JPS62290440A - Electronic hemomanometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] 3. Detailed description of the invention (b) Industrial application field This invention relates to improvements in electronic blood pressure monitors.

(B) Conventional technology Conventionally, electronic blood pressure monitors that use the so-called vibration method consist of a cuff, a pressure pump that pressurizes the air inside the cuff (hereinafter referred to as pressurizing the cuff), and a cuff that pressurizes the air inside the cuff. an exhaust valve that reduces the pressure in the cuff, a pressure sensor that detects the air pressure inside the cuff (hereinafter referred to as cuff pressure), and a microcomputer (MP
U) is known.

The operation of this conventional electronic blood pressure monitor will be explained below.

First, a cuff wrapped around the upper arm of the person to be measured is pressurized to compress the upper arm of the person to be measured and stop the blood flow in the artery. Next, the air inside the cuff is evacuated with a constant slow-moving dust, and the cuff is depressurized.
.

At this time, as shown in FIG. 7(a), pulsations occur in the cuff pressure Pc. This pulsation is called a pulse wave, and occurs when blood tries to flow into an artery that has been stopped by the pressurization of the cuff. Volume changes in arterial blood vessels are transmitted to the cuff and detected.

The pulse wave component can be detected by the MPU performing digital filtering processing on the output signal of the pressure sensor (or passing it through an analog bandpass filter). As shown in the seventh report, the amplitude value of this pulse wave component gradually increases (becomes thicker) as the cuff pressure Pc decreases, reaches a maximum value at a certain point, and then attenuates.

Figure 7(C) shows the MP
A pulse wave amplitude value data string A0ρ(n) calculated by U at regular intervals is shown. Although the pulse wave amplitude value AOp(n) changes smoothly in theory, the pulse wave amplitude value data string A'p(n) actually obtained from the subject is shown in Fig. 7(C). There is some rattling as shown.

In the pulse wave amplitude value data string A0p(n) with fluctuations,
It is not possible to accurately determine blood pressure values (systolic blood pressure, diastolic blood pressure, etc.). Therefore, the MPU performs smoothing processing (smoothing) on the pulse wave amplitude value data string A'p(n). . As an example of smoothing processing, moving average processing performed once or several times is known. The smoothed pulse wave amplitude value data string A'p (n) is shown in FIG. 7(d).

From the pulse wave amplitude value data string A'p(n), the systolic blood pressure value (S
YS) and the diastolic blood pressure value (DIA), a method using a threshold (threshold level method) is often adopted. The procedure for determining the blood pressure value by the threshold level method is to first extract the maximum value A' pmax from the pulse wave amplitude value data string A' p(n) [see FIG. 7 (dl)].

Next, in the process of increasing the pulse wave amplitude value data string A'p(n), a pulse wave amplitude value A'p(D) closest to a predetermined ratio of the maximum pulse wave amplitude value A'paiax is extracted. Figure (d) shows the case where the predetermined ratio is set to 60%].The cuff pressure Pc at the time ts when this pulse wave amplitude value A'p(j) is observed is the systolic blood pressure value (SYS). It is determined that

Next, in the process of decreasing the pulse wave amplitude data string A''p(n), the pulse wave amplitude value A'p(k) closest to a predetermined ratio of the maximum pulse wave amplitude value A'pmax is extracted [Fig. (
d) shows the case where the predetermined ratio is set to 70%]. The cuff pressure Pc at the time td when this pulse wave amplitude value Aip(k) is observed is determined as the diastolic blood pressure value (DIA).

Note that the threshold level method is clinically devised, and the two predetermined ratios are set experimentally or empirically.

(c) Problems to be Solved by the Invention In the above-mentioned conventional electronic blood pressure monitor, if the amount of smoothing (degree of smoothing) in the smoothing process of the pulse wave amplitude value data string A'p(n) is small ( For example, when the smoothing process is a moving average process (when the number of times the moving average process is small), there are the following disadvantages.

If the person to be measured has arrhythmia or if the person moves during the measurement, the observed pulse wave amplitude value data string A
'The wobbling of p(n) is large, and the wobbling remains even after smoothing processing is performed. When the threshold level method is applied to the pulse wave amplitude value data string A'p(n) with the remaining jitter to determine the blood pressure value, it is found that there is almost no change in the blood pressure value for the same subject. However, there was a disadvantage that the results differed greatly from measurement to measurement, that is, the reproducibility was low. Furthermore, there is a problem that the measurement results include large errors.

On the other hand, if the smoothing amount is increased in order to cope with the case where there is a large amount of wobbling as described above, there is a problem in that the measurement error increases for obese subjects and the reproducibility decreases. This can be explained in Figures 8(a) to 8+d.
This will be explained below with reference to 1.

Obese subjects have a thick subcutaneous fat layer, and a large proportion of pulse waves, which represent volume changes in blood vessels, are absorbed by this subcutaneous fat layer. Therefore, the pulse wave generated on the cuff pressure Pc has a small amplitude, as shown in FIG. 8(a).

FIG. 8(b) shows a pulse wave amplitude value data string A' p(n) calculated based on the pulse wave component detected by the pulse wave shown in FIG. 8(a). ing. This pulse wave amplitude value data string A'p(n) has a smaller degree of change than that shown in FIG. 7(C), that is, it is flat.

Pulse wave amplitude value data string A' p(n) shown in FIG. 8(b)
Pulse wave amplitude value data string A obtained by applying smoothing processing to
p (n) is shown in FIG. 8(C). By being smoothed, the pulse wave amplitude value data string A'p(n) becomes flatter than the pulse wave amplitude value data string A'p(n).

On the other hand, it has been confirmed that a pulse wave (hereinafter referred to as a background pulse wave) with a constant amplitude value Apx always exists in the cuff regardless of the cuff pressure Pc. This background pulse wave is observed when a minute volume change in a blood vessel that occurs when blood is flowing through the artery or occurs on the heart side of the artery when blood flow is stopped is transmitted to the cuff. Also,
It has been confirmed that there is little individual difference in the amplitude value of this background pulse wave, even for obese and slim people.

Pulse wave amplitude value data string A' p in a conventional electronic blood pressure monitor
(n) (or Am, p(n)) has the background pulse wave amplitude value Apx added thereto. In FIG. 8(C), the background pulse wave amplitude value Apx is shown by a broken line, and in FIG. 8(dl), the background pulse wave amplitude value is So-called true pulse wave amplitude value data string A with Apx subtracted
p g(n) (=A'p(n)-Ap x) is shown.

If the pulse wave amplitude value data string A' p(n) is not flat as shown in FIG. 7(d), the influence of the background pulse wave is small, but as shown in FIG. 8(C), If it is flat, the effect will be significant.

FIG. 8 (al) shows the systolic blood pressure value SYS and the diastolic blood pressure value DIA determined by applying the threshold level method to the pulse wave amplitude value data string A'' p(n) shown in FIG. 8 (C1). In addition, Fig. 8(a) shows Fig. 8(d).
A systolic blood pressure value SYSg and a diastolic blood pressure value DIAg determined by applying a similar threshold level method to the true pulse wave amplitude value data string A p g (n) shown in FIG. The systolic blood pressure value SYS is higher than the true systolic blood pressure value SYSg, and the diastolic blood pressure value DIA is higher than the true systolic blood pressure value DI.
This causes an error in that it appears lower than Ag.

Furthermore, if the threshold level method is applied to the flat pulse wave amplitude value data sequence A'p(n) as shown in FIG. 8 (C1), there will be a problem that the reproducibility of the measurement results will be low.

This invention was made in view of the above-mentioned disadvantages, and provides an electronic blood pressure monitor that eliminates measurement errors and low reproducibility that occur in subjects with arrhythmia or obesity due to the fixed smoothing amount. It is intended to.

(d) Means for Solving the Problems As a means for solving the above-mentioned disadvantages, the electronic blood pressure monitor of the present invention includes a cuff, a pressurizing means for pressurizing the fluid in the cuff, and a fluid in the cuff. a pressure reducing means for reducing the pressure of the cuff; a pressure detecting means for detecting the fluid pressure within the cuff; a pulse wave component detecting means for detecting a pulse wave component from an output signal of the pressure detecting means; Pulse wave amplitude value calculation means for calculating pulse wave amplitude value data from the detected pulse wave component; and pulse wave amplitude value smoothing means for smoothing the pulse wave amplitude value data obtained by the pulse wave amplitude value calculation means. and blood pressure value determining means for determining a blood pressure value based on the pulse wave amplitude value data smoothed by the pulse wave amplitude value smoothing means and the intra-cuff fluid pressure data detected by the pressure detecting means. and a flatness detection means for detecting the flatness of the pulse wave amplitude value data calculated by the pulse wave amplitude value calculation means, and a flatness detection means for detecting the flatness of the pulse wave amplitude value data calculated by the pulse wave amplitude value calculation means, and The present invention is characterized by a smoothness control means for controlling the smoothness of the value smoothing means.

E) Effect: In the electronic blood pressure monitor of the present invention, when the subject is obese and the degree of flatness of the pulse wave amplitude value data is large, the amount of smoothing in the smoothing process of the pulse wave amplitude value data is reduced. This prevents flattening of the pulse wave amplitude value data, and prevents occurrence of measurement errors and deterioration of reproducibility.

On the other hand, if the pulse wave amplitude value data is not flat, the amount of smoothing in the smoothing process of the pulse wave amplitude value data is increased. As a result, even when the subject is an arrhythmia patient, jitters included in the pulse wave amplitude value data are sufficiently removed, and measurement errors and deterioration of reproducibility are prevented.

Example) An example of this invention is shown in Figures 1 to 5 and Figure 6 (
The following description will be made based on FIGS. al to 6 (el).

First, an overview of the electronic blood pressure monitor of this embodiment will be explained.

First, a background pulse wave amplitude value Apx is calculated.

Next, a pulse wave amplitude value data string A' p(n) is calculated. In the process, the maximum pulse wave amplitude value A' pmax
is obtained, the difference between this Ac'pmax and the background pulse wave amplitude value Apx is taken, and the flattening parameter ΔA' p (=A' pmax - A p
Let xJ be.

The smoothing process of the pulse wave amplitude value data string A'p(n) is performed by taking a moving average. The amount of smoothing is increased or decreased by adjusting the number of times the moving average is taken.

The smoothing process limit number CaV is determined from the flattening parameter ΔAOp. The amount of smoothing is limited based on the number of times the moving average of the pulse wave amplitude value data string A'p(n) is taken, based on this smoothing processing limit number CAv (the subscript on the right shoulder indicates the smoothing processing number). ).

A threshold level method is applied to the smoothed pulse wave amplitude value data string A'p(n), and the systolic blood pressure value SYS and the diastolic blood pressure value DIA are determined.

Next, the specific configuration of the electronic blood pressure monitor 1 of this embodiment will be explained in the fourth section.
This will be explained below with reference to the figures and FIG.

FIG. 4 is an external perspective view of the electronic blood pressure monitor 1 according to this embodiment. 2 is a cuff made of a band-shaped air bag. This cuff 2 is connected to an electronic blood pressure monitor body 4 via a flexible tube 3. A display 5 made of a liquid crystal display element, a power switch 6, and a measurement switch 7 are provided on the top surface of the electronic blood pressure monitor main body 4.

FIG. 5 shows a diagram of the air system and measurement circuit of the electronic blood pressure monitor 1. The cuff 2 includes a tube 3 and piping 8a, 8b.
, 8C, a pressure pump (pressurizing means) 9, an exhaust valve (pressure reducing means) 10, and a pressure sensor (pressure detecting means) 11 are connected. The exhaust valve 10 is composed of two types of valves: a rapid exhaust valve and a slow exhaust valve. As the pressure sensor 11, a diaphragm pressure transducer using a strain gauge or a semiconductor pressure transducer element is used. Further, the pressurizing pump 9 and the exhaust valve IO are controlled by a microcomputer (MPU) 14, which will be described later.

The output signal of the pressure sensor 11 is amplified by an amplifier 12,
It is converted into a digital signal by an analog/digital (A/D) converter 13. The MPU 14 is an A/D converter 13
The digitally converted output signal of the pressure sensor 11 is taken in at a constant cycle.

The MPU 14 has a function of detecting a pulse wave component from the output signal of the pressure sensor 11, a function of calculating a background pulse wave amplitude value Apx and a pulse wave amplitude value data string A'p(nl), and a function of setting a smoothing process limit number CAv. This includes a function to perform moving average processing on the pulse wave amplitude value data string A'p(n) CA'p(n)) to smooth it, and a function to determine the blood pressure value.

Further, the MPU 14 is connected to the display 5 for displaying the systolic blood pressure value and the diastolic blood pressure value, as well as the power switch 6 and the measurement switch 7.

Next, the operation of the electronic blood pressure monitor 1 according to this embodiment will be mainly described in the first section.
2 and 3. First, the cuff 2 is wrapped around the upper arm of the person to be measured, the power switch 6 is turned on, and then the measurement switch 7 is turned on.

When the measurement switch 7 is turned on, the MPU 14 operates the pressure pump 9 [Step ST (hereinafter referred to as ST) 1
]. Subsequently, the MPU 14 closes the slow exhaust valve (also the rapid exhaust valve) of the exhaust valve 10 (Sr2), and pressurization of the cuff 2 is started.

In Sr1, it is determined whether the cuff pressure Pc has reached 30IIIHg. If the determination is No, this determination is repeated until the cuff pressure Pc reaches 3Qm+ml (g, and the process waits here.

When the determination of Sr1 becomes YES, the MPU 14 temporarily stops the pressurizing pump 9 (Sr4, see also FIG. 6 (al)).
, and the background pulse wave amplitude value Apx is calculated (Sr1). The procedure for calculating the background pulse wave amplitude value Apx from the cuff pressure Pc is the pulse wave amplitude value A' p(n) calculation process described below. Since it is the same as (STIO), it will be explained at 5TIO.

At Sr6, the MPU 14 operates the pressure pump 9 again. Then, in Sr7, it is determined whether the cuff pressure PC has reached a predetermined value, and if the determination is YES, the process proceeds to Sr1. At Sr1, the MPU 1°4 stops the pressurizing pump 9, and then at Sr9, the MPU 14 opens the slow exhaust valve of the exhaust valve 10 and starts slow exhausting [see also FIG. 6 (al)].

In the continuation <5TIO, calculation processing of the pulse wave amplitude value data string AOp(nl) is performed. The detailed procedure of this processing is shown in FIG.

At 5T30, first, timer T starts counting. This timer T calculates the pulse wave amplitude value A' p from the pulse wave component.
This is to determine the period for calculating (n), and is 1
It is set between seconds and 2 seconds.

Furthermore, at 5T31, the timer T2 starts counting. This timer T2 is set by the MPU 14 using the A/D converter 13.
This is to determine the sampling period for capturing more cuff pressure Pc. This period is set between lO and 50 ms.

Wait until timer T2 times up at 5T32,
5T33 when it is determined that timer T2 has timed up.
Proceed to. At 5T33, the MPU 14 takes in cuff pressure data P c (i) from the A/D converter 13 . Furthermore, at 5T34, a pulse wave component value P u (i) is detected from these cuff pressure data P c (i).

Analog means using bandpass filters are often used as means for detecting pulse wave components, but in this embodiment, a digital filter based on arithmetic processing by the MPU 14 is employed. The arithmetic processing of this digital filter begins with the P c taken into the current sampling data.
Let (i) be a variable x(i).

x (i) = P c (i) ...-(11
Next, the variable x (i
−1) and another variable y (i-1), the variable y (i)
The value of is calculated using the following equation (2).

Or y (i) −βy(i-1) = X (i)
-x (i-1) --(2) Furthermore, using other variables z (i-1) obtained in the previous sampling and the variables y (i) and y (i-'1), the following The variable z(i) for the current sampling is calculated according to equation (3).

tx z (i)-βz (i-1) = y (i)
-y (i-1) -... (31 z obtained by the above formula
(i) is the pulse wave component value P u in this sampling
(i).

P u (i) = z (i) "" (4) Note that the above α and β are usually set to the following values.

α=0.98 ・・・・・・(5) β=0.95 ・・・・・・(6) Also, when i=l, that is, the calculation process of the decimal filter is performed first. Time is the variable x(0), y(0)
Since z(0) and z(0) do not exist, these are set to zero as initial values in advance.

Furthermore, for the variable sequences x(0), y(0), and z(0), only the previous value is used in the actual calculation, so only the previous value is stored in memory during the actual calculation process. You can save memory capacity by storing it in

When the pulse wave component value P u (i) at Sr14 is detected, the process advances to 5T35 and it is determined whether or not the timer T has timed up. If the timer T1 has not timed up, the process returns to 5T31 and detection of the pulse wave component value P u (i) is continued.

When timer Tt times up, 5T36.5
Proceeding to T37, the pulse wave component value Pu detected during the current timer TI count (pulse wave amplitude value A'p from the 11 data sequence)
(n) is calculated. This A'p(n) can be calculated by searching the maximum value pumax and minimum value Pum1n from the pulse wave component value P u (i) data string during the current timer T+ count (5T46) and taking the difference between them. Become (
ST37).

A' p(n) = Pumax - Pumin
......(7) Pulse wave amplitude value A'p(n) in STIO
is calculated, the process proceeds to 5TII and this pulse wave amplitude value A'
It is determined whether p(n) is increasing (see FIG. 1). If the pulse wave amplitude value A' p(n) is increasing, it returns to 5TIO and the next pulse wave amplitude value A' p(n+1)
Continue the calculation process.

If the judgment at 5TII is YES, 5T12
, the pulse wave amplitude value data string A' p obtained so far is
Extract the maximum pulse wave amplitude value A' pmax from (n) [
FIG. 6 (see also bl) 30 Next, in 5T13, the bank ground pulse wave Ap is calculated from the maximum pulse wave amplitude value Aopmax.
Subtract x to calculate the flattening parameter ΔAOp. The smaller the flattening parameter ΔAOp, the greater the flatness of the pulse wave amplitude value data sequence A' p(n).

In the next step 5T14, the smoothing process limit number CAV is initialized based on the flattening parameter ΔA Op obtained in 5T13. The smoothing processing limit number of times CAV is set to be smaller as the flattening parameter ΔA0p is smaller, that is, the degree of flatness of the pulse wave amplitude value data string A'p(n) is larger.

FIG. 4 shows details of the processing in 5T14.

In 5T40, first, the flatness parameter ΔA Op is 3.
It is determined whether it is greater than (s+mHg). If this determination is YES, the smoothing process limit number CAv is set to 4 in 5T41, and the process returns to the main routine of FIG.

If the determination at 5T40 is No, the process proceeds to 5T42, where it is determined whether the flattening parameter ΔA0p is greater than 2 (mn+l1g). If the determination at 5T42 is YES, the limit number of smoothing operations CAv is set to 3 at 5T43, and the process returns to the main routine of FIG.

If the determination at 5T42 is NO, the process advances to 5T44. In 5T44, the flatness parameter ΔA Op is 1 (
mml1g). 5744
If the determination is YES, the smoothing process limit number CAv is set to 2 in 5T45, and the process returns to the main routine of FIG.

If the determination at 5T44 is No, the smoothing process limit number CAv is set to 1 at 5T46, and the process returns to the main routine.

In the next step 5T15, it is determined whether the pulse wave amplitude data string A' p(n) has become less than 60% of A' pmax. If this determination is NO, the process advances to 5T16 and continues the pulse wave amplitude value A' p(n) calculation process (see FIG. 1).

The processing of 5T16 is exactly the same as that of 5TIO.

Continuation<5T17 to 5T19 processing is the fluctuation ff1 of pulse wave amplitude value data string A' p(n) (Aip(n))
Calculate B0up and calculate this rattling I B'up(B
'up) is small, the blood pressure value is determined from the pulse wave amplitude value data string A'p(n) (Aip(n)) (
(after ST25), on the other hand, the amount of rattling B'up (B'
up) is large, the pulse wave amplitude value data string A'p
(n) Perform smoothing processing on (A' p(n)). In this embodiment, while the amount of wobbling B'up (B'up) is large, the smoothing process (ST20) is repeated a number of times within the range of the smoothing process limit number of times CAv.

If the determination at 5T15 is YES, the process advances to 5T17 and the pulse wave amplitude value data string A' p(n) (A''p(n
)) rattling component N' p(n) (N'' p(n)
) is calculated. This 5T17 processing is digital filter processing (first-order bypass filter, cutoff frequency 0.0511z) by MPLJ14.

The rattling component N' p(n) (N' p(n)) is gradually calculated based on the following equation (8).

1.235N' p(n+1) -0,765N' p
(n)=A'p(n+1) −A'p(n) −”・
・(8) First, in order to stabilize the digital filter,
.

p(n) and A' p(n+1), A' p( which is the first data of the pulse wave amplitude value data string A'p(n)) is
0) and execute equation (8) repeatedly. N'
After p(n+1) and N'p(n) are all equal,
Input data A' p (0), A' p (1), A' p
(2), ...... [Figure 6 (C1
reference〕.

For continuation < 5T18, the rattling component data string N'p(n)
Take the arithmetic mean of (N' p(n)) and calculate the amount of wobbling B
'up (B''up), and then in 5T19 it is determined whether this rattling it B'up (B'up) satisfies the following formula.

B'up<(A' pmax /M) ”・
-(9) Here, M is a constant, and is usually about 10 to 30. In this way, the maximum pulse wave amplitude value, A' pmax
The reason why the threshold value for the rattling ff1BOup is determined by dividing by a constant is that the rattling amount B'up depends on the maximum pulse wave amplitude value A'p+max.

If the determination in 5T19 is YES, it is assumed that the pulse wave amplitude value data sequence A' p(n) (A″p(n)) is smooth, and the process proceeds to 5T25. Hereinafter, the threshold level method is applied to this. Determine the blood pressure value (described below).

On the other hand, if the determination in 5T19 is NO, it is determined that the pulse wave amplitude value data string A'p(n) (A'p(n)) is not smooth and the process proceeds to 5T20. At 5T20, moving average processing is applied to the pulse wave amplitude value data string A' p (n) (A' p (n)), and the smoothed pulse wave amplitude value data string Atp (n
) (A' p(n)) [see Figure 6 (dl)].

This moving average processing is performed based on the following formula.

In the continuation <5T21, the smoothed pulse wave amplitude value data string A
'p(n) Maximum pulse wave amplitude value A from (A'p(n))
'Extract pm+ax. For continuation<5T22, 5TI4
IN from the smoothing processing limit number CAv initially set in . This is the pulse wave amplitude data string A'p(n)(A'p(
n)) is smoothed once.

Next, in 5T23, it is determined whether the smoothing process limit number of times CAv is O or not. When the smoothing processing limit number CAv becomes 0, the pulse wave amplitude value data string A'p (nl) is subjected to excessive smoothing processing and becomes flat, and the blood pressure value is determined by applying the threshold level method. As it is unbearable to do so, proceed to 5T24.

In 5T24, the user is notified by sounding a buzzer or the like that measurement is not possible.

If the determination in 5T23 is No, the process returns to 5T17 and the rattling component N'p (nl (N' p(n)) is calculated [see Fig. 6(e)].This rattling Component N1
The amount of wobbling B' u from p(n) (N' p(n))
p (B' up) is calculated (5T18) and compared with a threshold value obtained by dividing the maximum pulse wave amplitude value AIpmax (A″pmax) by a constant (ST19).

5T21 to 5T23 until the judgment of 5T19 becomes YES
→The processes from 5T17 to 5T19 are repeated. However, 5T
If the smoothing process limit number CAV becomes O in step 23, a notification indicating that measurement is not possible is issued (5T24). Interrupt measurement.

If the determination at 5T19 is YES, it is assumed that the pulse wave amplitude value data string A' p(n) has been smoothed, and the process proceeds to 5T25.

5T25, search for the pulse wave amplitude value A·p(D) closest to 60% of the maximum pulse wave amplitude value A' pmax on the increasing side of the pulse wave amplitude value data string Ap(n). ), and the corresponding cuff pressure Pc is determined as the systolic blood pressure value SYS [see FIG. 6(a)].

Continuation < In ST26, pulse wave amplitude value data string A' p(n
l On the decreasing side, search for the pulse wave amplitude value A' p(k) closest to 70% of the maximum pulse wave amplitude value A' pmax [Fig.
dl], and the corresponding cuff pressure Pc is defined as the diastolic blood pressure value D.
It is determined to be IA [see Figure 6(a)].

Next, at 5T27, the MPU 14 displays the systolic blood pressure value SYS and the diastolic blood pressure value DIA on the display 5. Another 5T
At 28, based on the command from the MPU 14, the exhaust valve 10
The rapid exhaust valve of the cuff 2 opens and the air inside the cuff 2 is rapidly exhausted.
Measurement ends.

In the above embodiment, the pulse wave amplitude value data string A'
wobbleff1B' from p(nl (A' p(n))
Up (B'up) is calculated, and this rattling it B'
While up (B' up) is larger than a predetermined threshold, the smoothing process is repeated a number of times within the range of the smoothing process limit number of times CAv, but this is not limited to this (for example, the smoothing process It is not necessary to perform the smoothing process the number of times set by the limit number of times CAv, and this can be changed as appropriate.

In addition, in the above embodiment, the maximum pulse wave amplitude value A"p
max and the bank ground pulse wave amplitude value Apx, the flatness parameter ΔAOp representing the flatness degree is calculated, but the invention is not limited to this. For example, the maximum pulse wave amplitude value A
It is possible to change it as appropriate, such as by using 'pmax itself as a parameter of flatness.

Furthermore, in order to obtain the background pulse wave amplitude value Apx, in the above embodiment, the background pulse wave amplitude value is obtained at a cuff pressure Pc that is sufficiently lower than the diastolic blood pressure value DIA during the pressurization process of the cuff 2. However, during the rapid evacuation process of the cuff, the diastolic blood pressure value DI
The background pulse wave amplitude value may be determined at a cuff pressure outside the blood pressure measurement range, such as a cuff pressure that is sufficiently lower than A, or a cuff pressure that is sufficiently higher than the systolic blood pressure value Sys during the cuff pressurization process, and can be changed as appropriate. It is.

(G) Effects of the Invention The electronic blood pressure monitor of the present invention includes a flatness detection means for detecting the flatness of pulse wave amplitude value data calculated by the pulse wave amplitude value calculation means, and a flatness detection means for detecting the flatness of pulse wave amplitude value data calculated by the pulse wave amplitude value calculation means. Since the device is characterized by a smoothness control means for controlling the amount of smoothing of the pulse wave amplitude value smoothing means based on the degree of flatness, the amount of smoothing is fixed, which makes it difficult to measure subjects who are obese. This has the advantage of eliminating errors and poor reproducibility that previously occurred.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram explaining the operation of an electronic blood pressure monitor according to an embodiment of the present invention, FIG. 2 is a flow diagram explaining the pulse wave amplitude value calculation process in the electronic blood pressure monitor, and FIG. , a flowchart explaining the initial setting of the limit number of smoothing processes in the electronic blood pressure monitor, FIG. 4 is an external perspective view of the electronic blood pressure monitor, FIG. 5 is a circuit block diagram of the electronic blood pressure monitor, and FIG. figure(
a), FIG. 6(b), FIG. 6(C), FIG. 6(d) and FIG. 6(e) are diagrams explaining the operation of the electronic blood pressure monitor, FIG. 7(8), Figure 7 (bl, Figure 7 (C) and Figure 7 (
dl is a diagram explaining the operation of a conventional electronic blood pressure monitor, and Figure 8 (al, 8th opening), Figure 8 (C), and Figure 8 (d) are diagrams explaining the problems of the conventional electronic blood pressure monitor. FIG. 2: Cuff, 9: Pressure pump, lO: Exhaust valve,
11: Pressure sensor, 14: Microcomputer (MPU). Patent applicant Tateishi Electric Co., Ltd. (and 1 others)
Name) Agent Patent Attorney Shigeru Nakamura Nobuo Nakamura Figure 4 r shout' IFJ Page 6 (Figure 6 Cd) Figure 6 (6') E Elt→

Claims (3)

[Claims] (1) A cuff, a pressurizing means for pressurizing the fluid within the cuff, a pressure reducing means for reducing the pressure of the fluid within the cuff, a pressure detecting means for detecting the fluid pressure within the cuff, and a pressure detecting means for detecting the fluid pressure within the cuff. pulse wave component detection means for detecting a pulse wave component from an output signal; pulse wave amplitude value calculation means for calculating pulse wave amplitude value data from the pulse wave component detected by the pulse wave component detection means; a pulse wave amplitude value smoothing means for smoothing the pulse wave amplitude value data obtained by the value calculating means; and a pulse wave amplitude value data smoothed by the pulse wave amplitude value smoothing means and detected by the pressure detecting means. and a blood pressure value determining means for determining a blood pressure value based on the intra-cuff fluid pressure data, the flatness of the pulse wave amplitude value data calculated by the pulse wave amplitude value calculating means is detected. and a smoothing amount control means for controlling the smoothing amount of the pulse wave amplitude value smoothing means based on the flatness detected by the flatness detecting means. Total. (2) The electronic blood pressure monitor according to claim 1, wherein the flatness detection means detects the flatness based on the maximum pulse wave amplitude value in the pulse wave amplitude value data. (3) The flatness detection means detects the background pulse wave amplitude value calculated by the pulse wave amplitude value calculation means and the pulse wave amplitude value when the fluid pressure in the cuff is set outside the blood pressure measurement range. The electronic blood pressure monitor according to claim 1, wherein the degree of flatness is detected based on the maximum pulse wave amplitude value in the data.