JPH07275216A - Blood pressure measuring device - Google Patents

Abstract

PURPOSE:To reduce power consumption with a simple constitution, and also to prevent the occurrence of vibrational sound or the like. CONSTITUTION:This blood pressure measuring device is provided with an orifice that is connected to a cuff 1 for reducing the pressure of the cuff 1 by discharging the fluid from the cuff 1, a solenoid valve 10 for opening or closing the opening of the orifice, a first driving circuit 12a for supplying a relatively low driving current in such a degree by which the solenoid valve 10 can be kept at least in a closed condition, and a second driving circuit 12b for supplying a relatively high driving current for closing the solenoid valve 10. In such a condition that the orifice is closed by a control unit 6 and the pressure reduction of the cuff 1 is stopped, only the first driving circuit 12a is operated, while, when the solenoid valve 10 is operated for closing the orifice from the open condition, at least the second driving circuit 12b is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood pressure measuring device for measuring blood pressure by compressing a blood vessel by pressurizing a cuff with a fluid.

[0002]

2. Description of the Related Art When measuring blood pressure in a blood vessel from the body surface using a cuff or the like to measure the intravascular pressure, first, the cuff pressure is increased to a pressure higher than the intravascular pressure to indicate that the blood flow is blocked. Infrared sensor, impedance sensor, or pressure sensor detects Korotkoff sound sensor or Doppler sensor that detects blood flow on the peripheral side of blood vessel Judge by doing.

Next, when decompression is slowly started and the cuff pressure falls below the intravascular pressure even a little, blood flow flows to the periphery of the cuff due to contraction of the heart, and this blood flow is detected by a sensor placed in the periphery. The cuff pressure when the blood flow occurs, or the volume under the cuff when the blood flow occurs or the cuff pressure when the pressure change accompanying the detection is detected as the systolic blood pressure. In addition, the slow depressurization is continued. The blood flow accompanying the contraction of the heart gradually increases in volume because the vascular stenosis damage due to the cuff gradually decreases. And that the obstacles due to the cuff have disappeared,
The sensor placed on the periphery detects the disappearance of vascular noise associated with vascular stenosis, or judges the cuff pressure when it is detected by a change in the cuff pressure under the cuff or a change in the cuff pressure accompanying this, as the diastolic pressure. .

As described above, in the non-invasive blood pressure measurement, the blood pressure is measured by detecting the state of the blood flow under the cuff generated by the contraction of the heart and obtaining the cuff pressure under a certain characteristic state. is doing. That is, the blood pressure can be measured only at the timing synchronized with the contraction of the heart. Therefore, what is important is that the slower the depressurization speed of the cuff pressure between heartbeats, the higher the accuracy of blood pressure measurement.

However, when the blood vessel is ischemic, the tissue on the peripheral side of the cuff becomes oxygen deficient and the venous pressure is usually 20 to 30 mmHg. Therefore, the venous blood vessel under the cuff remains closed. However, even if blood flow occurs, reflux is not performed, and the pooling amount of blood on the peripheral side of the cuff increases, resulting in hyperemia, numbness, tingling and the like. Therefore, the shorter the ischemic time, that is, the faster the decompression speed is, the less invasive the living body is, which is preferable.

Therefore, normally, the decompression speed in blood pressure measurement is a compromise between the measurement accuracy and the pain on the living body. Generally, AHA, WHO, etc. are ideally 2-3 mmHg per beat. Has been done.

However, considering that the change in the pulse cycle easily reaches 50% due to the influence of breathing, etc., and that the pulse rate per hour may be small depending on the person, etc., It is often difficult to control the depressurization pressure to a constant value, and the depressurization method used for general blood pressure measurement is a method in which the depressurization pressure is kept constant for a constant time regardless of the pulse rate. Therefore, when the pulse is fast, the measurement time is longer than the time actually required for blood pressure measurement, and the burden on the patient (subject) is large as described above. However, there is a problem that the measurement accuracy becomes poor.

In order to deal with this problem, a method is known in which the pressure of the cuff is reduced stepwise by 2 to 3 mmHg for each beat. This method stops the decompression and generates blood flow on the peripheral side of the cuff in synchronism with the contraction of the heart, or the cuff pressure change that reflects the change in blood vessel volume under the cuff. If the change of is detected, 2-3mmH
This is a system in which rapid depressurization of g is repeated, and since it corresponds to a fast pulse rate, it is necessary to rapidly depressurize when a pulse is detected. Especially at high cuff pressures, the dynamic pressures are also high and a considerable torque is required to overcome them and close the valve. In order to generate this large torque, it is necessary to flow a large current through the electromagnetic valve, and therefore, there is a problem that the battery life is short when the battery is driven.

In order to deal with this, conventionally, the winding of the electromagnetic valve is composed of two kinds of windings, and the winding is switched between when the valve is closed and when the valve is held in a closed state to reduce power consumption. Reduce or PWM (pulse width modulation)
In driving, a large current is applied when the valve is closed, and a relatively small drive current sufficient to hold the valve is applied when the valve is held closed. In addition, current switching was performed at the same time.

[0010]

However, when two types of electromagnetic valve windings are used, it is necessary to wind them in a stacked manner, and the coil diameter becomes large, leading to an increase in the size of the outer shape. Due to such problems, the manufacturing becomes complicated and the cost increases.

In the case of PWM driving, only one switching element is required and the circuit can be simplified.
Since it is driven by alternating current, vibration is generated, which causes annoying noise. Further, if the simultaneous switching is performed at the time of switching the current, an unstable state occurs transiently.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a blood pressure measuring device which can reduce power consumption with a simple structure and does not generate vibration noise. To provide.

[0013]

[Means for Solving the Problems]
In order to achieve the object, the blood pressure measurement device of the present invention is a blood pressure measurement device that pressurizes a cuff with a fluid to close the blood vessel to measure blood pressure, and is connected to the cuff, An orifice for discharging fluid to reduce the pressure of the cuff, an electromagnetic valve for opening and closing the opening of the orifice, and a relatively low drive for the electromagnetic valve so that the electromagnetic valve can be kept at least in a closed state. A first drive circuit that supplies a current, and a second drive circuit that is provided in parallel with the first drive circuit and that supplies a relatively high drive current for closing the electromagnetic valve to the electromagnetic valve. When the orifice is closed and the decompression of the cuff is stopped, only the first drive circuit is operated and the electromagnetic valve is changed from the open state to the closed state. When to be created is characterized by comprising a control means for controlling so as to operate at least the second drive circuit.

Further, in the blood pressure measuring device according to the present invention, the first drive circuit includes a current limiting resistor and a first switching element which are connected in series to the electromagnetic valve, and the second drive circuit is provided. The drive circuit includes a second switching element connected in series to the electromagnetic valve, and the control means switches between the first switching element and the second switching element,
It is characterized in that the operations of the first and second drive circuits are controlled.

Further, in the blood pressure measuring device according to the present invention, the control means, when switching from a state in which the cuff is depressurized to a state in which the depressurization is stopped, the second means is used.
Controlling the first and second switching circuits so as to turn on the switching circuit, turn on the first switching element, and then turn off the second switching circuit. There is.

[0016]

Since the blood pressure measuring device according to the present invention is constructed as described above, when the electromagnetic valve is held in a closed state, the valve can be held in a closed state by the first drive circuit. Low current, and when closing the electromagnetic valve from the open state, supply a high current that can close the valve by the second drive circuit provided in parallel with the first drive circuit. As a result, it is possible to provide a blood pressure measurement device that can reduce power consumption with a simple configuration.

Further, since the first drive circuit and the second drive circuit are electrically switched by the first and second switching elements, noise and the like can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a blood pressure measuring device according to an embodiment.

In FIG. 1, reference numeral 1 is a cuff for blood flow prevention,
A microphone 2 for detecting a K sound (Korotokov sound) is attached. A pressure sensor 3 is connected to the cuff 1 via air pipes 20 and 20a. The output of the pressure sensor 3 is input to the CPU 6 via the pressure signal amplifier 4 and the A / D converter 5.

A K sound signal amplifying section 8 for amplifying the K sound is connected to the microphone 2, and the K sound amplified by this is inputted to the A / D converter 6a in the CPU 6 for A / D conversion.
D converted.

The cuff 1 also has air pipes 20 and 20b.
A pump 9 for feeding air as a fluid into the cuff 1 to raise the pressure thereof and an exhaust valve 10 for discharging the air from the cuff 1 are connected via the. A pump drive circuit 21 is connected to the pump 9, and this circuit is controlled by the CPU 6.

The exhaust valve 10 has a first valve drive circuit 12a for supplying a drive current to the exhaust valve 10 and a second valve drive circuit 12a.
Is connected to the valve drive circuit 12b. The valve drive circuit 12 is formed by these first and second valve drive circuits.
Is configured. The first valve drive circuit 12a is configured by connecting a transistor as a switching element and a current limiting resistor 12c in series. The second valve drive circuit 12b is mainly composed of a transistor as a switching element. Then, from the first valve drive circuit 12a, a current having a relatively low current value for maintaining the normally open type exhaust valve 10 in a closed state is supplied to the exhaust valve 10. Also,
The second valve drive circuit 12b supplies the exhaust valve 10 with a current having a relatively high current value necessary for shifting the exhaust valve 10 from the open state to the closed state.

The transistors of the first valve drive circuit 12a and the second valve drive circuit 12b are the signal lines 18 and 19.
Is connected to the CPU 6 via.

In the CPU 6, a RAM 6b for recording the cuff vibration arterial wave signal output from the pressure sensor 3, a ROM 6c for storing decompression time corresponding to the cuff pressure as a table as shown in FIG. 5, and a cuff pressure. When the decompression rate (decompression pressure) for each beat exceeds a predetermined value, the correction values for correcting it are stored as a table as shown in FIG.
M6d is built in.

Further, the CPU 6 is connected with an LCD 7 for displaying the pressure value of the cuff 1, a reset circuit 13 for resetting the CPU 6, and a switch 14 for starting or stopping the measurement operation of the blood pressure measuring device. Has been done.

The power supply circuit 22 is composed of a battery 15, a power supply control circuit 16 and a constant voltage circuit 17, and is configured to supply power to each part of the blood pressure measurement device.

Next, FIG. 2 is a schematic view showing the structure of the exhaust valve 10. In FIG. 2, 10a is a driving coil, 10b is a plunger, and 10c is a plunger 1.
This is a spring for urging 0b to open the valve. Electric current is supplied to the exhaust valve 10 so that the coil 10
When a is energized, the plunger 10b is driven in the direction of the arrow, and the closing member 10e made of rubber or the like attached to the tip of the plunger 10b causes the air pipe 20b to move.
The exhaust valve 10 is closed by being pressed against the front end of the exhaust valve 10.

Next, the operation of the blood pressure measuring device configured as described above will be described with reference to the flow charts shown in FIGS.

First, when the start switch 14 is turned on (step S2), the CPU reset signal and the measurement start signal are input to the CPU 6, and the CPU 6 causes the pressure detection unit 23 and K to be detected.
The power of the sound signal amplification unit 8 is turned on. Continue to cuff 1
Zero pressure is set (step S4). Then, the CPU 6 sets the signal line 18 to the L level to turn on the holding drive circuit 12a of the valve drive circuit 12, and sets the signal line 19 to the H level to turn off the drive circuit 12b. As a result, the exhaust valve 10 is closed with a small current value for holding (step S6). afterwards,
The pump 9 is driven to start pressurizing the cuff 1 (step S8). While pressurizing the cuff 1, the pressure detection unit 23 detects the cuff pressure, and this detection signal is converted into a digital signal by the A / D conversion unit 5 and input to the CPU 6.

The pressure signal input to the CPU 6 is classified into a cuff pressure signal and a cuff vibration arterial wave signal, and the cuff pressure signal is processed and numerically displayed on the LCD 7. On the other hand, the magnitude of the cuff vibration arterial wave signal is detected and recorded in the internal RAM 6b of the CPU 6. The CPU 6 observes the change in the magnitude of the recorded cuff vibration arterial wave, and when it detects a change that gradually increases and reaches a peak and then gradually decreases, it interprets that the cuff pressure is close to the systolic blood pressure (step S10). ) As in the normal blood pressure measurement, about 30 mmHg from the systolic blood pressure is set as the cuff pressurization target value (step S12), and the pump 9 is stopped when the cuff pressure value reaches this target value.

Next, it is determined whether the pressure of the cuff 1 when the pump 9 is stopped has been increased to a value sufficient to start measuring blood pressure. First, the cuff vibration arterial wave is detected from the signal from the pressure detection unit 23. Further, the K sound signal from the microphone 2 arranged on the peripheral side of the cuff is sent to the K sound amplifying unit 8
A / D converter 6 built in CPU 6
It is converted into a digital signal by a. The CPU 6 checks whether the K signal is detected in synchronization with the cuff vibration arterial wave (step S14).

When the K sound is confirmed (step S14Y
In ES), it is considered that the ischemia is insufficient and the pressure of the cuff 1 is insufficient.
Re-pressurization is performed by using a value obtained by adding mHg as a new target pressure value.

If the K sound is not recognized (step S
14NO), since it is considered that the first ischemia is sufficient, the operation proceeds to the blood pressure measurement operation.

First, the parameter i = 0 is set (step S16). Next, in the ROM 6c in the CPU 6, as shown in FIG. 5, the opening time of the exhaust valve 10 required to reduce the cuff pressure by 2 to 3 mmHg from the current value according to the cuff pressure is stored in a table. Is remembered as
Particularly in the case of a cuff wrapped around a living body, the relationship between the amount of air discharged from the cuff and the decompression amount of the cuff is that the air is a compressible fluid, and the amount of air due to dead space until it comes into close contact with the arm is There is a non-linear relationship due to the large size, the expansion of the cuff bladder, and the viscoelastic property of the living body. Therefore, in this embodiment,
How long is the exhaust valve 10 depending on the pressure of the cuff 1
It is provided as a table as to whether or not a constant decompression amount (2 to 3 mmHg) can be obtained by opening. That is, for example, the current pressure of the cuff 1 is 150 mmHg and 20
If it is between 0 mmHg, set the exhaust valve 10 to 3
By opening for 0 msec, a pressure reduction of 2-3 mmHg is performed. However, what is shown in FIG. 6 is an example of a table, and if the shape of the cuff 1 is changed,
It goes without saying that this table also changes.

In step S18, the exhaust valve 10 is opened for the time based on the above table, and the pressure of the cuff 1 is reduced by 2 to 3 mmHg. Here, the operation of opening and closing the exhaust valve 10 will be described. First, when opening the exhaust valve 10, the signal line 18 is set to H level and the supply of current from the holding drive circuit 12a is stopped. . Since the signal line 19 is already at the H level at step S6 and the current is not supplied from the drive circuit 12b, the exhaust valve 10 is opened by the above operation. As a result, the pressure of the cuff 1 is rapidly reduced. Then, after holding the open state for the time set in the above table, the signal line 19 is set to L.
The exhaust valve 10 is set to a level and the exhaust valve 10 is closed by supplying a large current from the drive circuit 12b to the exhaust valve 10 to overcome the pressure including the dynamic pressure. Next, the signal line 18
Is set to L level, and a small current is also supplied to the exhaust valve from the holding drive circuit 12a. After that, the signal line 19 is set to the H level again and the supply of the large current from the drive circuit 12b is stopped. If the exhaust valve 10 is operated in this order,
A large current can be passed through the exhaust valve 10 when the exhaust valve is changed from the open state to the closed state, and a small current can be passed through when the exhaust valve 10 is kept in the closed state. As a result, consumption of the battery 15 can be reduced.

Next, the cuff vibration arterial wave is recognized from the signal from the pressure detecting section, and the K sound signal synchronized with it is checked (step S20). If the K sound is detected here, it is judged whether or not the K sound was detected during the pressure reduction one step before (step S22), and if the K sound was not detected one step before (step S22N).
Since K sound was detected for the first time in O),
The cuff pressure at this time is stored as systolic blood pressure.

Then, it is judged whether the difference value obtained by subtracting the target value (2 to 3 mmHg) from the depressurized value of the cuff performed in step S18 is less than zero (step S26). Increment (step S28), and if it exceeds zero, set i = 0 (step S30).

At step S32, the count value of i is N.
Determine if it is more than once. If i <N, step S20
Return to. If i ≧ N, it is determined that the pressure reduction amount is continuously less than or equal to the target value, and in this case, the correction time is added to the previous opening time based on the correction table as shown in FIG. The time is set (step S34), and the process returns to step S20. Here, N is a natural number of 2 or more. When the pressure reduction amount does not fall below the target value, the previous valve opening time is used as it is as the next valve opening time. When the pressure decreases, the amount of air discharged per unit time decreases because the air is a compressive fluid.
Eventually, when the depressurization amount falls below the target value N times in a row, the average value of the difference between the N times target depressurization value and the actual depressurization value and the correction opening time calculated by the correction table are added to change the air exhaust amount. By increasing and repeating this, 2-3m
The decompression amount of each step of mHg is maintained.

The loop of steps S18 to S34 is controlled so that one loop operation is performed for each heart beat based on the cuff vibration arterial wave. By controlling the operations of steps S18 to S34 to be performed once per one night of the heartbeat in this way, the pressure of the cuff 1 is stepped by 2 to 3 mmHg in synchronization with the heartbeat as shown in FIG. The pressure will be reduced. Thus, by reducing the cuff pressure by a constant value in synchronization with the heartbeat, it is possible to shorten the blood pressure measurement time and improve the measurement accuracy.

Further, when steps S16 to S32 are repeated, the pressure of the cuff 1 gradually decreases, and the resistance of the blood vessel is narrowed to obstruct the blood flow. Then, in step S20, the K sound is no longer detected (step S20 NO). At this point, it is determined whether or not the K sound was detected during the decompression one step before (step S34). If the K sound was detected one step before, the K sound is detected. Since it is considered that the K sound is no longer detected for the first time from the state, the cuff pressure at this time is stored as the diastolic blood pressure (step S3).
6).

In this way, if the diastolic blood pressure can be detected,
The CPU 6 sets the signal line 18 to the H level, and the exhaust valve 1
Turn off the holding current of 0, open the exhaust valve 10,
Reduce the cuff pressure to atmospheric pressure. Further, the CPU 6 calculates the pulse rate from the detected K-sound cycle, and numerically displays the systolic blood pressure, the diastolic blood pressure, and the pulse rate on the LCD 7. This completes the blood pressure measurement operation.

As described above, according to the above embodiment, the first drive circuit for supplying a small current to the exhaust valve and the second drive circuit for supplying a large current to the exhaust valve are provided in parallel. By switching between these and changing the current supplied to the exhaust valve, it is possible to reduce the consumption of the battery.

The present invention can be applied to a modified or modified version of the above embodiment for children, adults, etc. without departing from the spirit of the invention. In particular, it is preferably applied to an integrated electronic blood pressure monitor in which the cuff and the blood pressure monitor main body are integrated.

[0045]

As described above, according to the blood pressure measuring device of the present invention, when the electromagnetic valve is held closed, the valve can be held closed by the first drive circuit. Low current, and when closing the electromagnetic valve from the open state, supply a high current that can close the valve by the second drive circuit provided in parallel with the first drive circuit. As a result, it is possible to provide a blood pressure measurement device that can reduce power consumption with a simple configuration. This effect is particularly remarkable in an integrated electronic blood pressure monitor in which the cuff and the blood pressure monitor main body are integrated.

Further, since the first drive circuit and the second drive circuit are electrically switched by the first and second switching elements, noise and the like can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a blood pressure measurement device according to an embodiment.

FIG. 2 is a schematic diagram showing the structure of an exhaust valve.

FIG. 3 is a flowchart showing the operation of the blood pressure measurement device according to one embodiment.

FIG. 4 is a flowchart showing the operation of the blood pressure measurement device according to the embodiment.

FIG. 5 is a table of opening times of exhaust valves for reducing the cuff pressure by a constant value.

FIG. 6 is a diagram showing how the cuff pressure decreases stepwise in synchronization with the heartbeat.

FIG. 7 is a table of a correction value of an opening time of an exhaust valve.

[Explanation of symbols]

 1 Cuff 2 Microphone 3 Pressure sensor 4 Pressure signal amplification unit 5 A / D conversion unit 6 CPU 7 LCD 8 K sound signal amplification unit 9 Pump 10 Exhaust valve 12 Drive circuit 13 Reset circuit 14 Switch 15 Battery 16 Power supply control unit 17 Constant voltage Circuits 18 and 19 Signal lines 20 Air pipes 21 Pump drive circuits 22 Power supply circuits 23 Pressure detectors

Claims (3)

[Claims] 1. A blood pressure measuring device for measuring blood pressure by compressing a blood vessel by pressurizing a cuff with a fluid, which is connected to the cuff and discharges the fluid from the cuff to decompress the cuff. And an electromagnetic valve that opens and closes the opening of the orifice, and a first drive circuit that supplies a relatively low drive current to the electromagnetic valve so that the electromagnetic valve can be kept at least closed. A second drive circuit that is provided in parallel with the first drive circuit and supplies a relatively high drive current to the electromagnetic valve to close the electromagnetic valve; In the state where the pressure reduction is stopped, only the first drive circuit is operated,
A blood pressure measuring device comprising: a control unit that controls at least the second drive circuit to operate when the electromagnetic valve is operated from the open state to the closed state of the orifice. 2. The first drive circuit includes a current limiting resistor connected in series to the electromagnetic valve and a first switching element, and the second drive circuit is connected to the electromagnetic valve in series. A second switching element connected to the first switching element, and the control means controls the operation of the first and second drive circuits by switching between the first switching element and the second switching element. The blood pressure measurement device according to claim 1, wherein the blood pressure measurement device is a blood pressure measurement device. 3. The control means, when switching from a state in which the cuff is depressurized to a state in which the depressurization is stopped,
The second switching circuit is turned on, and then the first switching circuit is turned on.
3. The blood pressure measuring device according to claim 2, wherein the first and second switching circuits are controlled so that the switching element of 1 is turned on and then the second switching circuit is turned off.