JPH0343A - Electronic blood pressure gauge - Google Patents

Abstract

PURPOSE:To enable rapid measurement of a blood pressure and to prevent a blood pressure gauge from inability to measure a blood pressure due to shortage in pressurization by a method wherein given logic calculation is applied on a membership function regarding each parameter selected by a membership function selecting means to infere a relative pressure, and 8 blood pressure value is decided. CONSTITUTION:A cuff 2 is wound around the upper arm part of a person to be tested to start measurement of a blood pressure. First, an MPU 10 brings an exhaust valve 3 into a closed state and turns ON a pressurizing pump 4. The MPU 10 inputs a cuff pressure signal from an A/D converter 8 and decides whether a present cuff pressure is increased to a given pressure PCO. When the cuff pressure is increased to the given pressure PCO, the MPU 10 stops the pressurizing pump 4. The MPU 10 inputs a brain wave signal. The MPU 10 applies a threshold THO and divides a bran wave and decides whether division points Tst and Ten can be detected. When the division points can be detected, the MPU 10 calculates brain wave parameters AMP, RAV, WID, and CON, and by using the parameters, a blood pressure value is decided. THE MPU 10 brings the exhaust valve 3 into an opening state to reduce a cuff pressure to zero, and a decided blood pressure is displayed on a display device 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an electronic blood pressure monitor that determines blood pressure values using pulse waves, and more specifically, to an electronic blood pressure monitor that can significantly shorten measurement time.

(b) Prior art As a conventional electronic blood pressure monitor, one that measures blood pressure by wrapping a cuff around the upper arm or the like (Rivalotchi method) is known. This electronic blood pressure monitor changes the air pressure inside the cuff (hereinafter simply referred to as cuff pressure) at a predetermined rate, and detects cardiovascular information (pulse waves, Korotkoff sounds, etc.) generated during this change process to determine systolic pressure, diastolic pressure, etc. Determine the phase pressure (so-called systolic blood pressure, diastolic blood pressure).

(c) Problems to be Solved by the Invention In the above-mentioned conventional electronic blood pressure monitor, the cuff pressure needs to be varied over a range from systolic pressure or higher to diastolic pressure or lower, so the measurement time can range from several seconds to over 1 minute. However, there were problems in that it took time to measure and that rapid changes in blood pressure could not be detected.

Further, in the conventional electronic sphygmomanometer described above, blood pressure cannot be determined if the cuff is insufficiently pressurized and the initial cuff pressure is low. especially,
With electronic blood pressure monitors that use pulse waves as cardiovascular information (so-called oscillometric method), it is difficult to detect insufficient pressurization during measurement, and if a measurement is performed with insufficient pressurization, the measurement must be repeated. There were often problems that required redoing.

The present invention has been made in view of the above, and an object of the present invention is to provide an electronic blood pressure monitor that can quickly measure blood pressure and is less likely to be unable to measure due to insufficient pressurization.

(d) Means for Solving the Problems In order to solve the above problems, the electronic blood pressure monitor of the present invention has the configurations listed in the following items i-N.

: a cuff to be worn on the subject; ii: a pressurizing means for pressurizing the air within the cuff to a predetermined pressure; iii: an exhaust means for exhausting the air within the cuff; i.
v: pressure detection means for detecting the air pressure in the cuff, ■ = pulse wave detection means for detecting the pulse wave of the subject, vi
: Pulse wave parameter calculating means for calculating a plurality of parameters representing this pulse wave waveform from the pulse wave detected by this pulse wave detecting means; membership function storage means storing a membership function whose variable is the relative pressure of air to the blood pressure value (difference between cuff pressure and systolic pressure or diastolic pressure), and viii: the pulse wave parameter calculation means membership function selection means for selecting membership functions corresponding to each parameter calculated by the membership functions stored in the membership function storage means; iX: selected by the membership function selection means; blood pressure value determining means for estimating the relative pressure by performing predetermined logical calculations on the membership functions for each of the parameters, and determining the blood pressure value;

(E) Function The function of the electronic blood pressure monitor of this invention is shown in Figures 1, 2 and 9.
This will be explained with reference to the figures. It is known that the pulse waveform changes with cuff pressure, and it is possible to estimate how far the current cuff pressure is from the systolic pressure (or diastolic pressure), that is, the relative pressure, from the pulse waveform. You can expect to do so.

To evaluate the pulse wave waveform, for example, as shown in FIG. 2, the pulse wave amplitude AMP, pulse wave integral level RAV, and waveform width ratio WI are used.
Parameters such as D and curvature CON may be calculated and used. Now, considering the pulse wave amplitude AMP, Fig. 9(a) shows the pulse wave amplitude AMP obtained for a large number of subjects.
This is a dot plot of the relationship between Pc' and relative cuff pressure Pc'. What is shown in FIG. 2(a) is, so to speak, a probability distribution function with the pulse wave amplitude AMP and the relative cuff pressure Pc' as variables, and this can be employed as the membership function.

If the pulse wave amplitude AMP is actually measured, this pulse wave amplitude AMP”
When the membership function in FIG. 9(a) is cut, the cut section becomes as shown in FIG. 1(a), and corresponds to the membership function of the relative cuff pressure with respect to the pulse wave amplitude AMP''. Such membership functions can be obtained similarly for other parameters [(b) in Figure 1.
(C) (See d3).The function obtained by performing predetermined logical calculations such as multiplication and addition on the membership function for each parameter obtained in this way is, for example, as shown in (e) in Figure 1. The relative cuff pressure corresponding to the maximum value of this function can be estimated to be the most likely one.

If the relative cuff pressure can be estimated, the systolic pressure (or diastolic pressure) can be easily calculated using this relative cuff pressure and the current cuff pressure.

As described above, blood pressure values can be determined from pulse wave parameters, but in principle only one beat of the pulse wave needs to be detected in order to calculate the pulse wave parameters. The measurement time can be shortened, and drastic blood pressure fluctuations can also be detected. In addition, it is still necessary to pressurize the cuff to detect pulse waves, but
Since the pressure need only be a value that allows pulse waves to be detected, it is unlikely that measurement will not be possible due to insufficient pressurization.

(f) Example An embodiment of the present invention will be described below based on the drawings.

50 is a block diagram illustrating the configuration of the electronic blood pressure monitor of this embodiment. A cuff 2 is attached to the upper arm of the subject, and an exhaust valve 3, a pressurizing pump (pressurizing means) 4, and a pressure sensor (pressure detecting means) 5 are connected to the cuff 2. The exhaust valve 3 and the pressure pump 4 are controlled by MPU10. The output signal of the pressure sensor 4 (hereinafter referred to as a cuff pressure signal) is amplified by an amplifier 6, and one signal is directly input to an analog/digital (A/D) converter 8, where it is converted into a digital signal, and then taken into the MPU10. . - On the other hand, the cuff pressure signal is input to a bandpass filter and a pulse wave signal is detected. This pulse wave signal is also digitally converted by the A/D converter 8 and taken into the MPU10.

MPU10 has a function to calculate pulse wave waveform parameters,
It has a function of selecting a membership function based on the calculated parameters, a function of performing a logical operation on the selected membership function and determining a blood pressure value, etc.

A data table and an operation program for the membership function described above are stored in the memory 10a in the MPU10. Furthermore, a display 9 is connected to the MPU10, and the determined blood pressure value and the like are displayed.

Next, the overall operation of the electronic sphygmomanometer according to the embodiment will be described below with reference to FIGS. 3, 4, and 6.

First, the cuff 2 is wrapped around the upper arm of the subject, and blood pressure measurement is started. First, the MPU10 closes the exhaust valve 3 [step (hereinafter referred to as ST) 1, see FIG. 6], and turns on the pressurizing pump 4 (Sr1, ■ in FIG. 3). M.P.
U1.0 takes in the cuff pressure signal from the A/D converter 8 (Sr1) and determines whether the current cuff pressure has reached a predetermined pressure p co (Sr1). If this determination is NO, the process branches to Sr1, and if this determination is YES, the process branches to Sr5.

That is, the processes Sr1 and Sr1 are repeated until the current cuff pressure reaches the predetermined pressure p co. This predetermined pressure p
Although co is preferably lower than the systolic pressure and higher than the diastolic pressure, it is not necessary to set it strictly.

At S T 5, MPU10 stops the pressurizing pump 4 (■ in FIG. 3). Then, MPU10 takes in the cuff pressure signal (Sr1) and further takes in the pulse wave signal (Sr1).
). MPU10 has a threshold value TH, as shown in FIG.
is applied to divide the pulse wave (Sr1), dividing points T□, T
It is determined whether or not an has been detected (Sr1). If this determination is No, the process branches to Sr1, and if this determination is YES, the process branches to STIO. That is, the processes Sr5 to ST9 are repeated until one pulse wave is obtained.

In 5TIO, MPU10 is pulse wave parameter A.

MP, , RAV, WID, , CON are calculated and the blood pressure value is determined using these parameters (STII).

Details of the processing of 5TIO1STII will be described later.

At 5T12, the MPU10 opens the exhaust valve 3 to make the cuff pressure zero (■ in FIG. 3), displays the blood pressure value determined at 5TII on the display 9 (ST13), and ends the measurement.

In addition, in the above explanation, it is assumed that one pulse wave is taken and a pulse wave parameter is calculated for this one beat, but it is assumed that several pulse waves are taken, pulse wave parameters are calculated for each of these several beats, and these are averaged. Doing so will improve credibility.

Next, pulse wave parameter calculation processing (STIO) will be explained with reference to FIGS. 2 and 7.

The electronic blood pressure needle of this embodiment employs four types of pulse wave parameters: pulse wave amplitude AMP, integral level RAV, waveform width ratio WID, and curvature rate CON. Of course, the pulse wave parameters are not limited to these four.

First, MPU10 searches for the time T1□8, T m i , , at which the pulse wave Pw(t) is maximum and minimum, and searches for the time T, 18,
The pulse wave maximum value PWmax and pulse wave minimum value P Main corresponding to T1 and T7, respectively, are stored in the memory 10a (ST
IOI, see (a) in Figure 2). And P L'1l
la! The pulse wave amplitude AMP is calculated by subtracting P Wm1n from
(%) is calculated using the following formula (1) (ST103,
See (b) in Figure 2].

T H+ = Pw, A+, l + A M P
x ” (2) Next, the time t is T ffl 11
5T105), the sampling width Δt is added to this (ST106), and it is determined whether the pulse wave Pw(t) for this t has become TH or less (ST107).

If the determination at 5T107 is No, the process branches to 5T106, and if the determination is YES, the process branches to 5T108. 5T108
Now, WID is calculated using the following equation (3).

Next, the waveform width ratio WID [%] is calculated (
ST104 to 5T108, see Figure 2 (C)], this W
ID is a value obtained by normalizing the time from the appearance of the maximum value PWmsx of the pulse wave Pw(t) until it decreases to a predetermined threshold value TH by the period of the pulse wave (T-TSt).

First, the threshold value TH, is set using the following equation (2).
X in this formula (2) is a constant predetermined in the range of O to 1 (ST104).

Here, T d * c is the time when Pw(t)≦TH.

Finally, calculate the curvature CON (%) (ST109~
STI 11). This CON connects the maximum and minimum points of the pulse wave at a point T c a n that internally divides the time interval [T08, T61,] between the maximum and minimum points within one beat by a certain predetermined ratio y. This is the relative ratio between the reference straight line and the pulse wave Pw(t).

First, calculate T e 11 using the following equation (4) (
ST109). Here, y is a constant preset in the range of 0 to 1.

Tce, = Tm*x+ (Ten-Tmax) xy
-(4) Next, the level Ref of the reference straight line at T c * n is calculated using the following equation (5) (STI
IO).

Ref = P w−X A M P X y ・
-(5) Then, CON is calculated using the following equation (6).

Next, the blood pressure determination process will be explained with reference to FIGS. 1, 8, and 9. In addition, although the following explanation explains systolic pressure, diastolic pressure can be similarly determined.

First, for Sr101 to Sr204, a classification (ranking) process is performed for each of the parameters AMP, RAV, WID, and CON obtained from 5T-10't'. Since the data table of the membership function, which will be described later, is discrete, a classification process is required to accommodate this, and specifically, this is performed using the following equations (7) to 0ω.

R, , -AMP/1. ,, ・・・
(7) R,,v = (RAV-0,,v)/L,
, −(8) Rwia” (W r D
0-id)/I-ia-(9)Re,,,
=C0N/r,. , ・O■Here, ■□ts , Liv s Iwia, r,. 7
are rank widths, respectively. Also, O, av, 0i1.
is the offset value. Since the lowest values of RAV and WID are both not zero, the offset value ○l is used for these.
``After subtracting aV and Owta, rank width r
Division is performed by riv, ■a.

After 5T205, the parameters Ramp, RI'lV % Rwta, RC ranked in this way
On is used to determine the blood pressure value. Before explaining the specific processing, the data table will be explained.

Figure 9 (a3 et al.) (C) and (d) are dot plots of the measured data of AMP, RAV, WID, and CON obtained for a large number of subjects, with the relative pressure Pc'' on the horizontal axis. What is shown in the figure is a so-called probability distribution function with parameters and relative pressure as variables, and these are adopted as membership functions. In Figure 9, each pulse wave parameter is AMP", RAV ”, W.I.
D “, CON”, AMP”, RAV”,
If we cut each membership function at WTD "5CON", the cuts are shown in Figure 1 (a).
(b) (C) As shown in (d). Figure 1 (
a) (b) (c) (cl) are respectively AMP umbrella,
It can be viewed as a membership function selected for RAV", WID", CON".

In the electronic blood pressure monitor of this embodiment, the parameters and relative cuff pressure Pc' are classified into ranks, and the membership functions are discretized and stored in the memory 10a in the form of a data table.

For example, if PcAMP is classified into ranks m and n, the data table of the membership function for AMP can be expressed by the following matrix.

If AMP is calculated and its ranked value is R
o, then one vertical column corresponding to Rop is selected from the above matrix as the membership function corresponding to the value of AMP.

Returning to the explanation of the processing of Sr105 again, in 5T205, the initial values of the pointer j of the relative cuff pressure Pc' and the variable P□, which stores the maximum value of the multiplied membership function, are set to O. In Sr106, the above j is incremented by 1, and in Sr107, the membership function is multiplied by the following equation (11).

P=Ps, p(j, Ranp)XPriv(j+R
riv)XP', 1d(J, Rwia)XPcon(J
, Rcoj "" (II) In ST20B, Sr10
It is determined whether P calculated in step 7 is greater than or equal to P□8. If this determination is YES, the process branches to 5T210, and if this determination is NO, the process branches to Sr109. At Sr109, the jSP at this time was M IRmX % P Ill. Put it in. At 5T210, it is determined whether j is greater than or equal to m, and if this determination is NO, the process branches to 5T206, and if YES, the process branches to Sr111.

For the processing of Sr106-210, the judgment of Sr110 is YES
This is repeated until the parameters AMPSRAV, WID are set as shown in FIG.

This can be said to be a process of calculating a function P by multiplying CON by a membership function, and extracting its maximum value P maw.

In Sr111, the relative cuff pressure p c+ is estimated from the obtained M, □, and P IIIX according to 02) 2 below.

PC', = PcM, fi+ (M,,,-1) XR9
C-(+2) where Rlle is the rank width of relative cuff pressure p%.

At Sr112, the current cuff pressure Pc is added to the estimated relative cuff pressure Pc' to calculate the systolic pressure SYS.

5ys=pc', +p, -Q3) Furthermore,
Although multiplication is applied in this embodiment to estimate the relative cuff pressure Pc'', logical calculations such as addition may be applied, and the design can be changed as appropriate.

(G) As described in detail, the electronic blood pressure monitor of the present invention includes a cuff worn by a subject, a pressurizing means for pressurizing the air within the cuff to a predetermined pressure, and an exhaust system for exhausting the air within the cuff. a pressure detection means for detecting the air pressure in the cuff; a pulse wave detection means for detecting the pulse wave of the subject; and a pulse waveform detected by the pulse wave detection means. pulse wave parameter calculating means for calculating a plurality of parameters expressed; and a membership function storing, for each of these parameters, each parameter and a relative pressure of air in the cuff with respect to a blood pressure value as variables. function storage means, and membership function selection means for selecting membership functions corresponding to each parameter calculated by the pulse wave parameter calculation means from membership functions stored in the membership function storage means; The blood pressure value determination means performs a predetermined logical calculation on the membership function for each parameter selected by the membership function selection means to estimate the relative pressure and determine the blood pressure value. ,
It has the advantage that the time required for blood pressure measurement can be shortened, and measurement failure due to insufficient pressurization is less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing membership functions for explaining the blood pressure value determination process of an electronic blood pressure monitor according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining the pulse wave parameter calculation process of the electronic blood pressure monitor. Figure 3 is a diagram showing the relationship between cuff pressure and elapsed time to explain the overall operation of the electronic blood pressure monitor, and Figure 4 is a pulse wave segmentation process of the electronic blood pressure monitor. FIG. 5 is a block diagram explaining the configuration of the electronic blood pressure monitor, FIG. 6 is a flow diagram explaining the overall operation of the electronic blood pressure monitor, and FIG. 7 is the electronic blood pressure needle. FIG. 8 is a flowchart explaining the pulse wave parameter calculation process of the electronic blood pressure monitor, and FIG.
), FIG. 9(b), FIG. 9(C) and FIG. 9(d) are
FIG. 6 is a diagram showing actually measured data for explaining the relationship between relative cuff pressure and pulse wave amplitude, integral level, waveform width ratio, and curvature ratio, respectively. 2: Cuff, 3: Exhaust valve, 4: Pressure pump, 7: Bandpass filter, 10a: Memory, Pe': Relative cuff pressure, AMP: Pulse wave amplitude value, WID: Waveform width ratio, 5: Pressure sensor, 10: MPU. Pc z cuff pressure, Pga (t): pulse wave, RAV: integral level, CON: curvature ratio.

Claims (1)

[Claims] (1) A cuff worn by a subject; a pressurizing means for pressurizing the air within the cuff to a predetermined pressure; an exhaust means for exhausting the air within the cuff; and a pressure detection means for detecting the air pressure within the cuff. a pulse wave detection means for detecting the pulse wave of the subject; a pulse wave parameter calculation means for calculating a plurality of parameters representing the pulse wave waveform from the pulse wave detected by the pulse wave detection means; and these parameters. membership function storage means storing a membership function whose variables are each parameter and the relative pressure of the air in the cuff with respect to the blood pressure value; and each of the parameters calculated by the pulse wave parameter calculation means. membership function selection means for selecting membership functions corresponding to the parameters from membership functions stored in the membership function storage means; and membership for each parameter selected by the membership function selection means. An electronic sphygmomanometer comprising blood pressure value determining means for estimating the relative pressure by performing predetermined logical calculations on a function and determining a blood pressure value.