KR890002763B1 - Electronic blood pressure meter - Google Patents

Abstract

A cuff with a cavity is fitted around the arm of the patient whose blood pressure is to be measured. The pressure in the cavity can be altered. A sensor detects the cavity pressure and outputs a representative signal. The amplitude of the pulse wave component of the signal is used to determine compensated values for the systolic and diastolic blood pressures. A compensation parameter is determined which may be used to compensate the amplitude of the pulse wave component of the sensor output. Alternatively an arithmetic compensation operation may be performed on at least one of the values for systolic and diastolic blood pressure.

Description

Electronic sphygmomanometer

1 is a flow diagram illustrating the operation of the electronic blood pressure monitor according to the first embodiment of the present invention.

2 is an external perspective view of an electronic blood pressure monitor according to the present invention.

3 is a circuit block diagram of an electronic blood pressure meter according to the present invention.

4 (a) to 4 (c) are views for explaining the procedure for correcting the pulse amplitude of the electronic blood pressure monitor according to the present invention.

5 (a) to 5 (d) are diagrams illustrating a problem of a conventional electronic blood pressure monitor.

* Explanation of symbols for main parts of the drawings

2: Cap 9: Pressurized pump

10 exhaust valve 11 pressure sensor

14: microcomputer (MPU)

The present invention relates to an electronic blood pressure monitor employing a vibration method. Conventionally, an electromagnetic sphygmomanometer employing a vibrating method is a cap and an exhaust valve for pressurizing the air in the cap (hereinafter referred to as capping) and an air pressure in the cap and a pressure valve for reducing the air in the cap. It is known to equip a pressure sensor for detecting the cap pressure) and a microcomputer (MPU) for quantifying the blood pressure value according to the output signal of the pressure sensor.

The operation of the conventional electronic blood pressure meter will be described below with reference to FIGS. 5 (a), 5 (b) and 5 (c). FIG. 5 (a) shows the change in the cap pressure when the cap is pressurized above the maximum blood pressure value and then depressurized at a constant speed, and the pulse wave w appears in the process of decreasing the cap pressure pc. In addition, in FIG. 5 (c), the amplitude value for each period of the pulse wave is indicated by a solid line. In FIG. 5 (c), the envelope of the amplitude value of FIG. 5 (b) is represented by a solid line. Moreover, all the horizontal axes of 5th (a) th-5th (c) show an elapsed time.

In Fig. 5 (c), it is clinically confirmed that the cap pressure corresponding to the point M having the maximum amplitude amplitude Ap max corresponds to the average blood pressure value. For example, at the left side of the point M in FIG. 5 (c) (the pulse wave amplitude rising process), the cap pressure corresponding to the point S corresponding to 5% of the maximum amplitude value Ap max is the highest blood pressure SYS and the point M right side. The cap pressure corresponding to the point D corresponding to 70% of the maximum amplitude Ap max in the pulse wave amplitude reduction process is determined as the lowest blood pressure value DIA.

Next, a problem to be solved by the present invention will be described. In general, the envelope of the amplitude value of the pulse wave becomes flat as the change in the pulse amplitude is smaller as the obesity of the subject increases.

This is because the obese person has a thick subcutaneous fat layer and pulse wave, which is a volume change of the artery blocked by blood flow, is attenuated in the subcutaneous layer and transmitted to the cap.

On the other hand, in a state where the cap is wrapped around the arm and pressurized, pulsation (hereinafter referred to as background pulse wave) having an almost constant amplitude value is always observed. This background pulse wave occurs when blood flows through the arteries. In addition, minute volume changes of arteries occurring in the heart side of the artery in which blood flow is blocked are transmitted to the calf and observed. This background pulse wave always takes a constant amplitude value regardless of the cap pressure, and it is confirmed by the data collected by the present inventor in the hospital that the individual difference is small even if the obese person or the person is thin.

In FIG. 5 (c), the above background pulse wave is displayed, and its amplitude value is Ab. Therefore, the true maximum pulse wave amplitude value Apmg is subtracted from the background pulse wave Ab from the maximum pulse wave amplitude value Apmax observed. If the subject is not obese, Apmx is sufficiently large compared to Ab, and the effect of the background pulse wave is almost negligible.

However, when the subject is obese, Apmax is not necessarily large enough for Ab, and there is a defect that a large error occurs in the measured blood pressure value. If this is demonstrated according to FIG. 5 (a) and 5 (c), the point S and the point D in FIG. 5 (c) are determined by the maximum pulse wave amplitude Apmax.

On the other hand, in FIG. 5 (c), the point Sg and pulse wave amplitude value corresponding to 50% of the true maximum pulse wave amplitude value Apmg on the side of the pulse wave amplitude increase side with respect to the portion where the pulse wave amplitude value Ap is reduced in the background pulse wave amplitude Ab The point Dg corresponding to 70% of the true maximum pulse wave amplitude Apmg on the decreasing side is indicated.

In Fig. 5 (a), the cap phase Pc corresponding to the points S and Sg is shown as the measured maximum blood pressure value SYS and the true maximum blood pressure value SYSg, respectively.

The measured maximum blood pressure value SYS is higher than the true maximum blood pressure value SYSg. Similarly, in FIG. 5 (a), the cap pressure Pc corresponding to the point D and the point Dg is shown as the measured minimum blood pressure value DIA and the true minimum blood pressure value DIAg, respectively. In this case, the measured minimum blood pressure DIA is lower than the true minimum blood pressure DIAg.

As described above, when the subject is obese, there is a defect that the difference between the measurement becomes large and the reproducibility decreases. The broken lines shown in FIGS. 5 (b) and 5 (c) show pulse wave amplitude values Ap from which the results of different measurements under the same conditions are obtained for the same subject. The point S 'and the point D' set for the pulse wave amplitude value Ap of this broken line are shown in the fifth (c). 5 (a) shows the measured highest blood pressure value SYS and the measured minimum blood pressure value DIA 'corresponding to the points S' and D '. The measured maximum blood pressure values SYS and SYS 'and the measured minimum blood pressure values DIA and DIA' are different.

In addition, when the subject's obesity is enhanced, the envelope of the pulse wave amplitude Ap becomes flatter, and as shown in FIG. 5 (d), there is no point corresponding to 50% (or 70%) of the maximum pulse wave amplitude Apmas already. There was a defect which caused a measurement error.

The present invention has been studied in consideration of the above combination, and an object of the present invention is to provide an electronic sphygmomanometer which can reliably measure blood pressure values even for a subject with increased obesity, and has excellent measurement accuracy and reproducibility.

Next, the means for solving the problem will be described. As the means, the electronic blood pressure monitor according to the present invention includes a pressurizing means for pressurizing the cap and the fluid in the cap, and the fluid in the cap at a constant microspeed or rapidly. Pressure reducing means for reducing the pressure, pressure detecting means for detecting the fluid pressure in the pape, pulse wave component detecting means for detecting pulse wave components contained in the output signal of the pressure detecting means, and pulse wave from the output signal of the pulse wave component detecting means Pulse wave amplitude calculation means for calculating an amplitude value, blood pressure determination means for determining a blood pressure value in accordance with an output signal of the pulse wave amplitude calculation means and the pressure detection means, comprising correction parameter determining means and the correction parameter. Therefore, the pulse wave amplitude value correcting means for correcting the pulse wave amplitude value calculated by the pulse wave amplitude value calculating means is characterized. . The electronic sphygmomanometer of the present invention determines a correction parameter (including an integer of 1 or 2 or more predetermined values) indicating the degree of influence on the measurement result of the background pulse wave amplitude value, and corrects and measures the pulse wave amplitude data according to the correction parameter. The result is improved reproducibility while eliminating errors due to background pulse waves. In addition, even when the subject's obesity is improved, the pulse wave amplitude value corresponding to a predetermined ratio of the maximum pulse wave amplitude value can be reliably extracted, and the blood pressure value can be accurately measured.

EXAMPLE

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, 4 (a), 4 (b) and 4 (c).

First, the outline of the pulse wave amplitude value and blood pressure value determination procedures in this embodiment will be described with reference to FIGS. 4 (a) to 4 (c).

Fig. 4 (a) shows an example of data of the white wave component value Pu (i). However, since the sampling period is short, it is indicated by the envelope.

4 (b) shows a data string of the pulse wave amplitude value Ap (n) calculated from the pulse wave component value pu (i) data string shown in FIG. 4 (a).

The data string of the pulse wave amplitude value Ap (n) is shown. Apmas is the largest one in the pulse wave amplitude value Ap (n) data string.

Ab shown in FIG. 4 (b) is a background pulse wave amplitude value. In this embodiment, this Ab is used as a correction parameter to determine the maximum pulse wave amplitude value Apmas.

In FIG. 4 (c), the correction pulse wave amplitude value A'P (n) data string corrected by subtracting the background pulse wave amplitude value Ab from the pulse wave amplitude value Ap (n) data string is shown. The correction pulse wave amplitude value A'P (n) data string is excluded from the influence of the background pulse wave. Accordingly, high blood pressure value determination can be obtained.

In this embodiment, the corrected pulse wave amplitude value A'p (n) on the side of the pulse amplitude increase side closest to 50% of the corrected maximum pulse wave amplitude value A'pmas is defined as the point S, and the cap pressure Pc corresponding to this is the highest blood pressure value. I am doing it. Moreover, the correction pulse wave amplitude value A'P (n) which is closest to 70% of the correction maximum pulse wave amplitude value A'pmas on the pulse amplitude reduction side is made into point D, and the cap pressure Pc corresponding to this is made into the minimum blood pressure value. .

Even if the subject is obese and the pulse wave amplitude Ap curve is flat, the corrected pulse wave amplitude A'P (n), which is 50% of the corrected maximum pulse wave amplitude A'p (n), can be extracted. Measurement miss does not occur.

Next, a specific configuration of the electronic blood pressure monitor 1 according to the present embodiment will be described with reference to FIGS. 2 and 3.

2 is an external perspective view of the electronic sphygmomanometer 1. (2) is a cap consisting of the air bag of the object (帶狀: belt shape).

The cap 2 is connected to the electronic blood pressure monitor main body 4 via a distribution tube 3 made of rubber or the like. On the upper surface of the hypotensive body 4, an indicator 5 composed of a liquid crystal indicator light, a power switch 6, and a measurement switch 7 are provided.

3 shows a block diagram of an air gauge and a measuring circuit of the electronic sphygmomanometer 1. The cap 2 has a pressure pump (pressurizing means) 9, an exhaust valve (reducing pressure means) 10, and a pressure sensor (pressure detecting means) via a tube 3 and pipes 8a, 8b, and 8c. (11) is connected. The exhaust valve 10 is provided with two valves, a metal exhaust valve and a slow exhaust valve. The pressure sensor 11 uses a diaphragm pressure transducer or a semiconductor pressure transducer using a strain gage.

The pressure pump 9 and the discharge valve 10 are controlled by a microcomputer (MPU) 14.

The output signal of the pressure sensor 11 is amplified by the amplifier 12 and converted into a digital signal by the analog / digital (A / D) converter 13.

The MPU 14 takes in the output signal of the pressure sensor 11 digitally converted by the A / D converter 13 at regular intervals. The MPU 14 detects the pulse wave component from the output signal of the pressure sensor 11, calculates the pulse wave amplitude value, corrects the pulse wave amplitude value, determines the blood pressure value, the pressure pump 9 and the exhaust valve ( 10) and the like to control the function.

The MPU 14 is further connected with an indicator 5, a power switch 6 and a measurement switch 7 for displaying the determined blood pressure value.

Next, the operation of the electronic blood pressure monitor 1 according to the present embodiment will be described below with reference to FIG. 1 mainly.

Initially, the cap 2 is wound around the upper arm of the subject, and the power source switch 6 is turned on. When the power switch 6 is turned on, the MPU 14 determines whether the measurement switch 7 is turned on, and if it is not turned on, the MPU 14 repeatedly waits for this determination process. [Step ST (hereinafter referred to as ST) (1), see FIG. 1]

When the measurement switch 7 is turned on at ST1, the MPU 14 operates the pressurized pump 9 to pressurize the ST2 so that the cap 2 is pressurized. The MPU 14 takes in the cap pressure PC therebetween by the A / D converter 13 and determines whether or not the predetermined cap pressure PC has been reached. When it is determined that the cap pressure has reached the predetermined value, it advances to ST4, and the MPU 14 stops the pressure pump 9, and starts the slow-speed exhaust gas from the ST 5 to the exhaust valve 10 again.

Next, in ST6, the count of timer T1 is started first. This timer T1 is for determining the period for calculating the pulse amplitude Ap (n) from the pulse wave component and is set between 1 and 2 seconds. At ST7, the count of timer T2 is started. This timer T2 is for determining the sampling period at which the MPU 14 takes in the cap pressure PC i from the A / D converter 13. This period is set between 10-50 ms.

At ST8, wait until timer T2 times up, and advance to ST9 if it is determined that timer T2 has timed up.

In ST9, the MPU 14 takes in the cap pressure data Pc (i) from the A / D converter 13. In ST10, the pulse wave component value pu (i) is detected from these cap pressure data PC (i). In FIG. 4 (a), the pulse wave component value is displayed by taking time t on the horizontal axis.

As a means for detecting the pulse wave component, analog means using a band pass filter is also widely used. However, in the above embodiment, a digital filter by arithmetic processing of the MPU 14 is employed.

In the arithmetic processing of the digital filter, first, Pc (i) taken in this sampling is determined as a variable x.

X (i) = Pc (i)... … … … … … … … … … … … … … … … … … … … … … … … … … (One)

Next, the value of the variable y (i) in the variable y in the variable y (i-1) and the variable y (i-1) different from the variable X (i-1) obtained by the previous sampling is less than or equal to (2). Calculate from

Y(i)-

Y(i-1)=X(i)-X(i-1) ………………………………………………(2)

Y (i)-

Y (i-1) = X (i) -X (i-1)... … … … … … … … … … … … … … … … … … (2)

Again, the variable Z (i) in this sampling is expressed by the following equation (3) by the other variables Z (i-1) obtained by the previous sampling and the variables y (i) and Y (i-1). The pulse wave component value Pu (i) in this sampling.

z(i)-

z(i-1)=Y(i)-

y(i-1) ………………………………………………(3)

z (i)-

z (i-1) = Y (i)-

y (i-1)... … … … … … … … … … … … … … … … … … (3)

Z (i) obtained in the above formula is the pulse wave component value Pu (i) at this sampling.

Pc (i) = z (i)... … … … … … … … … … … … … … … … … … … … … … … … … … … (4)

및

는 통상적으로 각각 하기와 같이 설정되어 있다.Also above

And

Are usually set as follows, respectively.

=0.98 ………………………………………………………………………(5)

= 0.98... … … … … … … … … … … … … … … … … … … … … … … … … … … (5)

=0.95 ………………………………………………………………………(6)

= 0.95... … … … … … … … … … … … … … … … … … … … … … … … … … … (6)

When i = i, i.e., when the digital filter is first processed, the variables X (0), Y (0) and Z (0) do not exist. Set to.

Again, since only one value is used for the variable strings X (i), y (i), and Z (i) in the actual operation, only one value in the actual operation is stored in the memory. It can save memory capacity.

When the pulse wave component value Pu (i) is detected in ST10, when it advances to ST11 and the timer T1 does not time up, it returns to ST7 and detection of the pulse wave component value PU (i) continues.

When the timer T1 times up, it advances to ST12, and the pulse amplitude amplitude Ap (n) is calculated from the data string of the pulse wave component value Pu (i) in which this timer T1 is detected in the count. This Ap (n) calculation is performed by extracting the maximum body Pumax and the minimum value Pumin from the data sequence of the pulse wave component value Pu (i) and taking the difference between them.

Ap (n) = Pumax-Pumin... … … … … … … … … … … … … … … … … … … … … … (7)

In following ST13, it is determined whether the pulse wave amplitude Ap (n) is increasing or not. If the pulse amplitude amplitude Ap (n) is increasing, return to ST6 with plug F as 1 in ST14, and calculate the next pulse amplitude Ap (n + 1).

In step ST13, when it is determined that the pulse wave amplitude Ap (n) is not increasing, it advances to ST15 to determine whether the plug F is 1 or not. If it is determined as F = 1, the processing advances to ST16, otherwise the processing advances to ST21.

In ST16, the plug F is first set to zero. In ST17, the largest Apmas is extracted from the data sequence of the pulse amplitude Ap (n).

In the following ST18, the ground pulse wave amplitude Ab is calculated from the maximum pulse wave amplitude Apmax according to the following expression (8).

Equation (8) is a correlation equation determined according to data collected by the inventor of the hospital.

Ab = 0.12Apmsx + 0.3... … … … … … … … … … … … … … … … … … … … … … (8)

In ST19, Ab is subtracted from each value of the pulse amplitude amplitude Ap (n) data string, and it is set as the data string of the correction pulse amplitude amplitude A'p (n). At this time, Ab is subtracted from the maximum pulse amplitude Apmam to become the corrected maximum pulse amplitude A'pmax.

In ST20, the corrected maximum pulse wave amplitude A'p (n) is searched for, and the corresponding cap pressure pc (i) is set as the maximum blood pressure SYS. Once SYS is determined, return to ST6 to continue collecting pulse amplitude Ap (n) data strings for determination of the lowest blood pressure (DIA).

As described above, in ST13 where the processing to ST6-ST12 is performed and the pulse amplitude ap (n) is calculated, the pulse amplitude Ap (n) is already taken to the maximum value and is in the decreasing process (see also the fourth (b)). ), It is determined that it is not increasing and advances to ST15. In ST15, since plug F is set to 0 in ST16, it is determined as NO and advances to ST21.

In ST21, the background pulse wave amplitude Ab is subtracted from the pulse wave amplitude Ap (n) to obtain a corrected pulse amplitude A'P (n). In ST22, it is determined whether or not the corrected pulse wave amplitude value A'P (n) is less than 70% of the corrected maximum pulse wave amplitude value A'pmax. If this determination is NO, the process returns to ST6 to calculate the next pulse wave amplitude value Ap (n + 1).

In ST22, the correction pulse amplitude A '(n) is searched (but after the maximum pulse wave amplitude Apmax), and the corresponding cap pressure Pc (i) is set as the minimum blood pressure value DIA.

Subsequently, in ST24, the MPU14 displays the SYS and the DIA on the indicator 5. In ST35, the MPU14 commands the exhaust valve 10 to rapidly exhaust the air in the cap 2 to complete the measurement.

In the above embodiment, the background pulse wave amplitude Ab is calculated from the maximum pulse wave amplitude Apmax, but may be calculated from other numerical values such as the pulse wave amplitude increase rate. Alternatively, since the individual difference of the background pulse wave amplitude Ab is small, it can be set as an integer. In addition, although the background pulse wave amplitude value is used as a correction parameter in the said Example, it is not limited to this, It can change suitably. In addition, the order of the blood pressure value determining means is not limited to that of the above embodiment, but can be changed appropriately.

Next, the effects of the present invention will be described. The electronic blood pressure monitor according to the present invention comprises correction parameter determining means and pulse amplitude correction means for correcting the pulse amplitude according to the correction parameter. Edo also has the advantage of preventing errors caused by the background pulse wave and improving the reproducibility of the measurement, and there is no meas- urement of measurement even if the subject is extremely obese, and there is an advantage of measuring the blood pressure value.

Claims (2)

Pressurizing means for pressurizing the cap and the fluid in the cap, pressure reducing means for decompressing the fluid in the cap at a constant microspeed or rapidly, pressure detecting means for detecting the fluid pressure in the cap, and an output signal of the pressure detecting means Pulse wave component detection means for detecting a pulse wave component contained therein; pulse wave amplitude calculation means for calculating a pulse wave amplitude value from an output signal of the pulse wave component detection means; and output signal of the pulse wave amplitude value calculation means and the pressure detection means. An electronic sphygmomanometer comprising a blood pressure value determining means for determining a blood pressure value according to the present invention, wherein the pulse wave amplitude value calculated by the pulse amplitude amplitude calculation means is corrected according to the correction parameter determining means and the correction parameter determined by the correction parameter determining means. An electronic shunt gauge comprising a pulse wave amplitude correction means. The pulse wave amplitude correction means according to claim 1, wherein the correction parameter determining means determines the correction parameter according to the maximum of the pulse amplitude amplitude values calculated by the pulse amplitude amplitude calculating means. An electronic sphygmomanometer, wherein the pulse amplitude is corrected by subtracting the correction parameter from the calculated pulse amplitude.

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