JPH0212087B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an electronic blood pressure monitor.

[Background technology]

In this type of blood pressure monitor, in order to accurately measure blood pressure, it is necessary to correct the pressure sensor's drift over time and temperature, and to do this, the pressure inside the cuff band must be brought to atmospheric pressure before blood pressure measurement. be. Automatic blood pressure monitors have a built-in solenoid valve, so
The offset value of the sensor output can be measured by opening the solenoid valve to release the pressure sensor to atmospheric pressure each time the power is turned on or when blood pressure measurement starts. However, for manual blood pressure monitors that do not have a built-in solenoid valve, However, there is a problem in that it is not possible to distinguish between the sensor output based on the previous residual pressure during continuous blood pressure measurement or the pressure generated when the user wears the cuff band on the arm, and the output due to offset. Conventionally, a circuit was constructed using a thermistor or the like to offset the temperature characteristics of the sensor, but this is difficult to compensate for with high precision because the circuit is complex and there are variations in the amount and direction of drift in the pressure sensor. There was a problem. A method has also been proposed (Japanese Patent Laid-Open No. 57-20250) in which a timer is started when the power is turned on or when the pressure within the cuff band falls below a set value, and the offset value is measured after a certain period of time has elapsed. However, this method has the problem that even when there is no residual pressure, it is impossible to distinguish between offset and residual pressure, so a certain waiting time is always required, making it inconvenient to use.

[Purpose of the invention]

The present invention aims to solve the above-mentioned problems in the conventional example, and in particular, when the power is turned on, there is always a certain waiting time even though the residual pressure in the cuff band is zero in most cases. The purpose is to resolve the contradiction that it is necessary.

[Disclosure of the invention]

The sphygmomanometer of the present invention includes means for measuring the pressure within the cuff band at regular time intervals before blood pressure measurement, means for calculating the difference between the previous measurement value and the current measurement value, and a means for calculating the difference between the previous measurement value and the current measurement value, and converting the above calculation result into a reference value. and means for storing the previous or current measurement value when the calculation result falls below the reference value as an offset value, and calculates the value obtained by subtracting the offset value from the measured blood pressure value. It is configured to be displayed on a display, and by measuring the pressure at regular time intervals and taking the difference from the previous time, the rate of change in pressure within the cuff band is determined, and when this rate of change becomes almost zero. This is intended to shorten the above-mentioned waiting time by determining an offset value at a certain point in time and allowing blood pressure measurement to be started immediately.

FIG. 1 is a block diagram showing the construction of an embodiment of the blood pressure monitor of the present invention, in which a cuff band 1 is connected to a pressure pump 3, a pressure sensor 4, and an exhaust valve 5 through an air tube 2. The measured value output from the pressure sensor 4 is A/D converted by the A/D converter 7 according to a signal of a certain period (for example, 1 second) sent from the timer 6, and then input to the storage circuit 8. However, at the same time, the previous measured value held in the memory circuit 8 is transferred to the memory circuit 9. Here, the data in both memory circuits 8 and 9 is transferred to the subtraction circuit 10.
The difference data is sent to the comparator circuit 11 and compared with a reference value (for example, 0.1 mmHg).
If the difference is smaller than the reference value, the output of the comparison circuit is inverted, thereby stopping the transfer timing signal output from the operation control circuit 12, and the data in the storage circuit 8 is held as is as an offset value. At the same time, a ready display is displayed. Reference numeral 13 denotes a Korotkoff sound detection circuit, which passes an audio signal input from a microphone 14 mounted inside the cuff band 1 through an amplifier 15 to a bandpass filter 1.
6 and a low-pass filter 17 to separate the Korotkoff sound and the pulse sound, and a level detector 1, respectively.
Detected by 8 and 19, Korotkoff sound discriminator 20
In addition, Korotkoff sounds are detected. When the Korotkoff sound is input in the operation control circuit 12, a control signal is sent to the subtraction circuit 21, which subtracts the blood pressure measurement value input from the A/D converter 7 and the offset value input from the memory circuit 8. The difference is output to the display 22 as a true blood pressure value.

FIG. 2 shows the operation of the blood pressure monitor of the present invention in comparison with a conventional example. In the same figure a, () indicates that when blood pressure is measured once and then is rapidly evacuated, ()
If you wrap the cuff band around your arm and turn on the power, ()
shows the case where the power is turned on without the cuff band being wrapped around the arm, that is, when the pressure inside the cuff band is atmospheric pressure. In the case of (), the timer was started from time _t1 when the pressure sensor output decreased to the set value, and the pressure sensor output at time _t2 after a certain period of time td was used as the offset value. Therefore, even if the pressure at t ₀ when the power is turned on is not so high () or the pressure is not different from atmospheric pressure (), it is necessary to wait for a certain period of time td as in (), and in reality t Even though the pressure is equal to the atmospheric pressure at time ₃ or _t4 , the offset value is measured by waiting until _t5 , which is a certain period of time td from the time _t0 when the power is turned on. However, in the present invention, the rate of change in the pressure sensor output is detected as shown in Figure b, so in the cases of () and (), there is no need to wait until t ₅ , and it is not necessary to wait until t ₄ and t 5, respectively.
Blood pressure measurement can be started at time _t3 .

The embodiment shown in FIG. 3 shows a flowchart of a processing program when the part A in FIG. 1 is replaced with a microcomputer. In the same figure,
_P1 is a register corresponding to the memory circuit 8 in FIG. 1, and the reference value is 0.1 mmHg, and the timer setting time is 1 second.

〔Effect of the invention〕

The blood pressure monitor of the present invention is configured as described above, and includes a means for measuring the pressure in the cuff band at regular time intervals using a timer before blood pressure measurement, and a means for subtracting the difference between the previous measurement value and the current measurement value. The rate of change in pressure within the cuff band is detected by a means for calculating using a circuit and a means for comparing the above calculation result with a reference value using a comparison circuit, and the point in time when the rate of change becomes almost zero. Since the offset value is determined by the offset value and blood pressure measurement is started immediately after that value, blood pressure measurement can be started more quickly than with conventional methods, except in exceptional cases where blood pressure is measured continuously. Since the cuff band is often wrapped around the arm after the power is turned on, there is an advantage that almost no waiting time is required.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIGS. 2a and 2b are graphs explaining the operation of the same as above, and FIG. 3 is a flowchart showing the operation of another embodiment of the same. 1 is a cuff band, 2 is an air tube, 3 is a pressurizing pump, 4 is a pressure sensor, 5 is an exhaust valve, 6 is a timer,
7 is an A/D converter, 8 and 9 are memory circuits, 10
11 is a subtraction circuit, 11 is a comparison circuit, 12 is an operation control circuit, 13 is a Korotkoff sound detection circuit, 14 is a microphone, 15 is an amplifier, 16 is a band pass filter, 17 is a low pass filter, 18 and 19 are level detectors. , 20 is a Korotkoff sound discriminator, 21
2 is a subtraction circuit, and 22 is a display.

Claims (1)

[Claims] 1. A means for measuring the pressure within the cuff band at regular time intervals before blood pressure measurement, a means for calculating the difference between the previous measured value and the current measured value, and a means for comparing the above calculation result with a reference value. , means for storing the previous or current measurement value when the calculation result falls below the reference value as an offset value, and causes the display to display a value obtained by subtracting the offset value from the measured blood pressure value. A blood pressure monitor characterized in that it is constructed as follows.