JPH0376130B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a cuff that can be attached to a part of a living body and whose pressurized state can be changed, a sensor that detects arterial pulsation under the cuff, and a sensor that detects arterial pulsation under the cuff. By providing a means for recognizing the systolic and diastolic blood pressure from the cuff pressure corresponding to a specific change in the signal and a means for displaying the recognized value, the systolic and diastolic blood pressure can be automatically determined in the process of gradually lowering the pressure after pressurization. The present invention relates to a non-invasive automatic blood pressure measuring device that measures blood pressure.

[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. According to this method, the problem caused by the instability of the Korotkoff sound generation mentioned above is solved, but in order to detect the pulse wave as a pressure change inside the cuff, the pulse waves at different points in the cuff width direction are added together. Therefore, there are still problems with measurement accuracy.

Therefore, an object of the present invention is to provide an automatic blood pressure measuring device with higher accuracy.

[Means for solving problems]

In achieving this objective, the present invention aims to achieve the highest measurement accuracy by detecting the pulse wave of the artery that is substantially pressurized the most, and that the pressure on the blood vessel under the cuff is mechanically considered. We focused on the fact that the pulse wave is highest at the center in the width direction of the cuff, as shown in Figure 5, and that the pulse wave detected on the body surface directly above the blood vessel under the cuff is thought to be correlated with the vibration amplitude of the blood vessel wall. . A cuff is attached to a part of the living body to change its pressurization state, and a cuff is attached to the center of the inside of the cuff in the width direction of the cuff so as to detect the pulse of the artery under the cuff. The pulse wave sensor automatically detects the point at which the pulse wave signal amplitude starts to increase in the time series output by the pulse wave sensor during the decompression process in which the pressure is gradually lowered after arterial blood flow is stopped by pressurization. A systolic blood pressure recognition means that recognizes the cuff pressure at the time of detection as the systolic blood pressure, and also automatically detects the starting point of decrease in the time-series pulse wave signal during the pressure reduction process and recognizes the cuff pressure at this detection time as the diastolic blood pressure. The present invention is characterized by comprising a diastolic blood pressure recognition means for recognizing the diastolic blood pressure, and a display means for displaying the recognized systolic and diastolic blood pressures.

[Effect]

In the process of gradually lowering the pressure after stopping the arterial blood flow by pressurization, the pulse wave sensor detects a pulse wave signal that correlates to the widthwise central portion of the artery, which is most compressed by the cuff pressure. At this time, the systolic blood pressure recognition means and the diastolic blood pressure recognition means detect the increase start point and the decrease start point of the time-series pulse wave signal amplitude, respectively, and recognize the cuff pressures at these times as the systolic and diastolic blood pressures. The display means displays the measured systolic and diastolic blood pressure.

[Embodiments of the invention]

In FIG. 1, reference numeral 1 denotes a cuff attached to the upper arm of the subject, and the inner side of the cuff inner surface 1c is inside the air layer of this cuff, which is pressurized and depressurized by a pressurization control unit 2 in a well-known manner. As shown in FIG. 2, the pressurization control unit 2, in which the pulse wave sensor 3 is attached substantially at the center in the cuff width direction, starts operating in response to a command from the microcomputer 10, and the pressurization control unit 2 After pressurizing the cuff 1 with the pressure pump to the pressure value commanded by the microcomputer 10, the exhaust valve is controlled to gradually exhaust and depressurize the compressed air, and the command is also issued from the microcomputer 10 when detecting diastolic blood pressure. fully open the exhaust valve. During this time, a pressure value signal detected by the built-in pressure sensor is sent to the microcomputer 10. 4 is an amplifier for amplifying the detection signal of the pulse wave sensor 3; 5 is a low-pass filter with a cut-off frequency of 10 Hz; 6 is an A/D converter; and 7 is a numerical display for systolic and diastolic blood pressure. As a display means, a recorder can be used instead of this numerical display. 8 is a pressurization value setting switch which sets the cuff pressurization value depending on the person to be measured, and 9 is a start switch.

In the microcomputer 10, CPU1
0a operates according to the program stored in the ROM 10b, controls each part by sending and receiving control signals and data via the built-in I/O port, and performs the above-mentioned operations based on the pulse wave amplitude data stored in the RAM 10c. To constitute the systolic blood pressure recognition means and the diastolic blood pressure recognition means, detect the increase start point and decrease start point of the pulse wave signal amplitude, respectively, and recognize the cuff pressure at these times as the systolic and diastolic blood pressure values.The operation is as follows. It is as follows.

When the start switch 9 is set, the microcomputer 10 is initialized and the CPU 1
0a sends the pressurization value data set by the pressurization value setting switch 8 and an operation start signal to the pressurization control unit 2, and pressurizes the cuff 1 to the set pressurization value.
Next, pressure reduction is started, and the pulse wave signal detected by the pulse wave sensor 3 is amplified by the amplifier 4, and the noise of the Korotkoff sound component is removed by the filter 5, resulting in a pulse wave signal as shown in FIG. 4b. can get. This series of time-series pulse wave signals is digitized by the A/D converter 6, and is converted into pulse wave amplitude data in the RAM 1.
Stored in 0c. During this time, the CPU 10a sequentially compares adjacent pulse wave amplitudes according to the flowchart shown in FIG. That is, Fig. 4 shows the pulse wave amplitude waveform that appears when the cuff pressure is gradually decreased. The pulse wave B, that is, the pulse wave B immediately after the highest amplitude pulse wave P1 is detected, and the cuff pressure at each time point is recognized as the maximum and diastolic blood pressures. When detecting the diastolic blood pressure, an exhaust valve opening signal is sent to the pressurization control section 2 to fully open the exhaust valve and end the measurement.

4a and 4c show the low-pass filter 5 for the case where the pulse wave sensor 3 is shifted to the upstream end position 1a and downstream position 1b of the cuff 1 in FIG. 1 as a comparative example.
This is the output waveform of As is clear from the figure, on the upstream side, pulsation signals further upstream than cuff 1 are mixed in, and on the downstream side, the pressure applied to the artery under the cuff is insufficient, so the pulse wave signal is determined from the highest and lowest values. Blood pressure recognition becomes difficult. Figure 4d shows a pulse wave signal obtained by measuring the cuff internal pressure using the conventional method.Since the pulse waves at different points in the cuff width direction are detected additively, the systolic and diastolic pressures are The cognitive logic that determines blood pressure becomes unclear, and there is a possibility that there will be a discrepancy with the conventional decision logic of systolic and diastolic blood pressure.

〔Effect of the invention〕

As described above, according to the present invention, since blood pressure is measured based on the arterial pulsation at the point where cuff pressure is optimally applied to the subcuff artery, the influence of noise is suppressed compared to the conventional Korotkoff sound recognition method. Not only that, but compared to the conventional oscillometric method, which estimates diastolic blood pressure by detecting the average value of the cuff internal pressure using a pressurizing pump, etc., it is in principle more compatible with open blood pressure determination logic.
Moreover, measurement accuracy is also improved. In other words, the return of the blood vessels to their normal state, which should be the point at which the diastolic blood pressure is detected, is
Correlation is possible as the maximum amplitude of the pulse wave signal, and diastolic blood pressure, which is particularly problematic, can be recognized only from amplitude changes. Furthermore, since the pulse wave sensor is mounted within the cuff, the blood vessel portion that comes into contact with the sensor is not deformed, which is advantageous in terms of measurement accuracy, and does not cause pain to the subject.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an automatic blood pressure measuring device according to an embodiment of the present invention, Fig. 2 is a cross-sectional view in the cuff width direction when the cuff is attached, and Fig. 3 is a recognition operation of systolic and diastolic blood pressure by the microcomputer. FIG. 4 is a flowchart illustrating the pulse wave signal and the pulse wave signal of a comparative example, and FIG. 5 is a diagram showing the extravascular pressure distribution in the cuff width direction due to the cuff. 1... Cuff, 3... Pulse wave sensor.

Claims (1)

[Scope of Claims] 1. A cuff that is attached to a part of a living body to change its pressurized state, and a cuff that extends in the cuff width direction on the inside of the cuff so as to detect the pulsation of an artery under the cuff. A pulse wave sensor attached to the central part and a time-series pulse wave signal amplitude starting point outputted by the pulse wave sensor during a decompression process in which the pressure is gradually lowered after stopping arterial blood flow by pressurization are detected. A systolic blood pressure recognition means that automatically detects and recognizes the cuff pressure at the time of this detection as the systolic blood pressure; An automatic blood pressure measuring device comprising: a diastolic blood pressure recognition means that recognizes the cuff pressure at the time of detection as the diastolic blood pressure; and a display means that displays the recognized systolic and diastolic blood pressures.