JPH0459891B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a non-invasive method for detecting systolic blood pressure and diastolic blood pressure in a non-invasive manner during the decompression process after pressurization by attaching a cuff to a part of a living body. This invention relates to an automatic blood pressure measuring device.

[Conventional technology]

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 decompression process and measures the cuff pressure at the time when the sound begins and disappears, and another method uses the Korotkoff sound recognition method, which is caused by arterial pulsations. Pulse waves are captured as vibrations in the cuff internal pressure,
There is a method based on the so-called oscillometric method based on changes in this vibration.

[Problem that the invention seeks to solve]

However, the former method is susceptible to noise, and Korotkoff sounds may disappear or may not disappear even when the blood pressure drops below the diastolic blood pressure, resulting in problems in measurement accuracy. According to the latter pressure 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 wave at different points in the cuff width direction is detected. Waves are detected additively, and there are still problems with measurement accuracy. Furthermore, since it is difficult to detect the diastolic blood pressure value from the vibration itself, there remains a problem in terms of accuracy since the diastolic blood pressure value is estimated by calculation from the average blood pressure value.

Therefore, an object of the present invention is to provide a non-invasive automatic blood pressure measuring device based on a novel method that enables more accurate blood pressure measurement.

[Means for solving problems]

In order to achieve this object, the present invention provides a cuff 1 that is attached to a part of a living body and is pressurized by a pressure control unit 1a and then depressurized for measurement, and A blood flow meter 2 non-invasively detects blood flow in side arteries, and the average value between the peak value and the bottom value of the pulsation component of the blood flow signal output from this blood flow meter is sequentially calculated and averaged. An average blood flow data creation means 3 for creating flow signal data, a measurement data storage means 4 for storing averaged blood flow signal data that changes depending on the steady state and cuff pressure, and temporally corresponding cuff pressure data, and a decompression process. blood flow rise point detection means 5 for detecting the rise point of the averaged blood flow signal data; and blood flow return point detection means 6 for detecting the point of return to the steady state averaged blood flow signal data in the subsequent pressure reduction process. , systolic blood pressure holding means 7 that holds the cuff pressure at the time of rising as the systolic blood pressure value, diastolic blood pressure holding means 8 that holds the cuff pressure at the time of return as the diastolic blood pressure value, and these held systolic and diastolic blood pressure values. and output means 9 for displaying or printing out.

[Effect]

When measuring blood pressure, the cuff 1 is pressurized and then depressurized by the pressurization control section 1a. During this pressure reduction process (Figure 2a), the blood flow signal detected by the blood flow meter (Figure 2b) gradually increases in vibration amplitude from the blood flow cutoff state, and reaches its maximum in the mean blood pressure region. , as the decompression continues,
Gradually, a steady state is reached in which pulsations with a constant vibration amplitude are superimposed on the DC component.

During such blood pressure measurement, the average blood flow data creation means 3 sequentially calculates the average value between the peak value and bottom value of the pulsating component of the direct blood flow signal output from the blood flow meter 2 or the once stored blood flow signal. The calculation is performed to create averaged blood flow signal data. The averaged blood flow signal data that changes depending on the steady state and cuff pressure, and the temporally corresponding cuff pressure data are stored in the measurement data storage means 4.

The blood flow rise time detection means 5 detects the rise time of the averaged blood flow signal data at which blood flow starts from the blocked state, and causes the systolic blood pressure holding means 7 to hold the cuff pressure data at this time as the systolic blood pressure value.

On the other hand, the blood flow return time detection means 6 detects the time when the averaged blood flow signal data returns to a steady value as the blood flow return time, causes the diastolic blood pressure holding means 7 to hold the diastolic blood pressure value, and outputs the respective output means 9. give instructions.

Incidentally, as shown in FIG. 2c, the pulse wave signal caused by the cuff internal pressure vibration obtained by the oscillometric method has a poor correlation with the S/N ratio and cuff pressure change compared to the blood flow signal.

[Embodiments of the invention]

FIG. 3 shows the circuit configuration of a non-invasive automatic blood pressure measuring device according to an embodiment of the present invention using a microcomputer (hereinafter referred to as microcomputer) 20, in which 11 is attached to the upper arm of the subject. It is an attached cuff, and is pressurized and depressurized by a pressurization control unit 12 in a well-known manner. 13 is an ultrasonic blood flow meter equipped with a probe 13a that is set on the upper arm adjacent to the centripetal side of the cuff 11. 14 is an A/D converter that digitizes blood flow signals, and 15 is a numerical display for systolic and diastolic blood pressure. A recorder can also be used instead of this output means. 16 is a start switch.

The pressurization control unit 12 pressurizes the compressed air to a predetermined pressure value using the pressurization pump according to a command from the microcomputer 20, and then gradually exhausts and depressurizes the compressed air by controlling the exhaust valve. The exhaust valve is fully opened according to the command 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, the CPU 20a operates according to the program stored in the ROM 20b, and the built-in I/
It exchanges control signals or data with each of the above-mentioned sections 12, 14 to 16 via the O port, and functions as a blood flow rise time point and blood flow return time point detection means and a systolic and diastolic blood pressure maintaining means according to the present invention. In other words, the RAM 20c stores the amplitude data (the fourth
Figure a) and cuff pressure data (Figure 4 b) are stored in chronological order, and the CPU 20a takes in the timer signal of the timer 20d based on these stored data.
The following arithmetic processing is performed according to the program stored in the ROM 20b.

That is, first, the top and bottom values of the input amplitude data are sequentially detected to create averaged amplitude data (FIG. 4c), which is similarly stored in the RAM 20c in temporal correspondence with the cuff pressure data. Furthermore, moving averaged amplitude data (FIG. 4d) for 4 seconds, for example, is created at 0.1 second intervals, and stored in the RAM 20c in a temporally corresponding manner. Furthermore, moving averaged amplitude data before the start of pressurization is also created, its 1% value is calculated, and an operation start signal is sent to the pressurization control section 12. Then, the time when the moving averaged data in the decompression process increases from the cutoff state to the above-mentioned 1% value is detected as the blood flow rising time T _H , and the cuff pressure at this time is held as the systolic blood pressure value and displayed on the display 15. Display. Furthermore, in the subsequent pressure reduction process, the rate of increase of the moving averaged data of the blood flow signal, that is, the differential data, is created, and the time point when this rate of increase once increases and then decreases to 1% of its maximum value is the blood flow return time T _L The cuff pressure at that time is held as the diastolic blood pressure value and displayed on the display 15.

Next, the operation of the non-invasive automatic blood pressure measuring device configured as described above will be explained.

The ultrasonic blood flow meter 13 non-invasively detects blood flow by applying a probe 13a to an artery on the distal side of the cuff 11. When the start switch 16 is set, the microcomputer 20 is initialized and takes in the digitized blood flow signal before the start of pressurization to create moving averaged amplitude data. Then, after a predetermined period of time has elapsed and the pressure is increased to a predetermined pressure value,
Start depressurization. During this pressure reduction process, the microcomputer 20 averages the top and bottom values of the oscillatory blood flow signal and performs moving average processing on the averaged data as described above (FIGS. 4a to 4d). In parallel with this arithmetic processing, the blood flow rise time T _H and blood flow return time T _L are detected using the processing method described above, and the corresponding cuff pressures are detected and held as the systolic and diastolic blood pressure values, and the display 15 to be displayed. After detecting the diastolic blood pressure value, the cuff pressure suddenly decreases by fully opening the exhaust valve and the measurement ends.

According to blood pressure measurement using this blood flow detection method, the amplitude of the pulsation signal changes smoothly in response to cuff pressure.
Moreover, since the moving average follows cuff decompression with high precision, the systolic and diastolic blood pressures can be detected with high precision directly from the blood flow signal.

〔Effect of the invention〕

As described above, according to the present invention, by temporarily storing the averaged blood flow signal data in the change process and the steady state together with the cuff pressure data, the point in time when the averaged blood flow signal data returns asymptotically to the steady state value can be detected with high accuracy. It becomes possible. Therefore, it becomes possible to detect the diastolic blood pressure value by blood flow measurement, which has been considered difficult in the past, with high accuracy, and it becomes possible to put into practical use a non-invasive automatic blood pressure measurement device based on blood flow signals that is compatible with the principle of blood pressure measurement. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a non-invasive automatic blood pressure measuring device according to the present invention, FIG. 2 is a diagram explaining its operation, and FIG. 3 is a diagram showing the non-invasive automatic blood pressure measuring device according to an embodiment of the present invention. The diagram showing the configuration of the embodiment and FIG. 4 are diagrams explaining the operation of the embodiment. 1,11...cuff.

Claims (1)

[Claims] 1. A cuff that is attached to a part of a living body and pressurized and then depressurized for measurement, and non-invasive detection of blood flow in an artery on the afferent side or distal side of this cuff. and an average blood flow data creation means for creating averaged blood flow signal data by sequentially calculating an average value between a peak value and a bottom value of a pulsating component of a blood flow signal output from the blood flow meter. , measurement data storage means for storing the averaged blood flow signal data that changes depending on the steady state and cuff pressure, and temporally corresponding cuff pressure data; and detecting the rising point of the averaged blood flow signal data during the pressure reduction process. Blood flow return point detection means detects a point in time when the averaged blood flow signal data in a steady state is returned to the steady state in the subsequent pressure reduction process; systolic blood pressure holding means for holding the cuff pressure data at the time of return as a diastolic blood pressure value; and output means for displaying or printing out the held systolic and diastolic blood pressure values. A non-invasive automatic blood pressure measuring device comprising: