JPH03280932A - Electronic blood pressure gauge - Google Patents

Abstract

PURPOSE:To prevent the obtained blood pressure value from deviating out of a physiological range even when the pulse wave-form is disturbed by pressure noises and part of parameters are affected by providing a means estimating the relative pressure with the estimated range limited membership function in addition to the selected membership function. CONSTITUTION:Multiple parameters indicating the pulse wave-form are calcu lated by a calculating means based on the pulse detected by a pulse detecting means. The membership function using the parameters and the relative pressure of the air pressure in a cuff against the blood pressure value as variables is stored in a memory means 10, and the estimated range limited membership function Pabs limiting the estimated range of the relative pressure is stored. The relative pressure is estimated by a blood pressure value determining means 10 to determine the blood pressure value with the estimated range limited membership function Pabs in addition to the membership function selected by a membership function selecting means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field This invention relates to an electronic blood pressure needle that can determine blood pressure values in a short time using fuzzy theory.

(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.) in the process of this change to determine the systolic pressure. , determine the diastolic pressure (so-called systolic, diastolic blood pressure).

With the above-mentioned conventional electronic sphygmomanometer, the cuff pressure needs to be varied over the range from systolic pressure or higher to diastolic pressure or lower, so the measurement time ranges from several seconds to over 1 minute, which makes measurement time-consuming and increases blood pressure. There was a problem with not being able to capture sudden changes.

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 problems that often occurred where the process had to be redone.

Therefore, in order to solve the above problems, the applicant of the present application has already applied for an electronic blood pressure monitor to which fuzzy theory is applied.

The electronic sphygmomanometer according to this prior application focuses on the fact that the waveform of the pulse wave changes depending on the cuff pressure level (hereinafter referred to as relative cuff pressure) based on systolic pressure or diastolic pressure, Relative cuff pressure is estimated from the pulse waveform.

To evaluate the pulse wave waveform, waveform parameters such as the pulse wave amplitude AMP, the pulse wave integral level RAV, the waveform width ratio WID and the curvature CON are used. Now, considering the pulse wave amplitude AMP, Figure 9(a) is a dot plot of the relationship between the pulse wave amplitude 1iAMP and the relative cuff pressure (systolic pressure P37. standard) PC' obtained for a large number of subjects. This is what I did. What is shown in FIG. 9(a) is, so to speak, a probability density distribution with pulse wave amplitude AMP and relative cuff pressure PC' as variables, and a membership function can be generated using this. .

If the pulse wave amplitude AMP is actually measured, this pulse wave amplitude AMP”
When the probability density distribution in Fig. 9(a) is cut, the cut is shown in Fig. 1(a), and this pulse wave amplitude A
It can be expressed as a membership function P with relative cuff pressure as a variable for MP". Such a membership function can also be used for other parameters as well. ",CON"
[(b) and (c) in Figure 1]
(d), see FIGS. 9(b), (c), and (d)] The membership function P thus obtained. p, P 1
．． ! The function P obtained by performing predetermined logical calculations such as multiplication and addition on IV % P wtd % P con becomes, for example, as shown in (e) in Figure 1, and the maximum value P mxX of this function P is The corresponding relative cuff pressure p C+, can be estimated to be the most likely one. If the relative cuff pressure PC' can be estimated, this relative cuff pressure p c+.

The systolic or diastolic pressure can be easily calculated using the current cuff pressure and the current cuff pressure.

In the electronic blood pressure monitor according to the above-mentioned prior application, the probability density distribution for each parameter is stored in the memory as data in the form of a discretized matrix, and the pulse wave parameters are calculated from the actually detected pulse waves. It has a configuration in which a membership function for each parameter is selected from data in the memory, and a predetermined logical operation is performed on the selected membership function to determine a blood pressure value. In principle, it is sufficient to detect only one pulse wave in order to calculate pulse wave parameters, which shortens measurement time and enables rapid measurement. Furthermore, although it is necessary to pressurize the cuff to detect a pulse wave, the pressure only needs to be at a value that allows the pulse wave to be detected, so measurement is unlikely to be impossible due to insufficient pressurization.

(c) Problems to be solved by the invention In the electronic blood pressure monitor according to the above-mentioned prior application, the function P obtained as a result of logical calculation should always become large near the actual relative cuff pressure, but sometimes it becomes larger than that. Relative cuff pressure p
%. Also, a large local maximum point may occur as shown by the broken line [see FIG. 1(e)]. This can occur when pressure noise or the like gets mixed in during measurement, disrupting the pulse waveform and affecting some waveform parameters. In such a case, if the blood pressure value is determined using this relative cuff pressure PC0, a large error will occur.

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 accurately determine blood pressure values even when the pulse waveform is disturbed.

(d) Means for Solving the Problems In order to solve the above problems, 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; an exhaust means for exhausting air within the cuff, 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, and a pulse wave detected by the pulse wave detection means. , a pulse wave parameter calculation means for calculating a plurality of parameters representing this pulse wave waveform, and a membership function for each of these parameters, each parameter and the relative pressure of the air pressure in the cuff with respect to the blood pressure value as variables. Membership function storage means storing , and membership functions corresponding to each parameter calculated by the pulse wave parameter calculation means are selected from among the membership functions stored in the membership function storage means. membership function selection means; and blood pressure value determination means for estimating the relative pressure and determining the blood pressure value by performing a predetermined logical calculation on the membership function for each parameter selected by the membership function selection means. In the electronic blood pressure monitor, the membership function storage means stores an estimation range limited membership function that limits the estimation range of the relative pressure, and the blood pressure value determination means stores an estimation range limited membership function that limits the estimation range of the relative pressure, and the blood pressure value determination means stores an estimation range limited membership function that limits the estimation range of the relative pressure. In addition, the relative pressure is estimated using this estimation range limited membership function.

(E) Systolic pressure in affected organisms is usually 50 mmHg to 26 Oa
It is in the nHg range (physiological range). Therefore, a membership function that limits the relative cuff pressure within this physiological range,
For example, if a logical calculation is performed using a membership function that is zero outside the physiological range together with the membership function for each parameter, the estimated relative cuff pressure will fall within the physiological range.

Therefore, even if pressure noise or the like is mixed in and the pulse waveform is disturbed, the determined blood pressure value can be prevented from falling outside the physiological range.

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

FIG. 5 is a block diagram illustrating the configuration of the electronic blood pressure needle 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 the limited estimation range membership function, and determining a blood pressure value.

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 blood pressure needle according to the embodiment will be explained below with reference to FIGS. 3 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 pressure pump 4 (Sr2). MPUl0 is A
/D converter 8 takes in the cuff pressure signal (Sr1),
It is determined whether the current cuff pressure has reached a predetermined pressure P Co (Sr4).

If this determination is NO, the process branches to Sr1, and if this determination is YES, the process branches to Sr1. That is, the processes Sr1 and Sr4 are repeated until the current cuff pressure reaches the set value pco. This set value p co is desirably lower than the systolic pressure and higher than the diastolic pressure, but does not need to be set exactly.

At Sr1, MPU10 stops the pressurizing pump 4. Then, MPU10 takes in the cuff pressure PC (Sr6),
Furthermore, a pulse wave signal is taken in (Sr7). MPUl0 is
As shown in FIG. 3, the pulse wave Pw(t) is divided (Sr1) by applying the threshold value T Ho, and the division point T s L %
Determine whether T e n has been detected (Sr9)
. If this determination is NO, the process branches to Sr7, and if this determination is YES, the process branches to 5TIO. That is, the processes Sr6 to Sr9 are repeated until one pulse wave is obtained. In addition,
The timing at which the cuff pressure PC is taken may be during pulse wave detection or after pulse wave breakpoint detection, or it may be sampled together with the pulse wave signal and its average value taken.

In 5TIO, MPU10 is the pulse wave parameter AMP, R
Calculate AV, WID, CON and determine blood pressure value using these parameters (STII) STIO2ST11
Details of the processing will be described later.

At 5T12, MPU10 opens the exhaust valve 3 to make the cuff pressure zero, displays the blood pressure value determined at 5T11 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, the pulse wave parameter calculation process (STIO) will be explained with reference to FIGS. 4 and 7.

In the electronic blood pressure monitor of this embodiment, the pulse wave parameters include pulse wave amplitude AMP, integral level RAV, and waveform width ratio WID.
, curvature ratio CON are adopted. Of course, the pulse wave parameters are not limited to these four.

First, MPU10 searches for the time T+naxs Tarn at which the pulse wave Pw(t) is maximum and minimum, and searches for T1111
Pulse wave maximum value P Wm corresponding to X and T1.7, respectively
xx, pulse wave minimum value P W n 4 n is stored in the memory 10a [5TIOI, see (a) in FIG. 4]. And Ph, than p wma. The pulse wave amplitude AMP
(ST102) Next, the integral level RA, which is the value obtained by normalizing the time average of the pulse wave Pw(t) by the amplitude AMP, is calculated.
Calculate V (%) using (1) 2 below (ST10
3, see (b) in Figure 4].

Next, the waveform width ratio trD (%) is calculated (S
T104 to 5T108, see Figure 4 (C)], this WI
D is the time from the appearance of the maximum value Pl'i+yiX of the pulse wave Pw(t) until it decreases to a predetermined threshold value TH,
This is a value normalized by the pulse wave period (T, -'r −t ).

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 0 to 1 (ST104).

TH,=Pw win +AMPxχ (2) Next, set the time t to T ni a x5T105), add the sampling width Δt to this t (ST106), and set this t
It is determined whether the pulse wave Pw(t) has become equal to or less than TH (ST107), and if the determination in 5TI07 is No, the process branches to 5T106, and in the case of YES, the process branches to 5T10.
Branch to 8. In 5T108, W is determined by the following equation (3).
Calculate the ID.

Here, T a gr c is the time when Pw(t)≦TH.

Finally, calculate the curvature CON [:%] (ST109
~5TIII), this CON is the pulse wave at a point T~, which internally divides the time interval [T-8, T, i, ) between the maximum point and minimum point within one beat by a certain predetermined ratio y. This is the relative ratio between the reference straight line connecting the maximum point and the minimum point and the pulse wave Pw(t).

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

Tce,,=Tm,,+(T,,-T,,X) xy
...(4) Next, the level Ref of the reference straight line at Tc, , is calculated using the following equation (5) (ST
IIO).

Ref=PwlIix-AMPxy-(5) Then, CON is calculated by the following (6) 2.

Ref -PWsin 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, in 5T201, the parameter A obtained by 5TIO
Classification (ranking) processing is performed for each of MP, RAV, WID, and CON.

Since the data table of the member-ship function described later is discrete, a classing process is required to accommodate this, and specifically, this is performed using the following equations (7) to 00).

R,,P=AMP/1. m, ・C1
)Rr,v=(RAV-0,a,)/r,,v-(
8) R,, d= (W I D O, ta ) /
I-id...(9) Rc,, = CON/
I con -00) where I
m, ,, p −, Fav −, I+i, a % Ic
o, , are rank widths, respectively. Also, 0rlV, 0
Wid is an offset value. Since the lowest values of RAV and WID are both not zero, the offset values 0rav, 0i, and d are subtracted from each other, and then division is performed by the rank widths 1r, v, I, and □6.

After ST205, the parameters Rmap, Rrav-, Rwid, Reo ranked in this way are
A blood pressure value is determined using n. Before explaining the specific processing, the data table will be explained.

Figure 9 (a), (b), (c), and (a) are dot plots of the measured data of AMP, RAV, WID, and CON obtained for a large number of subjects, with the relative cuff pressure p% on the horizontal axis. be. What is shown in each figure is a so-called probability density distribution with parameters and relative cuff pressure as variables, and these are employed as membership functions. In Kintei 9 diagram, each pulse wave parameter is AMP”, R
If AV''', WID'', CON'', then AMP
If the membership functions are cut at ", RAV'", and WID "CON", the cuts will be as shown in FIGS. 1(a), (b), (C), and (d), respectively. Figure 1 (a), (b), (C), and (d) are respectively A.
It can be viewed as a membership function selected for MP'', RAV'', WID'', and CON''.

In the electronic sphygmomanometer of this embodiment, the parameters and relative cuff pressure P,' (fixed in the range of -60 to +40 m+nHg, for example) are classified into ranks, and the membership functions are discretized and stored in the memory 10a in the form of a data table. ing. For example, if PcAMP is classified into ranks m and n, the data table of the membership function for AMP can be expressed as the following matrix.

If AMP is calculated and its ranked value is R
If it is l1llp, the introduction column corresponding to R1 and R2 is selected from the above matrix as the membership function corresponding to this value of AMP.

Returning to the explanation of the process in ST202 again, in 5T202, the initial value of the pointer j of the relative cuff pressure Pc' and the variable P□8 that stores the maximum value of the multiplied membership function is set to 0. In 5T203, the above j is incremented by 1, and in 5T204, the membership function is multiplied by the following 01)2.

P (j)-P mff1p(j, Rm+-p) X
P rav(J , Rrmv)xP,, 1d(j, R
,td)xPc,(j,Rcon)-(II)S
In r105, an estimated range-limited membership function P is added to P(j). , (j) to obtain P'(j).

P' (J) = P (J) X P abs
(j) =・QT) As shown in Figure 2, the estimated range membership function limits the range of absolute cuff pressure to within the physiological range, and in the case of systolic pressure, to the range of 50 to 260 mmHg. belongs to. The systolic pressure is this 50~
It is very rare for it to be outside the 260mmHg range.
It only occurs in very serious and special cases, and cannot be measured with general electronic blood pressure monitors.

Even if a local maximum value of P(j) occurs at a value far away from the relative cuff pressure corresponding to the actual systolic pressure, such as when the pulse waveform is disturbed, at such a value Pubs (j
) is zero, and as a result of multiplying by this, such local maximum values are excluded from P'(j), and the relative cuff pressure is prevented from being erroneously estimated outside the physiological range [first Figure (e) (
f) (see g)].

This estimated range-limited membership function P abs is also mo
The data are ranked and stored in the memory 10a in the form of a matrix.

(P, , (1) , -..., P, b, (k) ,...
.P-b-(m')) Here, k is a pointer of absolute cuff pressure, as shown in FIG. 2, so it is converted to pointer j of relative cuff pressure using the following 02. Here, Rp
c is the discretization interval or P. , n is the lowest value of the defined range of relative cuff pressure, and if it is defined as -60 to +4QmmHg, it becomes -60mmHg.

j = k + P emin/ Rpc - (1
3) FIG. 1(f) shows the estimated range-limited membership function Pubs (j) converted in this way.

Sr106 determines whether P'(j) calculated at 5T207 is greater than P***.

If this determination is YES, the process branches to 5T207, and if NO, the process branches to Sr108. In 5T207,
Put j and P'(j) into M@mX and P II□8, respectively. 5T208 determines whether j is greater than or equal to m,
If this judgment is NO, branch to Sr103 and YE
In the case of S, the process branches to Sr109.

Regarding the processing of Sr103-208, the judgment of Sr108 is YE.
This is repeated until S is reached, and as shown in Figure 1, a function P' is calculated by multiplying the membership function and the estimated range limited membership function for each parameter AMP, RAV, WID, CON. Its maximum value P□8
It can be said to be a process of extracting.

In 5T209, the relative cuff pressure P3° is estimated from the obtained M m m x and P□8 according to the following measurement formula.

P('* = pc, =-+ (Msxx 1)
X R2C=Q4) Here, P Cll11%...
Rpc is the minimum value of the defined range of relative cuff pressure and the discretization interval, respectively, as described above.

At Sr110, the estimated relative cuff pressure P,' and the current cuff pressure PC (Sr6) are added to give the systolic pressure P. , is calculated.

P svs = P C'-+ PC-O5)
In this example, the estimated range-limited membership function P a
Although bs is a trapezoidal function as shown in FIG. 2, it is not limited to this, and the design can be changed as appropriate.

Further, in this embodiment, multiplication is applied to the logical calculations, but logical calculations such as addition or the like may also be applied, and the design can be changed as appropriate.

(G) As described in detail of the invention, in the electronic blood pressure needle of the present invention, the membership function storage means stores an estimation range limited membership function that limits the estimation range of relative pressure, and the blood pressure value determination means includes: In addition to the selected membership function, this estimation range limited membership function is used to estimate the relative pressure. Therefore, even if the pulse waveform is disturbed due to pressure noise, etc. and some parameters are affected, the obtained blood pressure value is prevented from falling outside the physiological range, which has the advantage of allowing accurate blood pressure measurement. are doing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a membership function 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 showing an estimation range limited membership function of the electronic blood pressure monitor. Figure 3 is a waveform diagram for explaining the pulse wave divisions of the electronic blood pressure monitor, Figure 4 is a waveform diagram for explaining the pulse wave parameter calculation process of the electronic blood pressure monitor, and Figure 5 is a waveform diagram for explaining the pulse wave parameter calculation process of the electronic blood pressure monitor. , a block diagram explaining the configuration of the electronic blood pressure needle, FIG. 6 is a flow diagram explaining the overall operation of the electronic blood pressure monitor, and FIG. 7 is a flow diagram explaining the parameter calculation process of the electronic blood pressure monitor. FIG. 8 is a flowchart explaining the blood pressure value determination process of the electronic blood pressure monitor, FIG. 9(a), FIG. 9, etc.), FIG.
) and FIG. 9(d) are diagrams showing actually measured data for explaining the relationship of pulse wave amplitude, integral level, waveform width ratio, and curvature ratio with relative cuff pressure, respectively. 2: Cuff, 3: Exhaust valve, 4: Pressure pump, 5: Pressure sensor, 7: Bandpass filter, 10: MPU. 10a: memory, Pc: cuff pressure, pcl: relative cuff pressure, AMP
: Pulse wave amplitude, RAV: Integral level, WID: Pulse wave width ratio, CON: Curvature ratio, PIIIGI
' P rav ' P wid ' P can
: Membership function, P, bS : Estimated range limited membership function.

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. For each of the parameters, the membership function storage means stores a membership function whose variables are the relative pressure of the air pressure in the cuff with respect to the blood pressure value, and the pulse wave parameter calculation means calculates the membership function. membership function selection means for selecting a membership function corresponding to each parameter from the membership functions stored in the membership function storage means; and a member for each parameter selected by the membership function selection means. an electronic blood pressure value determining means for estimating the relative pressure and determining the blood pressure value by performing a predetermined logical calculation on the ship function; an estimated range-limited membership function is stored, and the blood pressure value determining means estimates the relative pressure using this estimated range-limited membership function in addition to the selected membership function. Electronic blood pressure monitor.