JPH0345647B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a cuff that is attached to a part of a living body and can change its pressurized state, a sensor that detects arterial pulsation under the cuff, and a sensor that detects arterial pulses under the cuff. A non-observable system for automatically measuring systolic and diastolic blood pressures is equipped with means for recognizing systolic and diastolic blood pressures from cuff pressure corresponding to specific changes in the detection signal during the process, and means for displaying the recognized values. This invention relates to a blood type automatic blood pressure measuring device.

[Problems to be solved by conventional technology and invention]

This type of automatic blood pressure measuring device uses the Korotkoff sound recognition method, which first detects the Korotkoff sound with a microphone during the pressure reduction process and measures the cuff pressure when the sound begins and disappears. However, this method is susceptible to noise, and there are cases in which Korotkoff sounds disappear or do not disappear even when the blood pressure drops below the diastolic blood pressure, which poses problems in terms of measurement accuracy. Therefore, a so-called oscillometric method is known in which the pulse waves caused by the pulsation of the artery are captured as vibrations in the internal pressure of the cuff, and the blood pressure is measured based on these vibrations. This method solves the aforementioned problem caused by the instability of Korotkoff sound generation, but in order to detect pulse waves as pressure changes within the cuff, pulse waves at different points in the cuff width direction are detected. Since detection is performed additively, there is still a problem with measurement accuracy.

It is therefore an object of the present invention to provide an automatic blood pressure measuring device of the type mentioned at the outset, which is more accurate.

[Means for solving problems]

The highest accuracy in blood pressure measurement should be obtained by detecting the pulse wave at the most pressurized artery position, rather than by using the cuff internal pressure sensor to detect additive pulse waves at each part. Therefore, the pulse wave detected on the body surface directly above the blood vessel under the cuff should be most correlated with the vibration amplitude of the blood vessel wall, so mechanically speaking, the pulse wave sensor should be placed at the center of the inner surface of the cuff in the width direction. When attached to a certain area, blood pressure measurement accuracy is greatly improved. However, if the optimal position deviates from the center due to the way the cuff is wrapped or the shape of the body, there remains a problem that affects measurement accuracy, but accuracy is further improved if the optimal position is always on the inner surface of the cuff. It should be done.

Therefore, the present invention focuses on the principle that the time point at which the maximum pulse wave amplitude detected by the pulse wave sensor at the position where the external arterial pressure caused by the cuff is greatest is the later than the time point at which the maximum amplitude occurs at the pulse wave sensor at other positions. The system was constructed as shown in FIG. That is, the automatic blood pressure measuring device according to the present invention includes a cuff 1 that is attached to a part of a living body, pressurized, and then depressurized for measurement;
A plurality of pulse wave sensors 3 ₁ to 3 _o are arranged in the cuff width direction on the inner surface of the air layer of the cuff to detect the pulsation of the arteries under the cuff, and each pulse wave sensor detects the pulsation of the artery under the cuff during the decompression process. A pulse wave sensor identifying means 4 that identifies a pulse wave sensor to be used for measurement by determining which of the maximum pulse wave amplitudes occurred the latest, and a pulse wave sensor identifying means 4 that identifies a pulse wave sensor to be used for measurement by determining which of the maximum pulse wave amplitudes occurred latest; By searching the wave amplitude data, the points at which the pulse wave amplitude starts to increase and the points at which it starts to decrease are detected,
It is comprised of systolic and diastolic blood pressure recognition means 5 which determines the cuff pressures at the time of the start of increase and the time of the start of decrease as systolic and diastolic blood pressure values, respectively, and display means 6 which displays the recognized systolic and diastolic blood pressure values.

[Effect]

The pulse wave signal of the direct artery detected by the pulse wave sensors 3 ₁ to 3 _o during the cuff decompression process after stopping the arterial blood flow is amplified, low-passed, etc. The signal is supplied to the sensor identifying means 4. The pulse wave sensor identifying means 4 detects the time point at which the maximum pulse wave amplitude occurs for each sensor, and identifies the pulse wave sensor at which the maximum pulse wave amplitude occurs last. The systolic/diastolic blood pressure recognition means 5 detects the point at which the pulse wave amplitude starts to increase by searching for time-series pulse wave amplitude data during the pressure reduction process of the specified pulse wave sensor, and determines the cuff pressure at this point. The cuff pressure at this point is recognized as the systolic blood pressure value, and the cuff pressure at this point is recognized as the diastolic blood pressure value by similarly searching to detect the point at which the pulse wave amplitude starts to decrease. The recognized systolic and diastolic blood pressure values are displayed on the display means 6, respectively.

[Embodiments of the invention]

In FIG. 2, reference numeral 11 denotes a cuff attached to the upper arm of the person to be measured, and the pressure is increased or decreased by a pressurization control section 12 in a well-known manner. Five pulse wave sensors 13 ₁ to 13 ₅ are attached to the inner wall of the inner surface of the air layer of the cuff in the width direction of the cuff.
It is also conceivable that these sensors be exposed so as to come into direct contact with the body surface in order to further increase their sensitivity. 14 is a multi-channel amplifier that amplifies the detection signals of the pulse wave sensors 13 ₁ to 13 ₅ ; 15 is a multi-channel low-pass filter with a cut-off frequency of 10 Hz; and 16 is A that sequentially digitizes the pulse wave signals selected by the multiplexer 16a. /D converter,
17 is a numerical display for systolic and diastolic blood pressure. As a display means, a recorder can be used instead of this numerical display. 18 is a pressurization value setting switch for setting the cuff pressurization value according to the subject; 19
is the start switch.

The pressurization control section 12 is controlled by a microcomputer 20
After the pressurization pump pressurizes the cuff 11 to the pressure value commanded by the microcomputer 20, the exhaust valve is controlled to gradually exhaust and depressurize the compressed air. The exhaust valve is fully opened in response to a command issued from 20 when the diastolic blood pressure is detected. During this time, cuff pressure data detected by the built-in pressure sensor is sent to the microcomputer 20.

In the microcomputer 20, CPU2
0a operates according to a program stored in the ROM 20b, and sends and receives control signals or data to and from each of the aforementioned sections 12, 16a, 16 to 19 via the built-in I/O port, and pulse wave sensor specifying means 4 according to the present invention. It also functions as a systolic/diastolic blood pressure recognition means 5. In other words, RAM20c is for each pulse wave sensor 1.
Pulse wave amplitude and cuff pressure data from 3 ₁ to 13 ₅ are stored in time series. Based on these stored data, the CPU 20a operates as described below according to the program stored in the ROM 20b, identifies the pulse wave sensor used for measurement, and determines the maximum cuff pressure from the point at which the pulse wave amplitude starts to increase and decrease. and recognize diastolic blood pressure.

The operation is as follows.

When the start switch 19 is set, the microcomputer 20 is initialized, and also sends the pressurization value data set by the pressurization value setting switch 18 and an operation start signal to the pressurization control unit 12 to set the cuff 11. Pressure is increased to the specified pressure value. Next, pressure reduction is started, and the pulse wave signals detected by the pulse wave sensors 13 ₁ to 13 ₅ are amplified by the amplifier 14 and passed through the filter 1.
5, high-frequency noise such as Korotkoff sound components is removed. FIG. 3 shows pulse wave signal waveforms obtained by experimental examples of these pulse wave sensors after passing through the low-pass filter 15, in which five pulse wave sensors have a width of 12
This is a case in which two cuffs 11 are arranged at the center position in the cuff width direction, and two each on the upstream and downstream sides thereof with a center spacing of 25 mm. In this case, the maximum pulse wave amplitude of the pulse wave sensor ₁₃₄ shifted 25 mm downstream from the center position appears the latest. These series of pulse wave signals are repeatedly selected in order by multiplexer 16a and digitized by A/D converter 16.

Thereafter, the CPU 20a measures blood pressure according to the flowchart shown in FIG. That is, the digitized pulse wave amplitude data and cuff pressure data of each pulse wave sensor 13 ₁ to 13 ₅ are sequentially stored in the RAM 20 in chronological order.
During this time, the CPU 20a searches for the time point at which the maximum pulse wave amplitude occurs for each sensor, and registers the sensor numbers in the order of occurrence. When the last, that is, the fifth sensor NO (pulse wave sensor 13 ₄ ) is registered, the pulse wave amplitude data from the start of decompression of that pulse wave sensor is read out from the RAM 22c, and the pulse wave amplitude data from the start of amplitude increase (Fig. 3 d) is read out from the RAM 22c. Search for P). Then, the cuff pressure data at that time is read out and recognized as the systolic blood pressure. Next, the time point (B) at which the amplitude suddenly decreases after the maximum amplitude time point (P1) is searched, and the corresponding cuff pressure is recognized as the diastolic blood pressure.

These systolic and diastolic blood pressure data are displayed on display 1.
7 to hold it and display the value. Furthermore, when sending out blood pressure data, an exhaust valve control signal is sent to the blood pressure control section 12 to fully open the valve and complete the measurement process.

〔Effect of the invention〕

As described above, according to the present invention, since blood pressure is measured based on the arterial pulsation to which cuff pressure is optimally applied, the influence of noise is not only suppressed compared to the conventional Korotkoff sound recognition method. In principle, measurement accuracy is greatly improved compared to the oscillometric method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an automatic blood pressure measuring device according to the present invention, FIG. 2 is a diagram showing the configuration of an automatic blood pressure measuring device according to an embodiment of the present invention, and FIG. 3 is a diagram showing each pulse wave of the device according to FIG. FIG. 4, which is a diagram showing the detection signal of the sensor, is a flowchart explaining the sensor specifying operation and the systolic/diastolic blood pressure recognition operation of the microcomputer. 1, 11...cuff, 3, 13...pulse wave sensor.

Claims (1)

[Scope of Claims] 1. A cuff that is attached to a part of a living body and is pressurized and then depressurized for measurement; A plurality of pulse wave sensors that detect arterial pulsations; and a pulse wave used for measurement by determining which of the maximum pulse wave amplitudes detected by each of the pulse wave sensors during the decompression process occurs latest. A pulse wave sensor specifying means for specifying the sensor, and a time-series pulse wave amplitude data during the decompression process of the pulse wave sensor specified by the pulse wave sensor specifying means are searched to determine the start point of increase and decrease in pulse wave amplitude. A systolic and diastolic blood pressure recognition means that detects the respective starting points and sets the cuff pressures at the start of increase and the cuff pressure at the beginning of decrease as the systolic and diastolic blood pressure values, respectively; An automatic blood pressure measuring device comprising: display means for displaying a diastolic blood pressure value.