JPH0759232B2 - Electronic blood pressure monitor - Google Patents

Description

The present invention relates to an electronic sphygmomanometer, and more particularly to an electronic sphygmomanometer that measures blood pressure based on recognition of Korotkoff sounds.

[Prior Art] Conventionally, in this type of electronic blood pressure monitor, a device that exceeds a predetermined threshold level is recognized as a Korotkoff sound (hereinafter, also referred to as a K sound) to determine a systolic blood pressure value and a diastolic blood pressure value.
This threshold level is a fixed value or is an average of the output signals of blood flow sounds in a predetermined time period.

[Problems to be Solved by the Invention] However, when such a conventional electronic sphygmomanometer has a fixed value, when the subject is a person with a weak K sound signal, or when the position of the microphone is displaced from the radial artery, etc. However, the maximum blood pressure value is lower than the original blood pressure value, and the minimum blood pressure value is high.

Also, if an averaged output signal of blood flow sound in a predetermined time period is used, the threshold level is set to a low level, and there is fluctuation in the biological noise that is considered to be generated from the circulatory system. The biological noise signal at the time of tapping was erroneously recognized as a K sound, and the systolic blood pressure value was higher than the original blood pressure value, and the diastolic blood pressure value was measured low.

Further, since the threshold level for recognizing the systolic blood pressure and the threshold level for recognizing the diastolic blood pressure are set to the same value, there is a problem in that the measured value at the systolic blood pressure or the diastolic blood pressure does not match the original blood pressure value.

The present invention has been made in view of such drawbacks of the conventional electronic sphygmomanometer, and reduces erroneous recognition of K sound due to fluctuation of biological noise generated from the circulatory system and enables highly accurate blood pressure measurement. To provide a simple electronic blood pressure monitor.

[Means for Solving the Problem] In order to solve this problem, the electronic blood pressure monitor of the present invention is
An electronic sphygmomanometer that measures a blood pressure based on the occurrence or disappearance of Korotkoff sound by pressing a part of the living body with a pressure cuff, and the maximum blood flow sound detected during a predetermined time period before the Korotkoff sound is generated. The present invention is characterized by including changing means for changing the threshold level for judging the Korotkoff sound based on the value and the minimum value.

Here, the predetermined time period is a period in which the cuff vibration arterial wave superimposed on the cuff pressure is less than or equal to a certain threshold value, and the changing means sets the maximum value and the minimum value of the detected blood flow sound. Change the threshold level based on the difference value. Further, the changing means gives different threshold levels for recognizing the maximum blood pressure and for recognizing the minimum blood pressure.

[Operation] In such a configuration, when the systolic blood pressure value and the diastolic blood pressure value are determined, by varying the threshold level based on the maximum value and the minimum value of the blood flow sound, highly accurate blood pressure measurement can be performed. become.

[Embodiment] FIG. 1 is a block diagram showing the configuration of the electronic blood pressure monitor of this embodiment.

This electronic sphygmomanometer is a K-sound detector 10 that detects Korotkoff sounds.
And a cuff pressure / pulse wave detector that detects cuff pressure and oscillating arterial waves
20, a control unit 30 for recognizing the blood pressure value from the K sound detection signal and the cuff / pulse wave detection signal and controlling the operation of the electronic sphygmomanometer, a display for displaying the measurement result, and an operator operation key. It is composed of an input unit 50. A motor, a valve and the like for controlling the cuff pressure are not shown.

The K sound detector 10 is composed of a microphone 11, an amplifier 12, a bandpass filter 13 and an A / D converter 14, and a cuff pressure / pulse wave detector 20 is a pressure sensor 21, an amplifier 22 and an A / D converter. 2
Composed of 3 and. The control unit 30 includes a CPU 31 for arithmetic / control connected by a bus and a ROM 32 for storing a control program.
For auxiliary memory, blood flow noise level memory 33a, systolic blood pressure threshold level 33b, diastolic blood pressure threshold level 33c
A RAM 33 for storing the data, an interface 34 for inputting signals from the K sound detector 10 and the cuff pressure / pulse wave detector,
An interface 35 for exchanging signals with the display 40 and the key input unit 50.

FIG. 2 is a diagram showing signals of the electronic sphygmomanometer of the present embodiment,
Based on this, the principle of the method for determining the threshold level in this embodiment will be described.

In FIG. 2, 80 is a pulse wave signal. At the first beat of the pulse wave, the maximum value and the minimum value of the blood flow sound signal in the gate 80a above the threshold level T ₁ are detected. Originally, since there is no K sound in the gate 80a, the maximum noise level B _N is detected. Based on the maximum level of this noise, the threshold level T _R for determining the K sound included in the following blood flow sound signals is determined.
From the second beat onward, the K sound signal 81, for example 81a, having the threshold level T ₂ or more and the determined threshold level T _R or more in the gate 80b is recognized as the K sound.

3A to 3C are flow charts showing the processing procedure of the electronic sphygmomanometer of the present embodiment.

When the power is turned on, the electronic sphygmomanometer opens the valve in step S31, and initializes the zero set of the pressure sensor. After the pressure is increased to a predetermined pressure by the pump in steps S32 and S33, the depressurization process is started in step S34.

In step S35, the control unit 30 determines the threshold levels for recognizing the highest and lowest blood pressures. Therefore, the first beat after the detection of the pulse wave detects the maximum value and the minimum value in a section below a certain threshold value. Remember as the difference B _N.

FIG. 3B is a flow chart showing a processing procedure of a routine for detecting the noise level B _N of the blood flow sound.

A detection gate (80a in FIG. 2) is created in step S51.
The maximum value of the blood flow sound signal between the gates is detected in step S52, and the minimum value of the blood flow sound signal is detected in step S53.
The value of (maximum value-minimum value) is stored in the blood flow sound noise level storage unit 33a as the level B _N of the blood flow sound signal.

Returning to step S36 of FIG. 3A, the gate 8 of FIG.
Within 0b - storing in correspondence with the cuff pressure levels (maximum value-minimum value) that exceeds T _R as K sound signal.
At step S37, the measurement is completed, for example, when the above (maximum value-minimum value) falls below a predetermined level for three consecutive beats, the exhaust gas is exhausted at step S38 and the measurement cycle ends.

Next, at step S39, the threshold level T _S for the systolic blood pressure and the threshold level T _D for the diastolic blood pressure are determined to recognize the systolic blood pressure and the diastolic blood pressure.

FIG. 3C shows a flowchart of the processing procedure of the threshold level determination routine.

In the normal case, ie A> B _N > B, step S6
Going from 1 → S62 → S63, the threshold level is T _S = S ₁ for maximum blood pressure recognition (S ₁ is a fixed value) and T _D = D ₁ (D ₁ for minimum blood pressure recognition).
Is a fixed value) and is set separately.

However, if a person with a weak K sound measures with this setting, the systolic blood pressure will be lower than the original value and the diastolic blood pressure will be higher. Therefore, for such a person, that is, a person of B _N ≦ B, the process proceeds from step S62 to S64 to perform the process of lowering the threshold level of the K sound. Since Suretsushiyureberu value might become Jitsutsu a too small noise, and to take greater than B _N determined at the beginning, Suretsushiyureberu for recognition systolic blood _{T S = B N + α (} <S 1: Set α ≈ 10) and the minimum blood pressure recognition threshold level T _D = B _N + β (<D ₂ : β ≈40).

Although the K sound output signal B _N has individual differences, if this value is large, that is, if B _N ≧ A, noise may be erroneously recognized as K sound if the threshold value is fixed. In such a case, proceed from step S61 to step S65, and the threshold level for maximum blood pressure recognition T _S = B _N + γ (> S ₁ γ≈40), the threshold level for minimum blood pressure recognition T _D = B Set _N + δ (> D ₁ δ ≈ 100).

Returning to step S40, the K sound signal data stored in the RAM is read out, and the systolic blood pressure exceeds the threshold level at step S41 for the first time when the determined threshold level T _S or more continues for 2 beats. If the beat is the maximum blood pressure value, and if it is smaller than the threshold level T _D determined in step S42 by 2 beats in a row, the pulse one beat before the threshold level is determined in step S43 as the minimum blood pressure value. To do.

At step S44, these blood pressure values are displayed and the measurement is completed.

[Effects of the Invention] According to the present invention, it is possible to provide an electronic sphygmomanometer capable of highly accurate blood pressure measurement by reducing false recognition of K sound due to fluctuations in biological noise generated from the circulatory system.

That is, by varying the threshold level of the K sound according to the magnitude of the K sound level and the magnitude of the K sound output signal (B _N ), it is difficult to measure blood pressure accurately until now. Even a person or a person with a large K sound output signal (B _N ) can measure blood pressure accurately. Further, by changing the threshold level of the systolic blood pressure and the diastolic blood pressure, highly accurate blood pressure measurement becomes possible. Further, when the threshold level is set when the K sound is low, it is possible to prevent erroneous setting of the threshold level due to fluctuations in biological noise (in the case of large fluctuations). In addition, since the maximum blood pressure and the minimum blood pressure are recognized by individual threshold levels, accurate identification of the 1st and 5th points of the swan is possible without providing a frequency discrimination filter for the maximum blood pressure or a filter for the minimum blood pressure. Can be done.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the electronic sphygmomanometer of the present embodiment, FIG. 2 is a diagram showing the measurement principle of the electronic sphygmomanometer of the present embodiment, and FIGS. 3A to 3C are electronic blood pressures of the present embodiment. It is a flow chart which shows the operation procedure of a meter. In the figure, 10 ... K sound detector, 11 ... Microphone, 12 ... Amplifier, 13 ... Bandpass filter, 14 ... A / D converter, 20 ... Cuff pressure / pulse wave detector, 21 ... Pressure sensor, 22 ... Amplifier, 23 ...
A / D converter, 24 ... Bide pass filter, 30 ... Control section, 31
... CPU, 32 ... ROM, 33 ... RAM, 33a ... Blood flow noise level storage unit, 33b ... Maximum blood pressure threshold level, 33c ... Minimum blood pressure threshold level, 34, 35 ... Interface, 40 ... Indicator, 50 … Key input section.

Claims (3)

[Claims] 1. An electronic sphygmomanometer that measures a blood pressure based on the occurrence or disappearance of Korotkoff sound by pressing a part of a living body with a pressure cuff, which is detected in a predetermined time period before the Korotkoff sound is generated. An electronic sphygmomanometer comprising a changing means for changing a threshold level for judging Korotkoff sounds based on the maximum value and the minimum value of blood flow sounds. 2. The predetermined time period is a period in which the cuff vibration arterial wave superimposed on the cuff pressure is below a certain threshold value, and the changing means has a maximum value and a minimum value of the detected blood flow sound. The electronic blood pressure monitor according to claim 1, wherein the threshold level is changed based on a difference value between 3. The electronic sphygmomanometer according to claim 1, wherein the changing means provides different threshold levels for recognizing the systolic blood pressure and for recognizing the diastolic blood pressure.