JPS6229050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a pressure correction device for a digital blood pressure monitor.

(B) Conventional technology Pressure sensors used in blood pressure monitors have a precise structure in order to detect minute changes, and are therefore susceptible to the effects of the external environment, often causing detection output to drift. . This drift is caused by something that changes over time, such as temperature. As a countermeasure, conventionally, before turning on the power, the conduit (rubber tube) connecting the pressure sensor section and the cuff was removed, the pressure sensor was completely exposed to the atmosphere, and the output of the sensor section when the power was turned on was corrected. Store as a value.
When measuring blood pressure, the value obtained by subtracting the correction value from the output of the pressure sensor is used as the measured pressure, and the blood pressure is determined based on this pressure value, thereby correcting variations in the detected output such as drift. .

(c) Problems to be solved by the invention In the digital blood pressure monitor using the conventional pressure correction device described above, if accurate pressure correction is to be performed,
It is desirable to disconnect the pipe line and completely open the pressure sensor to the atmosphere before starting each measurement. However, it is extremely troublesome to perform the above-mentioned scan, which involves completely opening the pressure sensor section to the atmosphere, for each measurement.
In reality, measurement is started by turning on the power while the arm cuff is connected to the blood pressure monitor body through a conduit.
Therefore, when there is residual pressure in the wristband, this residual pressure may be stored as a correction value as if it were atmospheric pressure.

In particular, if a cuff with insufficient exhaust is wrapped tightly around the arm with the rapid exhaust valve closed, the air remaining in the cuff will be squeezed and the internal pressure of the cuff will decrease. It will rise considerably. In this way, when the power is turned on and measurement is started in a state where the internal pressure is rising, a pressure higher than atmospheric pressure is stored as a correction value before the start. In other words, assuming that the output of the pressure sensor when open to the atmosphere is 0 mmHg, the output of the pressure sensor when there is residual pressure in the cuff is 10 mm.
Hg, if the residual pressure of 10 mmHg is stored as a correction value, and the output of a certain pressure sensor during blood pressure measurement is 20 mmHg, the residual pressure will be 20 mmHg when corrected with the corrected value when completely vented to the atmosphere. If the atmospheric pressure of 10mmHg is used as the correction value, 20−10=10
mmHg results are lower than the true value, making accurate measurements impossible. The above problem will be specifically explained with reference to FIG.

Figure 4 shows that in a conventional digital blood pressure monitor, t ₀
An example of change in arm cuff pressure is shown when the power is turned on at time t and pressurization is started at time _t1 .

As shown in the figure, if there is a residual pressure Pr when the power is turned on, the pressure decreases as shown by straight line A until time _t1 due to slow exhaustion. Therefore, the pressure value at time t ₁
If Pc ₁ is the correction value, a correction value closer to atmospheric pressure than the pressure value Pc ₀ at time t ₀ will be stored. Furthermore, if the measurer operates the rapid exhaust valve between the time _t0 when the power is turned on and the start of pressurization, the pressure will drop rapidly as shown by straight line B. Therefore, if the pressure sensor output is stored as a correction value after rapid evacuation, a correction value approximately close to atmospheric pressure will be stored. However, as mentioned above, conventionally, the output Pc ₀ of the pressure sensor is stored as a correction value when the power is turned on, which has the disadvantage that the pressure closer to the atmosphere due to the slow exhaust or rapid exhaust is not utilized for correction. It was hot.

The above-mentioned malfunctions are caused by the user's erroneous operations, but in home-use blood pressure monitors, they frequently occur due to the user's insufficient knowledge.

In view of the above, an object of the present invention is to provide a pressure correction device for a digital blood pressure monitor that can correct the correction value to an appropriate correction value even if an inappropriate correction value happens to be stored due to residual pressure or the like. There is.

(d) Means for solving the problems The pressure correction device for the digital blood pressure monitor of this invention has the following features:
In response to turning on the power, the output of the pressure sensor is stored as a correction value in the storage means, the pressure is measured by the pressure sensor at predetermined time intervals, and the arm cuff pressure used in the blood pressure measurement process is calculated. The correction value is obtained by subtracting the correction value from the pressure sensor output during each pressure measurement at the time, and the correction value is compared with the pressure sensor output during pressure measurement, and the pressure sensor output is determined to be the correction value. It is characteristically equipped with a comparison means that outputs an output when the pressure is smaller, and a correction value updating means that updates and stores the pressure sensor output at that time as a new correction value based on the output of the comparison means.

(E) Function In the pressure correction device of this digital blood pressure monitor, if the pressure sensor is completely exposed to the atmosphere before the power is turned on, the output of the pressure sensor will correspond to the atmospheric pressure when the power is turned on. At this point, an appropriate correction value is stored in the storage means, and blood pressure measurement processing is performed using an appropriate cuff pressure value, allowing accurate measurement. However, this also applies to conventional pressure compensation devices.

If for some reason, for example, as shown in Figure 3, the power is turned on when there is a residual pressure Pc ₀ in the cuff, this pressure Pc ₀ is first detected by the pressure sensor and used as a correction value. The incorrect correction value is stored. However, if there is some time between the time t ₀ when the power is turned on and the time t ₁ when pressurization starts, the cuff internal pressure will decrease as shown by straight line A due to slow exhaustion. is smaller than the correction value Pc ₀ stored in the storage means, so the pressure sensor output every time the pressure is measured is stored as a new updated correction value, and the pressure value Pc ₁ , which is closer to atmospheric pressure, is stored as the correction value. . In addition, if the measurer operates the rapid exhaust valve before pressurization starts, the arm cuff pressure, which was Pc ₀ when the power was turned on, will immediately drop to a value close to atmospheric pressure, so each time the pressure is measured, The updated correction value also becomes approximately atmospheric pressure. Therefore,
In the pressure correction device of the present invention, even if the correction value at power-on is not appropriate, a correction value close to the atmospheric release level can be obtained before pressurization starts.

(f) Examples Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is a schematic configuration diagram of a digital blood pressure monitor in which the present invention is implemented.

In Figure 1, 1 is a pressure sensor, 2 is an AD converter that AD converts the output of pressure sensor 1, and 3 is an AD converter.
A microcomputer (hereinafter referred to as a microcomputer) that receives pressure information from the transducer 2 and Korotkoff sound and pulse sound information from a microphone (not shown) and determines a blood pressure measurement value.
(abbreviated as CPU), 4 is a display that displays the pressure measurement value determined by the CPU 3, 5 is a plug connected to the pressure sensor 1 through a rubber tube 6, 7 is a cuff 8 and a rubber bulb 9 for adding pressure to the exhaust valve. This is a rubber tube that connects the plug 5 with the plug 5.

As shown in FIG. 1, the blood pressure monitor configured as described above is placed in a state in which the rubber tube 7 is removed from the plug 5 prior to the start of measurement, and the power is turned on. After a certain period of time has elapsed, the acquisition of the correction value of the pressure sensor 1 is completed, and the rubber tube 7 that was disconnected is connected again to the plug 5 to enable blood pressure measurement.

FIG. 2 shows a flowchart for taking in and updating correction values, and the CPU 3 stores a program for executing this flowchart.

In this step, as described above, the pressure sensor 1 is opened to the atmosphere by turning on the power with the rubber tube 7 removed from the plug 5, and the pressure sensor output at that time is measured. In the step, the value measured in the step is stored as a correction value P1. The step is to start blood pressure measurement by connecting the rubber tube 7 to the plug 5 again, pressurize it to a predetermined pressure with the pressurizing rubber bulb 9, and then reduce the pressure with the exhaust valve. This is the step of measuring the pressure.

In the step, it is determined whether the measured value in the step is smaller than the correction value P1 stored in the step. When the measured value is larger than the correction value P1, the process moves to step, and the correction value P1 is subtracted from the measurement value to obtain the arm cuff pressure P.

In the step, the systolic blood pressure and the diastolic blood pressure are determined from the arm cuff pressure P calculated in the step and the Korotkoff sound and pulse sound information from the microphone.
In the step, it is determined whether the blood pressure measurement by the step has been completed or not, and if it has been completed, the execution of this flowchart is also completed, but if it has not been completed, the process returns to the step and repeats the same steps ~ to complete the blood pressure measurement process. Execute.

If the correction value P1 of the pressure sensor 1 is correctly taken in, the measured value is larger than the correction value P1 during the measurement process, the judgment of the step is NO, and the above steps , , 〓, 〓 are repeatedly executed. Finish blood pressure measurement.

However, if the power is turned on while the rubber tube 7 and the plug 5 are still connected and there is residual pressure inside the cuff, or if the power is turned on and measurement is started with residual pressure present, , the correction value P1 of the pressure sensor 1 is determined when the residual pressure of the cuff 8 is, for example, 20
If it is mmHg, it will be 20mmHg higher. Therefore, arm cuff pressure P in blood pressure measurement is indicated to be 20 mmHg lower.

In this way, if an incorrect correction value (this is referred to as P2) is stored, and the pressure measurement at the step is before pressurizing the pressurizing rubber ball 9, the exhaust by the slow exhaust valve or the rapid exhaust valve will be activated. Due to the exhaust caused by being opened, the measured pressure value is the correction value P2
(normal correction value P1+residual pressure), and as a result, it is determined in step that the measured value is smaller than the correction value P1. When it is determined in this way, the process moves to step 3, where the CPU 3 gives an alarm output to a notification means (not shown) (for example, using a buzzer, a lamp, or a part of the display tube) to urge re-measurement of the blood pressure, and returns to step 3. The current measured value is stored as a new correction value P1. Pressure measurement (step) and correction value update (step) are performed several times or more every second. Therefore, if pressure reduction corresponding to the residual pressure is continued thereafter, the correction value P1 will be approximately the same value as when the pressure sensor 1 was opened to the atmosphere, and subsequent blood pressure measurements can be performed correctly. .

Further, the step alarm allows the blood pressure measurement to be performed correctly according to the first step without waiting for automatic correction.

In the embodiment described above, an example using a microcomputer was shown as an optimal embodiment, so the comparison means corresponds to step discrimination.
It is possible to configure it with discrete circuits.

Although not shown in the drawings, as a storage means, since a microcomputer is used, a part of the random access memory is used as a storage area, and the configuration of such a storage means is well-known. I have omitted this because it is a technical matter.

(G) Effects of the Invention According to the present invention, the output of the pressure sensor at power-on is stored as a correction value, and this correction value is compared with the pressure sensor output at the time of pressure measurement to determine whether the pressure sensor output is lower than the correction value. If the pressure sensor output is small, the pressure sensor output is updated and stored as a new correction value, so even if the power is turned on in the presence of residual pressure and the initial correction value is not appropriate, the pressure will not change. If it decreases, the correction value is updated, and in the process until the start of pressurization, it is corrected to a more appropriate correction value by slow exhaust or rapid exhaust, so the arm cuff pressure used for blood pressure measurement processing is correct. This can prevent erroneous blood pressure measurements.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a schematic diagram of a digital blood pressure monitor, and Fig. 2 shows a diagram of a digital blood pressure monitor programmed into the microcomputer shown in Fig. 1 to correct the pressure sensor output. FIG. 3 is a diagram showing a flowchart, and FIG. 3 is a diagram used to explain the operation of the present invention. FIG. 4 is a diagram used to explain problems with the conventional pressure correction device. 1: Pressure sensor, 3: Microcomputer.

Claims (1)

[Claims] 1. In response to turning on the power, the output of the pressure sensor is stored as a correction value in the storage means, and the pressure is measured at predetermined intervals with the pressure sensor, and the arm used during the blood pressure measurement process is In a pressure correction device for a digital blood pressure monitor, in which the band pressure is obtained by subtracting the correction value from the pressure sensor output at each pressure measurement during blood pressure measurement processing, the correction value and the pressure sensor output at the time of pressure measurement are combined. and a correction value updating means for updating and storing the pressure sensor output at that time as a new correction value based on the output of the comparison means. Pressure correction device for digital blood pressure monitor.