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

Abstract

This blood pressure measurement device comprises a cuff that is wrapped around a part to be measured, a pressure detection unit for detecting cuff pressure, a pressure control unit for controlling the cuff pressure, a blood pressure calculation unit for performing blood pressure calculation processing on the basis of the cuff pressure, and a wrapping strength determination unit for performing wrapping strength determination processing for determining wrapping strength of the cuff, wherein: the pressure control unit performs constant pressure control for maintaining the cuff pressure at a constant target pressure value from the start of an increase in the cuff pressure to the end of the wrapping strength determination processing, and, after completion of the wrapping strength determination processing, performs constant-rate pressurization control in which the cuff pressure is increased at a constant rate in order to calculate the blood pressure; and the wrapping strength determination unit determines the wrapping strength during the constant pressure control.

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 this type of constant voltage drive, the initial inflation level cannot be set too low in order to ensure the time required to determine the cuff wrapping strength, and since the pressure pulse wave must be acquired for blood pressure calculation immediately after determining the cuff wrapping strength, noise generated at the timing of control switching could 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 can suppress the influence of noise at the timing of switching control from determining the wrapping strength of the cuff to calculating blood pressure.

[0007] In order to solve the above problems, the present invention provides a blood pressure measurement device comprising: a cuff to be wrapped around a portion to be measured; a pressure detection unit that detects the 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 to calculate the blood pressure of the subject based on the detected cuff pressure; and a wrapping strength determination unit that performs wrapping strength determination processing to determine the wrapping strength of the cuff around the portion to be measured, wherein the pressure control unit performs constant pressure control to maintain the cuff pressure at a constant target pressure value from the start of cuff pressure application until the wrapping strength determination processing is completed, and after the wrapping strength determination processing is completed, performs constant speed inflation control to increase the cuff pressure at a constant speed in order to calculate the blood pressure, and the wrapping strength determination unit determines the wrapping strength during the constant pressure control.

[0008] According to this, in the constant pressure control for determining the cuff wrapping strength, the control is switched from a state in which the cuff pressure is maintained at a constant target pressure value to a constant speed inflation control for blood pressure calculation, thereby suppressing the influence of noise on blood pressure calculation at the switching timing.

[0009] In addition, in the present invention, the wrapping strength determination unit may determine the wrapping strength based on a change in the cuff pressure during a determination time period, which is a time period from when the cuff pressure reaches the target pressure value from the initial pressure and becomes stable.

[0010] This makes it possible to determine the wrapping strength according to the magnitude of the cuff pressure applied to the part to be measured when the cuff is wrapped around the part to be measured.

[0011] In addition, in the present invention, the wrapping strength determination unit may determine the wrapping strength by comparing the number of times the cuff pressure falls below the target pressure value during the determination time period and the difference from the target pressure value with predetermined threshold values.

[0012] This makes it possible to determine whether the magnitude of the cuff pressure applied to the measurement target part when the cuff is wrapped around the measurement target part is smaller than an appropriate value, as the wrapping strength.

[0013] In the present invention, the wrapping strength determination unit may determine the wrapping strength based on whether the cuff pressure increases or decreases relative to the target pressure value during the determination time period.

[0014] This makes it possible to determine whether the magnitude of the cuff pressure applied to the measurement target part when the cuff is wrapped around the measurement target part is greater than an appropriate value, as the wrapping strength.

[0015] In the present invention, the target pressure value may be smaller than 30 mmHg.

[0016] According to this, constant pressure control is performed with a cuff pressure lower than 30 mmHg as the target pressure value, so that constant speed inflation control for blood pressure calculation can be started from a state where the cuff pressure is lower.

[0017] In the present invention, the pressure control unit may perform the constant speed pressurization control in accordance with a result of the wrapping strength determination process.

[0018] This allows for accurate blood pressure calculation by performing constant velocity inflation control when the wrapping strength is appropriate, while discharging air from the cuff without performing constant velocity inflation control when the wrapping strength is inappropriate, thereby reducing the burden on the subject.

[0019] In the present invention, the pressure control unit may perform the constant pressure control by PID control.

[0020] In the present invention, the pressure control unit may control a pump that supplies air to the cuff and an exhaust valve that controls exhaust from the cuff.

[0021] The present invention also provides a blood pressure measurement method comprising the steps of: detecting the cuff pressure in a cuff wrapped around a portion to be measured; performing constant pressure control to maintain the cuff pressure at a constant target pressure value; performing a wrapping strength determination process to determine the wrapping strength of the cuff around the portion to be measured during the constant pressure control; performing constant speed inflation control to increase the cuff pressure at a constant speed after completion of the wrapping strength determination process; and performing a blood pressure calculation process to calculate the blood pressure of the subject based on the cuff pressure during the constant speed inflation control.

[0022] According to this, in the constant pressure control for determining the cuff wrapping strength, the control is switched from a state in which the cuff pressure is maintained at a constant target pressure value to a constant speed inflation control for blood pressure calculation, thereby suppressing the influence of noise on blood pressure calculation at the switching timing.

[0023] The present invention also provides a blood pressure measurement program that causes a computer to execute the following steps: detecting the cuff pressure in a cuff wrapped around a portion to be measured; performing constant pressure control to maintain the cuff pressure at a constant target pressure value; performing a wrapping strength determination process to determine the wrapping strength of the cuff around the portion to be measured during the constant pressure control; performing constant speed inflation control to increase the cuff pressure at a constant speed after the wrapping strength determination process is completed; and performing a blood pressure calculation process to calculate the blood pressure of the subject based on the cuff pressure during the constant speed inflation control.

[0024] According to this, in the constant pressure control for determining the cuff wrapping strength, the control is switched from a state in which the cuff pressure is maintained at a constant target pressure value to a constant speed inflation control for blood pressure calculation, thereby suppressing the influence of noise on blood pressure calculation at the switching timing.

[0025] According to the present invention, it is possible to suppress the influence of noise at the timing of switching control from determining the wrapping strength of the cuff to calculating blood pressure.

[0026] FIG. 1 is a diagram illustrating an outline of the hardware configuration of a blood pressure measurement device according to a first embodiment. FIG. 2 is a functional block diagram of the blood pressure measurement device according to the first embodiment. FIG. 3 is a flowchart illustrating the overall processing procedure of the blood pressure measurement device according to the first embodiment. FIG. 4 is a graph showing temporal changes in cuff pressure and pressure pulse wave when the blood pressure measurement device according to the first embodiment is in use. FIG. 5 is a flowchart illustrating the procedure of wrapping strength determination processing of the blood pressure measurement device according to the first embodiment. FIG. 6 is a graph showing the variation pattern of cuff pressure for each wrapping strength in the blood pressure measurement device according to the first embodiment. FIG. 7 is a diagram illustrating an outline of the hardware configuration of a blood pressure measurement device according to a second embodiment.

[0027] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0028] 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.

[0029] (Device Configuration) FIG. 1 is a schematic diagram of the hardware configuration of a blood pressure measurement device 1 according to this embodiment.

[0030] 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, an operation switch 26, a power supply 27, and a CPU 100. The blood pressure measurement device 1 corresponds to the blood pressure measurement device of the present invention. The cuff 11, the pressure pump 13, and the exhaust valve 14 correspond to the cuff, the pump, and the exhaust valve of the present invention, respectively.

[0031] The cuff 11 includes an air bag 11a containing air. 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") via an air tube 15, 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 from the air bag 11a.

[0032] 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 executed for a wrapping strength determination process and a blood pressure measurement process (to be described later) and data such as blood pressure measurement results, a display unit 25 for displaying various information such as the wrapping strength determination results and blood pressure measurement results, an operation switch 26 for inputting various instructions for measurement, and a power supply 27 for supplying power to each part of the device, such as the CPU.

[0033] 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.

[0034] 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 condition determination 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.

[0035] 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 a high pass filter (HPF) unit that processes the pressure value signal with an HPF to extract and output a pressure pulse wave signal, and a low pass filter (LPF) unit that processes the pressure value signal with an LPF to extract and output an absolute pressure value signal.

[0036] 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 .

[0037] 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).

[0038] A cuff pressure signal indicating the cuff pressure detected in time series from the LPF unit of the pressure detection unit 110 is input to the condition determination unit 140. Based on the cuff pressure signal input in time series, the condition determination unit 141 determines whether or not a condition (determination condition) for determining the wrapping strength is satisfied.

[0039] The wrapping strength determination unit 150 receives a cuff pressure signal indicating the cuff pressure detected in time series from the LPF unit of the pressure detection unit 110, and stores the input cuff pressure signal in a predetermined area of ​​the memory 24. The wrapping strength determination unit 150 waits until a determination condition is satisfied, and then performs a wrapping strength determination, which will be described later, based on the cuff pressure signal read from the memory 24.

[0040] (Blood pressure measurement method) Fig. 3 is a flowchart showing the overall processing procedure 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 as a program in a predetermined area of ​​the memory 24, 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 from the storage medium into the blood pressure measurement device 1. Fig. 4 is a graph showing the time changes of the pressure pulse wave and cuff pressure detected during blood pressure measurement on the same time axis.

[0041] When measuring blood pressure, the subject wraps cuff 11 around the part to be measured, such as the upper arm or wrist, in advance. The following description assumes that the subject has made certain settings using operation switch 26 and issued a command to start blood pressure measurement. Upon receiving the command to start blood pressure measurement, blood pressure measurement device 1 performs certain initialization steps, such as opening exhaust valve 14 and setting the cuff pressure to atmospheric pressure (initial pressure).

[0042] When blood pressure measurement is started, the pressure control unit 120 starts constant pressure control (step S1). At this time, the pressure control unit 120 controls the pump drive circuit 22 so that the cuff pressure detected by the pressure sensor 12 is constant, using an initial inflation end pressure, which is the cuff pressure at which the initial inflation ends, as a target pressure value (referred to as "constant pressure control"). This constant pressure control can be performed by, for example, PID control, but the control method is not limited to this.

[0043] The condition determination unit 140 monitors the cuff pressure detected by the pressure sensor 12 and determines whether the cuff pressure has reached the target pressure value and is stable (step S2). Whether the cuff pressure is stable can be determined, for example, based on whether the deviation of the cuff pressure from the target pressure value is within a range of ±5%, but the determination criteria are not limited to this.

[0044] If it is determined in step S2 that the cuff pressure has not reached the target pressure value or is not stable, step S2 is repeated and the condition determination unit 140 continues to monitor the cuff pressure. Before proceeding to step S3, the sampled cuff pressure is stored in a predetermined area of ​​the memory 24 in association with sampling time information.

[0045] If the condition determination unit 140 determines in step S2 that the cuff pressure has reached the target pressure value and is stable, the wrapping strength determination unit 150 executes the wrapping strength determination process shown in Fig. 5 based on the time change information of the cuff pressure stored in the memory 24 (step S3). In this way, the wrapping strength determination process is performed under constant pressure control.

[0046] In the wrapping strength determination process of step S3, the wrapping strength determination unit 150 determines the wrapping strength based on the cuff pressure fluctuation pattern during constant pressure control, from the initial pressure until the cuff pressure reaches the target pressure value and stabilizes. Here, it determines whether the wrapping strength of the cuff 11 falls into one of three categories: loose, tight, or tight. 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 the 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 is 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 is 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 loosely wrapped around the part to be measured, and the pressure applied to the part to be measured by the cuff 11 is lower than the appropriate level. This state is considered to be loosely wrapped. Here, the time from when the cuff pressure reaches the target pressure value from the initial pressure and stabilizes under constant pressure control (time P1 until Tc in FIG. 4) corresponds to the determination time of the present invention. Time Tc corresponds to the end of the wrapping strength determination process.

[0047] Figure 6 is a graph showing an example of the cuff pressure change pattern when the wrapping strength is determined to be loose, tight, or tight. Figure 6 shows an enlarged view of the area surrounded by the dashed line in Figure 4 showing the cuff pressure change. In the loose wrapping state, the cuff pressure rises slowly during inflation and falls far below the target pressure, a so-called undershoot state, before reaching the target pressure. In the tight wrapping state, the cuff pressure rises sharply immediately after inflation begins and exceeds the target pressure, a so-called overshoot state, and then repeatedly increases and decreases, oscillating above and below the target pressure before reaching the target pressure. In the tight wrapping state, the cuff pressure rises with inflation but does not exceed the target pressure, but quickly approaches the target pressure before reaching the target pressure.

[0048] The wrapping strength determination unit 150 determines whether the number and amount of times the cuff pressure is less than the target pressure value before it reaches the target pressure value from the initial pressure are greater than a predetermined threshold (step S31). Here, the amount of time the cuff pressure is less than the target pressure value is the magnitude of the difference between the target pressure value and the cuff pressure. If it is determined in step S31 that the number and amount of times the cuff pressure is less than the target pressure value before it reaches the target pressure value are greater than the predetermined threshold, it determines that the wrapping strength is loose (step S32).

[0049] In step S31, if it is determined that the number of times and the amount by which the cuff pressure is less than the target pressure value before the cuff pressure reaches the target pressure value are equal to or less than the predetermined threshold, the wrapping strength determination unit 150 determines whether the pressure value increases or decreases relative to the target pressure value (step S33). In step S33, if the pressure value increases or decreases relative to the target pressure value before the cuff pressure reaches the target pressure value, it determines that the wrapping strength is tight (step S34).

[0050] In step S33, if the cuff pressure does not increase or decrease relative to the target pressure value before it reaches the target pressure value, the wrapping strength is determined to be snug (step S35).

[0051] If the wrapping strength is determined to be tight in step S3, the initial inflation by constant pressure control is terminated, and the pressure control unit 120 starts controlling the pump drive circuit 22 so that the cuff pressure increases at a constant rate (referred to as "constant rate inflation control") (step S5). The constant rate inflation control is executed at time P2 after Tc in FIG. 4.

[0052] The initial pressurization end pressure (target pressure) is set to, for example, about 10 mmHg, lower than the typical value of 30 mmHg in conventional constant voltage driving. By setting the initial pressurization end pressure low in this way, it is possible to acquire a blood pressure measurement pressure pulse wave from a lower pressure after the wrapping strength determination process is completed.

[0053] At the end of the wrapping strength determination process in step S3, the pump voltage (drive voltage of the pump drive circuit 22) is maintained in a balanced state under constant pressure control, and then the control is switched to constant-speed inflation control to begin acquiring a pressure pulse wave for blood pressure measurement. This prevents a sudden change in inflation speed, suppresses the influence of noise at the timing of the control switch, and enables clear changes in the pressure pulse wave to be acquired.

[0054] The blood pressure calculation unit 130 acquires a pressure pulse wave for blood pressure measurement from the HPF unit of the pressure detection unit 110 by constant velocity inflation control, and performs blood pressure calculation processing to calculate blood pressure values ​​such as systolic blood pressure and diastolic blood pressure by the oscillometric method (step S6).

[0055] The CPU 100 displays the measurement results, such as the blood pressure values ​​calculated in step S6, on the display unit 25 of the blood pressure measuring device 1 (step S7).The CPU 100 then records the measurement results, such as the blood pressure values ​​calculated in step S6, in a predetermined area of ​​the memory 24 of the blood pressure measuring device 1 (step S8), and ends the blood pressure measurement process.

[0056] If the wrapping strength is determined to be insufficient in the wrapping strength determination process of step S3, i.e., if the wrapping strength is determined to be loose or tight, the pressure control unit 12025 controls the valve drive circuit 23 to open the exhaust valve 14 and discharge air from the air bag 11a of the cuff 11 (step S9). Then, the CPU 100 displays an error on the display unit 25 (step S10) and ends the blood pressure measurement process.

[0057] 6 is a block diagram showing an outline of the hardware configuration of a blood pressure measurement device 2 according to Example 2. Components common to the blood pressure measurement device 1 according to Example 1 are denoted by common reference numerals, and detailed description thereof will be omitted.

[0058] Blood pressure measurement device 2 includes control valve 16 and control valve drive circuit 28 instead of exhaust valve 14 and valve drive circuit 23, and further includes quick exhaust valve 17 and quick exhaust valve drive circuit 30. Blood pressure measurement device 2 corresponds to the blood pressure measurement device of the present invention. Also, control valve 16 corresponds to the exhaust valve of the present invention.

[0059] The control valve 16 is a valve whose opening degree can be continuously controlled, and the control valve drive circuit 28 controls the opening degree of the control valve 16 based on a control signal output from the CPU 100. The quick exhaust valve 17 is a valve that can rapidly exhaust air by opening the valve, thereby immediately reducing the cuff pressure. The quick exhaust valve drive circuit 30 controls the opening and closing of the quick exhaust valve 17 based on a control signal output from the CPU 100. In the blood pressure measurement device 2, the pressure control unit 120 controls the operation of the pump drive circuit 22, the control valve drive circuit 28, and the quick exhaust valve drive circuit 29.

[0060] Since it is difficult to precisely control the cuff pressure using the pressure pump 13, constant pressure control at low pressure can be achieved in a shorter time by combining it with a control valve 16 that is capable of slow exhaust. During constant pressure control, the control valve 16 is controlled to open and close, but during constant speed inflation control, the control valve 16 is kept closed.

[0061] The overall procedure for blood pressure measurement, including the wrapping strength determination process, is the same as that of the blood pressure measurement device 1 according to the first embodiment, and therefore will not be described again.

[0062] Furthermore, since the blood pressure measurement device 2 is provided with the quick exhaust valve 17, the cuff pressure can be reduced in a short time when the cuff is exhausted, which reduces the burden on the person being measured.

[0063] DESCRIPTION OF SYMBOLS 1, 2... 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 that is wrapped around a part to be measured; a pressure detection unit that detects the 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 person to be measured based on the detected cuff pressure; and a wrapping strength determination unit that performs wrapping strength determination processing that determines the strength of wrapping of the cuff around the part to be measured, wherein the pressure control unit performs constant pressure control that attempts to maintain the cuff pressure at a constant target pressure value from the start of cuff pressure inflation until the wrapping strength determination processing is completed, and after the wrapping strength determination processing is completed, performs constant speed inflation control that increases the cuff pressure at a constant speed in order to calculate the blood pressure, and the wrapping strength determination unit determines the wrapping strength during the constant pressure control.

2. The blood pressure measurement device of claim 1, characterized in that the wrapping strength determination unit determines the wrapping strength based on the change in the cuff pressure during a determination time period, which is the time period from the initial pressure until the cuff pressure reaches the target pressure value and stabilizes.

3. The blood pressure measurement device of claim 2, characterized in that the wrapping strength determination unit determines the wrapping strength by comparing the number of times the cuff pressure falls below the target pressure value during the determination time and the difference from the target pressure value with predetermined threshold values.

4. A blood pressure measuring device as described in claim 2 or 3, characterized in that the wrapping strength determination unit determines the wrapping strength based on whether the cuff pressure increases or decreases relative to the target pressure value during the determination time.

5. A blood pressure measuring device according to claim 1 or 2, characterized in that the target pressure value is less than 30 mmHg.

6. The blood pressure measuring device according to claim 1 or 2, characterized in that the pressure control unit performs the constant speed pressurization control depending on the result of the wrapping strength determination process.

7. A blood pressure measuring device according to claim 1 or 2, wherein the pressure control section performs the constant pressure control by PID control.

8. A blood pressure measuring device according to claim 1 or 2, characterized in that the pressure control unit controls a pump that supplies air to the cuff and an exhaust valve that controls exhaust from the cuff.

9. A blood pressure measurement method comprising the steps of: detecting the cuff pressure in a cuff wrapped around a part to be measured; performing constant pressure control to maintain the cuff pressure at a constant target pressure value; performing a wrapping strength determination process to determine the wrapping strength of the cuff around the part to be measured during the constant pressure control; performing constant speed inflation control to increase the cuff pressure at a constant speed after the wrapping strength determination process is completed; and performing a blood pressure calculation process to calculate the blood pressure of the person to be measured based on the cuff pressure during the constant speed inflation control.

10. A blood pressure measurement program that causes a computer to execute the following steps: detecting the cuff pressure in a cuff wrapped around a part to be measured; performing constant pressure control to maintain the cuff pressure at a constant target pressure value; performing a wrapping strength determination process to determine the wrapping strength of the cuff around the part to be measured during the constant pressure control; performing constant speed inflation control to increase the cuff pressure at a constant speed after the wrapping strength determination process is completed; and performing a blood pressure calculation process to calculate the blood pressure of the person to be measured based on the cuff pressure during the constant speed inflation control.

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