple additional peak values and multiple additional valley values of the multiple peaks and valleys remaining in the third wave signal, respectively, depending on the systolic blood pressure value and the diastolic blood pressure value.

[0011] In a modified example, the control unit can determine the first time point by obtaining an average line of the second wave signal, smoothing the envelope signal to obtain a modified envelope signal, and determining the first time point as the time when the upper limit value of the modified envelope signal intersects the average line.

[0012] In another example, the control unit uses a predetermined amplitude between 50% and 90% of the maximum amplitude of the envelope signal.

[0013] The pressing unit disclosed in this specification can be configured to be worn on the arm or wrist, the control unit is configured to cause the pressing unit to apply pressure during a first pressing period and a second pressing period, and the biometric information measuring device is configured to detect a first wave signal and a second wave signal from the finger.

[0014] The present disclosure also includes a blood pressure measurement method including the steps of: detecting a first wave signal from a blood vessel using a biological information measurement device during a first pressing period of a wearable pressing unit, where the wearable pressing unit applies pressure to an upstream blood vessel relative to the blood vessel; generating an envelope signal of the first wave signal in response to the first wave signal; detecting a second wave signal from the blood vessel using the biological information measurement device during a second pressing period of the wearable pressing unit; determining a first time point at which a waveform of the second wave signal intersects with a waveform of the envelope signal; outputting the pressure value applied by the wearable pressing unit to the upstream blood vessel at the first time point as a systolic blood pressure value; determining a second time point at which the envelope signal has a predetermined amplitude; and outputting the pressure value applied by the wearable pressing unit to the upstream blood vessel at the second time point as a diastolic blood pressure value.

[0015] Another example of a blood pressure measurement device includes a wearable pressing unit, a biometric information measurement device, and a control unit having a signal connecting to the wearable pressing unit and the biometric information measurement device, and the control unit performs any of the methods disclosed in this specification.

[0016] The pressure member disclosed herein may be any type of device, such as a blood pressure cuff, that functions to reduce flow in an upstream blood vessel. Additionally, the vital sign measurement device may be a finger clip device having pressure sensors for detecting the first, second, and third wave signals. The finger clip device may include an optical sensor or any other sensor capable of detecting wave signals from a downstream blood vessel.

[0017] In one aspect, the system and method provide a blood pressure measurement that includes detecting a first wave signal from a blood vessel during a first pressing period of a wearable pressing unit, the wearable pressing unit exerting pressure on an upstream blood vessel relative to the blood vessel during the first pressing period, generating an envelope signal of the first wave signal in response to the first wave signal, detecting a second wave signal from the blood vessel during a second pressing period of the wearable pressing unit, determining a first time point at which a waveform of the second wave signal intersects with a waveform of the envelope signal, outputting a pressure value exerted by the wearable pressing unit on the upstream blood vessel at the first time point as a systolic blood pressure value, determining a second time point at which the envelope signal has a predetermined amplitude, and outputting a pressure value exerted by the wearable pressing unit on the upstream blood vessel at the second time point as a diastolic blood pressure value.

[0018] Another proposal of the present invention is to provide a blood pressure measurement device including a wearable pressing unit, a biological information measurement device, and a control unit, wherein a signal from the control unit is connected to the wearable pressing unit and the biological information measurement device to perform the above-mentioned blood pressure measurement method. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the flow of a blood pressure measurement method according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the blood pressure measurement device according to the first embodiment of the present invention. [Figure 3] FIG. 3 shows the pressure applied to the wearable pressing unit as a function of time in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the first and second wave signals of the first embodiment. [Figure 5] FIG. 5 is a diagram showing one mode of generating an envelope signal in the first embodiment. [Figure 6] FIG. 6 is a diagram showing a modified example of the envelope signal and the modified envelope signal in the first embodiment. [Figure 7]FIG. 7 is a modified example of the first embodiment, showing the pressure applied to the wearable pressing unit as a function of time. [Figure 8] FIG. 8 is a diagram showing the flow of generating an envelope signal in the second embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an envelope signal according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing an envelope signal and an associated modified envelope signal according to the second embodiment. [Figure 11] FIG. 11 shows the pressure applied to the wearable pressing unit as a function of time in the second embodiment. [Figure 12] FIG. 12 is a diagram showing the flow of a blood pressure measurement method according to the third embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing the results of continuous blood pressure measurement by the blood pressure measurement method of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] While the present invention provides a new and improved method for measuring blood pressure, there remains a need to produce improved blood pressure measurements that reduce error and increase the accuracy of measuring actual blood pressure.

[0021] FIG. 1 illustrates an example of a process for obtaining a blood pressure measurement. FIG. 2 illustrates an exemplary configuration of a blood pressure measurement device for use in an improved blood pressure measurement process. The blood pressure measurement device of FIG. 2 includes a wearable pressure device 1, such as a blood pressure cuff, that compresses the arm N1 of a person N, a biological information measurement device 2, and a control unit 3. In this embodiment, the control unit 3 is connected to the wearable pressure device 1 and the biological information measurement device 2 to provide one or more signals that execute the blood pressure measurement method schematically illustrated in FIG. 1. In FIG. 1, the blood pressure measurement method according to the first aspect includes step S100 of detecting a first wave signal from a blood vessel using the biological information measurement device 2. The wave signal is generally a blood pressure waveform generated in the body when the heart pumps blood into the blood vessel. In this embodiment, the measurement device 2 detects the first wave signal during a first pressure period P1 of the wearable pressure device 1, during which the wearable pressure device 1 applies pressure to a blood vessel upstream of the blood vessel being measured by the measurement device 2. Specifically, the wearable pressing unit 1 can be a blood pressure measurement cuff that inflates and deflates in a manner controlled by the control unit 3, and the biological information measurement device 2 can be a finger clip device including any sensor (e.g., a pressure sensor) capable of measuring pressure. Therefore, the system measures the pressure of the blood vessels upstream of the arm N1. In addition, the measurement device 2 measures a first wave signal, which is a blood pressure signal from the blood vessels of the finger N2.

[0022] It should be noted that the flowcharts shown in Figures 1, 5, and 8 are intended to provide a detailed description of operations relating to the systems and / or methods. Each item or box identified in the figures is for convenience only. Unless otherwise noted, it is contemplated that features of the flowcharts may combine operations occurring in individually identified elements and that elements may be arranged in a different order.

[0023] The method of the present disclosure may include a device other than the blood pressure measurement device described above. In some examples, the wearable pressing unit 1 may be any pressing device other than a blood pressure cuff, as long as it can controllably apply pressure to an upstream blood vessel. In an additional variation, the installation location of the wearable pressing unit 1 is not limited to the arm N1. For example, the pressing location may be the wrist N3 of the person N, as long as the biological information measurement device 2 detects a blood pressure signal from a blood vessel N2 downstream of the blood vessel compressed by the pressing unit 1. In an additional variation, the sensor of the finger clip may be a pressure sensor, an optical sensor, an ultrasonic sensor, an electromagnetic sensor, or a combination thereof.

[0024] FIG. 4 shows a wave signal when the control unit 3 controls the expansion of the wearable pressure unit 1 during the first pressure period P1 (i.e., the phase in which the pressure unit 1 compresses the artery). During this first pressure period P1, the biological information measurement device 2 detects a first wave signal W1 from the finger N2. FIG. 3 shows the pressure applied by the wearable pressure unit 1 to the arm N1 as a function of time. During the first pressure period P1, the pressure applied by the wearable pressure unit 1 to the upstream blood vessels of the arm N1 increases linearly. As a result, the blood flow through the upstream blood vessels gradually decreases over time. As a result, the blood flow received by the finger N1 in the downstream blood vessels also gradually decreases over time, as shown by the decrease in the amplitude of the first wave signal W1 in FIG. 4.

[0025] As shown in FIG. 1, the blood pressure measurement method of the first embodiment further includes step S102: generating an envelope signal E1 of the first wave signal W1 in response to the first wave signal W1; step S104: detecting a second wave signal W2 of the blood vessel using the biological information measurement device 2 during a second pressure period P2 of the wearable pressure unit 1; step S106: determining a first time point T1a at which the waveform of the second wave signal W2 intersects with the waveform of the envelope signal E1; and step S108: outputting the pressure value applied by the wearable pressure unit 1 to the upstream blood vessel at the first time point T1a as a systolic blood pressure value. FIGS. 2 to 4 relate to steps S102 to S108. As shown in FIG. 4, the first wave signal W1 of the first embodiment includes multiple periodic waves (C1, C2, ..., Cn). In FIG. 4, only C1, C2, and Cn are shown to explain the definition of the periodic waves in this embodiment. Specifically, each periodic wave in this modification is defined as a signal between two adjacent valleys of the first wave signal W1, and the envelope signal E1 is generated by connecting adjacent peaks and valleys of all periodic waves.

[0026] In step S104 of the first embodiment, when the pressure exerted by the wearable pressing unit 1 on the upstream blood vessel exceeds a certain level at which the biological information measurement device 2 does not detect a waveform, the wearable pressing unit 1 enters a second pressing period P2. As illustrated in FIG. 4, the blood pressure signal detected by the biological information measurement device 2 during the second pressing period P2 is the second wave signal W2. Subsequently, in steps S106 and S108, the moment when the waveform of the envelope signal E1 intersects with the waveform of the second wave signal W2 is defined as a first time point T1a. Furthermore, according to the graph of the pressure exerted by the pressing device 1 as a function of time in FIG. 3, a pressure value Sa is obtained at the first time point T1a. The pressure value Sa is then set as the systolic blood pressure value. Specifically, the envelope signal E1 ends when the first pressing period P1 ends, and the waveform of the second wave signal W2 begins when the second pressing period P2 begins. In step S106, the second time point T2a is defined as the moment when the extension of the envelope signal E1 intersects with the waveform of the second wave signal W2. It should be noted that in this modification, the second pressure period P2 begins immediately after the first pressure period P1 ends. Therefore, the first wave signal W1 and the second wave signal W2 are detected within a single pressure period of the wearable pressure unit 1. However, this method does not limit additional modifications. Alternatively, the first wave signal W1 and the second wave signal W2 can be detected in separate pressure periods. In particular, a significant difference between the first pressure period P1 and the second pressure period P2 is that the biological information measurement device 2 can detect the systolic blood pressure waveform and the diastolic blood pressure waveform during the first pressure period P1. On the other hand, the biological information measuring device 2 cannot detect a blood pressure waveform during the second pressure period P2 because the pressure applied to the upstream blood vessel by the wearable pressure unit 1 reduces blood flow in the blood vessel. Note that the present invention is not limited to whether the wearable pressure unit 2 increases, decreases, or maintains a constant pressure during the second pressure period P2. Furthermore, in this embodiment, the order of steps S102 and S104 is not limited to this. The envelope signal E1 can be generated after both the first wave signal W1 and the second wave signal W2 are detected.

[0027] After step S108, the blood pressure measurement process further includes step S110: determining a second time point T2a at which the envelope signal E1 has a predetermined amplitude A2; and step S112: outputting the pressure value exerted by the wearable pressing unit 1 on the upstream blood vessel at the second time point T2a as a diastolic blood pressure value. In this modification, the predetermined amplitude A2 of the envelope signal E1 is 85% of the maximum amplitude A1. That is, the moment when the amplitude of the envelope signal E1 decreases to 85% of the maximum amplitude A1 is defined as the second time point T2a. However, in an additional modification, the predetermined amplitude A2 can be 50% to 90% of the maximum amplitude. In another modification, the predetermined amplitude A2 can be determined according to the sample group to which the person belongs. For example, the sample group can be classified based on heart rate, blood pressure waveform, age, gender, height, weight, etc. Next, according to the pressure-time curve of FIG. 3, the pressure Da that the wearable pressing unit 1 exerts on the arm N1 at the second time point T2a is output as the diastolic blood pressure value.

[0028] In this variation, the diastolic and systolic blood pressure values can be displayed on a monitor of the control unit 3. However, alternative means of displaying or transmitting the diastolic and systolic blood pressure values are within the scope of this disclosure. In some variations, the vital sign measurement unit 2 may include a small display that displays the diastolic and systolic blood pressure values.

[0029] By using the above method, the present invention can directly measure the systolic blood pressure according to the first wave signal W1 detected from the blood vessel of the subject N. Compared to conventional blood pressure measurement methods, the present invention does not require calculating the systolic blood pressure from the mean blood pressure, thereby improving the accuracy of blood pressure measurement.

[0030] 5 and 6 illustrate a variation of the method described herein, in which step S102 can further include steps S200: obtaining a mean line W2' of the second wave signal; S202: smoothing the envelope signal E1 to obtain a modified envelope signal E1'; and S204: determining a first time point T1b as the moment when the upper limit of the modified envelope signal E1' intersects with the mean line W2'. As shown in FIG. 6, in step S200, the mean line W2' is a line segment having signal intensities obtained by averaging the second wave signal W2. In step S202, the envelope signal E1 can be smoothed by fitting the envelope signal E1 with a regression or interpolation curve. In FIG. 6, the envelope signal E1 is illustrated with a dashed line, and the modified envelope signal E1' is illustrated with a solid line. Steps S202 and S204 can reduce errors in the first wave signal W1 due to motion artifacts and respiratory fluctuations of the human N. When the second wave signal W2 is detected, the upstream blood vessel is occluded, reducing the blood flow in the blood vessel of the test finger. Therefore, the second wave signal W2 is less susceptible to motion artifacts and respiratory fluctuations. Therefore, in step S204, the first time point T1b obtained from the average line W2' of the corrected envelope signal E1' and the second wave signal W2 is set as the time point of the systolic blood pressure after error suppression.

[0031] Furthermore, as shown in Figures 6 and 7, when step S108 is performed, a more accurate systolic blood pressure value Sb can be obtained from the first time point T1b according to steps S200 to S204. In addition, in this modification, the second time point T2b can be determined from the time point of the predetermined amplitude A2 of the modified envelope signal E1'. Because the modified envelope signal E1' reduces errors caused by motion artifacts and respiratory fluctuations, the second time point T2b obtained from the modified envelope signal E1' is closer to the actual time point of the diastolic blood pressure. Therefore, the diastolic blood pressure value Db obtained from the second time point T2b is more accurate.

[0032] 8 to 11 show another example of a method for measuring blood pressure. In this example, step S102 (obtaining an envelope signal of the first wave signal in the example) includes steps S302 (calculating the average value of each periodic wave of the first wave signal W1), S304 (subtracting the average value from the amplitude of each corresponding periodic wave to obtain a first corrected wave signal W1'), and S306 (connecting all peaks and valleys of the first corrected wave signal W1' to obtain an envelope signal E2 of the first wave signal W1). Specifically, in this example, the average value of each periodic wave (C1, C2, ..., Cn) of the first wave signal W1 in FIG. 4 is first calculated. Then, the calculated average value is subtracted from the amplitude of each corresponding periodic wave (C1, C2, ..., Cn) to obtain the first corrected signal W1'. For example, the average value of the periodic wave C1 is subtracted from the amplitude of the periodic wave C1, the average value of the periodic wave C2 is subtracted from the amplitude of the periodic wave C2, etc. The envelope signal E2 of the second embodiment is obtained by connecting all the peaks and valleys of the first modified wave signal W1'.

[0033] Steps S302 and S304 function as a high-pass filter and perform processing to remove baseline drift in the first wave signal W1 in FIG. 4. Specifically, as shown in FIGS. 2 and 4, when the wearable pressing unit 1 continuously applies pressure during the pressing period P1, the blood vessels on the upstream side of the arm N1 are compressed beyond a predetermined level. This prevents arterial blood measurements from being obtained from the blood vessels in the downstream finger N2, and prevents venous blood on the relatively downstream side from returning to the heart through the upstream blood vessels. As a result, the venous blood stagnating on the relatively downstream side causes the baseline of the first wave signal W1 to drift upward, as shown by the first wave signal W1 after 20 seconds in FIG. 4. When the second pressing period P2 begins, water in the venous blood on the relatively downstream side gradually diffuses out of the blood vessels. As a result, the baseline of the second wave signal W2 gradually drifts downward. In addition, low-frequency fluctuations such as respiratory fluctuations, vascular movement, and fluid drift in tissues may cause baseline drift in the first wave signal W1. Through steps S302 and S304 of this modification, the baseline drift can be filtered to obtain a first modified wave signal W1', as illustrated in Figure 9. Then, the envelope signal E2 of the second embodiment is obtained by connecting all the peaks and valleys of the first modified wave signal W1'.

[0034] Furthermore, after obtaining the envelope signal E2, the modifications detailed in FIG. 5 can be performed. As shown in FIGS. 8 and 10, a first time point T1c can be obtained by curve fitting the first modified wave signal W1. Specifically, in step S310, the average value of the second wave signal W2 is calculated to obtain an average line W2'. Next, in step S312, the envelope signal E2 is smoothed to obtain a modified envelope signal E2'. Then, in step S314, a first time point T1c at which the average line W2' and the modified envelope signal E2' intersect is determined.

[0035] In this variant, steps S314 to S310 are similar to steps S106 to S112. The modified envelope signal E2' of the second variant replaces the envelope signal E1 of the first embodiment to determine the first time point T1c and the second time point T2c. In this variant, the first modified envelope signal E2' reduces errors due to low-frequency fluctuations, and the modified envelope signal E2' further reduces noise in the first modified signal W1' due to motion artifacts and respiratory fluctuations. The noise in the average line W2' due to motion artifacts and respiratory fluctuations is negligible. Therefore, the first time point T1c obtained at the intersection of the modified envelope signal E2' and the average line W2' is closer to the actual systolic blood pressure time point.

[0036] Furthermore, in step S318, the obtained second time point T2c at the predetermined amplitude A2 of the modified envelope signal E2' is closer to the actual time point of the diastolic blood pressure because errors due to motion artifacts, respiratory fluctuations, and signal drift are reduced. As shown in FIG. 11, in the second modified example, the pressure values Sc and Dc applied by the wearable pressing unit 1 to the upstream blood vessel at the first time point T1c and the second time point T2c, respectively, are closer to the subject's actual systolic blood pressure and diastolic blood pressure. From this perspective, steps S302 to S306 of the second embodiment improve the accuracy of blood pressure measurement by reducing errors due to drift of the first wave signal.

[0037] 12 and 13 show an additional variation of the blood pressure measurement method. This variation uses the blood pressure measurement device D described above and can be applied after the first embodiment. The blood pressure measurement method of this variation includes the following steps: step S400: detecting a third wave signal from a blood vessel using a biological information measurement device during a period when the wearable pressing unit is not being pressed (the third wave signal is a continuous wave); step S402: outputting a systolic blood pressure value Sc as the peak value of a peak in the third wave signal; step S404: outputting a diastolic blood pressure value Dc as the valley value of a valley temporally adjacent to the peak in the third wave signal; and step S406: calculating the peak values and valley values of the remaining peaks and valleys in the third wave signal, respectively, according to the systolic blood pressure value and the diastolic blood pressure value.

[0038] 2 and 13 specifically show step S400, in which the biological information measurement device 2 detects the third wave signal W3 with the finger N2 when the wearable pressure unit 1 is not pressing against the upstream blood vessel. In step S402, this embodiment outputs the systolic blood pressure value Sc obtained in the second embodiment as the peak value of the first peak in the third wave signal W3. In step S404, this modification outputs the diastolic blood pressure value Dc obtained in the second modification as the valley value of the first valley in the third wave signal W3. Next, in step S406, this modification linearly scales the vertical axis of the third wave signal W3 according to the systolic blood pressure value Sc and the diastolic blood pressure value Dc. Therefore, the remaining peak and valley values of the third wave signal W3 can be calculated. Because the systolic blood pressure value Sc and the diastolic blood pressure value Dc are directly measured by signal processing of the blood pressure waveform, calculation based on the systolic blood pressure value Sc and the diastolic blood pressure value Dc makes the remaining systolic blood pressure values of the continuous blood pressure waveform more accurate. In step S402 of another embodiment, the systolic blood pressure value Sc may be output as the peak value of any peak in the third wave signal W3. In step S404 of another embodiment, the diastolic blood pressure value Dc may be output as the valley value of any valley in the third wave signal W3. The present invention is not limited to the embodiment illustrated in FIG. 13.

[0039] Well-known structures, materials, or operations have not been shown or described in detail so as not to obscure aspects of the described devices. Those skilled in the art can modify the described embodiments in various different ways without departing from the spirit and scope of the present invention. It should be noted that example elements can be combined with each other in embodiments of the present invention without contradiction. Therefore, it should be understood that the embodiments described herein are not intended to be exhaustive of all possible embodiments in accordance with the present disclosure, and that additional embodiments are contemplated based on the subject matter disclosed herein.

Claims

1. The device includes a pressing unit (1) and a control unit (3) coupled to a biological information measuring device (2), the control unit (3) is configured to gradually increase the pressure applied to the human body part by the pressing unit (1) during a first pressing period (P1) and a second pressing period (P2), compressing the body part so that the pressing unit (1) applies pressure to an upstream blood vessel relative to a downstream blood vessel measured by the biological information measuring device (2); the biological information measuring device (2) is configured to generate a first wave signal (W1) indicating blood pressure activity from the downstream blood vessel during the first pressing period (P1) and transmit the first wave signal (W1) to the control unit (3); the control unit (3) generates an envelope signal (E1) having an upper limit and a lower limit, the upper limit of the envelope signal (E1) being generated by connecting adjacent crests of the first wave signal (W1), and the lower limit of the envelope signal (E1) being generated by connecting adjacent troughs of the first wave signal (W1); the control unit (3) is configured to generate a second wave signal (W2) indicating blood pressure activity from the downstream blood vessel during the second pressure period (P2) and transmit the second wave signal (W2) to the control unit (3), and the second pressure period (P2) starts when the biological information measurement device (2) no longer detects the blood pressure activity from the downstream blood vessel; The control unit (3) determines a first time point (T1a) at which the waveform of the second wave signal (W2) intersects with the waveform of the envelope signal (E1), and the control unit (3) determines a first pressure value applied by the pressing unit (1) to the upstream blood vessel at the first time point (T1a) to thereby determine a systolic blood pressure value (Sa); the control unit (3) determines a point at which the envelope signal (E1) has a predetermined amplitude (A2) to determine a second time point (T2a); the control unit (3) determines a second pressure value exerted by the pressing unit (1) on the upstream blood vessel at the second time point (T2a) to determine a diastolic blood pressure value (Da); The control unit (3) obtaining a mean line (W2') of the second wave signal (W2); smoothing the envelope signal (E1) to obtain a modified envelope signal (E1'); 1. A system for measuring blood pressure of a human, configured to determine a first time point (T1b) by determining the first time point (T1b) as the time when an upper limit of the modified envelope signal (E1') crosses the mean line (W2').

2. 2. The system of claim 1, wherein the first wave signal (W1) has a plurality of periodic waves (C1, C2, ..., Cn), and the control unit (3) generates the envelope signal (E1) by connecting the crests of each periodic wave (C1, C2, ..., Cn) and the troughs of each periodic wave (C1, C2, ..., Cn) (S306).

3. 2. The system of claim 1, wherein the predetermined amplitude (A2) of the envelope signal (E1) is between 50% and 90% of the maximum amplitude (A1) of the envelope signal (E1).

4. 2. The system according to claim 1, wherein the pressing unit (1) is configured to be worn on an arm or wrist, the control unit (3) is configured to cause the pressing unit (1) to apply pressure during the first pressing period (P1) and the second pressing period (P2), and the biometric information measuring device (2) is configured to detect the first wave signal (W1) and the second wave signal (W2) from a finger.

5. a step of detecting a first pressure wave signal (W1) indicating blood pressure activity from a downstream blood vessel using a biological information measuring device (2) during a first pressing period (P1) of a wearable pressing unit (1), wherein the wearable pressing unit (1) exerts pressure on an upstream blood vessel relative to the blood vessel; generating an envelope signal (E1) of the first pressure wave signal (W1) in response to the first pressure wave signal (W1), the envelope signal (E1) having an upper limit and a lower limit, the upper limit of the envelope signal (E1) being generated by connecting adjacent peaks of the first pressure wave signal (W1), and the lower limit of the envelope signal (E1) being generated by connecting adjacent valleys of the first pressure wave signal (W1); a step of detecting a second pressure wave signal (W2) indicating blood pressure activity from the downstream blood vessel using the biological information measuring device (2) during a second pressing period (P2) of the wearable pressing unit (1), the second pressing period (P2) starting when the biological information measuring device (2) no longer detects the blood pressure activity from the downstream blood vessel; determining a first time point (T1a) at which the waveform of the second pressure wave signal (W2) intersects with the waveform of the envelope signal (E1); At the first time point (T1a), outputting the pressure value exerted by the wearable pressing unit (1) on the upstream blood vessel as a systolic blood pressure value (Sa); determining a second time point (T2a) at which the envelope signal (E1) has a predetermined amplitude (A2); At the second time point (T1b), outputting the pressure value exerted by the wearable pressing unit (1) on the upstream blood vessel as a diastolic blood pressure value (Da); obtaining a mean line (W2') of the second pressure wave signal (W2); smoothing the envelope signal (E1) to obtain a modified envelope signal (E1'); determining a first time point (T1b) by determining said first time point (T1b) as the time when an upper limit of said modified envelope signal (E1') crosses said mean line (W2'); A blood pressure measuring method comprising:

6. 6. The method of claim 5, wherein the first pressure wave signal (W1) has a plurality of periodic waves (C1, C2, ..., Cn), and the step of generating the envelope signal (E1) further comprises the step of obtaining the envelope signal (E1) by connecting a crest of each periodic wave (C1, C2, ..., Cn) with a trough of each periodic wave (C1, C2, ..., Cn).

7. The step of determining the first time point (T1b) comprises: obtaining a mean line (W2') of the second pressure wave signal (W2); smoothing the envelope signal (E1) to obtain a modified envelope signal (E1'); determining said first time point (T1b) as the time when the upper limit of said modified envelope signal (E1') crosses said mean line (W2'); The method of claim 5 further comprising:

8. 6. The method of claim 5, wherein the predetermined amplitude (A2) of the envelope signal (E1) is between 50% and 90% of the maximum amplitude (A1) of the envelope signal (E1).

9. 6. The method of claim 5, wherein the wearable pressing unit (1) applies pressure to an arm or wrist during the first pressing period (P1) and the second pressing period (P2), and the biometric information measuring device (2) detects the first pressure wave signal (W1) and the second pressure wave signal (W2) from a finger.

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