JP7025917B2 - Sphygmomanometer and its control method - Google Patents

Description

The present invention relates to a sphygmomanometer and a control method thereof, and more particularly to a sphygmomanometer for measuring blood pressure using an airbag and a control method thereof.

As a sphygmomanometer for measuring pulse waves and blood pressure, a sphygmomanometer that measures blood pressure by an oscillometric method using a band-shaped cuff with a built-in airbag is known. In blood pressure measurement by the oscillometric method, a cuff is attached to the measurement site of the person to be measured, and the measurement site is pressurized by supplying air to the airbag with a pump to drive blood, and then the amplitude of the pulse wave measured while depressurizing. The blood pressure value is determined based on.

In such a sphygmomanometer, an exhaust valve is provided in the gas flow path connected to the inside of the airbag, the exhaust valve is closed during blood removal, and the exhaust valve is closed until the blood pressure value is determined (during measurement) after blood pressure removal. Partially open to depressurize the inside of the airbag at a constant rate. Then, when the blood pressure value is determined, the exhaust valve is fully opened to rapidly reduce the pressure inside the airbag. When two exhaust valves are provided, only one is partially opened during measurement and both are fully opened when the blood pressure value is determined.

As the exhaust valve, a solenoid valve whose opening degree can be adjusted by using a solenoid is widely used. The solenoid has a hollow cylindrical coil and a plunger (movable element) inserted in the central axis of the coil, and is an electric machine that linearly moves the plunger along the central axis by a magnetic field generated by a current flowing through the coil. It is a conversion element. Some solenoids can control the position of the plunger only on (fully open) and off (fully closed), while others can control the position of the plunger at any position from fully open to fully closed. The latter is also a proportional solenoid. Called. By controlling the position (movement amount) of the plunger using the proportional solenoid, the size (opening degree) of the gap between the solenoid valve and the exhaust port can be controlled.

The proportional solenoid has the same drive current for the solenoid valve when the opening degree is controlled from 0% (fully closed) to 100% (fully open) and when the opening degree is controlled from 100% to 0%. Some have a hysteresis characteristic that the degree of opening is different from that of (Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-75435 (FIG. 19)

Since it is desirable that the decompression rate be constant during blood pressure measurement, the pressure is monitored and feedback control is performed to increase the opening degree when the pressure is higher than the target value or target range and decrease the opening degree when the pressure is low. May be done. At this time, if the hysteresis of the solenoid valve is large, the accuracy of the feedback control is lowered, and there is a problem that the measurement accuracy of the blood pressure value is also lowered.

The present invention has been made in view of the above-mentioned problems of the prior art, and even if an electromagnetic valve having hysteresis in the relationship between the opening degree and the magnitude of the drive current is used as the exhaust valve, the exhaust flow rate can be controlled with high accuracy. The main purpose is to provide a sphygmomanometer and its control method.

The above-mentioned object is a blood pressure monitor having an air bag attached to the measurement site of the subject, an electromagnetic valve for reducing the internal pressure of the air bag, and a drive circuit for controlling the opening degree of the electromagnetic valve. The drive circuit is lower than the frequency corresponding to the time constant of the solenoid valve, and is lower than the cutoff frequency of the low-pass filter for extracting the pulse wave signal used for measuring blood pressure from the signal representing the internal pressure of the airbag. It is achieved by a blood pressure monitor characterized in that a solenoid valve is driven using a pulse signal having a high frequency and the opening degree of the solenoid valve is controlled.

With such a configuration, according to the present invention, a sphygmomanometer capable of accurately controlling the exhaust flow rate and its control even when an electromagnetic valve having hysteresis in the relationship between the opening degree and the magnitude of the drive current is used as the exhaust valve. A method can be provided.

It is a block diagram which shows the functional composition example of the sphygmomanometer which concerns on embodiment of this invention. It is a flowchart about the operation of the sphygmomanometer which concerns on embodiment. It is a figure which shows the structural example of the constant discharge valve drive circuit which concerns on embodiment. It is a figure for demonstrating the effect of the driving method of the constant discharge valve which concerns on embodiment.

Hereinafter, the present invention will be described in detail with reference to the drawings based on an exemplary embodiment. In the following, a configuration in which the present invention is applied to a sphygmomanometer will be described. However, the present invention is not limited to sphygmomanometers, but can be applied to biometric information measuring devices such as pulse wave meters and blood flow meters that are attached to the person to be measured and measure biometric information using an airbag supplied by a pump. Is. Further, a computer device capable of functioning as a sphygmomanometer or a biometric information measuring device to which the present invention is applied by executing application software is also included in the sphygmomanometer or the biometric information measuring device of the present invention.

● (Structure of blood pressure monitor)
FIG. 1 is a block diagram showing a functional configuration example of an automatic sphygmomanometer 150 as an example of a sphygmomanometer according to an embodiment. The automatic sphygmomanometer 150 measures blood pressure by an oscillometric method using a cuff 10.
The cuff 10 has a built-in airbag 11 connected to one end of the air hose H, and is attached to a part of the subject whose blood pressure is to be measured (for example, one or more of limbs and toes). The cuff 10 is attached to the automatic blood pressure monitor 150 by attaching the connector provided at the other end of the air hose H to the air connector 24 of the automatic blood pressure monitor 150. The air connector 24 is connected to the pressure sensor 12, the constant discharge valve 14, the rapid discharge valve 16, and the pump 18 by a common gas flow path R. Therefore, with the cuff 10 attached to the automatic blood pressure monitor 150, the airbag 11, the air hose H, and the gas flow path R form one continuous space.

The pressure sensor 12 is a pressure-electric conversion sensor using, for example, a piezo element, and outputs an electric signal (sensor output signal) representing the internal pressure of the airbag 11. Since the internal pressure of the airbag 11 changes depending on the pulse, the sensor output signal contains a pulse wave component. The sensor output signal is sampled at a predetermined frequency by the AD converter 22 and converted into digital data.

The constant exhaust valve 14 and the rapid exhaust valve 16 are exhaust valves for reducing the internal pressure of the airbag 11. The constant exhaust valve 14 has a variable opening degree (exhaust flow rate) and is used to gradually reduce the internal pressure of the airbag 11 from the blood-driving state. On the other hand, the rapid exhaust valve 16 is used to rapidly reduce the internal pressure of the airbag 11 and is opened at the end of measurement. The rapid discharge valve 16 may be capable of controlling two states with an opening degree of 0% and 100% (fully closed and fully open). The constant discharge valve 14 and the rapid discharge valve 16 can be realized by, for example, a solenoid valve using a solenoid.

The pump 18 is used to supply air to the airbag 11 to increase the internal pressure.
The cuff control unit 20 controls the opening degree of the constant discharge valve 14 and the rapid discharge valve 16 and the start / stop of the pump 18. The cuff control unit 20 operates according to the control of the main control unit 30. For the constant discharge valve 14 having a variable opening degree, the constant discharge valve drive circuit 21 is driven so as to have an opening degree according to the instruction of the cuff control unit 20. Since the sudden discharge valve 16 only needs to control two states in which the opening degree is 100% (fully open) and 0% (fully closed), the cuff control unit 20 is directly driven.

In the present embodiment, for ease of explanation and understanding, one cuff 10 is connected to the automatic blood pressure monitor 150, but a plurality of cuffs 10 may be connected. When a plurality of cuffs 10 are connected, in principle, the same number of air connectors 24, pressure sensors 12, constant discharge valves 14, rapid discharge valves 16 and pumps 18 are provided. On the other hand, it is not always necessary to provide the same number of cuff control units 20 and AD converters 22 as the cuffs 10.

The sensor output signal digitized by the AD converter 22 is supplied to the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51.
The pulse wave signal extraction filter 50 extracts a volumetric pulse wave signal component (hereinafter, simply referred to as a pulse wave signal component) from the sensor output signal and outputs the pulse wave signal to the main control unit 30.
The pressure signal extraction filter 51 removes a pump noise component and a pulse wave signal component from the sensor output signal, and outputs the pressure signal to the main control unit 30.

All of these filters can be realized by a filter having a frequency characteristic that allows the band of the signal component to be extracted to pass through and blocks or significantly attenuates other bands. For example, the pulse wave signal extraction filter 50 can be realized by a bandpass filter that passes through a general pulse frequency. The frequency band differs between the pulse wave measured at the limbs such as the upper arm and ankle and the pulse wave measured at the toes. Therefore, it is possible to switchably provide a bandpass filter having a frequency characteristic according to a measurement site (a site where the cuff 10 is attached), or to configure the frequency characteristic of the filter to be changeable according to the measurement site.
The pressure signal extraction filter 51 can be configured by a low-pass filter that removes AC components such as a pump noise component and a pulse wave signal component from the sensor output signal.

The main control unit 30 includes, for example, one or more programmable processors (MPUs) and a memory, and executes a program stored in the memory in the MPU to control the operation of each unit of the automatic sphygmomanometer 150. It realizes 150 functions. Information used for program execution (various constants, set values, etc.) may also be stored in the memory. Although the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51 are described as separate configurations from the main control unit 30 in FIG. 1, the functions of these filters can be obtained by executing the program by the MPU of the main control unit 30. May be realized.

The main control unit 30 acquires a pulse wave signal and a pressure signal, and controls the operation of the pump 18, the constant discharge valve 14, and the rapid discharge valve 16 through the cuff control unit 20 based on the pressure signal. Further, the main control unit 30 determines the blood pressure value (systolic blood pressure, mean blood pressure, and diastolic blood pressure) based on the value of the pressure signal when the amplitude of the pulse wave signal satisfies a specific condition.

The operation unit 60 is, for example, a key, a switch, a button, or the like, and receives instructions and settings from the user. For example, a power button / switch, a switch / button for instructing the start of blood pressure measurement, a switch / button for instructing the stop of blood pressure measurement during execution, and the like are included. When the display unit 70 has a touch panel, the combination of the GUI display and the touch panel on the display unit 70 also constitutes a part of the operation unit 60. The operation of the operation unit 60 is monitored by the main control unit 30, and the main control unit 30 executes an operation according to the detected operation.

The display unit 70 is composed of, for example, a dot matrix type display such as an LCD, an LED lamp, or the like, and displays an operating state, measurement results, guidance, and the like of the automatic blood pressure monitor 150 under the control of the main control unit 30. The automatic blood pressure monitor 150 may be provided with another output device such as a speaker or a printer in place of the display unit 70 or in addition to the display unit 70.

The storage unit 80 is a storage device that stores information related to measurement data (information on the subject, etc.), measurement data, and the like, and may be, for example, a non-volatile memory. The storage unit 80 may be configured to use a recording medium that can be removed from the automatic blood pressure monitor 150, such as a memory card. It should be noted that at least a part of the program executed by the MPU of the main control unit 30 and the information used for executing the program may be stored in the storage unit 80.

The external interface (I / F) 90 is a wired and / or wireless communication interface for connecting, for example, an external device using the measured blood pressure value to the automatic sphygmomanometer 150. The automatic sphygmomanometer 150 can communicate with an external device through the external interface (I / F) 90. Further, power may be supplied from an external device through the external interface (I / F) 90.

● (Operation of automatic blood pressure monitor)
FIG. 2 is a flowchart for explaining the blood pressure measurement process of the automatic sphygmomanometer 150 of the present embodiment. For example, when the start of the blood pressure measurement operation is instructed by pressing the start button or the like of the operation unit 60, the main control unit 30 instructs the cuff control unit 20 to start supplying air to the cuff 10 in S101.

The cuff control unit 20 operates the pump 18 in response to this instruction. As a result, air supply to the airbag 11 is started. During air supply, the cuff control unit 20 controls both the constant discharge valve 14 and the rapid discharge valve 16 to be fully closed. The sensor output signal output by the pressure sensor 12 is a signal representing the static internal pressure (cuff pressure) of the airbag 11, pressure fluctuation (volume pulse wave component) due to the pulse of the mounting portion of the cuff 10, and operating noise of the pump 18. (Pump noise component) is an superimposed electrical signal.

The sensor output signal is digitized by the AD converter 22, and then supplied to the pulse wave signal extraction filter 50 and the pressure signal extraction filter 51. The pulse wave signal extraction filter 50 supplies the pulse wave signal component extracted from the sensor output signal to the main control unit 30 as a pulse wave signal. The pressure signal extraction filter 51 supplies a signal obtained by removing the pump noise component and the pulse wave signal component from the sensor output signal to the main control unit 30 as a pressure signal.

In S103, the main control unit 30 determines whether or not the cuff pressure represented by the pressure signal has reached a predetermined target value. Proceed with each process.

In S121, the main control unit 30 determines whether or not an abnormality has been detected, and if it is not determined that an abnormality has been detected, the process is returned to S103 to continue air supply, and if it is determined that an abnormality has been detected, the process proceeds to S123. For example, whether the main control unit 30 normally pressurizes the cuff 10 when the elapsed time from the start of air supply exceeds the threshold value or when the amplitude of the sensor output signal is less than the threshold value. It can be determined that the abnormality has been detected when it is determined that there is an abnormality in the circuit component, or when the operation unit 60 instructs to stop the measurement.

In S123, the main control unit 30 forcibly terminates the blood pressure measurement.
Specifically, the main control unit 30 is attached to the cuff control unit 20.
・ Pump 18 operation stop (air supply stop)
-Instruct to fully open the constant discharge valve 14 and the rapid discharge valve 16.

In S125, the cuff control unit 20 stops the operation of the pump 18 according to the instruction of the main control unit 30, and makes the constant discharge valve 14 and the rapid discharge valve 16 fully open.

In S127, the main control unit 30 displays a message on the display unit 70, outputs an alarm sound, for example, notifies the device abnormality, and ends the blood pressure measurement process. After giving an instruction to the cuff control unit 20 in S123, the main control unit 30 may proceed to S127 without waiting for the operation completion of the cuff control unit 20.

On the other hand, when it is determined in S103 that the cuff pressure has reached the target value, the main control unit 30 instructs the cuff control unit 20 to stop supplying air in S105. Alternatively, even if it is not determined in S103 that the cuff pressure represented by the pressure signal has reached a predetermined target value, the process proceeds to S105 when it is confirmed that the pulse wave signal has continuously disappeared for a certain period of time. You may. The cuff control unit 20 stops the operation (supply) of the pump 18 in response to the instruction to stop the supply air.

Next, the main control unit 30 starts the blood pressure determination process. The blood pressure determination process can be performed by a method based on a known oscillometric method. To explain a feasible example, first, in S107, the main control unit 30 opens the constant discharge valve 14 to the cuff control unit 20 with an opening degree corresponding to a predetermined target value (for example, 5 mmHg / sec) of the decompression rate. Instruct. The cuff control unit 20 notifies the constant discharge valve drive circuit 21 of the opening degree or the flow rate instructed by the main control unit 30. The constant discharge valve drive circuit 21 generates a drive current according to the notified opening degree or flow rate, and drives the constant discharge valve 14. As a result, the opening degree of the constant exhaust valve 14 becomes larger than 0 (fully closed), exhaust from the constant exhaust valve 14 is started, and the internal pressure of the airbag 11 of the cuff 10 also starts to decrease.

When the initial opening degree at the time of opening the constant discharge valve 14 is preset in the cuff control unit 20, the main control unit 30 simply opens the constant discharge valve 14 without designating the opening degree in S107. You may instruct the cuff control unit 20 to do so.

When the main control unit 30 instructs the cuff control unit 20 to open the constant discharge valve 14, the main control unit 30 starts the blood pressure value determination process based on the pulse wave signal and the pressure signal. The main control unit 30 sets the systolic blood pressure as the pressure value indicated by the pressure signal at the time when the amplitude of the pulse wave signal corresponds to a predetermined ratio of the maximum amplitude, for example, before and after the time when the amplitude of the pulse wave signal becomes maximum. And can be determined as diastolic blood pressure. Alternatively, the main control unit 30 can determine the pressure value indicated by the pressure signal at the time when the amplitude of the pulse wave signal is significantly changed as the systolic blood pressure and the diastolic blood pressure. The provisional blood pressure value may be determined during decompression, and the final blood pressure value may be determined after the decompression treatment is completed.

In S109, the main control unit 30 monitors the pressure signal while executing the blood pressure determination process, and determines whether or not the decompression rate is within the target range. Specifically, the main control unit 30 determines whether or not the current cuff pressure is within the current target value ± the target range of the permissible error obtained from the elapsed time since the constant discharge valve 14 is opened and the target decompression rate. judge.

If it is determined that the decompression rate is within the target range, the main control unit 30 advances the process to S111 and determines whether or not the blood pressure determination process is completed. If it is determined that the blood pressure determination process is completed, the main control unit 30 advances the process to S113, and if it is not determined that the blood pressure determination process is completed, the process returns to S109. As described above, in the blood pressure determination process, a provisional blood pressure value may be determined.

In S113, the main control unit 30 instructs the cuff control unit 20 to fully open both the constant discharge valve 14 and the rapid discharge valve 16. In response to this, the cuff control unit 20 controls the constant discharge valve 14 and the rapid discharge valve 16 to the fully open state.
In S120, the main control unit 30 presents the measured value such as the blood pressure value determined during depressurization or after S113, the reliability of the blood pressure value, and other information obtained during the measurement, and ends the blood pressure measurement process. The presentation of the information may be, for example, a display to the display unit 70, a voice notification, or a combination thereof. Here, it is displayed for the display unit 70.

On the other hand, when the decompression rate is not determined to be within the target range in S109, the main control unit 30 adjusts the opening degree of the constant discharge valve 14 in S115 to S119. Specifically, in S115, the main control unit 30 determines whether or not the current cuff pressure) is lower than the target range, and if it is determined to be low, the process proceeds to S119, and if it is determined to be low, the process proceeds to S117. Proceed.

In S119, the main control unit 30 instructs the cuff control unit 20 to increase the opening degree of the constant exhaust valve 14 in order to increase the exhaust flow rate, and returns the process to S109. Further, in S117, the main control unit 30 instructs the cuff control unit 20 to reduce the opening degree of the constant exhaust valve 14 in order to reduce the exhaust flow rate, and returns the process to S109. The cuff control unit 20 instructs the constant discharge valve drive circuit 21 to increase or decrease the opening degree of the constant discharge valve 14 by a predetermined ratio according to the instruction from the main control unit 30.

● (Constant discharge valve drive circuit 21)
FIG. 3 is a diagram showing a configuration example of the constant discharge valve drive circuit 21. In the present embodiment, the constant discharge valve 14 is an electromagnetic valve using a solenoid, and the constant discharge valve drive circuit 21 is a modulation signal obtained by pulse width modulation (PWM) of a pulse signal (square wave) having a predetermined frequency. Is used to drive the constant discharge valve 14. The PWM circuit 211 can be realized by, for example, an FPGA (Field Programmable Gate Array). The PWM circuit 211 adjusts the frequency of the pulse signal supplied as a clock signal (carrier signal) as necessary, and then pulses so as to have a duty ratio according to the opening degree or the flow rate instructed by the cuff control unit 20. Width-modulated and output. Here, the clock signal is supplied from the outside of the constant discharge valve drive circuit 21, but an oscillator may be provided in the constant discharge valve drive circuit 21 to generate a clock signal.

The pulse signal output by the PWM circuit 211 is input to the base of the transistor 212 as a switching element. The transistor 212 turns on when the pulse signal is high level and turns off when the pulse signal is low level. The constant discharge valve 14 is connected between the power supply E and the collector of the transistor 212.

The higher the duty ratio of the pulse signal output by the PWM circuit 211, the larger the drive current of the constant discharge valve 14. Upon receiving the notification of the opening degree or the flow rate from the cuff control unit 20, the PWM circuit 211 follows the duty ratio of the pulse signal according to the table or the relational expression which shows the relationship between the opening degree or the flow rate and the duty ratio stored in advance. To determine. Then, the PWM circuit 211 generates and outputs a pulse having a determined duty ratio.

In the present embodiment, the PWM circuit 211 controls the duty ratio of the pulse signal having a frequency such that the drive current of the constant discharge valve 14 becomes a pulsating current or a pulsating current (a current whose magnitude changes periodically).

The solenoid can be regarded as an LR series circuit consisting of a coil and a parasitic resistor. Therefore, the equation of the drive circuit can be expressed by the following equation (1), where L is the inductance of the coil, Rs is the parasitic resistance, e is the power supply voltage, and i is the current.

となる。ここで、Ｅは電源電圧[V]である。 The drive current of the constant discharge valve 14 obtained by switching the transistor 212 with the pulse signal output by the PWM circuit 211 follows the voltage with a characteristic of first-order lag. Here, when the equation (1) is solved with the frequency of the pulse signal (carrier signal) for which the PWM circuit 211 controls the duty ratio as ω _c , the amplitude current I of the PWM pulse signal component in the drive current of the constant discharge valve becomes.

Will be. Here, E is the power supply voltage [V].

From equation (2), it can be seen that the amplitude current I decreases as the frequency ω _c of the pulse signal increases. In the present embodiment, the frequency ω _c of the pulse signal is reduced to make the drive current a pulsating current, so that the plunger is constantly slightly vibrated and the hysteresis of the drive amount depending on the drive direction is suppressed. As described above, since the solenoid can be regarded as an RL series circuit, when the frequency ω _c of the pulse signal is higher than the frequency corresponding to the time constant of the solenoid, the magnitude of the drive current becomes almost constant. Therefore, the frequency ω _c of the pulse signal is set to a value lower than the frequency corresponding to the time constant of the solenoid valve used for the constant discharge valve 14. Further, since it does not affect the blood pressure measurement, the value is set higher than the cutoff frequency (for example, 150 Hz) of the low-pass filter used as the pulse wave signal extraction filter.

As the frequency ω _c of the pulse signal, the frequency ω _c of the pulse signal can be determined within a range in which the hysteresis [%] is less than a predetermined threshold value. The threshold value can be, for example, about 3 [%], but this is not the case.

Since the constant discharge valve drive circuit 21 shown in FIG. 3 is configured to directly PWM drive the constant discharge valve 14, for example, the current control parameter of the constant current circuit is periodically changed to pulse the drive current of the constant discharge valve 14. It is simpler than the flow configuration.

FIG. 4 is a diagram showing a specific example of the relationship between the drive current and the exhaust flow rate in a sphygmomanometer using a proportional solenoid as a constant exhaust valve. Here, the drive voltage E of the constant discharge valve 14 is set to 6 [V], and the internal pressure of the airbag 11 detected by the pressure sensor 12 is 300 mmHg, and the direction is from fully closed to fully open and from fully open to fully closed. The drive current (duty ratio) was changed depending on the direction of travel, and the exhaust flow rate was measured. The inductance L of the proportional solenoid was 49 [mmH] (1 kHz), and the parasitic resistance Rs was 137 [Ω]. Therefore, the time constant τ = L / R = 3.58 × 10 ^-4 [sec] of the solenoid valve, and the frequency 1 / t = 2795.9 [Hz] corresponding to the time constant τ. The cutoff frequency of the pulse wave signal extraction filter 50 applied to the pulse wave signal is 150 [Hz].

The measurement results for each of the case where the frequency ω _c of the pulse signal is higher than the frequency corresponding to the time constant τ (ω _c = 32 kHz) and the case where the frequency ω c is lower (ω _c = 1 kHz and 300 Hz) are shown in FIG. 4 (a). -Shown in FIG. 4 (c).

As shown in FIG. 4, when the frequency ω _c of the pulse signal is higher than the frequency corresponding to the time constant τ, the hysteresis is large, and it is suitable for the feedback control as performed in S109 and S115 to S119 in FIG. do not have. On the other hand, when the frequency ω _c of the pulse signal is lower than the frequency corresponding to the time constant τ, the hysteresis is significantly suppressed, and especially when ω _c = 300 Hz, the hysteresis is almost eliminated.

As described above, according to the present invention, even when the solenoid valve used as the constant discharge valve has a hysteresis in the relationship between the opening degree and the drive current, the feedback control of the opening degree can be performed with high accuracy. As a result, the measurement accuracy of blood pressure can be improved. Also, in general, a solenoid valve with a small hysteresis is more expensive than a solenoid valve with a large hysteresis. According to the present invention, since the influence of hysteresis can be significantly suppressed, accurate blood pressure measurement can be performed even by using a solenoid valve having a relatively large hysteresis, which is very useful from the viewpoint of cost reduction of the sphygmomanometer. Is.

The method for driving the constant discharge valve according to the present invention is realized as a program (application software) for causing one or more programmable processors (computers) of the cuff control unit 20 to execute the same operations as the PWM circuit 211. You can also. Therefore, such a program and a storage medium (an optical recording medium such as a CD-ROM or a DVD-ROM, a magnetic recording medium such as a magnetic disk, a semiconductor memory card, etc.) containing the program also constitute the present invention. ..

10 ... Cuff, 11 ... Airbag, 12 ... Pressure sensor, 14 ... Constant discharge valve, 16 ... Rapid discharge valve, 18 ... Pump, 20 ... Cuff control unit, 21 ... Constant discharge valve drive circuit, 22 ... AD converter, 30 ... main control unit, 51 ... pulse wave extraction filter, 52 ... pressure extraction filter, 150 ... sphygmomanometer

Claims (6)

An airbag attached to the subject's measurement site,
A solenoid valve for reducing the internal pressure of the airbag,
A sphygmomanometer having a drive circuit for controlling the opening degree of the solenoid valve.
The drive circuit has a frequency lower than the frequency corresponding to the time constant of the electromagnetic valve, and is a cutoff frequency of a low-pass filter for extracting a pulse wave signal used for measuring blood pressure from a signal representing the internal pressure of the airbag. A blood pressure monitor characterized in that the electromagnetic valve is driven by using a pulse signal having a higher frequency to control the opening degree of the electromagnetic valve. The sphygmomanometer according to claim 1 , wherein the frequency is determined in a range in which the hysteresis between the magnitude of the driving current of the solenoid valve and the opening degree of the solenoid valve is less than a predetermined threshold value. The sphygmomanometer according to claim 1 or 2 , wherein the drive circuit controls the opening degree of the solenoid valve by changing the duty ratio of the pulse signal. The sphygmomanometer according to any one of claims 1 to 3 , wherein the solenoid valve is used as a constant discharge valve. Claims 1 to 4 further include a control means for controlling the opening degree of the solenoid valve by using the drive circuit so that the internal pressure of the airbag becomes a target value during blood pressure measurement. The sphygmomanometer according to any one of the above. An airbag attached to the subject's measurement site,
A method for controlling a sphygmomanometer having a solenoid valve for reducing the internal pressure of the airbag.
A frequency lower than the frequency corresponding to the time constant of the electromagnetic valve and higher than the cutoff frequency of the low-pass filter for extracting the pulse wave signal used for measuring blood pressure from the signal representing the internal pressure of the airbag. A control method for a blood pressure monitor, comprising a control step of driving the electromagnetic valve using a pulse signal and controlling the opening degree of the electromagnetic valve.

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