JPS61265127A - Apparatus for continuously measuring blood pressure - 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 (Field of Industrial Application) The present invention relates to a continuous blood pressure measuring device, and more particularly to a continuous blood pressure measuring device that can easily measure blood pressure indirectly and continuously.

(Prior art) The desire for quantitative and simple follow-up measurement of blood pressure response is desired from the viewpoint of biological stress testing, especially circulatory system function tests (evaluation of arterial blood vessel elasticity, etc., and examination of rapid blood pressure fluctuations). It is extremely strong in a wide range of fields, and its immediate realization is awaited.

Conventionally, there has been a desire for a method to continuously measure blood pressure using an indirect method without causing mental stress such as pain or discomfort to the person being measured, and without invading the living body. A measurement method based on the volume compensation method has been proposed.

This method basically applies cuff pressure to the finger area, and sequentially feedback-compensates the cuff pressure using external pressure so that the arterial vascular bed volume at this area becomes a constant value corresponding to the unloaded state of the blood vessel wall. The cuff pressure required for volume compensation is measured as intravascular pressure (blood pressure).

Specifically, a rigid chamber into which the finger to be measured is inserted is filled with a fluid such as water, a light emitting element and a light receiving element are provided on opposite sides of the inner surface of the chamber, and light from the light emitting element passes through the oriented blood vessel. By detecting the emitted light with a light-receiving element, the blood volume (volume 81) and pulse wave in the canal were measured. Such photoelectric measurement utilizes the fact that hemoglobin contained in blood (red blood cells) has a strong absorption band in the visible light region.

(Problem to be solved by the invention) However, in this method, a chamber is filled with fluid to control cuff pressure application, and the pressure of this fluid is controlled by a bellows connected to one side of the chamber that vibrates and expands and contracts using a diaphragm. Since the adjustment is made by doing this, the entire device becomes large and heavy, making it unsuitable for, for example, measuring blood pressure during interlocking, and is also inconvenient to carry. Furthermore, in order to expand and contract the bellows, an electromagnetic sliding adjustment (electromagnetic pressurizer) including a spring is required, which results in an even larger size and electric resistance welding.

The present invention has been made in view of these points, and it is an object of the present invention to provide a continuous blood pressure measuring device that has an extremely simple structure and can be made smaller and lighter.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a chamber into which a test site is inserted, a gas supply means for filling the chamber with gas, and a gas supply unit for filling the test site with gas. a photoelectric detection means for photoelectrically detecting a change in volume that varies with a pulsating change in blood pressure of a blood vessel; a comparison means for comparing an output signal from the photoelectric detection means with a reference signal; and an output of the comparison means. and an adjusting means for controlling the flow of gas from the chamber based on the pressure of the gas, and the pressure of the gas is measured as blood pressure.

(Function) In this invention, while adjusting the cuff pressure with gas,
Since the solenoid valve is driven and controlled by duty factor controlled pulses, no special mechanical pressurizing means is required.
Moreover, a small solenoid valve can be selected, and the measuring device can be made much smaller and lighter.

(Embodiment) FIG. 1 is a block diagram showing the basic configuration of the present invention.

In the figure, reference numeral 1 denotes an annular chamber, into which a part to be measured, for example, a finger 2, is inserted as shown in FIG. A light emitting element 1 such as an LED 3 and a light receiving element such as a transistor 4 are provided on opposing surfaces in the chamber 1 with the finger 2 in between.

7 Leon gas at a pressure of 1.8 atmospheres is always supplied to the chamber 1 from a Freon gas pump 5 as a gas at a constant pressure via a fixed throttle valve 6, and is applied as cuff pressure. Freon gas is suitable for use because it is stable, non-toxic and non-flammable.

The light signal transmitted through the blood vessel of the finger 2 or the like detected by the light receiving element 4 indicates a change in the blood flow volume of the blood vessel based on the absorption characteristics of hemoglobin in the blood as described above, and is amplified by the direct current (DC) amplifier 7. After that, the AC
) A comparator 14 compares the level with a reference level set by an initial setter 13 consisting of an amplifier 9, a peak detector 10, a low-pass filter 11, and a sample-and-hold circuit 12. The comparison result is then sent to the pulse width modulation (PWM) circuit 15.

On the other hand, the Freon gas sent into the chamber I is supplied to the electromagnetic valve 17 via the switching valve 16. This electromagnetic valve 17 adjusts the pressure (cuff pressure) in the chamber 1 by changing its opening/closing ratio using a pulse whose duty factor is controlled from the PWM circuit 15.

A pressure cadence transducer 18 is provided in a branch pipe on the upstream side of the switching valve 16.
8, the cuff pressure during measurement is converted into an electrical signal, and the recorder 19
and record it as a change in blood pressure. The circuit associated with the pressure transducer 18 is equipped with a low-pass filter (not shown) in order to remove high frequency components generated by the operation of the solenoid valve 17.
It has a built-in LPF) and notch filter.

Further, the switching valve 16, together with the initial setting device 12 and the fixed throttle 20, is used to initialize the target value of the servo 11 for volume compensation, and at the time of initial setting, the supply of Freon gas to the solenoid valve 17 is stopped. It is supplied only to the fixed iris 20. In this initial setting, the intravascular volume at which the volume pulse wave component corresponding to pulse pressure fluctuations becomes maximum is preset.

The intravascular volume is detected by measuring the transmitted infrared rays from the light emitting element 3 using the light receiving element 4.

FIGS. 3(A), (B), (C) and (D) show the cuff pressure due to Freon gas, the photoplethysmographic signal, the pulse wave component and the low frequency component.

Referring to the figure, when the cuff pressure caused by Freon gas is gradually reduced from a pressure sufficiently higher than the systolic blood pressure using the fixed squeezer 20, a sinusoidal fluctuation component (pulse component) superimposed on the photoelectric volume signal appears at a certain point. do. As is clear from the principle of volume compensation, the cuff pressure at this point of appearance corresponds to the systolic blood pressure. Furthermore, when the cuff pressure is reduced, the low frequency component of the photoelectric volume signal drops almost linearly, and the pulse wave component reaches a maximum at a certain point. Since the cuff pressure at this point corresponds to the average blood pressure, it is sufficient to preset the low frequency component of the photoelectric volume signal at that time.

The electrical operation will be explained in more detail using FIGS. 1 and 4.

Now, if the cuff pressure is gradually lowered as shown in Fig. 4 (A), the detection signal from the light receiving element 4 (Fig. 4 (B)
) passes through the DC amplifier 7, and one signal passes through the AC amplifier 9, leaving only the pulse wave component (Fig. 4 (C)). The peak is detected by the peak detector IO (Fig. 4 (D)). )) and outputs the corresponding signal (FIG. 4(E)).

The output of the DC amplifier 7 is also passed through a low pass filter (LPF) 11.
A signal indicating the average amount of transmission is output. When this signal is sampled by the sample-hold circuit 13 using the peak value signal of the pulse wave component from the peak detector 10 as a trigger, it corresponds to the blood pressure value of the control target value and is output as a reference signal to an external circuit.

When the initial settings are completed in this manner, the switching valve 16 is switched to the electromagnetic valve 17 side, and the switch 8 is turned off, thereby completing preparations for automatic blood pressure measurement.

The transmission amount signal from the light receiving element 4 is supplied to a comparator 14,
It is compared with the reference signal from the sample and hold circuit 13,
The comparison result (deviation (difference) between the transmission amount signal and the reference signal) is sent to the PWM circuit 15. The pulse width modulation circuit 15 controls the duty factor of the pulse of a predetermined period based on the comparison result, and controls the cuff internal pressure by controlling the opening/closing ratio of the electromagnetic valve 17 using the pulse width-controlled pulse.

In the embodiments described in 1-1 below, the fingers and fingers were tested, but since the present invention is small and lightweight, measurements can be easily performed on other peripheral parts as well.

For example, the chamber can be attached to the concha as shown in FIG. In Figure 2, changes in blood volume were measured using a transmission photoplethysmography method that measures the amount of transmitted light, but in this example, changes in the amount of reflected light are measured taking into account the thickness of the living body's sevcent (concha). It uses reflection photoplethysmography. That is, a light-emitting element (for example, an LED) 22 and a light-receiving element (phototransistor) 23 are arranged side by side on one side of the concha part 21, and a chamber l is connected to the opposite part through the test part of the concha part 21. is provided and cuff pressure is applied with a supply of Freon gas.

Furthermore, visible light or red light is used as the light used in the photoplethysmography method in the above embodiments.

Furthermore, it is clear that other gases may be used instead of Freon gas for applying cuff pressure.

FIG. 6(A) shows the measurement data obtained in the above manner. The data obtained in this way is filtered using a low-pass filter to remove frequency components of 30 Hz or more generated by the operation of the solenoid valve 17, and the measured data is shown in Figure 6 (B
) is shown.

Here, it is assumed that the blood waveform does not include frequency components of 20 Hz or higher.

(Effects of the Invention) As explained above, in this invention, cuff pressure is applied using gas pressure, and no special mechanical pressure means is required. However, a suitable means of pressurization is required.

In this invention, gas can be compressed and stored in a small container, and the pressure of this gas can be used as cuff pressure, making it extremely easy to reduce the size and weight.

Further, in the present invention, cuff pressure is adjusted by a miniature solenoid valve using pulses controlled by a duty factor, which particularly facilitates miniaturization and weight reduction, making it possible to carry and use the device. In addition, the present invention allows measurement at various sites, and is particularly easy to measure at peripheral sites, so it has a wide range of medical applications, such as measurement during exercise.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a schematic diagram of a test subject (hand and finger) according to an embodiment of the invention, and Figs. 3 (A) -
(D) and FIGS. 4(A) to (G) are timing charts for explaining the servo target standard setting in this invention, and FIG. FIGS. 6(A) and 6(B) are diagrams of the photoelectric signal obtained according to the present invention and the blood pressure waveform obtained by signal processing the photoelectric signal. l...Chamber 2...Finger 3.22...Light emitting element 4.23...Light receiving element 5...Freon gas cylinder 6.20...Fixed squeezer 7...DCklIIg device 9... AC amplifier lO... peak detector 11... low pass filter (LPF) 13... sample hold circuit 14... comparator 15... pulse width modulator 16... switching valve 17... ...Solenoid valve 18...Pressure transducer 19...Recorder 21...Ear concha

Claims (2)

[Claims] (1) A chamber into which the test site is inserted, a gas supply means for filling the chamber with gas, and a photoelectric system that measures changes in volume that vary with blood pressure pulsation changes in the blood vessels of the test site. comprising: a photoelectric detection means for detecting, a comparison means for comparing an output signal from the photoelectric detection means with a reference signal, and an adjustment means for controlling the flow rate of gas from the chamber based on the output of the comparison means, A continuous blood pressure measuring device, characterized in that the pressure of the gas is measured as blood pressure. (2) The adjustment means includes a pulse width modulation means that controls and outputs a duty factor of a pulse of a predetermined frequency based on the output of the comparison means, and a pulse width modulation means that adjusts the opening/closing ratio according to the pulse from the pulse width modulation means. 2. The blood pressure measuring device according to claim 1, further comprising a controlled solenoid valve.