JP2576451B2 - Electronic sphygmomanometer - Google Patents

Description

The present invention relates to an electronic sphygmomanometer to which a vibration method is applied. More specifically, the sharpness of a negative peak of a pulse wave generated during diastole is maximum. The present invention relates to an electronic sphygmomanometer that sets the cuff pressure at the point of time as a minimum blood pressure value.

(B) Conventional technology Conventionally, an electronic sphygmomanometer to which a vibration method is applied measures a systolic blood pressure value and a diastolic blood pressure value as follows. First,
For example, a cuff is attached to the upper arm of the subject, and the air in the cuff is pressurized by a pump or the like to compress the upper arm and temporarily block the artery.

Next, as the air in the cuff is gradually exhausted at a constant speed, a fluctuation component appears in the air pressure in the cuff (hereinafter referred to as cuff pressure) as shown in FIG. 6 (a). This fluctuating component is called a pressure pulse wave, and a change in the volume in the artery is transmitted to the cuff through the upper arm soft tissue and appears as a pressure change.

This pressure pulse wave is separated by a filtering process [see FIG. 6 (b)], and an amplitude value _AP is calculated [see FIG. 6 (c)]. From the amplitude value _AP column, the maximum amplitude value A _Pmax
Is extracted, and before this maximum pulse wave amplitude value A _Pmax appears, A _Pmax
The amplitude value A _{P 0.7} corresponding to 70% of the above is extracted. Cuff pressure P _C of the A _{P 0.7} appeared at t _0.7 is a systolic blood pressure value SYS.

On the other hand, the maximum pulse wave amplitude value A _Pmax after the appearance, the pulse wave amplitude value A _P
Point A when the transition from a rapid decrease to a slow decrease
_PD is extracted. Cuff pressure P with respect to this A _PD appearance at the time t _D
C is the diastolic blood pressure value DIA.

(C) Problems to be Solved by the Invention Since the above-mentioned conventional blood pressure determination method is only statistical, there has been a problem that the measurement error increases in the case of elderly or hypertensive patients. Also, the change point A of the pulse wave vibration value
_PD has a problem that, depending on the subject, it is often unclear and the diastolic blood pressure value DIA cannot be determined.

The present invention has been made in view of the above, and has as its object to provide an electronic sphygmomanometer capable of accurately and reliably measuring a diastolic blood pressure value.

(D) Means for Solving the Problems In order to solve the above problems, the electronic sphygmomanometer of the present invention has the following configurations i to viii.

i: a cuff; ii: a pressurizing means for pressurizing a fluid in the cuff; iii: a depressurizing means for decompressing the fluid in the cuff rapidly or slowly; iv: a pressure for detecting a fluid pressure in the cuff. Detecting means, v: pulse wave detecting means for detecting a pulse wave at the cuff mounting site, vi: based on the fluid pressure detected by the pressure detecting means and the pulse wave detected by the pulse wave detecting means Vii: the geometrically sharpest valley shape among the valleys of the pulse wave waveform detected by the pulse wave detection means. Viii: the blood pressure value determining means corresponds to the lowest position of the sharpest valley-shaped part extracted by the peak extracting means,
The fluid pressure in the cuff is determined as a diastolic blood pressure value.

(E) Operation The operation of the electronic sphygmomanometer of the present invention will be described below with reference to FIG.

The pressure _Pc of the cuff transmits the soft tissue at the cuff mounting site and reaches the outer wall of the blood vessel. This pressure acts in the direction of applanation vascular, whereas, intravascular pressure P _a is acting in a direction to expand the blood vessels. The two forces, i.e. the force relationship between the cuff pressure P _c and intravascular pressure P _a, the volume V of the vessel is determined. FIG. 5 shows the relationship between the transmural pressure P _t (= P _a −P _c , intra- and extra-vascular pressure difference) and the intra-vascular volume V.

Intravascular pressure P _a is constantly changing, the change alters the intravascular volume V. This internal volume change is transmitted to the cuff through the soft tissue. At this time, since the volume change amount of the cuff is sufficiently smaller than the cuff internal volume, the intravascular volume is considered to be proportional to the cuff pressure change. That is, it can be said that the pressure pulse wave generated in the cuff is substantially proportional to the intravascular volume V.

In FIG. 5, the transmural pressure P _t is shown on the horizontal axis, and the intravascular volume V is shown on the vertical axis. Transmural pressure P _t
Is represented by the following equation using the blood pressure fluctuation component ΔP, the average blood pressure M, and the cuff pressure _Pc .

_{P t = ΔP + M-P} c ... (1) M, P c contributes to the variable operating point of the P _t -V curve. Δ
P is the P _t -V curve is converted into a volume pulse wave. This change in volume can be captured as a pressure pulse wave as described above.

Now, the blood vessel characteristics, as can be seen from Figure 5, when P _t is zero, the change in intravascular volume V with a constant amount change of P _t is maximum. In other words, the transformer Mural pressure P _t is most vessels is soft when the zero.

Accordingly, as shown in intravascular pressure waveform W _4, (in the waveform W _4, FIG. 5 paper leftmost point) diastolic blood pressure point P _t =
0 and when made, negative peaks of intravascular volume converted by P _t -V curve, i.e. the negative peak of the pulse waveform P ₄ which is proportional to the most sharp.

In contrast, when the vessel pressure waveform W ₁ is a state in which almost blood pressure is applanation, against the vessel inner pressure fluctuations,
Less change in intravascular volume, the pulse waveform P ₁ is also negative peak becomes dull. When intravascular pressure waveform W ₆ being reversed, a state where a relatively no resistance blood into a blood vessel flowing again against the vessel inner pressure fluctuations, changes in intravascular volume is small, the pulse waveform P ₆
The negative peak of becomes dull.

Therefore, the cuff pressure at the time when the negative peak of the pulse wave waveform is the sharpest can be determined as the minimum blood pressure value.

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

In this embodiment, the present invention is applied to an arm-band type electronic sphygmomanometer, and FIG. 3 is a block diagram illustrating the configuration of the electronic sphygmomanometer in the embodiment.

Reference numeral 2 denotes a well-known cuff. The cuff 2 includes a pressure sensor (pressure detecting means) 3, a pressurizing pump (pressurizing means) 4, a rapid exhaust valve (depressurizing means) 5, and a slow exhaust valve (depressurizing means). 6 are connected. The output signal of the pressure sensor 3 is read by the CPU 7. Further, the pressurizing pump 4, the rapid exhaust valve 5, and the slow exhaust valve 6 are controlled by the CPU 7.

The CPU 7 has a function of detecting a pulse wave from an output signal of the pressure sensor 3, a function of detecting a sharpest negative peak from the detected pulse wave, and the like. A display 8 such as a liquid crystal display and a start switch 9 are connected to the CPU 7.

 Next, the operation of the electronic blood pressure monitor of this embodiment will be described.

First, the cuff 2 is attached to the upper arm of the subject. And
The start switch 9 is turned on, the pressurizing pump 4 starts operating, and pressurization starts [Step (hereinafter referred to as ST)].
1]. In ST2, the cuff pressure P _c is whether it is equal to the pressurization target value P _s is determined. If this determination is NO,
Branch to ST3.

In ST3, the CPU 7 stops the pressurizing pump 3 and
The slow exhaust valve 6 is opened to start the slow exhaust.

In ST4, the cuff pressure _{Pc (i)} is sampled. The sampling period is usually set to 10 to 50 msec, and i is the number of the sampling point. In ST5, digital sampling processing is performed on the sampled _{Pc (i)} to detect a pulse wave Pw1 _(i) . Further, in ST6, the pulse wave Pw
_{1 (i)} is differentiated to calculate a differential pulse wave Pw _{2 (i)} (see FIG. 1).

In ST7, the differential pulse wave Pw _{2 (i)} is changed to a predetermined threshold Th.
It is determined whether a point _{Cp (n)} exceeding α has been detected. C
_{p (n)} is a point that separates the pulse wave, and if this determination is NO, the process returns to ST4 to continue sampling the cuff pressure _{Pc (i)} . When the determination in ST7 is YES, the process proceeds to the determination in ST8. ST8
Then, it is determined whether or not _{Cp (n)} is equal to Cp ₍₁₎ . If this determination is YES, the process also returns to ST4. This judgment is C
_If the data of _{p (n)} is not two or more, the processing of ST9 and below cannot be performed, and therefore it is provided to determine that there are two or more _{Cp (n)} data.

If the determination of ST8 is YES, and branches to ST9, and detects the minimum value of C _p cuff pressure near the time of the _{(n) C p (i)} , and P _{cc (n).} In ST10, Pcc _(n-1) detected earlier and the current
A straight line L _(n-1) passing between two points of _{Pcc (n )} is calculated. And
From the cuff pressure waveform _{Pc (n-1)} between Pcc _(n-1) and _{Pcc (n)} , the straight line L _(n-1) is subtracted to calculate the pulse wave Pw3 _(i) . (ST11).

As described above, the pulse wave Pw _{3 (i)} is obtained by subtracting L _(n-1) from P _{c (n-1)} because the pulse wave Pw _{1 (i)} detected by digital filtering is obtained. This is because the waveform is inevitably distorted and is not suitable for detecting the sharpest negative peak.

In ST12, Pw _{3 (i)} is cut at the threshold Thβ,
₃ points intersect at dropper of _{(i) t D (n-} 1), detects a point intersect at elevated portion t _{U (n-1).} This Thβ is usually 0.1 to 0.5 mmH
g, but not such an absolute value, the pulse wave Pw
_It may be a relative value of% of the wave height of each peak in _{3 (i)} .

In the next ST13, a time T _(n-1) is calculated from tD _(n-1) to tU _(n-1) and stored. The time T _(n-1) is a variable for evaluating the sharpness of the negative peak, and the smaller the value, the sharper the sharpness.

In ST14, the T _{m (n-1)} by smoothing the T _(n-1) based on the following equation (2).

_{Tm (n-1)} = (T _(n-2) + T _(n-1) + T _(n) ) / 3 ... (2) This is because T _(n-1) is a respiratory arrhythmia or body movement. This is done to reduce these effects, as they are affected by iso-artifacts.

In ST15 and ST16, _{Tm (n-1)} < _{Tm (n-2)} , _{Tm (n-1)} <Tm
It is determined whether or not _{m (n−3). If} both the determinations are YES, the process proceeds to ST17, and if any of the determinations is NO, the process returns to ST4.

In ST17, a minimum value is detected from _{Tm (1) to Tm (n-1)} calculated up to the present time and is set as _TmMIN . In the next ST18, T
The cuff pressure P _c corresponding to _mMIN and diastolic blood pressure P _DIA. Then, the diastolic blood pressure value P _DIA is displayed on the display 8 together with the systolic blood pressure value P _SYS (ST19), and the quick exhaust valve 5 is opened.
The subject's upper arm is released from the pressure (ST20). In addition, since the present invention does not include the determination of the systolic blood pressure value as a main part, the description is omitted.

In the above embodiment, in order to obtain the pulse wave Pw3 _(i) , a straight line L connecting the breakpoints _{Pcc (n-1)} and _{Pcc (n)} is obtained from the cuff pressure waveform _{Pc (n-1). (n-1)} is subtracted. However, as another method, a method as shown in FIG. 2 may be adopted.

In this method, a pulse wave derivative Pw _{2 (i)} is calculated, a threshold Thα is applied to this, a C _{p (n)} is obtained, and a point P _{cc (n)} which divides the cuff pressure P _{c (i)} waveform is obtained. Up to this point, it is the same as the above embodiment. Then P _{cc (n-1)} of the cuff pressure P _{c (i)} waveform, detecting the maximum value P _cp at intervals sandwiched _{P cc (n) (n-} 1). And
A straight line L _(n-1) connecting _{Pcp (n-1)} and _{Pcp (n)} is calculated. The cuff pressure P _{c (i) is calculated} from the interval between P _{cp (n-1)} and P _{cp (n)} of the waveform.
_(n-1) by subtracting the pulse wave Pw ₃ 'then obtain _(i), the pulse wave Pw _3' in _(i), P _{cp (n-1),} a section sandwiched P _{cp (n)} The minimum value Pw _{p (n)} is detected. A point at which the threshold Thβ set on the higher side than Pw _{p (n)} intersects at the descending part of Pw _{3 (i)} is t _{D (n)} , and a point at which it intersects at the ascending part is t _{U (n)} . Then, tU _(n) -tD _(n) is calculated and set as T _(n) .
Hereinafter, the sharpest negative peak is detected based on T _(N) as in the above embodiment.

Further, in the above embodiment, the wristband-type electronic sphygmomanometer is described, but the present invention is also applicable to a finger-type electronic sphygmomanometer using a photoelectric pulse wave.

(G) Effects of the Invention As described above, the electronic sphygmomanometer according to the present invention has a geometrically sharpest valley-shaped portion among the valley portions of the waveform of the pulse wave detected by the pulse wave detecting means. The blood pressure value determining means determines the cuff pressure corresponding to the lowest position of the sharpest valley-shaped portion extracted by the peak extracting means as the lowest blood pressure value. Therefore, there is an advantage that the diastolic blood pressure value can be accurately and reliably determined.

[Brief description of the drawings]

FIG. 1 is a waveform diagram illustrating pulse wave data processing in an electronic sphygmomanometer according to one embodiment of the present invention, FIG. 2 is a waveform diagram illustrating a modification of the same pulse wave data processing, and FIG. FIG. 4 is a block diagram illustrating the configuration of the electronic sphygmomanometer, FIG. 4 is a flowchart illustrating the operation of the electronic sphygmomanometer, and FIG. 5 is a diagram illustrating the relationship between the vascular volume and transmural pressure illustrating the operation of the present invention. FIGS. 6 (a), 6 (b), and 6 (c) are diagrams illustrating the relationship between blood pressure values of a conventional electronic sphygmomanometer. 2: Cuff, 3: Pressure sensor, 4: Pressurizing pump, 5: Quick exhaust valve, 6: Slow exhaust valve, 7: CPU.

Claims (3)

(57) [Claims] 1. A cuff, a pressurizing means for pressurizing a fluid in the cuff, a pressure reducing means for rapidly or very slowly reducing the fluid in the cuff, and a pressure detecting means for detecting a fluid pressure in the cuff. A pulse wave detecting means for detecting a pulse wave at a position where the cuff is attached, and a blood pressure for determining a blood pressure value based on the fluid pressure detected by the pressure detecting means and the pulse wave detected by the pulse wave detecting means. An electronic sphygmomanometer comprising a value determining unit, wherein a lowest position of a geometrically sharpest valley-shaped portion is extracted from valley portions of a pulse wave waveform detected by the pulse wave detecting unit. The blood pressure value determining means comprises a peak extracting means,
An electronic sphygmomanometer, wherein a fluid pressure in the cuff corresponding to a lowest position of the sharpest valley-shaped portion extracted by the peak extracting means is determined as a minimum blood pressure value. 2. The negative peak point detecting means for detecting a lowest position (negative peak point) of a geometrically sharpest valley-shaped part in a valley part of a waveform of each pulse wave. When,
With reference to the level of the detected negative peak point, an intersection detecting means for detecting a point where a predetermined level line and each pulse wave intersect, and a time measuring means for measuring a time between the intersections sandwiching each negative peak point. The electronic sphygmomanometer according to claim 1, wherein the lowest position of the sharpest valley-shaped portion is extracted based on the measurement time. 3. A negative peak point detecting means for detecting a lowest position (negative peak point) of a geometrically sharpest valley-shaped portion in a valley portion of a waveform of each pulse wave. When,
An intersection detecting means for detecting an intersection between a level drop portion of each pulse wave and a level line higher by a predetermined level than the level of the negative peak point, and an intersection between a level rise portion of each pulse wave and the level line; And a time minimum value extracting means for extracting a minimum value of the time, and a cuff pressure corresponding to the extracted time minimum value. 2. The electronic sphygmomanometer according to claim 1, wherein the electronic sphygmomanometer determines the minimum blood pressure value.