JPS62268532A - 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 (a) Field of Industrial Application This invention relates to an improvement in an electronic blood pressure monitor employing a vibration method.

(b) Conventional technology Conventionally, electronic blood pressure monitors using the vibration method have a cuff,
A pressure pump that pressurizes the air inside the cuff (hereinafter referred to as cuff pressurization), an exhaust valve that reduces the air pressure inside the cuff, a pressure sensor that detects the air pressure inside the cuff (hereinafter referred to as cuff pressure), A device equipped with a microcomputer (MPU) that quantifies a blood pressure value based on an output signal from a pressure sensor is known.

The operation of this conventional electronic blood pressure monitor will be explained below based on FIG. 5(a), FIG. 5fbl, and FIG. 5(C1).

Figure 5(a) shows that once the cuff is pressurized above the systolic blood pressure value,
It shows the change in cuff pressure when the pressure is then reduced at a constant speed, and a pulse wave W appears in the process of decreasing cuff pressure Pc. In addition, Fig. 5 (bl) shows the amplitude value for each cycle of this pulse wave as a solid line.Furthermore, Fig. 5 (C) shows the pulse wave that is the envelope of the amplitude value of Fig. 5 (bl). The amplitude value curve is shown by a solid line.The horizontal axes of FIGS. 5(al) to 5(C1) are the elapsed time t.

It has been clinically confirmed that the cuff pressure corresponding to the point M where the maximum pulse wave amplitude value Apmax is taken in Figure 5 (C1) corresponds to the mean blood pressure value. On the left side (pulse wave amplitude value increasing process), the cuff pressure corresponding to point S corresponding to 50% of the maximum pulse wave amplitude value Apmax is the systolic blood pressure value SYS, and on the right side of point M (pulse wave amplitude value decreasing process)
In this step, the cuff pressure corresponding to the point corresponding to 70% of the maximum pulse wave amplitude value Apmax is determined as the diastolic blood pressure value DIA.

(C) Problems to be Solved by the Invention In general, the pulse wave amplitude value curve becomes flatter as the degree of obesity of the subject increases, with less change in the pulse wave amplitude value. This is because obese people have a thick subcutaneous fat layer, and pulse waves, which represent volume changes in arteries where blood flow is stopped, are attenuated by this subcutaneous fat layer and transmitted to the cuff.

On the other hand, when the cuff is wrapped around the arm and pressurized, a pulse wave having a substantially constant amplitude value (hereinafter referred to as hack ground pulse wave) is always observed. This hack ground pulse wave is observed when minute volume changes in the artery that occur when blood flows through the artery or occur in the heart-side portion of the artery where blood flow is stopped are transmitted to the cuff. This background pulse wave always has a constant amplitude value regardless of the cuff pressure, and the inventors of the present invention have collected information at hospitals that there is little individual variation in the amplitude value, regardless of the cuff pressure. Confirmed by data.

In FIG. 5 (C1), the background pulse wave is shown, and its amplitude value is Ab. Therefore, the true maximum pulse wave amplitude value Apmg is equal to the observed maximum pulse wave amplitude value Apmg.
It is obtained by subtracting the background pulse wave Ab from ax. If the subject is not obese, Apmax is Ab
It is sufficiently large compared to the background pulse wave, and the shadow sound caused by the background pulse wave can be almost ignored.

However, when the subject is obese, Apmax cannot be said to be sufficiently large compared to Ab, resulting in a disadvantage that a large error occurs in the measured blood pressure value.

To explain this based on FIG. 5(a) and FIG. .

On the other hand, in Fig. 5 FC+, the portion where the background pulse wave amplitude value Ab has disappeared from the pulse wave amplitude value Ap corresponds to 50% of the true maximum pulse wave amplitude value Apmg on the pulse wave amplitude increasing side. A point Sg and a point Dg corresponding to 70% of the true maximum pulse wave amplitude value Apmg on the increasing side of the pulse wave amplitude value are shown.

In FIG. 5(a), the cuff pressures Pc corresponding to the points S and Sg are shown as the measured systolic blood pressure value SYS and the true systolic blood pressure value sysg, respectively.

The measured systolic blood pressure value sys is higher than the true systolic blood pressure value SYSg. Similarly, in FIG. 5 ta+, the cuff pressures Pc corresponding to the light and point Dg are shown as the measured diastolic blood pressure value DiA and the true diastolic blood pressure value DIAg, respectively. In this case, the measured diastolic blood pressure value DIA is lower than the true diastolic blood pressure value DIAg.

As mentioned above, when the subject is obese, the measurement error becomes large (but there is also the disadvantage that the reproducibility decreases, as shown in Fig. 5(b) and Fig. 5tc). The broken line indicates the pulse wave amplitude value Ap obtained as a result of other measurements on the same subject under the same conditions. Point S゛ and point D determined for the pulse wave amplitude Ap on this broken line
'' is shown in FIG. 5(C). FIG. 5(a) shows the measured systolic blood pressure value S corresponding to this point S'' and point D°.
YS' and the measured diastolic blood pressure value D I A' are shown. Measured systolic blood pressure value 5YS(!: SYS', 'Measured systolic blood pressure value DI A and DIA' are different from each other.

As the subject's degree of obesity further progresses, the pulse wave amplitude value curve becomes even flatter, and as shown in Fig. 5(d), it is no longer 50% (or 70%) of the maximum pulse wave amplitude value A p max. There was an inconvenience that a corresponding point no longer existed, resulting in a measurement error.

This invention was made in view of the above-mentioned disadvantages, and an object of the present invention is to provide an electronic blood pressure monitor that can reliably measure blood pressure values of subjects no matter how obese they are and has excellent measurement accuracy and reproducibility. It is said that

(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. pressure-reducing means for reducing the pressure at a constant slow rate or rapidly; pressure-detecting means for detecting the fluid pressure within the cuff; and pulse-wave component detecting means for detecting a pulse-wave component included in the output signal of the pressure detecting means. , a pulse wave amplitude value calculation means for calculating a pulse wave amplitude value from the output signal of the pulse wave component detection means, and a blood pressure value for determining the blood pressure value based on the output signal of the pulse wave amplitude value calculation means and the pressure detection means. In the device comprising a value determining means, the fluid pressure in the cuff is set to a predetermined pressure outside the blood pressure measurement range, and the pulse wave amplitude value calculated by the pulse wave amplitude value calculating means at this time is set as a background value. A background pulse wave amplitude value determining means that determines the background pulse wave amplitude value as a pulse wave amplitude value, and a background pulse wave amplitude value determined by the background pulse wave amplitude value determining means is calculated by the pulse wave amplitude value calculating means. The present invention is characterized by a background pulse wave amplitude value subtraction means for subtracting from a pulse wave amplitude value for determining a blood pressure value.

(e) Function The function of the electronic blood pressure monitor of the present invention will be explained below with reference to FIGS. 4(a), 4(bl) and 4(c).

Fig. 4 (al indicates the data string of the pulse wave component value p u (i) (however, because the sampling period is short, the envelope line is shown). Figure fa
) shows the pulse wave amplitude value A p (nl data string) calculated from the it data string. The maximum value in this pulse wave amplitude value A p (n) data string is Apmax. .

Ab shown in the fourth [D(bl) is the background pulse wave amplitude value. As described above, the background pulse wave amplitude value Ab is constant regardless of the magnitude of the cuff pressure.

Therefore, the cuff pressure is outside the blood pressure determination range [cuff pressure that is sufficiently larger than the systolic blood pressure value or sufficiently smaller than the diastolic blood pressure value and where no true pulse wave is detected, i.e., other than region 2 in Figure 5 (a)] cuff pressure] is set to a predetermined value, the pulse wave observed is only the background pulse wave. Therefore, the amplitude value Ab of the background pulse wave at this time is detected,
If subtracted from the pulse wave amplitude value A p (nl data string shown in FIG. 4 (bl), the influence of the background pulse wave as shown in FIG. 4 (C) is eliminated, the subtracted pulse wave amplitude value A'
P (nl data strings are obtained.

If the blood pressure value is determined based on this subtracted pulse wave amplitude value A''P (n) data string, errors and low reproducibility caused by the background pulse wave can be eliminated. Even if the pulse wave amplitude value curve becomes flat as the pulse wave amplitude progresses, the subtracted pulse wave amplitude value A'P (nl) corresponding to a predetermined ratio of the subtracted maximum pulse wave amplitude value A'Pmax can be extracted without fail, Blood pressure values can be determined reliably.

(F) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 2 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. 3 shows a block 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 10 are operated by a microcomputer (
Controlled by MPU) 14.

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.

MPtJ14 has a function of detecting a pulse wave component from the output signal of the pressure sensor 11, a function of calculating a pulse wave amplitude value, a function of determining a ground pulse wave amplitude value and subtracting it from the pulse wave amplitude value, and a blood pressure value. It has a function to determine the pressure pump 9 and an exhaust valve 10, and a function to control the pressure pump 9 and the exhaust valve 10.

The MPU 14 is further connected to the display 5 for displaying the determined blood pressure value, as well as a power switch 6 and a measurement switch 7.

Next, the operation of the electronic blood pressure monitor 1 according to this embodiment will be explained below, mainly referring to FIG.

First, the cuff 2 is wrapped around the upper arm of the person to be measured, and the power 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 or not, and if it is not turned on, repeats this determination process,
Wait here [Step ST (hereinafter referred to as ST) 1,
See Figure 1].

When the measurement switch 7 is turned on in STI, the MPU 14
activates the pressurizing pump 9 (Sr2), closes the exhaust valve 10 (5T3), and the cuff 2 is pressurized. The MPU14 is
The cuff pressure Pc during this period is taken in by the A/D converter 13, and it is determined whether the cuff pressure Pc has reached a predetermined value outside the blood pressure measurement range (30n+ml1g in this embodiment).

When it is determined that the cuff pressure Pc has reached the predetermined value, Sr
The process advances from 1 to Sr5, and the MPU 14 stops the pressure pump 9. Then, while maintaining this state, the pulse wave amplitude value Apx
is calculated (Sr1).The procedure for calculating the pulse wave amplitude value Apx is similar to the procedure for calculating the pulse wave amplitude value Ap+nl (Sr1), which will be described later.
T12 to 5T18). In Sr7, this pulse wave amplitude value Apx is set as the background pulse wave amplitude value Ab.

At the next Sr8, the MPU 14 operates the pressurizing pump 9 again to pressurize the cuff 2 to a predetermined value for blood pressure measurement. At Sr1, it is determined whether the cuff pressure Pc has reached this predetermined value.

When it is determined that the cuff pressure Pc has reached the predetermined value at Sr1,
Proceeding to 5TIO, the MPU 14 stops the pressurizing pump 9, opens the slow exhaust valve of the exhaust valve 10, and starts slow exhausting of the cuff 2 (ST11).

At the next 5T12, first, the timer T1 starts counting. This timer T1 determines the pulse wave amplitude value (
Pulse wave amplitude value for determining blood pressure value) A p (This value is for determining the period for calculating n+, and is set between 1 second and 2 seconds. Furthermore, in 5T13, timer T2
counting starts. This timer T2 is
4 is for determining the sampling period for acquiring the cuff pressure P C (il) from the A/D converter 13. This period is set between 10 and 50 m5.

Waits until timer T2 times up at 5T14, and when it is determined that timer T2 times up, 5T
Proceed to step 15. At 5T15, the MPU 14 takes in cuff pressure data PC(i) from the A/D converter 13. 5 more
At T16, pulse wave component value Pu(1) is detected from these cuff pressure data Pc(1).

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 P c
Let (1) be a variable x fl).

x (il-P c (it -------・(1) Next, the variable x (i-
1) From the other variables y(i-1), the value of the variable y(i) is calculated using the following equation (2).

αy(1)−βY(i−1) = x(if −
x (i-1)... (2) Furthermore, with other variables z (i-1) obtained in the previous sampling and the variables y (1) and y (i-1), The variable z(1) in the current sampling is calculated according to the following equation (3).

α2(1)−βz(i−1) = y(i)−
y (l-1)...(3) z obtained by the above formula
(11 is the pulse wave component value P u in this sampling
(1).

P u (il = z (11...-(41)
The above α and β are usually set as follows.

α=0.98 ・・・・・・(5) β=0.95 ・・・・・・(6) Also, when i=1, that is, when the digital filter calculation process is performed first are the variables x(0), y(O)
Since and z (o) do not exist, these variables are set to zero as initial values in advance (.

Furthermore, for the variable sequence x (1), ) r (1), z (il, only the previous value is used in actual calculations, so only the previous value is stored in memory You can save memory capacity by storing it in

When the pulse wave component value Pu(1) at 5T16 is detected, 5
Proceeding to T17, it is determined whether or not the timer TI has timed up. If the timer T1 has not timed up, the process returns to 5T13 and the detection of the pulse wave component value Pu(i) is continued.

If the timer T times out, the process advances to 5T18, and the pulse wave amplitude value A p (n) is calculated from the pulse wave component value Pu (il) data string detected during the current timer T count. The calculation of A p (n) is performed by extracting the maximum value Pumax and the minimum value Pum1n from the pulse wave component value pu('+1) data string during the current timer T count, and taking the difference between them.

A p (1) = P umax − P umin −
(7) At the next 5T19, the background pulse wave amplitude value A is calculated from the pulse wave amplitude value A p (n) calculated at 5T18.
b is subtracted to calculate the subtracted pulse wave amplitude value A'P(n).

In the next 5T20, the subtracted pulse wave amplitude value A' P (n)
is increasing. Subtraction pulse wave amplitude value A'P
(n) is increasing, the flag F is set to 1 in Sr11, the process returns to 5T12, and the next pulse wave amplitude value A p (n
+1) is calculated.

At 5T20, if it is determined that the subtracted pulse wave amplitude value A'P (nl is not increasing), proceed to 5T22 and determine whether the flag F is 1. If it is determined that F=1, proceed to 5T23. , otherwise proceed to 5T26.

At 5T23, flag F is first set to zero. Furthermore 5T2
4, the subtracted pulse wave amplitude value A'P (the maximum value A'Pmax is extracted from the nl data string).

In 5T25, the subtracted pulse wave amplitude value A'P(nl) closest to 50% of the subtracted maximum pulse wave amplitude value A'Pmax is searched, and the corresponding cuff pressure Pc(i) is determined as the systolic blood pressure value (SYS). When SYS is determined, the process returns to Sr6 and the pulse wave amplitude value A for determining the diastolic blood pressure value (DIA) is determined.
p (n) Continue collecting data.

As before, processing from 5T12 to 5T19 is performed,
A subtracted pulse wave amplitude value A'P(n) is calculated. At 5720, since the subtracted pulse wave amplitude value A'P(n) has already reached its maximum value and is in the process of decreasing [see FIG. 4(b)], it is determined that it is not increasing, and the process proceeds to 5T22. Further, at 5T22, since the flag F was previously set to zero at 5T21, the determination is No, and the process proceeds to 5T26.

In 5T26, it is determined whether the subtracted pulse wave amplitude value A'P(nl is less than 70% of the subtracted maximum pulse wave amplitude value A'Pmax. If this determination is No, the process returns to 5T12 and the next subtracted pulse wave amplitude value A'Pmax is determined. An amplitude value A'P(n+1) is calculated.

In 5T26, if it is determined that the subtracted pulse wave amplitude value A'P (nl is less than 70% of the subtracted maximum pulse wave amplitude value A'Pmax, the process proceeds to 5T27. In 5T27, the subtracted maximum pulse wave amplitude value A'Pmax is determined. The subtracted pulse wave amplitude value A'P closest to the value of 70% of Pmax (search for nl, but after the subtracted maximum pulse wave amplitude value A'P appears), and the corresponding cuff pressure p c (i). Let it be the diastolic blood pressure value (I)IA).

Next, at 5T28, the MPU 14 displays the above SY on the display 5.
Display S and DIA. Finally, in 5T29, MP
U14 gives a command to the exhaust valve 10 to open the rapid exhaust valve, rapidly evacuate the cuff 2, and end the measurement.

In the above example, the background pulse wave amplitude value Ab is determined at a relatively low cuff pressure during the initial pressurization of the cuff. It is also possible to perform the pumping at a high place, or to temporarily interrupt the pumping during the rapid pumping and determine the background pulse wave amplitude value Ab there, and the design can be changed as appropriate.

Furthermore, the procedure for determining blood pressure is not limited to that shown in the above embodiments, and can be modified as appropriate.

(G) Effects of the Invention The electronic blood pressure monitor of the present invention sets the cuff pressure to a predetermined pressure outside the blood pressure value measurement range, and calculates the pulse wave amplitude value calculated by the pulse wave amplitude value calculation means at this time as a hack-ground pulse. It is characterized by comprising a hack ground pulse wave amplitude value determining means for determining the hack ground pulse wave amplitude value as a wave amplitude value, and a bank ground pulse wave amplitude value subtracting means for subtracting the hack ground pulse wave amplitude value from the pulse wave amplitude value. Therefore, even if the subject is obese, it has the advantage of effectively preventing errors and deterioration in reproducibility due to the presence of background pulse waves, and even if the subject is obese. This has the advantage of effectively preventing measurement errors that would otherwise occur and ensuring reliable blood pressure measurements.

[Brief explanation of drawings]

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 an external perspective view of the electronic blood pressure monitor, and FIG. 3 is a circuit block of the electronic blood pressure monitor. Figure, 4th
Figures (al, 41(b) and 41(b) are diagrams explaining the details of the present invention, Figure 5(al), Figure 5(
b), FIG. 5(C), and FIG. 5(dl) are diagrams explaining the problems of the prior art. 2: Cuff, 9: Pressurizing pump, 10: Exhaust valve, 11: Pressure sensor , 14: Microcomputer (MPU). Patent applicant Tateishi Electric Co., Ltd. (Baka 1
Name) Agent Patent Attorney Shigeru Nakamura Figure 2 Figure 4 <a) Figure 4 R)) t→ t→ t→ t→

Claims (1)

[Claims] (1) A cuff, a pressurizing means for pressurizing the fluid within the cuff, a depressurizing means for reducing the pressure of the fluid within the cuff at a constant slow speed or rapidly, and a pressure detecting means for detecting the fluid pressure within the cuff. , a pulse wave component detection means for detecting a pulse wave component included in the output signal of the pressure detection means; a pulse wave amplitude value calculation means for calculating a pulse wave amplitude value from the output signal of the pulse wave component detection means; In the electronic sphygmomanometer comprising this pulse wave amplitude value calculating means and a blood pressure value determining means for determining a blood pressure value based on the output signal of the pressure detecting means, background pulse wave amplitude value determining means for setting the pressure to a predetermined pressure and determining the pulse wave amplitude value calculated by the pulse wave amplitude value calculating means at this time as a background pulse wave amplitude value; background pulse wave amplitude value subtraction means for subtracting the background pulse wave amplitude value determined by the value determination means from the pulse wave amplitude value for blood pressure value determination calculated by the pulse wave amplitude value calculation means. An electronic blood pressure monitor characterized by: