JPS6122565Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blood pressure monitor, such as an automatic digital blood pressure monitor.

Conventionally, in blood pressure monitors such as automatic digital blood pressure monitors that have a built-in pressurizing means such as an electric pressure pump, there is a gap between the cuff band wrapped around the arm of the person being measured and the pressurizing means. In the past, pressure was applied through a tubular body like a rubber tube. Therefore, the air resistance of the tube cannot be ignored, especially when pressurizing, and the pressure difference becomes large between the internal pressure of the cuff band and the pressure detected by the pressure detection means, and as a result, when pressurization is stopped, the internal pressure of the cuff band and the pressure Since the pressure applied to the detection means was balanced, the detected pressure of the pressure detection means tended to decrease slightly. For this reason, when looking at the display on the display, the pressure once increased drops when pressurization is stopped, which is a problem for the user. In addition, in the case of manual pressurization control, the method is to pressurize and measure until the pressure is 30 to 40 mmHg higher than the normal systolic blood pressure value, but it is necessary to take into account the aforementioned pressure drop. This made it difficult to determine the timing to stop pressurization.

Therefore, a plate with small holes equal to the air resistance during pressurization from the cuff band to the pressure detection means was installed at the entrance of the pressure detection means to suppress the pressure during pressurization, thereby eliminating the above-mentioned drawbacks. A similar method was proposed, but the diameter of the small holes was small and there were concerns about clogging.

This invention was created in view of the above-mentioned drawbacks.
The purpose is to provide a blood pressure monitor that can display the same value as the internal pressure of the cuff band.

The present invention will be explained below with reference to examples. FIG. 1 is a circuit block diagram of one embodiment, and FIG. 2 is a diagram explaining the principle of the present invention. 1 is the cuff belt, this cuff belt 1
Pressurized air is sent through the tube body 2 from an electric pressurizing pump of the pressurizing means 3. The pressurizing means 3 consists of an electric pressurizing pump, a slow exhaust valve, a rapid exhaust valve, etc. A diaphragm 4 communicates with the cuff band 1 through a tube, and is designed to detect the internal pressure of the cuff band 1 (cuff pressure) and drive the core of the differential transformer 5. The oscillation output of the oscillation circuit 6 is applied to the primary side of the differential transformer 5, and the voltage signal serving as the secondary output thereof is changed in accordance with the displacement of the core. 7 is a rectifier circuit, and this rectifier circuit 7 rectifies the secondary output of the differential transformer 5. 8 is a holding circuit for holding the lower limit value of the ripple of the rectified output of the rectifier circuit 7, and a diode 9 in the opposite direction to the rectified output
, a resistor 10 , and a capacitor 11 charged by the power supply +V through the resistor 10 , and is connected between the rectifier circuit 7 and the A/D conversion circuit 12 . The operational role of this holding circuit 8 is as follows. That is, when the cuff band 1 is wrapped around the upper arm a and pressurized air is sent by the electric pressurizing pump of the pressurizing means 3,
The generated pressure increases the overall pressure while having pulsations as shown by curve A in Figure 2. Compared to this, the pressure within the cuff band 1 rises with a slight delay due to the resistance of the tube body 2, etc., as shown by the curve shown in FIG. On the other hand, if the rectified output of the rectifier circuit 7 corresponding to the displacement amount of the diaphragm 4 connected to the tube body 2' on the pressurizing means 3 side is directly A/D converted and displayed digitally, the pulsation Therefore, there is a problem that the output decreases at the same time as the pressurization is stopped, and the displayed value decreases. Here, the line connecting the lower limit of pulsation and the cuff band 1
It is clear from FIG. 2 that the increase in pressure within In other words, since the pressurizing means 3 is connected to the cuff band 1 via the tube body 2 such as a rubber tube, the pressure of the pressurizing means 3 is equal to (pressure of the cuff band 1 + flow path resistance of the tube body 2). Air flows into the cuff band 1 only after the air overcomes the pressure, and there is a time lag in which the pressure in the cuff band 1 rises, so when the pressure in the pressurizing means 3 settles down to a low level, that is, the lower limit of the pulsation shown by curve A in Figure 2. The pressure of this value can be considered to be approximately the pressure of the cuff band 1. Even if the pressure starts to rise from this point, the pressure within the cuff band 1 will rise with a delay. Here, the difference between the C curve and the B curve in FIG. 2 is considered to be equal to the pressure due to the flow path resistance, and the difference between the lower limit value of the B curve and the B curve is actually smaller than shown in the figure. Thus, the holding circuit 8 which holds and outputs the lower limit value of the ripple portion of the rectified output corresponding to the pulsation can generate an output approximately equal to the pressure rise within the cuff band 1 described above. The diaphragm 4, the differential transformer 5, the oscillation circuit 6, the rectifier circuit 7, and the holding circuit 8 constitute a pressure detection means. 12 is A/D
This A/D converter 12 is a converter for converting the output of the holding circuit 8 into a digital signal, and the digital output is input to a logic circuit 13 consisting of a microcomputer etc. This is for controlling the operation of the entire device, for example, calculating data from the A/D converter 12 according to a program, and reading the systolic blood pressure value and diastolic blood pressure value based on the output of the Korotkoff sound detector 15. , these blood pressure values are stored and displayed digitally on the display 14, or the pressurizing means 3 is controlled based on the pressure data of the cuff band 1 obtained from the pressure detecting means.

However, as shown in Figure 1, the cuff band 1 is attached to the upper arm a.
After that, the power switch and the measurement pushbutton switch are turned on in sequence, and when the measurement pushbutton switch is turned on, an output signal is generated and a reset pulse is generated. The logic circuit 13 then drives the electric pressurizing pump of the pressurizing means 3 to feed pressurized air into the cuff band 1. As the pressure in the cuff band 1 increases, the diaphragm 4 is displaced, and this amount of displacement results in a change in the output of the differential transformer, which in turn appears at point A in FIG. 1 as a change in the rectified output. In the holding circuit 8, the capacitor 11 is about to be charged from the power supply +V through the resistor 10, but when the rectified output appearing at the point A falls to the lower limit of the ripple, the potential at the point B of the capacitor 11 changes to the diode of the charge of the capacitor 11. 9 and becomes equal to the potential at point A. On the other hand, the voltage at point A will then rise towards the upper limit of ripple, but as shown in Figure 3, the potential at point B will rise slowly because capacitor 11 is charged through resistor 10. , the rising curve to the voltage corresponding to the lower limit of the next ripple is approximately at cuff band 1 shown by curve C in Figure 2.
is equal to the pressure curve within. Even if the rise is too large, discharge will occur at the lower limit of the next ripple, and a holding output approximately equal to the desired rise in cuff pressure will be obtained. The updated pressure display on the display 14 therefore accurately indicates the pressure within the cuff 1. Said cuff band 1
In the cuff band 1, where the internal pressure of
mmHg, and when the logic circuit 13 detects that the cuff pressure has reached the above 120 to 130 mmHg based on the output of the pressure detection means, the logic circuit 13 The drive of the electric pressure pump is stopped by the output of 13. On the other hand, when the drive of the electric pressure pump is stopped, detection and determination of Korotkoff sound is performed, and if Korotkoff sound is detected, the drive of the pressure pump is restarted. Here, in the detection and determination of Korotkoff sounds, a blood pressure signal collected at the cuff band 1 is converted into an electrical signal by the Korotkoff sound detector 15, and recognition and determination is performed by the logic circuit 13.
The above-described repressurization drive is then performed intermittently until the Korotkoff sound is no longer detected. When the cuff band 1 is sufficiently pressurized and the artery b is completely occluded, the Korotkoff sound is no longer detected, and the logic circuit 13
As a result, the slow exhaust valve of the pressurizing means 3 is driven to open, and the air pressure in the cuff band 1 is reduced to, for example, 2 to 3 mm.
Cuff band 1 is gradually exhausted at a rate of about Hg/sec.
pressure is gradually being reduced. When the first Korotkoff sound from the start of decompression is detected and determined,
The logic circuit 13 stores and holds the pressure value A/D converted by the A/D converter at that timing, and displays the pressure value on the display 14 as the systolic blood pressure value. Then, the pressure reduction continues and the final Korotkoff sound is detected and determined. The pressure value A/D converted by the A/D converter 12 at that timing is stored and held, and the pressure value is displayed on the display 14 as the diastolic blood pressure value. and logic circuit 1
Step 3 determines that the blood pressure measurement has been completed, opens the rapid exhaust valve of the pressurizing means 3, rapidly reduces the pressure in the cuff band 1, and ends the entire operation when the pressure reaches approximately 0 mmHg. . The display function of the display 14 is to display updates of the pressure every moment, and to hold and display the minimum and systolic blood pressure values, respectively. Furthermore, when measuring the pressure by decreasing it, the output of the holding circuit 8 is accurate because it always indicates the decreased pressure itself. In other words, with small diaphragm motor pumps normally available on the market, the pulsation width is 10~
15mmHg, but in this invention the average is 5-8mm
It became accurate at Hg level. In other words, the difference between the average pulsation (curve C) and the line connecting the lower limit of the pulsation (curve A) is 5.
~8mmHg is the correct amount. Also, when used as a pressure gauge, accurate measurements can be made as long as static pressure is measured.

The present invention includes a diaphragm connected to the cuff band,
A differential transformer that converts the amount of displacement of this diaphragm into a voltage signal, a rectifier circuit that rectifies the voltage signal of this differential transformer, and a holding circuit that holds and outputs the lower limit value of the ripple component of the rectified output of this rectifier circuit. Since the pressure detection means is configured to display the pressure value on the display based on the holding output, the pressure value displayed on the display when pressurizing is the effective value of the pressure inside the cuff band, and the pressure value is displayed on the display when pressurizing. As a result, there is no drop in the displayed pressure value at the end of pressurization, giving the user a sense of security.Also, since the effective value can be displayed, there is no need to make the inlet of the diaphragm smaller, which eliminates the problem of clogging. The effect is that there is no such thing.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.
Fig. 2 is an explanatory diagram of the same principle as above, and Fig. 3 is an explanatory diagram of the same operation as above, where 1 is a cuff band, 4 is a diaphragm,
5 is a differential transformer, 7 is a rectifier circuit, 8 is a holding circuit, and 14 is a display device.

Claims (1)

[Scope of utility model registration request] A diaphragm connected to the cuff band, a differential transformer that converts the amount of displacement of this diaphragm into a voltage signal, a rectifier circuit that rectifies the voltage signal of this differential transformer, and the lower limit of the ripple component of the rectified output of this rectifier circuit. 1. A blood pressure monitor comprising a pressure sensing means comprising a holding circuit that holds and outputs a value, and a blood pressure value is displayed on a display based on the held output.