JPS62270133A - Indirect lowest blood pressure measuring method by cuff vibration method - 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 C Industrial Field of Application] The present invention relates to an indirect diastolic blood pressure 1jll method using a cuff excitation method. The purpose is to obtain a new method for measuring diastolic blood pressure based on the principle of volume oscillation method.

[Conventional technology]

The blood pressure measurement method using the volumetric vibration method, which is generally performed by attaching a cuff to the subject's finger or arm, takes advantage of the strong nonlinearity of the pressure-volume characteristics of blood vessels. Pressure on the wall (Lransmural p
Based on the mechanical property of blood vessels that the compliance of blood vessels is maximum when stress (abbreviation: Pt) is zero, the extravascular pressure (cuff pressure Pc) is equal to the mean internal pressure (mean blood pressure Pa
m), the volume pulse wave ΔV was at its maximum, and it was possible to determine the mean blood pressure. The fact that the compliance of the blood vessel at pt=o is maximum in a wide frequency range is that
The river is clear.

[Problems to be solved by the invention] In the conventional mean blood pressure measurement method using the volume oscillation method, the compliance of the blood vessel reaches its maximum when the blood vessel wall is in an unloaded state, that is, when the pressure (Pt) applied to the blood vessel wall is zero. Taking advantage of this fact, the amplitude of the plethysmogram reaches its maximum value when the cuff pressure matches the mean blood pressure.

However, in the blood pressure measuring method using the volumetric oscillation method described above, although it was possible to measure the systolic blood pressure and the mean blood pressure, it was not possible to measure the diastolic blood pressure. Therefore, in order to measure the diastolic blood pressure, the diastolic blood pressure is calculated from the systolic blood pressure and the mean blood pressure using an arithmetic function, but the actual situation is that the calculated value is not necessarily appropriate.

[Means for Solving the Problems] Therefore, in order to achieve the object and solve the problems of the prior art, the present invention uses the volume pulse wave method in the indirect diastolic blood pressure measurement method using the cuff vibration method. Based on the volume oscillation method used, when a sinusoidal pressure with a frequency of about 10 Hz is superimposed on the pressure cuff, the pressure applied to the arterial blood vessel wall is determined by superimposing the excitation component of the cuff pressure on the blood pressure waveform, and here When the DC component of the cuff pressure is changed and the average pressure applied to the blood vessel wall becomes zero during diastole, the blood vessel compliance reaches its maximum and a diastolic volume pulse wave corresponding to the excitation component of the cuff pressure is generated. The amplitude of the cuff is maximized, and the diastolic blood pressure is measured from the DC component of the cuff pressure corresponding to this time.

〔Example〕

■ Basic principle In the conventional mean blood pressure measurement method using the volume oscillation method, the cuff pressure (
The method utilized the fact that the amplitude of the plethysmogram (ΔV) reaches its maximum value when Pc) matches the average blood pressure (Pam). By utilizing the nonlinearity of the pressure-volume characteristics of the vascular system, in which the compliance is maximum at Pt=OmmHg, the diastolic blood pressure can also be measured by the following method.

Figure 1 shows blood pressure waveform (Pa), Figure 2 shows cuff pressure (Pc),
Figure 3 shows transmural pressure (
Pt).

Cuff pressure (Pc) is DC (direct current) component pressure (Pc)
It is assumed that (AC) component pressures (ΔPc) are superimposed.

At this time, since Pt-Pa-Pc, Pt is in a state where an AC component is superimposed on the blood pressure pulse wave. This AC component is added to ■ as a sine wave whose frequency is sufficiently thicker than the fundamental frequency of the pulse wave, (Pc=Pc+ΔPc), and Pc is Qm
Suppose that it increases from mHg.

At this time, pt becomes Pt=Pa-Pc-ΔPc, and as shown in FIG. 4, the AC component of the constant amplitude of the pressure pulse wave is shifted in the linear axis direction while being superimposed.

■ Example 1 Figure 4 shows the pressure (P
t) shows the mechanism of occurrence of a change in the amplitude of the plethysmogram due to a change in t). A photoelectric plethysmography sensor and a pressure cuff (
2) When wearing the cuff (Figure 6), the pressure of the attached cuff (Pc
), when a sinusoidal pressure (ΔPc) of about 10 Hz is superimposed on the pressure (Pt) applied to the blood vessel wall, the AC component of the cuff pressure is superimposed on the blood pressure waveform. Here, cuff pressure (Pc)
When the pressure (Pt) applied to the blood vessel wall during diastole reaches zero (the maximum blood vessel compliance) (Fig. 4 (G)), the excitation component of the cuff pressure (ΔP) changes.
The amplitude of the photoplethysmogram corresponding to c) is maximum, and the diastolic blood pressure is indirectly measured from the corresponding average value (Pc) of the cuff pressure at this time.

In the present invention, the validity of the principle was confirmed through a large carotid artery model experiment and comparison with a direct method using domestic rabbits. In addition, in the fifth review, an example of the records obtained by implementing the present invention on the right middle part of a 22-year-old male is shown. When the hand cuff pressure (Pc) is excited only during the diastole and gradually increased, the amplitude of the excitation frequency component (PCAC) superimposed on the diastole of the photoplethysmogram (PG) is P
The maximum value is reached at c=72+nHg, which is determined to be the diastolic blood pressure value (Pcd) according to the present invention.

On the other hand, the maximum amplitude point of the -heartbeat amplitude of photoplethysmography (PG) is the mean blood pressure (Pcm), and the vanishing point of PG is the systolic blood pressure (Pcm).
cs) is determined as in the conventional volume vibration method.

In addition, the accuracy study of the present invention takes the base of the middle finger of the right hand of an adult as a measurement object, and compares it with the diastolic blood pressure value (Pkd) measured by the auscultation method (fifth point) on the left upper arm.
=1.131'kd -17,1<r =0.837)
I got it.

Example 2 In the experiment shown in FIG. 8, the cuff (2) shown in FIG. 7 is attached to two fingers of a subject, and a photoplethysmographic sensor is attached to the finger (B). Furthermore, without attaching an optical Tg or a pulse wave sensor to the finger (A), the cuff is continuously vibrated at a constant frequency and amplitude under an appropriate average cuff pressure. That is, by externally vibrating a blood vessel that is anatomically located relatively close to it, an excitation component is superimposed on the internal pressure around the blood vessel.

According to this method, as in the first embodiment, it is possible to cause the pressure (Pt) applied to the blood vessel wall to have a high frequency component.

Then, add an excitation component to the intravascular pressure with the finger (A),
When the cuff pressure of the finger (CB) is statically reduced (or increased), the blood pressure is measured by focusing on the superimposed component of the diastolic portion of the photoplethysmographic signal (PGAC) of the finger (B).

(2) Next, the system used to carry out the present invention is as follows.

First, as shown in the block diagram shown in FIG. 6, the main elements are (a) photoplethysmogram detection unit +11, (0) finger pressurization cuff (2), and (c) cuff pressurization and pressure detection unit ( 3) and (d) a recording section (4).

Each of its main elements will be explained in detail below.

(B) About the photoplethysmogram detection unit (1) The photoplethysmographic sensor uses [, ED,
Three phototransistors are connected in series, and two phototransistors are connected in parallel to the light receiving section. The phototransistor and LED are insulated by molding with a plastic material.

Further, the arterial intravascular volume change detection section is a circuit that receives and amplifies the charge flow change received by the optical sensor. The detection unit has two components: a DC (direct IJt) amplifier that detects the amount of transmitted light and an AC (alternating current) amplifier that detects changes in the amount of transmitted light.
It consists of two parts.

The DC amplifier detects the DC component of the photocurrent, that is, the amount of transmitted light, and detects the average light-receiving illuminance of the phototransistor corresponding to the change in intravascular volume caused by the adjustment of the bias pressure of the cuff pressure.

- A high cut-off frequency of 2° to 5 Hz, so as to have a frequency band that provides an average amount of transmitted light between heartbeats.
It is composed of the following high-pass cutoff filter, and is used in an AC amplifier to detect the AC component of photocurrent, that is, the change in the amount of transmitted light. The intravascular volume waveform detected photoelectrically changes according to the pulse pressure waveform of blood pressure itself. For this reason, faithful reproduction of photoelectric volume waves requires a band in which all frequency components of the blood pressure waveform can be detected.

It is said that the pulse pressure waveform can be reproduced if components up to a frequency up to eight times the fundamental frequency (corresponding to the heart rate) can be effectively detected.

Considering that the upper limit of normal heart rate is about 3112, the minimum heart rate is about 2
A frequency of 5Hz or higher is required. In this embodiment, the low-pass cut-off filter uses an amplification 2 with a bandwidth of 0.4 to 30 Hz (-3 dB) and has high-pass d-cut filter characteristics.

([]) Regarding the cuff for pressurizing fingers (2), FIG. 7 shows the configuration of the cuff for pressurizing fingers using the finger as the measurement target site.

Regarding the shape and dimensions of the cuff, if the finger is considered to be a cylinder, in order to accurately transmit cuff pressure at the center of the cuff to the measuring finger (arterial blood vessel), the cuff width must be at least 1.2 times the diameter of the object to be measured. It is said that In this example, we will consider attaching an optical sensor.
C, the sensor attachment part is set to 1.5 times the finger size. Furthermore, in order to maintain good characteristics of the :h control system in cuff excitation and to reduce the air capacity of the cuff, two types of cuffs are used depending on the finger diameter of the subject.

(c) Regarding the cuff pressurization and pressure detection unit (3), a micro pump (discharge 111ii 7) is used as a compressor.
(1/min'J discharge pressure 380 mmftg), and an air tank with a capacity of 240 cc was inserted in series to smooth out the pulsation of air pressure.

Furthermore, the pressurization base rate signal generating section generates a target value signal in the col system using air pressure control for excitation of the cuff pressure. The signal required by the cuff excitation method is a DC bias superimposed with an AC component, and the DC bias needs to rise and fall at a constant rate. The AC component was a sine wave signal, which was synthesized into a triangular wave forming circuit that can rise and fall at a constant speed. In this embodiment, the pressurization (!-) is caused by an increase in the vibration frequency, amplitude, and DC bias.
It has a function to change each parameter of descending speed.

Furthermore, in the leak valve unit, the cuff excitation method requires that a pulse pressure component of a constant frequency and constant amplitude be superimposed as the cuff pressure Pc, and that the pressure be increased or decreased at an arbitrary speed. Therefore, in this embodiment, a leak valve for cuff pressure control using a speaker is used.

The leak valve of this embodiment uses a full range speaker with a diameter of 7 cm as a driving section. An acrylic head is glued to the center dome of the speaker, and a steel ball is sandwiched between the base and the nozzle at the end of the conduit, which serves as the cuff, pressure sensor, and compressor parts. The steel ball moves up and down as the speaker cone moves up and down, and the amount of air leak changes as the partition area between the nozzle and the steel ball changes.

On the inflow side from a part of the compressor, a pipe resistance element can be varied via a needle valve.

It has been confirmed that the error in cuff pressure due to conduit resistance and dynamic pressure between the pressure transducer and the cuff is less than 11 g per 1 m by simultaneous measurement with the pressure transducer directly connected to the cuff. The pressure quadrature transducer uses a diffusion type semiconductor pressure quadrature transducer.

Next, the leak valve unit PID control device controls the signal from the pressure quadrature transducer that detects the cuff pressure by applying negative feedback to the drive circuit of the speaker of the leak valve unit.

The cuff pressure is determined by the difference between the reference signal from the pressurization reference signal generator and the signal from the pressure transducer.
ID control is performed to superimpose a low-distortion sine wave pressure of a constant frequency and constant amplitude on the bias pressure.

Figures 9 and 1O show the frequency characteristics of the cuff pressure of this leak valve unit during oven loop and PID compensation.The DC component of the cuff pressure when measuring the 0 frequency characteristic is 100 m
m1g, the amplitude of the excitation component is ±lQmml at 0.25Hz
It was set as 1g. In this characteristic test, an acrylic cuff was used instead of an actual hand, but the cuff air capacity of the hand was 4,
It was set to 8cc.

Incidentally, when the DC component of the cuff pressure was 501111 g, a frequency characteristic similar to that shown in the figure was obtained.

In addition, Fig. 11 shows the DC cuff pressure at an excitation frequency of 80Hz.
The cuff pressure waveform in components 50 to 180 ml is shown.

The cuff air capacity was also 4.8 cc.

(d) Recording section (4) During measurement, a memory recorder is used to record waveforms, and a three-phenomenon onroscope is used as a monitor during measurement.

〔Effect of the invention〕

Since the present invention has the above configuration, the phenomenon in which the compliance of the arterial blood vessel reaches its maximum when the intravascular pressure and the external pressure (cuff pressure) are equal in the basic principle of the volume oscillation method is realized in a wide frequency range. By using the cuff vibration method, it is possible to indirectly determine the diastolic blood pressure independently of the systolic blood pressure and the mean blood pressure.

By implementing the method of the present invention, long-term blood pressure measurement at regular intervals is realized, and it is also useful in clinical fields such as blood pressure management of outpatients, determining when to administer antihypertensive drugs for hypertensive patients, and understanding their effects. It is novel and useful in the field of chronobiology and as a research tool in blood pressure biofeedback.

[Brief explanation of the drawing]

The drawings show an example of the indirect diastolic blood pressure measurement method using the cuff vibration method according to the method of the present invention. 1 shows a blood pressure waveform, FIG. 2 shows a cuff pressure, FIG. 3 shows a change in pressure applied to a blood vessel wall, and FIG. 4 shows a waveform showing a mechanism of a change in the amplitude of a volume pulse wave. FIG. 5 is a waveform showing an example of waveform recording, FIG. 6 is a block diagram showing a system used to carry out the method of the present invention, FIG. 7 is a longitudinal cross-sectional view of a hand pressure cuff, and FIG. 8 is shown in FIG. A perspective view showing another example of the cuff excitation means in the measurement method, and Fig. 9 and Fig. 1O are graphs showing the frequency characteristics of the cuff pressure of KHARUBU UNINOTO. In the graph, fat in the same figure shows the swing-first characteristic, and Cb) in the same figure shows the phase characteristic. Figure 10 is a graph of the frequency characteristics during leak valve PID compensation, ia) in the same figure shows the amplitude characteristics, and Figure 11 shows the graph of the cuff pressure excitation waveform sample at a frequency of 80 Hz. (1)...Photoelectric plethysmogram detection section (2)...
・・Cuff for pressurizing fingers 3)・・・Cuff pressure and pressure detection part (4)・・・・
・Recording department

Claims (1)

[Claims] Based on the volume vibration method using the volume pulse wave method, when a sinusoidal pressure with a frequency of about 10 Hz is superimposed on the pressurizing cuff, the pressure applied to the arterial blood vessel wall includes an excitation component of the cuff pressure in the blood pressure waveform. Then, the DC component of the cuff pressure is changed, and during diastole, when the DC component of the pressure applied to the blood vessel wall becomes zero, the blood vessel compliance reaches its maximum and corresponds to the excitation component of the cuff pressure. An indirect diastolic blood pressure measurement method using a cuff excitation method, which is characterized in that the amplitude of the diastolic plethysmogram is maximized, and the diastolic blood pressure is measured from the DC component of the corresponding cuff pressure.