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

Abstract

A blood pressure measurement device comprising: a cuff to be wrapped around a measurement target portion; a pump; a pressure detection unit that detects a cuff pressure in the cuff; a pressure control unit that controls the cuff pressure; a blood pressure calculation unit that executes a blood pressure calculation process for calculating the blood pressure of a measurement subject on the basis of the cuff pressure; and a wrapping strength determination unit that executes a wrapping strength determination process for determining a wrapping strength at which the cuff is wrapped around the measurement target portion, wherein the pressure control unit performs a first cuff pressure control for executing the wrapping strength determination process, a second cuff pressure control for discharging a fluid retained in the cuff by the first cuff pressure control until the cuff pressure reaches atmospheric pressure, and a third cuff pressure control for executing the blood pressure calculation process after the cuff pressure has reached the atmospheric pressure.

Description

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

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

[0002] In recent years, health management has become commonplace by measuring information about an individual's physical and health, such as blood pressure, using a measuring device and recording and analyzing the measurement results. One example of such a measuring device is a blood pressure monitor that attaches a cuff to the subject's upper arm, wrist, or other part of the body to be measured and has a function for determining the wrapping strength of the cuff (see Patent Document 1).

[0003] In the blood pressure monitor disclosed in Patent Document 1, after the cuff is attached, a constant voltage is applied to the pump to drive it during initial inflation, and the wrapping strength of the cuff is determined from the cuff pressure-inflation time characteristic (cuff pressure curve) from the initial pressure until the pressure value reaches the initial inflation end pressure value, and then blood pressure is calculated.

[0004] However, with constant voltage driving, the initial pressure level cannot be set too low in order to ensure the time required to determine the wrapping strength, and since the pressure pulse wave for blood pressure calculation needs to be acquired immediately after determining the wrapping strength, noise generated at the timing of control switching can adversely affect the pressure pulse wave.

[0005] Patent No. 5408142

[0006] In view of the above-described conventional techniques, an object of the present invention is to provide a technique that does not switch control from determining the wrapping strength of the cuff to calculating blood pressure, and does not generate the noise that accompanies this.

[0007] In order to solve the above problems, the present invention provides a blood pressure measurement device comprising: a cuff that is wrapped around a portion to be measured; a pump that supplies fluid into the cuff; a pressure detection unit that detects cuff pressure in the cuff; a pressure control unit that controls the cuff pressure; a blood pressure calculation unit that performs blood pressure calculation processing that calculates the blood pressure of the subject based on the detected cuff pressure; and a wrapping strength determination unit that performs wrapping strength determination processing that determines the wrapping strength of the cuff around the portion to be measured, wherein the pressure control unit performs first cuff pressure control for performing the wrapping strength determination processing, second cuff pressure control for discharging the fluid stored in the cuff by the first cuff pressure control until the cuff pressure becomes atmospheric pressure, and third cuff pressure control for performing the blood pressure calculation processing after the cuff pressure has become atmospheric pressure by the second cuff pressure control.

[0008] According to this, between the first cuff pressure control for determining the wrapping strength and the third cuff pressure control for calculating the blood pressure, the second cuff pressure control is performed to discharge the fluid stored in the cuff by the first cuff pressure control until the cuff pressure reaches atmospheric pressure, so that there is no need to switch control from determining the wrapping strength to calculating the blood pressure. As a result, the blood pressure calculation can be performed without being affected by the first cuff pressure control for determining the wrapping strength, and no noise is generated due to the switching of control.

[0009] In addition, in the present invention, the pressure control unit may, in the first cuff pressure control, control the drive voltage of the pump to be constant until the cuff pressure reaches a predetermined target pressure from an initial pressure, and the wrapping strength determination unit may determine the wrapping strength based on the time it takes for the cuff pressure to reach the target pressure from the initial pressure.

[0010] In addition, in the present invention, the pressure control unit may perform constant speed inflation control in the third cuff pressure control, in which the cuff pressure is increased from the atmospheric pressure at a constant speed, and the blood pressure calculation unit may calculate the blood pressure based on the cuff pressure detected while the constant speed inflation control is being performed.

[0011] In addition, in the present invention, a valve for controlling the outflow of the fluid in the cuff may be provided, and the pressure control unit may perform the second cuff pressure control by opening the valve.

[0012] The present invention is also a blood pressure measurement method including the steps of: detecting a cuff pressure in a cuff wrapped around a portion to be measured; a cuff pressure control step of controlling the cuff pressure by supplying a fluid into the cuff or discharging the fluid stored in the cuff; performing a blood pressure calculation step of calculating the blood pressure of the subject based on the detected cuff pressure; and performing a wrapping strength determination step of determining the wrapping strength of the cuff around the portion to be measured, wherein the cuff pressure control step includes: a first cuff pressure control step for performing the wrapping strength determination step; a second cuff pressure control step for discharging the fluid stored in the cuff by the first cuff pressure control step until the cuff pressure reaches atmospheric pressure; and a third cuff pressure control step for performing the blood pressure calculation step after the cuff pressure has reached atmospheric pressure by the second cuff pressure control step.

[0013] According to this, between the first cuff pressure control step for determining the wrapping strength and the third cuff pressure control step for calculating the blood pressure, the second cuff pressure control step is performed to discharge the fluid stored in the cuff until the cuff pressure reaches atmospheric pressure, so that control does not switch from determining the wrapping strength to calculating the blood pressure. Therefore, the blood pressure calculation process can be performed without being affected by the first cuff pressure control step for determining the wrapping strength, and noise associated with the control switch does not occur.

[0014] The present invention also provides a blood pressure measurement program that causes a computer to execute the following steps: detecting a cuff pressure in a cuff wrapped around a portion to be measured; a cuff pressure control step of controlling the cuff pressure by supplying a fluid into the cuff or discharging the fluid stored in the cuff; a blood pressure calculation step of calculating the blood pressure of the subject based on the detected cuff pressure; and a wrapping strength determination step of determining the wrapping strength of the cuff around the portion to be measured, wherein the cuff pressure control step includes: a first cuff pressure control step for performing the wrapping strength determination step; a second cuff pressure control step for discharging the fluid stored in the cuff by the first cuff pressure control step until the cuff pressure reaches atmospheric pressure; and a third cuff pressure control step for performing the blood pressure calculation process after the cuff pressure has reached atmospheric pressure by the second cuff pressure control step.

[0015] According to this, between the first cuff pressure control for determining the wrapping strength and the third cuff pressure control for calculating the blood pressure, the second cuff pressure control is performed to discharge the fluid stored in the cuff by the first cuff pressure control until the cuff pressure reaches atmospheric pressure, so that there is no need to switch control from determining the wrapping strength to calculating the blood pressure. As a result, the blood pressure calculation can be performed without being affected by the first cuff pressure control for determining the wrapping strength, and no noise is generated due to the switching of control.

[0016] According to the present invention, there is no need to switch control from determining the wrapping strength of the cuff to calculating the blood pressure, and no noise is generated as a result.

[0017] FIG. 1 is a diagram illustrating an outline of the hardware configuration of a blood pressure measurement device according to an embodiment. FIG. 2 is a functional block diagram of the blood pressure measurement device according to an embodiment. FIG. 3 is a flowchart illustrating the overall processing procedure of the blood pressure measurement device according to an embodiment. FIG. 4 is a graph showing the time changes in cuff pressure and pressure pulse wave in the blood pressure measurement device according to an embodiment. FIG. 5 is a flowchart showing the procedure of wrapping strength determination processing in the blood pressure measurement device according to an embodiment. FIG. 6 is a graph showing the time changes in cuff pressure for each wrapping strength in the blood pressure measurement device according to an embodiment.

[0018] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0019] Example 1 An example of an embodiment of the present invention will be described below. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this example are not intended to limit the scope of the present invention to those only.

[0020] (Device Configuration) FIG. 1 is a schematic diagram of the hardware configuration of a blood pressure measurement device 1 according to this embodiment.

[0021] The blood pressure measurement device 1 includes a cuff 11, a pressure sensor 12, a pressure pump 13, an exhaust valve 14, an air tube 15, an oscillator circuit 21, a pump drive circuit 22, a valve drive circuit 23, a display unit 25, a memory 24, a timer unit 26, an operation switch 27, a power supply 28, and a CPU 100. The blood pressure measurement device 1 corresponds to the blood pressure measurement device of the present invention. The cuff 11 corresponds to the cuff of the present invention.

[0022] The cuff 11 includes an air bag 11a in which air is stored. The cuff 11 is provided with a pressure sensor 12 for detecting the pressure in the air bag 11a of the cuff 11 (hereinafter referred to as "cuff pressure"), a pressure pump 13 for supplying air to the air bag 11a, and an exhaust valve 14 that opens and closes to maintain the pressure in the air bag 11a or to exhaust the air stored in the air bag 11a, via an air tube 15. A quick exhaust valve can be used as the exhaust valve 14. Here, air corresponds to the fluid of the present invention.

[0023] Furthermore, the blood pressure measurement device 1 includes a CPU (Central Processing Unit) 100 for controlling each part of the device, a memory 24 for storing programs and parameters executed for determining the wrapping strength (described later), programs executed for the blood pressure measurement process, and data such as the cuff pressure, the pressure pump driving voltage, the inflation speed, and the blood pressure measurement results, a display unit 25 for displaying various information such as the wrapping strength determination results and the blood pressure measurement results, an operation switch 27 for inputting various instructions for measurement, and a power supply 28 for supplying power to each part of the device, such as the CPU.

[0024] Furthermore, the oscillator circuit 21 outputs a signal having an oscillation frequency corresponding to the output value of the pressure sensor 12 to the CPU 100. The pump drive circuit 22 controls the drive of the pressure pump 13 based on a control signal output from the CPU 100. The valve drive circuit 23 controls the opening and closing of the exhaust valve 14 based on the control signal output from the CPU 100.

[0025] 2 is a functional block diagram of the blood pressure measurement device 1. The CPU 100 includes a pressure detection unit 110, a pressure control unit 120, a blood pressure calculation unit 130, a target value arrival time acquisition unit 140, and a wrapping strength determination unit 150. The pressure detection unit 110, the pressure control unit 120, the blood pressure calculation unit 130, and the wrapping strength determination unit 150 correspond to the pressure detection unit, the pressure control unit, the blood pressure calculation unit, and the wrapping strength determination unit of the present invention, respectively.

[0026] The output signal of the oscillator 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 includes an HPF (High Pass Filter) unit that processes the pressure value signal through an HPF to extract and output a pressure pulse wave signal, and an LPF (Low Pass Filter) unit that processes the pressure value signal through an LPF to extract and output a cuff pressure signal. The cuff pressure signal, which indicates the cuff pressure detected in chronological order by the LPF unit of the pressure detection unit 110, is stored in a predetermined area of ​​the memory 24.

[0027] The pressure control unit 120 controls the operation of the pump drive circuit 22 and the valve drive circuit 23 to control the cuff pressure of the cuff 11 .

[0028] The blood pressure calculation unit 130 receives the pressure pulse wave signal extracted by the HPF unit of the pressure detection unit 110 and processes the received pressure pulse wave signal according to the oscillometric method to calculate the diastolic blood pressure (minimum blood pressure) and the systolic blood pressure (maximum blood pressure).

[0029] The target value reaching time acquisition unit 140 determines whether the cuff pressure output from the pressure detection unit 110 reaches a predetermined target value, and acquires from the timer unit 26 the time from when pressure starts to be applied until the target value is reached.

[0030] The wrapping strength determination unit 150 determines whether the wrapping strength is loose, tight, or tight, based on the target value arrival time acquired by the target value arrival time acquisition unit 140, using a method described below. When the cuff 11 is wrapped around the part to be measured, such as the upper arm, to form a cylinder, if the circumferential length of this cylinder is approximately equal to the circumferential length of the part to be measured, the pressure applied to the part to be measured by the cuff 11 will be at an appropriate level for blood pressure measurement, and this state is considered to be tight. If the circumferential length of the cylinder formed by the cuff 11 is shorter than the circumferential length of the part to be measured, the cuff 11 is wrapped too tightly around the part to be measured, and the pressure applied to the part to be measured by the cuff 11 will be higher than the appropriate level, and this state is considered to be tight. If the circumferential length of the cylinder formed by the cuff 11 is longer than the circumferential length of the part to be measured, the cuff 11 is wrapped loosely around the part to be measured, and the pressure applied to the part to be measured by the cuff 11 will be lower than the appropriate level, so this state is considered to be loosely wrapped.

[0031] (Blood pressure measurement method) Fig. 3 is a flowchart showing the procedure of the overall processing of the blood pressure measurement method by the blood pressure measurement device 1. The overall processing of blood pressure measurement shown in Fig. 3 is stored in advance in a predetermined area of ​​the memory 24 as a blood pressure measurement program, and is realized by the CPU 100 reading and executing the program from the memory 24. The program may be stored in a computer-readable storage medium and read into the blood pressure measurement device 1 from the storage medium.

[0032] When measuring blood pressure, the subject wraps the cuff 11 around the part to be measured in advance. In the following description, an example is given in which the part to be measured is the upper arm, but the part to be measured is not limited to this and may be the wrist, etc. The description also assumes that the subject performs predetermined settings using the operation switch 27 and issues a command to start blood pressure measurement. Upon receiving the command to start blood pressure measurement, the blood pressure measurement device 1 performs predetermined initialization, such as opening the exhaust valve 14 and setting the cuff pressure to atmospheric pressure (initial pressure).

[0033] When blood pressure measurement is started, the pressure control unit 120 starts constant voltage control (step S1). At this time, the pressure control unit 120 controls the pump drive circuit 22 so that the drive voltage applied to the pressure pump 13 becomes a predetermined target value (referred to as "constant voltage control"). This constant voltage control can be performed, for example, by PID control, but the control method is not limited to this. The constant voltage value may be set to a general value, or a different value may be set as the target value from the viewpoint of shortening the time required for determining the wrapping strength or improving the accuracy.

[0034] While performing the constant voltage control in this manner, the pressure control unit 120 monitors the cuff pressure detected by the pressure detection unit 110 and determines whether the cuff pressure reaches a predetermined target value (step S2).

[0035] The pressure control unit 120 continues monitoring until the cuff pressure reaches a predetermined target value (No in step S2). When the cuff pressure reaches the predetermined target value, it stops driving the pressurizing pump 13 and controls the valve drive circuit 23 to open the exhaust valve 14, thereby discharging the air stored in the air bag 11a of the cuff 11 until the cuff pressure reaches approximately atmospheric pressure (step S3). At this time, the target value reaching time acquiring unit 140 acquires from the timer unit 26 the time from when the inflation of the cuff 11 is started in step S1 until the cuff pressure reaches the target value, and stores the acquired time in a predetermined area of ​​the memory 24. The target value may be set to, for example, 30 mmHg, but is not limited to this. Another value may be set as the target value in terms of shortening the time required for determining the wrapping strength or improving the accuracy of the determination. In the graph at the bottom of Figure 4, which shows the change in cuff pressure over time, the area surrounded by the dashed line represents the process from the start of inflation of the cuff 11 until it reaches the target value (30 mmHg) and then decreases to the initial pressure by exhaustion. By using a rapid exhaust valve as the exhaust valve 14, the cuff pressure can be decreased from the target value to atmospheric pressure in a short time. Here, the constant voltage control performed until the cuff pressure reaches the target value from the initial pressure corresponds to the first cuff pressure control and the first cuff pressure control step of the present invention. Furthermore, the control of opening the exhaust valve 14 after the cuff pressure reaches the target value and discharging the air stored in the air bag 11a of the cuff 11 until the cuff pressure reaches atmospheric pressure corresponds to the second cuff pressure control and the second cuff pressure control step of the present invention.

[0036] Next, the wrapping strength determination unit 150 determines the wrapping strength (step S4). Fig. 5 is a flowchart showing the procedure for the wrapping strength determination process, and Fig. 6 is a graph showing an example of a wrapping strength determination criterion. As shown in Fig. 5, the wrapping strength of the cuff 11 is determined based on the time it takes for the cuff pressure to reach a target value (target pressure). As shown in Fig. 6, where the horizontal axis represents time and the vertical axis represents cuff pressure, a reference lower limit and a reference upper limit are set as criteria for determining the wrapping strength.

[0037] The winding strength determination process in step S4 will be described below with reference to the flowchart shown in FIG.

[0038] First, the wrapping strength determination unit 150 determines whether the time to reach the target pressure acquired by the target value arrival time acquisition unit 140 is longer than the upper reference limit (step S41). If it is determined that the time to reach the target pressure is longer than the upper reference limit, the wrapping strength determination unit 150 determines that the wrapping strength is loose (step S42). As shown in Figure 6, if the increase in cuff pressure is slow and the time to reach the target pressure is longer than the upper reference limit, the wrapping strength is determined to be loose.

[0039] If the target pressure arrival time acquisition unit 140 determines in step S41 that the time to reach the target pressure acquired by the target value arrival time acquisition unit 140 is not longer than the reference upper limit, the wrapping strength determination unit 150 further determines whether the target pressure arrival time acquired by the target value arrival time acquisition unit 140 is shorter than the reference lower limit (step S43). If the target pressure arrival time is determined to be shorter than the reference lower limit, the wrapping strength determination unit 150 determines that the wrapping strength is too tight (step S44). As shown in Figure 6, if the cuff pressure increases quickly and the time to reach the target pressure is shorter than the reference lower limit, the wrapping strength is determined to be too tight.

[0040] If it is determined in step S43 that the time required for the cuff pressure to reach the target pressure acquired by the target value arrival time acquisition unit 140 is not shorter than the reference lower limit, the wrapping strength determination unit 150 determines that the wrapping strength is tight (step S45). As shown in Figure 6, if the time required for the cuff pressure to reach the target pressure is longer than the reference lower limit and shorter than the reference upper limit, the wrapping strength is determined to be tight.

[0041] Returning to the description of FIG. 3 , if the wrapping strength is determined to be snug in the wrapping strength determination process of step S4, the pressure control unit 120 starts constant-speed inflation control, in which the cuff 11 is inflated at a constant speed (step S6). As a result, the cuff pressure, which has once reached atmospheric pressure, is increased at a constant speed, as shown in FIG. 4 . The constant-speed inflation control, in which the cuff 11 is inflated at a constant speed from atmospheric pressure when the wrapping strength is determined to be snug, corresponds to the third cuff pressure control and third cuff pressure control step of the present invention. The cuff pressure control step of the present invention includes the constant voltage control, which is performed until the cuff pressure reaches a target value from the initial pressure, the control, after the cuff pressure reaches the target value, of opening the exhaust valve 14 to discharge air stored in the air bag 11a of the cuff 11 until the cuff pressure reaches atmospheric pressure, and the constant-speed inflation control, in which the cuff 11 is inflated at a constant speed from atmospheric pressure when the wrapping strength is determined to be snug.

[0042] After starting the constant velocity inflation control, the blood pressure calculation unit 130 acquires the pressure pulse wave for blood pressure measurement from the HPF unit of the pressure detection unit 110, and performs blood pressure calculation processing to calculate blood pressure values ​​such as systolic blood pressure and diastolic blood pressure using the oscillometric method (step S7).

[0043] Here, in step S3, pressure control unit 120 discharges the air from air bladder 11a, which has been pressurized by constant voltage control, to return the cuff pressure to atmospheric pressure, and then starts constant-speed inflation control for blood pressure calculation. In this way, blood pressure calculation unit 130 starts acquiring a pressure pulse wave after constant-speed inflation control of the cuff pressure is started, so there is no control switching that can cause noise during pressure pulse wave acquisition, and a clear change in the pressure pulse wave can be acquired.

[0044] The CPU 100 displays the measurement results, such as the blood pressure values ​​calculated in step S7, on the display unit 25 of the blood pressure measuring device 1 (step S8).The CPU 100 then records the measurement results, such as the blood pressure values ​​calculated in step S7, in a predetermined area of ​​the memory 24 of the blood pressure measuring device 1 (step S9), and ends the blood pressure measurement process.

[0045] If the wrapping strength is determined to be insufficient in the wrapping strength determination process of step S4, i.e., if the wrapping strength is determined to be loose or tight, the CPU 100 displays an error on the display unit 25 (step S10) and terminates the blood pressure measurement process.

[0046] DESCRIPTION OF SYMBOLS 1... Blood pressure measurement device 11... Cuff 110... Pressure detection unit 120... Pressure control unit 130... Blood pressure calculation unit 150... Wrapping strength determination unit

Claims

1. A blood pressure measuring device comprising: a cuff to be wrapped around a part to be measured; a pump to supply fluid into the cuff; a pressure detection unit to detect cuff pressure in the cuff; a pressure control unit to control the cuff pressure; a blood pressure calculation unit to perform blood pressure calculation processing to calculate the blood pressure of the person to be measured based on the detected cuff pressure; and a wrapping strength determination unit to determine the wrapping strength of the cuff around the part to be measured, wherein the pressure control unit performs first cuff pressure control to perform the wrapping strength determination processing; second cuff pressure control to discharge the fluid stored in the cuff by the first cuff pressure control until the cuff pressure becomes atmospheric pressure; and third cuff pressure control to perform the blood pressure calculation processing after the cuff pressure has become atmospheric pressure by the second cuff pressure control.

2. The blood pressure measuring device of claim 1, characterized in that the pressure control unit, in the first cuff pressure control, controls the driving voltage of the pump to be constant until the cuff pressure reaches a predetermined target pressure from an initial pressure, and the wrapping strength determination unit determines the wrapping strength based on the time it takes for the cuff pressure to reach the target pressure from the initial pressure.

3. The blood pressure measuring device of claim 1 or 2, characterized in that the pressure control unit performs constant speed inflation control in the third cuff pressure control, in which the cuff pressure is increased from atmospheric pressure at a constant speed, and the blood pressure calculation unit calculates the blood pressure based on the cuff pressure detected while the constant speed inflation control is being performed.

4. The blood pressure measuring device according to claim 1, further comprising a valve for controlling the outflow of the fluid in the cuff, wherein the pressure control unit controls the second cuff pressure by opening the valve.

5. A blood pressure measurement method comprising: a step of detecting the cuff pressure in a cuff wrapped around a part to be measured; a cuff pressure control step of controlling the cuff pressure by supplying fluid into the cuff or discharging the fluid stored in the cuff; a step of performing a blood pressure calculation process of calculating the blood pressure of the person to be measured based on the detected cuff pressure; and a step of performing a wrapping strength determination process of determining the wrapping strength of the cuff around the part to be measured, wherein the cuff pressure control step comprises: a first cuff pressure control step for performing the wrapping strength determination process; a second cuff pressure control step for discharging the fluid stored in the cuff by the first cuff pressure control step until the cuff pressure becomes atmospheric pressure; and a third cuff pressure control step for performing the blood pressure calculation process after the cuff pressure has become atmospheric pressure by the second cuff pressure control step.

6. A blood pressure measurement program that causes a computer to execute the steps of: detecting the cuff pressure in a cuff wrapped around a part to be measured; a cuff pressure control step of controlling the cuff pressure by supplying fluid into the cuff or discharging the fluid stored in the cuff; a blood pressure calculation step of calculating the blood pressure of the person to be measured based on the detected cuff pressure; and a wrapping strength determination step of determining the strength with which the cuff is wrapped around the part to be measured, wherein the cuff pressure control step comprises: a first cuff pressure control step for performing the wrapping strength determination step; a second cuff pressure control step for discharging the fluid stored in the cuff by the first cuff pressure control step until the cuff pressure reaches atmospheric pressure; and a third cuff pressure control step for performing the blood pressure calculation process after the cuff pressure has reached atmospheric pressure by the second cuff pressure control step.

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