JP4398553B2 - Electronic blood pressure monitor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic sphygmomanometer characterized by a pulse wave amplitude detecting means for determining blood pressure, particularly a maximal blood pressure, in an electronic sphygmomanometer that determines a blood pressure value based on a change in amplitude of a pulse wave.
[0002]
[Prior art]
Conventionally, in an electronic sphygmomanometer that determines a blood pressure value based on the amplitude of a pulse wave, the amplitude of the pulse wave used to determine the maximum blood pressure is 1 of the pulse wave from the heart contraction start time to the next heart contraction start time. Use the difference between the maximum value (peak value) of the cycle and the first cardiac contraction start time (bottom) value, or the frequency band processed by the pulse wave detection means is AC (0.5 Hz to several tens Hz) In some cases, the difference between the peak value and the virtual zero level value of the AC amplifier or the minimum value of one period of the pulse wave is used.
[0003]
[Problems to be solved by the invention]
Normally, the pressure transmission efficiency of the cuff tends to be high at the cuff center and low at both ends. Therefore, even in the ischemic state where the cuff pressure is higher than the maximum blood pressure, the cuffing point of the artery under the cuff is only at the cuff center, and it pulsates below the cuff on the side closer to the heart (cuff upstream) than the cuff attachment site. Accompanied blood enters and leaves, the arteries under the cuff change in volume, and pulse waves are generated.
[0004]
When the cuff pressure becomes lower than the maximum blood pressure, blood flow is generated from the cuff upstream side to the cuff distal side (cuff downstream side). In determining the systolic blood pressure, the change in the pulse wave accompanying the change in volume under the cuff due to the generation of blood flow downstream of the cuff that overlaps the volume change in the upstream part of the cuff should be detected. When the wave amplitude is detected, there are cases where this change is clear and not clear. That is, in the conventional pulse wave detection method, the change in blood vessel volume in the upstream portion of the cuff is dominant, and the change in volume due to the blood flow generated from the upstream side to the downstream side of the cuff may not be detected.
[0005]
Therefore, in the conventional determination of the maximum blood pressure, the maximum pulse wave amplitude detected in the process of increasing the cuff pressure to the maximum blood pressure and then decreasing or about 0.5% of the maximum pulse wave amplitude detected during the pressurization. For example, the cuff pressure at the doubled amplitude is set to the highest blood pressure, and the measurement principle based on experience is inevitably unclear.
[0006]
An object of the present invention is to provide an electronic sphygmomanometer that solves the above-described problems and has a highly accurate and reliable maximum blood pressure determination method.
[0007]
[Means for Solving the Problems]
In order to achieve this object, the electronic sphygmomanometer of the present invention has the following configuration.
[0008]
(1) A cuff wound around a part of a living body, a cuff pressure adjusting means for adjusting the cuff pressure by increasing and decreasing the pressure in the cuff, a pressure sensor for detecting the pressure and pulse wave in the cuff, and the pressure In an electronic sphygmomanometer including an arithmetic processing unit that performs arithmetic processing on output data from the sensor to measure blood pressure, the arithmetic processing unit includes a pulse wave rising point detecting unit accompanying the start of cardiac contraction, and a time measurement from the rising point. Means, a pulse wave amplitude detecting means for detecting a pulse wave peak value corresponding to the time measuring means as a pulse wave amplitude, and a blood pressure determining means , wherein the blood pressure determining means is defined as a time measuring means from the rising point. An electronic sphygmomanometer , wherein a maximum blood pressure value is determined based on a change in pulse wave amplitude detected by the pulse wave amplitude detection unit corresponding to the time measuring unit .
[0009]
(2) The electronic device according to (1), wherein the blood pressure determining unit selects an arbitrary value from 80 milliseconds to 120 milliseconds as a specified value to be given to the time measuring unit from the rising point. Sphygmomanometer.
[0010]
(3) The electronic blood pressure monitor according to (1), wherein the blood pressure determining unit selects an arbitrary value based on the detected pulse wave as a specified value to be given to the time measuring unit from the rising point.
[0012]
The electronic sphygmomanometer with such a configuration captures the magnitude of the pulse wave at a point delayed by a certain time from the rising point associated with the start of cardiac contraction, and the change causes the blood flow phenomenon from upstream to downstream of the cuff. Is detected.
That is, this systolic blood pressure determination method has been devised based on the following phenomenon.
Due to the relationship between the cuff size and the thickness of the wearing part, how the cuff is wound, arterial elasticity, blood viscosity, etc., blood flow enters the upstream side of the cuff due to heart contraction, then passes through the center of the cuff and goes downstream It takes some time to get to the side.
[0013]
If the magnitude of the pulse wave from the peak to the bottom or the magnitude from the peak to the minimum value is detected as an amplitude as in the past, if the cuff pressure is higher than the maximum blood pressure, the upstream of the cuff The change due to the blood flow that entered the area became dominant, and the above-described volume change of the blood flow downstream of the cuff could not be detected accurately.
Therefore, in determining the systolic blood pressure, if the change in the amplitude of the time phase delayed by a certain time from the change in the pulse wave due to the change in the vascular volume in the upstream part of the cuff is captured, the generation of blood flow from the upstream side to the downstream side of the cuff The point can be detected with high sensitivity, and a highly accurate and reliable method for determining the maximum blood pressure can be realized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, in order to further clarify the gist of the electronic sphygmomanometer according to the present invention, embodiments will be described with reference to the drawings.
[0015]
<Configuration example of blood pressure monitor of the present embodiment>
FIG. 1 is a block diagram showing a specific embodiment of an air system and a measurement circuit of an electronic sphygmomanometer according to the present invention.
The cuff 1 is connected to a pressurizing pump 3, a constant speed pressure reducing valve 4, a rapid pressure reducing valve 5, and a pressure sensor 6 through a tube 2.
The output of the pressure sensor 6 is amplified by an amplifier 7 and converted from an analog value to a digital value by an A / D converter 8. This digital value is input to an MPU (arithmetic processing means) 9.
[0016]
Further, MPU9 (arithmetic processing means) detects a bottom point that coincides with the rising point accompanying the start of cardiac contraction from this digital input, and is a point that is delayed for a specified time (about 80 to about 120 milliseconds) from this bottom point. The difference obtained by subtracting the bottom point value from the crest value is measured as the amplitude, and stored in the storage unit 10 as a pair with the cuff pressure value at that time.
[0017]
The amplitude is measured and stored until the cuff pressure is reduced from the cuff pressure higher than the maximum blood pressure to the cuff pressure lower than the maximum blood pressure, or until the cuff pressure lower than the maximum blood pressure is increased to the cuff pressure higher than the maximum blood pressure. The stored amplitude values are arranged in time series, the amplitude change before and after each is calculated, and the cuff pressure value of the pulse wave in which the amplitude change exceeds a certain level is determined as the maximum blood pressure value .
[0018]
FIG. 2 is a flowchart showing a specific processing operation of the electronic blood pressure monitor according to the embodiment.
When the cuff 1 is attached to the measurement site and the start switch 11 is pressed, the pressure is set to zero (STEP 1), the quick pressure reducing valve 5 is closed, the pressurizing pump 3 is operated (STEP 2), and then gradually inside the cuff 1 Is pressurized. The inside of the cuff 1 is pressurized to a pressurization set value equal to or higher than the maximum blood pressure, and the blood vessel at the cuff wearing site is compressed and occluded. When it is detected that the cuff pressure exceeds the pressurization set value (STEP 3), the pressurization pump 3 stops and pressure reduction is started by the constant speed pressure reducing valve 4 (STEP 4).
[0019]
When decompression starts, the pulse wave bottom point detection (STEP 5) from the signal taken in by the MPU (arithmetic processing means) 9 and the peak value at the point after the specified time (about 80 to about 120 milliseconds) has been detected from the bottom point Then, the difference from the bottom point is calculated and set as the amplitude (STEP 6). The amplitude value and the cuff pressure value (bottom point value) are paired and stored in time series.
[0020]
Whenever a pulse is detected, a change in amplitude (Δh) with the pulse wave one beat before is calculated, and when Δh becomes larger than the threshold value (ΔSYS) (STEP 7), the cuff pressure value at that time Is stored as a systolic blood pressure value (Psys) (STEP 8). If Δh does not exceed the threshold value (ΔSYS), the process returns to STEP5.
[0021]
After detecting the systolic blood pressure, the diastolic blood pressure is continuously detected. When the minimum blood pressure is detected, the rapid pressure reducing valve 5 is opened, the cuff pressure is exhausted to the atmospheric pressure, the maximum blood pressure value and the minimum blood pressure value are displayed on the display 12, and the measurement ends.
[0022]
FIG. 3 is an example of a waveform obtained by the blood pressure monitor shown in FIG. FIG. 3 shows a time-series waveform detected by the pressure sensor, and shows a change in the internal pressure of the cuff when the blood pressure is detected while the pressure is gradually reduced after being pressurized above the systolic blood pressure.
[0023]
FIG. 4 is a pulse waveform obtained by applying a high-pass filter to the pressure waveforms at points A, B, and C near the systolic blood pressure shown in FIG. 3 and extracting only the AC component.
[0024]
As can be seen from FIG. 4, the peak values P1, P2, and P3 up to the maximum peak point of the pulse wave increase almost uniformly at points A, B, and C near the systolic blood pressure. On the other hand, when observing the crest value after 100 milliseconds (msec.) From the rising point of the pulse wave, the crest value P′2 at point B shows a marked increase compared to the crest value P′1 at point A. ing. Thus, the systolic blood pressure can be determined by obtaining the peak value after a certain time from the rise of the pulse wave and using it as the pulse wave amplitude.
[0025]
In the present embodiment, the specified time from the bottom point of the pulse wave is set to a fixed value of about 80 to 120 milliseconds (the specified time of 100 milliseconds in FIG. 4), and the peak value after the lapse of the specified time is detected. Although the method is shown, the method for determining the specified time in the present invention is not limited to the above-described embodiment. For example, before measuring blood pressure, pressurize to about 30 mmHg, detect the pulse wave, calculate the peak time from the rise of the pulse wave, and determine the prescribed time of the pulse wave based on the value, Alternatively, a method that does not use a fixed specified time, such as changing the time depending on the pulse rate, can be considered, but these are within the scope of the present invention.
[0026]
【The invention's effect】
As described above, according to the present invention, the difference between the peak value delayed from the rising point (bottom point) at the start of the heart contraction of the pulse wave and the bottom point is defined as the pulse wave amplitude, and the change in the pulse wave amplitude is used. Therefore, it is possible to accurately detect blood flow from the cuff upstream side to the cuff downstream side, it is clear in principle, and there is no possibility of errors due to individual differences. A good and reliable electronic sphygmomanometer can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electronic blood pressure monitor according to an embodiment of the present invention.
FIG. 2 is a flowchart showing the processing operation of the electronic blood pressure monitor according to the embodiment of the present invention.
3 is an example of a waveform obtained by the electronic sphygmomanometer of one embodiment of the present invention. FIG. 4 shows the principle of the present invention of the pressure waveform at points A, B, and C shown in FIG. It is an enlarged waveform to explain.
[Explanation of symbols]
1 Cuff 2 Tube 3 Pressurizing pump 4 Constant speed reducing valve 5 Rapid reducing valve 6 Pressure sensor 7 Amplifier 8 A / D converter 9 MPU (arithmetic processing means)
10 storage unit 13 battery 14 display unit

Claims (3)

A cuff wound around a part of the living body, cuff pressure adjusting means for adjusting the cuff pressure by increasing and decreasing the pressure in the cuff, a pressure sensor for detecting the pressure and pulse wave in the cuff, and the pressure sensor In an electronic sphygmomanometer including an arithmetic processing unit that performs arithmetic processing on output data to measure blood pressure, the arithmetic processing unit includes a pulse wave rising point detecting unit accompanying the start of cardiac contraction, a time measuring unit from the rising point, It comprises pulse wave amplitude detecting means for detecting a pulse wave peak value corresponding to the time measuring means as pulse wave amplitude, and blood pressure determining means, and the blood pressure determining means gives a prescribed value to the time measuring means from the rising point. An electronic sphygmomanometer , wherein a systolic blood pressure value is determined based on a change in pulse wave amplitude detected by the pulse wave amplitude detecting means corresponding to the time measuring means . 2. The electronic sphygmomanometer according to claim 1, wherein the blood pressure determining unit selects an arbitrary value from 80 milliseconds to 120 milliseconds as a specified value to be given to the time measuring unit from the rising point. 2. The electronic sphygmomanometer according to claim 1, wherein the blood pressure determining unit selects an arbitrary value based on the detected pulse wave as a specified value to be given to the time measuring unit from the rising point.

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