Blood pressure measuring device, blood pressure measuring method, and blood pressure measuring program

Abstract

This enables blood pressure calculation by applying pressure without exceeding the envelope peak. [Solution] A blood pressure measuring device comprising: a cuff wrapped around the part to be measured; a pressure detection unit for detecting cuff pressure; a pulse wave acquisition unit for acquiring the pulse wave of the person to be measured from the cuff pressure; a pressure control unit that controls the cuff pressure and stops pressurizing the cuff when it reaches a stop cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximum; a diastolic blood pressure calculation unit for calculating the diastolic blood pressure of the person to be measured based on the pulse wave acquired up to the stop cuff pressure; a mean blood pressure calculation unit for calculating the mean blood pressure of the person to be measured based on the pulse wave acquired up to the stop cuff pressure; and a systolic blood pressure calculation unit for extracting a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure, and calculating the systolic blood pressure of the person to be measured as a value corresponding to the maximum value of the single pulse wave, by correlating the diastolic blood pressure and mean blood pressure with the minimum value and area average value of the single pulse wave.

Description

[Technical Field]

[0001] The present invention relates to a blood pressure measurement device, a blood pressure measurement method, and a blood pressure measurement program. [Background Art]

[0002] In recent years, health management by measuring personal physical and health information such as blood pressure values with a measuring device, and recording and analyzing the measurement results has become widespread. As an example of such a measuring device, there has been proposed a blood pressure measurement device that calculates the systolic blood pressure from the actually measured diastolic blood pressure and mean blood pressure without the need to pressurize a cuff attached to a measurement site such as the upper arm or wrist of a subject to a pressure higher than the systolic blood pressure (for example, Patent Document 1).

[0003] However, with the technology described in Patent Document 1, it is necessary to pressurize the cuff until it exceeds the peak of the envelope connecting the peaks of the pressure pulse wave superimposed on the cuff pressure. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2003-284696 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In view of the above-described conventional technology, it is an object of the present invention to provide a technology that enables blood pressure calculation by pressurization that does not exceed the peak of the envelope. [Means for Solving the Problem]

[0006] In order to solve the above problems, the present invention provides: a cuff wound around a measurement site; a pressure detection unit that detects a cuff pressure inside the cuff; a pulse wave acquisition unit that acquires a pulse wave of a subject from the cuff pressure; A pressure control unit controls the cuff pressure and stops pressurizing the cuff when it reaches a stop cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximum. A diastolic blood pressure calculation unit calculates the subject's diastolic blood pressure based on the pulse wave acquired up to the point of reaching the stop cuff pressure, A mean blood pressure calculation unit that calculates the mean blood pressure of the subject based on the pulse wave acquired up to the point of reaching the stop cuff pressure, A systolic blood pressure calculation unit extracts a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure, correlates the diastolic blood pressure and the mean blood pressure with the minimum value and area average value of the single pulse wave, and calculates the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave. This blood pressure measuring device is characterized by having the following features:

[0007] According to this method, blood pressure, including diastolic, mean arterial pressure, and systolic arterial pressure, can be calculated even when the cuff pressure is increased to a level that does not exceed the envelope peak.

[0008] Furthermore, in the present invention, The diastolic blood pressure calculation unit may calculate the diastolic blood pressure based on the characteristics of the pulse wave acquired up to the point where the stopping cuff pressure is reached.

[0009] Furthermore, in the present invention, The diastolic blood pressure calculation unit extracts from the pulse wave acquired up to the point where the stop cuff pressure is reached. The minimum blood pressure may be calculated based on a mathematical model of the envelope.

[0010] Furthermore, in the present invention, The mean arterial pressure calculation unit may calculate the mean arterial pressure based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached.

[0011] Furthermore, in the present invention, The mean arterial pressure calculation unit may calculate the mean arterial pressure based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stopping cuff pressure is reached.

[0012] Furthermore, in the present invention, The diastolic blood pressure calculation unit may calculate the diastolic blood pressure by an arithmetic mean or weighted mean of a first diastolic blood pressure calculated based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached, and a second diastolic blood pressure calculated based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stop cuff pressure is reached.

[0013] Furthermore, in the present invention, The mean blood pressure calculation unit may calculate the mean blood pressure by an arithmetic mean or weighted mean of a first mean blood pressure calculated based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached, and a second mean blood pressure calculated based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stop cuff pressure is reached.

[0014] Furthermore, in the present invention, The systolic blood pressure calculation unit may be characterized by calculating the systolic blood pressure based on the ratio of the maximum amplitude, which is the difference between the maximum value and the minimum value of the pulse wave, and the area-average amplitude, which is the difference between the area-average value and the minimum value of the pulse wave, to the diastolic blood pressure and the mean blood pressure.

[0015] Furthermore, the present invention is A step of detecting the cuff pressure inside the cuff wrapped around the part to be measured, The steps include obtaining the pulse wave of the person being measured from the cuff pressure, The steps include controlling the cuff pressure and stopping the pressurization of the cuff when it reaches a stop cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximum, A step of calculating the diastolic blood pressure of the person being measured based on the pulse wave obtained up to the point of reaching the stop cuff pressure, The steps include: calculating the mean blood pressure of the person being measured based on the pulse wave acquired up to the point of reaching the stop cuff pressure; The steps include: extracting a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure; correlating the diastolic blood pressure and the mean blood pressure with the minimum value and area mean of the single pulse wave; and calculating the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave; This is a blood pressure measurement method characterized by including [a specific component].

[0016] According to this method, blood pressure, including diastolic, mean arterial pressure, and systolic arterial pressure, can be calculated even when the cuff pressure is increased to a level that does not exceed the envelope peak.

[0017] Furthermore, the present invention is On the computer, A step of detecting the cuff pressure inside the cuff wrapped around the part to be measured, The steps include obtaining the pulse wave of the person being measured from the cuff pressure, The cuff pressure is controlled to a stopping cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximized. The step of stopping pressurization of the cuff when the threshold is reached, A step of calculating the diastolic blood pressure of the person being measured based on the pulse wave obtained up to the point of reaching the stop cuff pressure, The steps include: calculating the mean blood pressure of the person being measured based on the pulse wave acquired up to the point of reaching the stop cuff pressure; The steps include: extracting a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure; correlating the diastolic blood pressure and the mean blood pressure with the minimum value and area mean of the single pulse wave; and calculating the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave; This is a blood pressure measurement program that performs the following actions.

[0018] According to this method, blood pressure, including diastolic, mean arterial pressure, and systolic arterial pressure, can be calculated even when the cuff pressure is increased to a level that does not exceed the envelope peak. [Effects of the Invention]

[0019] According to the present invention, it becomes possible to calculate blood pressure by applying pressure that does not exceed the peak of the envelope. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic diagram of the hardware configuration of a blood pressure measuring device according to an embodiment. [Figure 2] Figure 2 is a functional block diagram of a blood pressure measuring device according to an embodiment. [Figure 3] Figure 3 is a schematic diagram showing the relationship between cuff pressure and pulse wave in a blood pressure measuring device according to an embodiment. [Figure 4] Figure 4 is a flowchart illustrating the overall processing procedure of the blood pressure measurement device according to the embodiment. [Figure 5] Figures 5(A), 5(B), and 5(C) illustrate the indices associated with a single pulse wave in a blood pressure measuring device according to an embodiment. [Figure 6] Figure 6 is a flowchart illustrating the procedure for creating the envelope mathematical model. [Figure 7] Figure 7(A) shows the relationship between the pressure pulse wave and the envelope, Figure 7(B) shows the relationship between the envelope and its mathematical model, and Figure 7(C) explains the relationship between the mathematical model of the envelope and mean blood pressure. [Figure 8] Figure 8 illustrates the relationship between the index P and the envelope. [Figure 9] Figure 9 is a flowchart illustrating the procedure for calculating SBP. [Figure 10] Figures 10(A) and 10(B) illustrate the SBP calculation process. [Figure 11] Figure 11 is a diagram illustrating the DBP calculation process related to Modification Example 1. [Figure 12] Figure 12 is a diagram illustrating the DBP and MBP calculation process related to Modification Example 2. [Modes for carrying out the invention]

[0021] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0022] <Example 1> An example of an embodiment of the present invention is described below. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment are not intended to limit the scope of the present invention to those specifications only.

[0023] (Device configuration) Figure 1 is a schematic diagram of the hardware configuration of the blood pressure measuring device 1 according to this embodiment.

[0024] The blood pressure measuring device 1 includes a cuff 11, a pressure sensor 12, a pressurizing pump 13, an exhaust valve 14, and an air pump. The device comprises a tube 15, an oscillation circuit 21, a pump drive circuit 22, a valve drive circuit 23, a display unit 25, a memory unit 24, an operation switch 26, and a power supply 27. The blood pressure measuring device 1 corresponds to the blood pressure measuring device of the present invention. The cuff 11 corresponds to the cuff of the present invention. Furthermore, the blood pressure measuring device 1 having a control unit 100 and memory corresponds to the computer of the present invention.

[0025] The cuff 11 includes an air bag 11a containing air. The cuff 11 is equipped with a pressure sensor 12 for detecting the pressure inside the air bag 11a of the cuff 11 (hereinafter referred to as "cuff pressure") via an air tube 15, a pressurizing pump 13 for supplying air to the air bag 11a, and an exhaust valve 14 that can be opened and closed to maintain the pressure inside the air bag 11a or to discharge the air inside the air bag 11a.

[0026] Furthermore, the blood pressure measuring device 1 includes a control unit 100 for controlling each part of the device, a storage unit 24 for storing data such as a program 240 executed for blood pressure measurement processing, model data 241, cuff pressure, pulse wave, and blood pressure measurement results, a display unit 25 for displaying various information such as blood pressure measurement results, operation switches 26 for inputting various instructions for measurement, and a power supply 27 for supplying power to each part of the device, such as the control unit 100. The control unit 100 includes a hardware processor such as a CPU (Central Processing Unit) and is configured to perform information processing based on the program and various data.

[0027] Furthermore, the oscillation circuit 21 outputs a signal with an oscillation frequency corresponding to the output value of the pressure sensor 12 to the control unit 100. The pump drive circuit 22 controls the drive of the pressurizing pump 13 based on the control signal output from the control unit 100. The valve drive circuit 23 controls the opening and closing of the exhaust valve 14 based on the control signal output from the control unit 100.

[0028] Regarding the specific hardware configuration of the blood pressure measuring device 1, components can be omitted, replaced, and added as appropriate depending on the embodiment. For example, the control unit 100 may include multiple hardware processors. Hardware processors may consist of microprocessors, FPGAs, DSPs, ASICs, etc. The blood pressure measuring device 1 may be equipped with a communication interface. For example, the blood pressure measuring device 1 may be configured to communicate data with a user terminal such as a smartphone by including a proximity wireless communication module. This allows the blood pressure measuring device 1 to acquire arbitrary data via the user terminal. At least one of the program 240 and model data 241 may be stored on a storage medium of an external computer such as a NAS. The blood pressure measuring device 1 may acquire at least one of the program 240 and model data 241 from an external computer. The blood pressure measuring device 1 may acquire data directly from an external computer, or it may acquire data indirectly from an external computer via a user terminal. The blood pressure measuring device 1 may be configured as a general blood pressure monitor, or as a wearable device such as a wristwatch.

[0029] Figure 2 is a functional block diagram of the control unit 100 of the blood pressure measuring device 1. The control unit 100 includes a pressure detection unit 110, a pressure control unit 120, a DBP calculation unit 130, a stop cuff pressure calculation unit 140, a mathematical model creation unit 150, an MBP calculation unit 160, and an SBP calculation unit 170. The pressure detection unit 110, pressure control unit 120, DBP calculation unit 130, MBP calculation unit and SBP calculation unit 170 correspond to the pressure detection unit, pressure control unit, minimum blood pressure calculation unit, mean blood pressure calculation unit and maximum blood pressure calculation unit of the present invention, respectively.

[0030] The output signal from the oscillation circuit 21 is input to the pressure detection unit 110. The pressure detection unit 110 detects the oscillation frequency of the input signal and converts the detected oscillation frequency into a pressure value signal. The pressure detection unit 110 has an HPF (High Pass Filter) unit 111 that extracts and outputs a pressure pulse wave signal by processing the pressure value signal with an HPF (High Pass Filter), and an LPF (Low Pass Filter) unit that processes the pressure value signal with an LPF (Low Pass Filter). The pressure detection unit 110 includes an LPF unit 112 that extracts and outputs a cuff pressure signal. The pressure pulse wave signal detected in chronological order from the HPF unit 111 and the cuff pressure signal indicating cuff pressure detected in chronological order from the LPF unit 112 are stored in a predetermined area of ​​the storage unit 24. Here, the HPF unit 111 corresponds to the pulse wave acquisition unit of the present invention.

[0031] Figure 3 is a schematic graph showing the relationship between cuff pressure detected by the pressure detection unit 110 and the pressure pulse wave. Generally, as shown in Figure 3, the diastolic blood pressure (DBP) and systolic blood pressure (SBP) are calculated as cuff pressures corresponding to specific fluctuation patterns of the pressure pulse wave. When the cuff 11 is pressurized, the diastolic blood pressure is calculated, and after the peak of the pressure pulse wave envelope occurs, the systolic blood pressure is calculated at a higher cuff pressure.

[0032] The pressure control unit 120 controls the cuff pressure of the cuff 11 by controlling the operation of the pump drive circuit 22 and the valve drive circuit 23.

[0033] The DBP calculation unit 130 has the function of receiving the pressure pulse wave signal extracted by the HPF unit 111 of the pressure detection unit 110 and processing the input pressure pulse wave signal to calculate diastolic blood pressure (minimum blood pressure, DBP). The DBP calculation process will be described later.

[0034] The stop cuff pressure calculation unit 140 has a function to perform a stop cuff pressure calculation process, which calculates the value of the stop cuff pressure, which is the cuff pressure at which pressurization of the cuff 11 is stopped, from the cuff pressure corresponding to the DBP calculated by the DBP calculation unit 130. The stop cuff pressure calculation process will be described later.

[0035] The mathematical model creation unit 150 has the function of executing a mathematical model creation process to create mathematical models included in the model data 241 that are pre-stored in the storage unit 24. The mathematical model creation process will be described later.

[0036] The MBP calculation unit 160 has the function of performing an MBP calculation process to calculate mean blood pressure (MBP) based on the mathematical model created by the mathematical model creation process. The MBP calculation process will be described later.

[0037] The SBP calculation unit 170 extracts the single pulse wave signal at the lowest blood pressure point from the pressure pulse wave signal extracted by the HPF unit 111 of the pressure detection unit 110, and processes this signal to calculate SBP. The SBP calculation process will be described later.

[0038] (Method of measuring blood pressure) Figure 4 is a flowchart showing the overall procedure for blood pressure measurement using the blood pressure measuring device 1. The overall blood pressure measurement process shown in Figure 4 is achieved when the control unit 100 reads and executes a blood pressure measurement program contained in a program 240 that is pre-stored in the storage unit 24. This program may be stored in a computer-readable storage medium and read from that storage medium to the blood pressure measuring device 1.

[0039] When measuring blood pressure, the person being measured has already wrapped the cuff 11 around the part to be measured. The following explanation describes an example where the upper arm is the part to be measured, but the part to be measured is not limited to the upper arm; it may also be the wrist or other parts. Furthermore, it will be explained assuming that the person being measured has made the necessary settings using the operation switch 26 and has given the instruction to start blood pressure measurement. When the blood pressure measuring device 1 receives the instruction to start blood pressure measurement, it performs the necessary initialization, such as opening the exhaust valve 14 and setting the cuff pressure to atmospheric pressure (initial pressure).

[0040] When blood pressure measurement is started, the pressure control unit 120 starts pressurizing control to pressurize the cuff 11 (step S1).

[0041] During the pressurization control process, the HPF section 111 of the pressure detection unit 110 acquires the pressure pulse wave (step S2).

[0042] The DBP calculation unit 130 calculates DBP from the detected pressure pulse wave information (step S3). Specifically, the DBP calculation unit 130 determines whether the pressurized cuff pressure has reached the cuff pressure corresponding to DBP based on an index obtained from the pressure pulse wave information. Pressurization is continued and pressure pulse waves are further acquired until the cuff pressure reaches the cuff pressure corresponding to DBP (step S2), and the process in step S3 is repeated. The DBP calculation unit 130 then calculates the cuff pressure value corresponding to DBP as DBP and stores it in a predetermined area of ​​the storage unit 24.

[0043] As indices obtained based on pressure pulse wave information, RAV, WID, and DFN are known, as shown in Japanese Patent Publication No. 03-280932. These are indices calculated for each beat of the pressure pulse wave, and RAV, WID, and DFN represent the area, width, and slope of the pulse wave for one beat, respectively. Figure 5(A) illustrates RAV, Figure 5(B) illustrates WID, and Figure 5(C) illustrates DFN. The waveform in Figure 5(A) shows the pulse wave for one beat, and RAV is the pulse wave area for each beat, shown by the shaded area in Figure 5(A), normalized by the amplitude, and is expressed as (pulse wave area / pulse wave amplitude within one beat) × 100. As shown in Figure 5(B), WID is the time width from the maximum amplitude to the threshold, normalized by the pulse wave period, and is expressed as (waveform width / pulse wave period) × 100. As shown in Figure 5(C), the DFN is the minimum value of the first derivative of the pressure pulse wave normalized by the pulse wave amplitude, and is expressed as (minimum value of the first derivative of the pulse wave from 0 / pulse wave amplitude of the first derivative of the pulse wave).

[0044] When the cuff pressure at which DBP occurs is denoted as Pd, it can be expressed as a function of RAV, WID, and DFN, as Pd = f(RAV, WID, DFN). Here, Pd is expressed as a function of the three indices RAV, WID, and DFN, but it may also be expressed as one or two of these indices. The form of the function f is not particularly limited, but the DBP calculation unit 130 determines whether the cuff pressure has reached DBP by calculating these indices for each beat of the acquired pressure pulse wave. For example, it can be determined that the cuff pressure has reached DBP if RAV or WID becomes a local minimum, or if DFN becomes a local maximum.

[0045] When DBP is calculated in step S3, the stop cuff pressure calculation unit 140 calculates the value of the stop cuff pressure based on DBP (step S4). When the stop cuff pressure is P1.

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[0046] An appropriate value can be set for the stopping cuff pressure P1, but as described later, when the cuff pressure reaches the stopping cuff pressure P1, the compression of the area being measured by the cuff 11 stops. From the standpoint of reducing the burden on the person being measured, it is desirable to end the blood pressure measurement at an earlier timing after pressurization begins, that is, at a lower cuff pressure. On the other hand, since more data on cuff pressure (pressure pulse wave) after pressurization can be obtained, it is desirable to end the measurement at a later timing after pressurization begins. In other words, from the standpoint of ensuring the accuracy of blood pressure measurement, it is desirable to end the blood pressure measurement after pressurizing the cuff to a higher pressure. As shown in Figure 3, DBP can be detected in the envelope of the pressure pulse wave before the peak, that is, at a cuff pressure lower than the cuff pressure corresponding to the peak. Therefore, an appropriate stopping cuff pressure P1 is set considering this point of view. For example, as the stopping cuff pressure P1, a cuff pressure that does not exceed the peak of the envelope of the pressure pulse wave shown in Figure 3 can be adopted.

[0047] Once the value of the stop cuff pressure is calculated in step S4, the pressure control unit 120 determines whether the cuff pressure detected by the pressure detection unit 110 is greater than the stop cuff pressure (step S5). The determination in step S5 is repeated while continuing pressurization control.

[0048] When the pressure control unit 120 determines that the cuff pressure has become greater than the stop cuff pressure, it controls the pump drive circuit 22 to stop pressurizing the cuff 11 (step S6), and controls the valve drive circuit 23 to open the exhaust valve 14 and discharge the air from the air bag 11a.

[0049] (Mathematical model creation process) When the pressure on the cuff 11 is released, the mathematical model creation unit 150 creates an envelope mathematical model (step S7). Figure 6 is a flowchart showing the procedure for creating the envelope mathematical model. Figure 7 is a diagram illustrating the envelope mathematical model creation process and the MBP calculation process described later.

[0050] In Figure 7(A), the horizontal axis represents time (or cuff pressure), and the vertical axis represents the pressure pulse wave. In Figures 7(A), 7(B), and 7(C), the dashed line indicates the pressure release point. In Figure 7(A), the pulse wave P obtained up to the pressure release point is shown. W And the solid line, envelope E C This is indicated by a dashed line.

[0051] The mathematical model creation unit 150 extracts an envelope of the pulse wave up to the current time point based on pulse wave data for a plurality of heartbeats acquired up to the pressure stop position, as shown in FIG. 7(A) (step S71). A known method may be used to generate the envelope. For example, an envelope obtained by simply connecting the peak positions of pulses of each heartbeat may be used as the envelope, or an envelope may be obtained by fitting a curve to a sequence of points at the peak positions of pulses of each heartbeat. Although not shown in the drawings, the mathematical model creation unit 150 may perform preprocessing such as noise removal on the pulse wave data before acquiring the envelope.

[0052] As shown in FIG. 7(B), the mathematical model creation unit 150 extracts the envelope E C with a mathematical model M D fits a mathematical expression representing the mathematical model (step S72). In FIG. 7(B), the mathematical model M D is indicated by a solid line. Here, for the envelope E C , a Gaussian function represented by the following formula (3) is fitted as an example of a mathematical model of an envelope. The variable x in formula (3) is cuff pressure, and A, B, and C are parameters that define the shape of the Gaussian function. [Formula]

[0053] By fitting the Gaussian function represented by formula (3) to the envelope E C , the values of parameters A, B, and C can be estimated.

[0054] (MBP Calculation Processing) Returning to the description of the flowchart shown in FIG. 4. After the envelope mathematical model is created, the MBP calculation unit 160 calculates MBP (step S8). Specifically, based on the estimated values of the parameters of the mathematical model of the envelope E C obtained by the envelope mathematical model creation process (step S7) , the peak of the envelope E C is estimated. The envelope E C is represented by the mathematical model M shown in formula (3) DWhen fitting, the index P is defined for cuff pressure x and parameters B and C by the following equation (4).

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[0055] Figure 8 shows the relationship between the value of index P according to equation (4) and the amplitude of the envelope. Index P is 0 at the peak position where the amplitude of the envelope is at its maximum value, and the absolute value of index P is (2log2) at the position where the amplitude of the envelope is half of the maximum value. 1 / 2 We take the following, where log is the natural logarithm. As shown in Figure 7(C), statistically, the position where the amplitude of the envelope is maximum corresponds to MBP. At this time, the cuff pressure at which index P is 0 corresponds to MBP, so the mathematical model M D MBP calculated by MBP MM Therefore, MBP MM This is an estimated value of parameter B obtained by fitting. fit Therefore, it can be expressed by the following equation (5).

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[0056] Furthermore, as described above with respect to equation (1) or equation (2), our research has shown that there is a specific relationship between the envelope peak and DBP, so the mathematical model M D DBP calculated by DBP MM Similarly, the mathematical model M created in step S7 D DBP MM You may calculate this.

[0057] (SBP calculation process) Once MBP is calculated, the SBP calculation unit 170 calculates SBP (step S9). Figure 9 is a flowchart showing the procedure for the SBP calculation process. Figures 10(A) and 10(B) are diagrams illustrating the principle of the SBP calculation process.

[0058] Here, SBP is calculated based on the principle of the low-pressure pulse wave method disclosed in Patent Document 1. In Figure 10(A), the horizontal axis is cuff pressure and the vertical axis is the amplitude of the pressure pulse wave, with the thin solid line and dashed line representing the envelope E extracted from the pressure pulse wave. C This shows that the thick solid line is the envelope E. C A mathematical model M fitted to it D This shows the envelope E. C Of these, the thin solid line portion shows the region measured before the pressurization was stopped, and the dashed line portion shows the region extracted from the pressure pulse wave acquired without stopping the pressurization. As shown in Figure 10(A), the fitted mathematical model M D Even with this method, there is a possibility of errors between the measured value and the calculated value near the SBP. Therefore, by using the SBP calculation process described later, a more accurate SBP can be obtained. In Figure 10(A), the graph shown in the upper left is the pressure pulse wave waveform for one beat near the DBP. PW This is shown. Figure 10(B) shows the pressure pulse wave waveform S for one beat during this DBP. PW This is a magnified view.

[0059] First, the SBP calculation unit 170 acquires the pressure pulse wave data for one beat during DBP from the storage unit 24 (step S91).

[0060] Then, the SBP calculation unit 170 calculates the pressure pulse wave waveform S for one beat during DBP from the pressure pulse wave data for one beat during DBP. PW Maximum amplitude A m and area-average amplitude A av Calculate (step S92). Specifically, the pressure pulse wave waveform S for one beat during DBP. PW The minimum value P MIN , average area P AV , maximum value P MAX The maximum amplitude A is calculated using the following equation (6). m Calculate.

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[0061] Here, the average area P AV This refers to the pressure pulse wave waveform S for one beat during DBP.PW P, the average area AV This is the value at which, when the plane is cut, the upper area a and the lower area b+c are equal. In other words, it is the value that satisfies equation (7) below.

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[0062] The pressure pulse wave waveform S for one beat during DBP is calculated in this manner. PW Maximum amplitude A m and area-average amplitude A av Therefore, the SBP calculation unit 170 calculates the SBP (step S93). The low-pressure pulse wave method is based on the finding that the pressure pulse wave waveform is similar to the arterial pressure waveform. As shown by the dashed line in Figure 10(A), the minimum and average values ​​of the pressure pulse wave waveform are considered to be the DBP and MBP of the arterial pressure waveform, respectively, and the SBP is calculated by determining the value of the arterial pressure waveform corresponding to the maximum value of the pressure pulse wave. Specifically, as shown in the following equation (9), the maximum amplitude A m and area-average amplitude A av Then, SBP is calculated based on the ratio of DBP and MBP.

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[0063] The control unit 100 displays the measurement results, such as DBP calculated in step S3, MBP calculated in step S8, and SBP calculated in step S9, on the display unit 25 of the blood pressure measuring device 1 (step S10). The control unit 100 records the calculated blood pressure values ​​and other measurement results in a predetermined area of ​​the storage unit 24 of the blood pressure measuring device 1 and terminates the blood pressure measurement process.

[0064] In this way, blood pressure can be calculated by applying pressure that does not exceed the peak of the envelope.

[0065] <Example 1> The following describes Modification 1 of Example 1. In Example 1, DBP was calculated based on indicators such as RAV, but the method of calculating DBP is not limited to this. Figure 11 is a diagram illustrating Modification 1. The upper part of Figure 11 shows the pulse wave P obtained up to the pressurization stop position. W and envelope E C The lower part of Figure 11 shows the envelope E. C A mathematical model M fitted to it D This shows that, statistically, the position where the amplitude of the envelope is half of its maximum value roughly corresponds to DBP. Therefore, for the index P explained using Figure 8, P = -(2log2) 1 / 2 The position of approximately indicates the position of the DBP. Therefore, similar to the MBP in Example 1, the DBP calculation unit 130 calculates the envelope E C Mathematical model M D Using this, the cuff pressure corresponding to DBP is estimated by fitting the parameter C. fit and the estimated value of parameter B fit Using this, it can be calculated by the following formula (10).

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[0066] As DBP and MBP used in the above-mentioned SBP calculation, DBP MM and MBP MM Using these, the SBP calculation unit 170 calculates SBP using the following formula (11).

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[0067] <Modification 2> A modified example 2 of Example 1 is described below. In Example 1, DBP is calculated based on indicators such as RAV, and the envelope EC Mathematical model M D MBP was calculated using the method described above, but DBP and MBP are not limited to this. Figure 12 illustrates a modified example 2. The upper part of Figure 12 shows the pulse wave P obtained up to the pressurization stop position. W and envelope E C This is shown. The lower part of Figure 12 shows the minimum value DFN of the first derivative of the pressure pulse wave normalized by the pulse wave amplitude for one beat, as explained in Figure 5(C). Here, the DBP calculation unit 130 can calculate the DBP as the cuff pressure at which DFN is maximized. The DBP calculated in this way is then used as the DBP. sp This is how it is expressed. Also, as mentioned above, MBP is DBP sp Since it can be expressed by a predetermined relation, this is MBP sp This is how it is expressed.

[0068] As DBP and MBP used in the above-mentioned SBP calculation, DBP MM and MBP MM Using these, the SBP calculation unit 170 calculates SBP using the following formula (12).

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[0069] <Variation 3> The SBP calculation unit 170 calculates the DBP calculated in the above-described modified examples 1 and 2. MM and MBP MM DBP sp and MBP sp DBP calculated as a weighted average of ave and MBP ave SBP may be calculated using the following formula (13). For example, the SBP calculation unit 170 calculates DBP using the following formula (13). ave Calculate MBP using formula (14) ave Calculate.

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[0070] 1, 2... Blood pressure measuring device 11····Cuff 110... Pressure detection unit 120... Pressure Control Unit 130...DBP calculation section 140... Stop cuff pressure calculation unit 150...Mathematical Model Creation Department 160...MBP calculation section 170...SBP Calculation Unit

Claims

1. A cuff that is wrapped around the part to be measured, A pressure detection unit for detecting the cuff pressure inside the cuff, A pulse wave acquisition unit that acquires the pulse wave of the person being measured from the cuff pressure, A pressure control unit controls the cuff pressure and stops pressurizing the cuff when it reaches a stop cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximum. A diastolic blood pressure calculation unit calculates the subject's diastolic blood pressure based on the pulse wave acquired up to the point of reaching the stop cuff pressure, A mean blood pressure calculation unit that calculates the mean blood pressure of the subject based on the pulse wave acquired up to the point of reaching the stop cuff pressure, A systolic blood pressure calculation unit extracts a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure, correlates the diastolic blood pressure and the mean blood pressure with the minimum value and area average value of the single pulse wave, and calculates the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave. A blood pressure measuring device characterized by being equipped with the following features.

2. The blood pressure measuring device according to claim 1, characterized in that the diastolic blood pressure calculation unit calculates the diastolic blood pressure based on the characteristics of the pulse wave acquired up to the time the cuff stop pressure is reached.

3. The blood pressure measuring device according to claim 1, characterized in that the diastolic blood pressure calculation unit calculates the diastolic blood pressure based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stopping cuff pressure is reached.

4. The blood pressure measuring device according to claim 1, characterized in that the mean blood pressure calculation unit calculates the mean blood pressure based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached.

5. The blood pressure measuring device according to claim 1, characterized in that the mean blood pressure calculation unit calculates the mean blood pressure based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stop cuff pressure is reached.

6. The blood pressure measuring device according to claim 1, characterized in that the diastolic blood pressure calculation unit calculates the diastolic blood pressure by an arithmetic mean or weighted mean of a first diastolic blood pressure calculated based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached, and a second diastolic blood pressure calculated based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stop cuff pressure is reached.

7. The blood pressure measuring device according to claim 1, characterized in that the mean blood pressure calculation unit calculates the mean blood pressure by an arithmetic mean or weighted mean of a first mean blood pressure calculated based on the characteristics of the pulse wave acquired up to the time the stop cuff pressure is reached, and a second mean blood pressure calculated based on a mathematical model of the envelope extracted from the pulse wave acquired up to the time the stop cuff pressure is reached.

8. The blood pressure measuring device according to claim 1, characterized in that the systolic blood pressure calculation unit calculates the systolic blood pressure based on the ratio of the diastolic blood pressure and the mean blood pressure, which is the ratio of the maximum amplitude, which is the difference between the maximum value and the minimum value of the pulse wave, and the area average amplitude, which is the difference between the area average value and the minimum value of the pulse wave.

9. A step of detecting the cuff pressure inside the cuff wrapped around the part to be measured, The steps include obtaining the pulse wave of the person being measured from the cuff pressure, The cuff pressure is controlled to a stopping cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximized. The step of stopping pressurization of the cuff when the threshold is reached, A step of calculating the diastolic blood pressure of the person being measured based on the pulse wave obtained up to the point of reaching the stop cuff pressure, The steps include: calculating the mean blood pressure of the person being measured based on the pulse wave acquired up to the point of reaching the stop cuff pressure; The steps include: extracting a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure; correlating the diastolic blood pressure and the mean blood pressure with the minimum value and area mean of the single pulse wave; and calculating the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave; A blood pressure measurement method characterized by including the following.

10. On the computer, A step of detecting the cuff pressure inside the cuff wrapped around the part to be measured, The steps include obtaining the pulse wave of the person being measured from the cuff pressure, The steps include controlling the cuff pressure and stopping the pressurization of the cuff when it reaches a stop cuff pressure lower than the cuff pressure at which the amplitude of the pulse wave is maximum, A step of calculating the diastolic blood pressure of the person being measured based on the pulse wave obtained up to the point of reaching the stop cuff pressure, The steps include: calculating the mean blood pressure of the person being measured based on the pulse wave acquired up to the point of reaching the stop cuff pressure; The steps include: extracting a single pulse wave, which is the pulse wave for one beat near the diastolic blood pressure; correlating the diastolic blood pressure and the mean blood pressure with the minimum value and area mean of the single pulse wave; and calculating the subject's systolic blood pressure as the value corresponding to the maximum value of the single pulse wave; A blood pressure measurement program that executes this process.

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