JPH0523148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an improvement in a blood pressure measuring device that measures blood pressure by compressing a part of a living body with a cuff.

BACKGROUND OF THE INVENTION Blood pressure measuring devices that measure blood pressure by compressing a part of a living body with a cuff are conventionally known. For example, the oscillometric method determines the blood pressure value by detecting pulse waves whose size changes with changes in compression pressure by the cuff, and the oscillometric method determines the blood pressure value according to the occurrence and disappearance of Korotkoff sounds. The ultrasound method uses ultrasonic waves to detect waves on the arterial surface wall and determines blood pressure based on changes in the amplitude of the waves.
There are various methods.

By the way, blood pressure values measured in this way are widely used as important indicators of the state of physical health and as basic information for medical decisions, but blood pressure values vary depending on the measurement site. Generally, the blood pressure value at the upper arm, which is located at approximately the same height as the heart of the living body, is used as a standard. That is, if the height position of the site where the blood pressure value is measured and the heart differ, the blood pressure value will fluctuate due to the gravity acting on the blood itself. For this reason, for example, blood pressure values measured at sites located at different heights of the heart, such as the fingers and feet of a living body, may not be used as they are as basic information for medical judgment.

On the other hand, for example, by placing a tank containing a liquid with a specific gravity similar to that of blood at the same height as the heart of the living body, and introducing the liquid into the cuff to compress the measurement site in advance, A blood pressure measuring device is considered that prevents fluctuations in blood pressure values due to differences in height between the heart and the measurement site.

Problems to be Solved by the Invention However, in such a blood pressure measuring device, the liquid introduced into the cuff constantly presses the blood pressure measurement site, causing discomfort to the person being measured and causing congestion. There was a risk that this would occur.

Means for Solving the Problems The present invention was made against the background of the above-mentioned circumstances, and its gist is to use a cuff to attach a part of a living body located at a different height from the heart. The device measures the blood pressure value of the living body by applying pressure to the living body, and (1) contains a liquid and has an atmospheric pressure receiving part at one end to which the liquid receives atmospheric pressure;
(2) a flexible tube arranged such that its atmospheric pressure receiving part is at a height position that is in a constant relationship with the height position of the heart of the living body; (2) the cuff and the flexible tube; (3) a differential pressure sensor connected to the end and detecting the differential pressure between the pressure in the flexible tube and the pressure in the cuff at the same height position as the cuff; and (3) the pressure detected by the differential pressure sensor. blood pressure value determining means for determining the blood pressure value of the living body based on the pressure determined by the blood pressure.

Operation and Effects of the Invention According to the blood pressure measuring device configured as described above, in the differential pressure sensor, the pressure of the liquid at the same height position as the cuff in the flexible tube which receives atmospheric pressure in the atmospheric pressure receiving part ( The pressure difference between the pressure inside the cuff (fluid pressure) and the pressure inside the cuff (cuff pressure) is detected, and the blood pressure value of the living body is determined by the blood pressure value determination means based on the difference pressure. There is no need to guide the liquid in the flexible tube into the cuff to prevent fluctuations in blood pressure values due to differences in height from the heart, which may cause discomfort to the patient or cause congestion. This eliminates the risk of In addition, since the blood pressure value is determined based on the differential pressure detected by one differential pressure sensor, the device This has the effect of simplifying the process.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing the main parts of the blood pressure measuring device of this embodiment. The cuff 10 is a bag-shaped item that presses the finger of the person to be measured, and the cuff 10 includes a well-known differential pressure sensor 12, an electric pump 14 that supplies gas into the cuff 10, a tank (not shown), and a diaphragm (not shown). A pulsation prevention device 16 for suppressing vibrations of the gas supplied from the electric pump 14 to the cuff 10, and an exhaust valve device 18 for exhausting the gas in the cuff 10 to lower the pressure of the cuff 10 are connected. has been done.

The differential pressure sensor 12 includes a flexible tube 20
are connected to each other, and the tube 20 is constructed so that its internal volume hardly changes with bending. Further, the tube 20 contains a liquid 22 having the same specific gravity as blood (approximately 1.2) inside, and an atmospheric pressure receiving part 24 at the tip end is formed by an elastic thin film at the end of the tube 20, as shown in FIG. 26 and a retaining ring 28 to seal liquid-tightly and so that the liquid level of the liquid 22 becomes atmospheric pressure. Such an atmospheric pressure receiving part 24 is placed, for example, on the front chest when standing up, and on the left shoulder when lying down, so that the position where the elastic thin film 26 is provided is at approximately the same height as the heart of the subject. Ru.

Note that this atmospheric pressure receiving section 24 is connected to the tube 20.
The elastic thin film 26 is provided to prevent the liquid 22 from flowing out from the atmospheric pressure receiving part 24 in the event of a fall, etc., and has extremely soft elastic properties. The pressure applied to the liquid 22 by the elastic force during its elastic deformation is extremely small.

Differential pressure sensor 12 is configured as shown in FIG. 3 and is connected to cuff 10 and flexible tube 20 through pressure ports 30 and 32, respectively. A semiconductor chip 38 protected by a protective film 36 on the pressure port 30 side is provided inside the differential pressure sensor 12, and the semiconductor chip 38 is bonded to the first
It is attached to the substrate 42. Differential pressure sensor 12
Inside is a first chamber 44 communicating with the cuff 10 and a second chamber communicating with the tube 20 through the first substrate 42.
It is airtightly divided into chambers 46. semiconductor chip 3
8 is the cuff 1 in the first chamber 44 and second chamber 46 communicated through pressure ports 30 and 32.
By receiving strain based on the differential pressure between the zero pressure (cuff pressure) and the pressure of the liquid 22 in the tube 20 (hydraulic pressure), a signal representing the differential pressure is output. The signal output from the semiconductor chip 38, that is, the differential pressure signal SDP, is transmitted to the bonding wire 48,
After being amplified by an amplifier (not shown) through a pin 50 and the like, it is supplied to an A/D converter 52.

The A/D converter 52 receives the supplied differential pressure signal.
After converting the SDP into a digital signal, it is supplied to the I/O port 54. The I/O port 54 also has
A start/stop signal SC is supplied each time the start/stop switch 56 is closed. This I/O port 54 connects the CPU 58 and RAM that constitute the microcomputer via a data bus line.
60 and ROM 62, and the CPU 58 uses the temporary storage function of the RAM 60 and performs signal processing according to a program stored in the ROM 62 in advance, and generates a drive signal MP for operating the electric pump 14 and an exhaust valve device 18. A drive signal MV for switching is output from each I/O port 54. In addition, a display signal is sent to the display/recording device 64.
A DD is supplied, where numbers indicating the blood pressure value are displayed, or a bar graph whose upper and lower ends represent the systolic and diastolic blood pressure values, respectively, is continuously displayed on a cathode ray tube and printed on recording paper. Let it be recorded. Note that the CPU 58 receives a constant frequency pulse signal from a clock signal source 66.
CK is supplied.

Next, the operation of this embodiment will be explained according to the flowchart shown in FIG.

First, step S1 is executed through an initialization step (not shown), and it is determined whether or not the start/stop switch 56 has been closed (turned ON), in other words, whether the start/stop signal SC has been supplied.
After the atmospheric pressure receiving part 24 is placed at the predetermined height position mentioned above and the cuff 10 is wrapped around the finger of the subject, when the start/stop switch 56 is closed, the next step S2 is executed. be done. Step S2
, the count content T of the timer is reset to zero, and the timer is then turned back on to the clock signal source 6.
Counting of the pulse signal CK supplied from 6 is started.

Subsequently, step S3 corresponds to blood pressure determining means.
A blood pressure measurement routine is executed. This blood pressure measurement routine is based on the conventional oscillometric method. First, the exhaust valve device 1
8 to the closed state and the electric pump 14
the cuff 10 through the pulsation arrester 16.
The cuff 10 is gradually pressurized by pumping air into the cuff 10.

Next, based on the change in the magnitude of the pulse wave represented by the differential pressure signal SDP during the process of increasing the cuff pressure,
The maximum and diastolic blood pressure points are determined, and the cuff pressures represented by the differential pressure signal SDP at those times are defined as the systolic blood pressure value H (mmHg) and the diastolic blood pressure value L (mmHg). Thereafter, the exhaust valve device 18 is switched to the exhaust state to rapidly exhaust the gas in the cuff 10.

Next, step S4 and subsequent steps are executed, and step
In S4, the display signal DD representing the systolic blood pressure value H and the diastolic blood pressure value L is supplied to the display/recording device 64, and numbers or bar graphs representing the systolic blood pressure value H and the diastolic blood pressure value L are displayed. recorded on recording paper. Also, step
In S5, it is determined whether the count content T of the timer has reached the count content Ts predetermined as the time interval for continuously predicting the blood pressure value, and when the count content T reaches Ts, the process proceeds to step S6. is executed. In step S6, if the start/stop switch 56 is operated and turned off, the blood pressure measurement ends, but if it is not turned off, the execution from step S1 onwards is repeated.
Blood pressure values are continuously measured at the predetermined time intervals until the start/stop switch 56 is operated again.

At this time, the differential pressure P _D detected by the differential pressure sensor 12 is obtained by subtracting the fluid pressure P _F in the tube 20 at the same height position as the cuff 10 from the cuff pressure P _C , as shown in the following equation (1). It is something that

P _D = P _C - P _F ... (1) Also, since the specific gravity of the liquid 22 is the same as that of blood, the fluid pressure P _F is determined by the blood pressure value P _H at the height of the heart caused by gravity and the cuff 10. The amount of variation D in the blood pressure value based on the difference in height position between the blood pressure value at the height position (measurement site), that is, the cuff pressure P _C
matches. That is, as shown in the following equations (2) and (3), P _H = P _C - D ... (2) D = P _F ... (3) Differential pressure P _D detected by the differential pressure sensor 12 The blood pressure value determined as cuff pressure coincides with the blood pressure value P _H at the height of the heart, and the systolic blood pressure value H and the diastolic blood pressure value L are the systolic blood pressure value and the diastolic blood pressure value at the heart height position. They almost match.

As described above, in the blood pressure measuring device of this embodiment, the atmospheric pressure receiving section 24 is disposed at approximately the same height as the heart, and the atmospheric pressure receiving section 24 is disposed at the tip of the tube 20. 22 to cuff 1
The differential pressure sensor 12 connected to the tube 20 and cuff 10 detects the differential pressure between the fluid pressure at the same height as the cuff 10 and the cuff pressure, and Since the system determines the systolic and diastolic blood pressure values based on this, the blood pressure value is always approximately the same as the blood pressure value at the same height as the heart, regardless of the difference in the height of the blood pressure measurement site and the heart. Systolic blood pressure value H and diastolic blood pressure value L
is measured.

Therefore, in the blood pressure measuring device of this embodiment, since there is no need to introduce the liquid into the cuff 10, pressure caused by the weight of the liquid is constantly applied to the finger, causing discomfort and congestion to the person being measured. This will solve the problem.

Further, according to this embodiment, it is sufficient to use one differential pressure sensor 12 to measure the systolic blood pressure value H and the diastolic blood pressure value L. By providing two pressure sensors and subtracting a correction value based on the fluid pressure in the tube detected by the pressure sensors from the cuff pressure also detected by the pressure sensor, the blood pressure value at the level of the heart can be measured. This has the advantage that the device is simpler than one that matches blood pressure values at different sites.

Further, according to this embodiment, since the specific gravity of the liquid 22 in the tube 20 is approximately the same as the specific gravity of blood,
Since the differential pressure detected by the differential pressure sensor 12 almost matches the blood pressure value at the height of the heart, the blood pressure value measured at the height of the cuff 10 is used as the blood pressure value at the height of the heart. There is no need for a correction calculation to match the , and there is no need for a process for that, which has the advantage of simplifying the device.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can be implemented in other embodiments as well. Note that parts common to the above embodiments are given the same reference numerals, and explanations thereof will be omitted.

For example, in the embodiment described above, the blood pressure value was measured when the cuff 10 was gradually raised by the electric pump 14 and the pressure booster 16, but the blood pressure was also measured when the pressure was lowered when gas was discharged from the cuff 10. It can be done. In this case, it is desirable that the pressure in the cuff 10 is lowered gradually, and the exhaust valve device 18 is equipped with a slow exhaust valve for this purpose and a rapid exhaust valve for rapid exhaustion of gas at the end of blood pressure measurement.
It is necessary to provide a

Further, in the above embodiment, the atmospheric pressure receiving part 24 was provided at the tip of the tube 20, but instead of the atmospheric pressure receiving part 24, a rubber or the like is provided at an intermediate position in the vertical direction as shown in FIG. A tank 74 may be used in which an elastic thin film 68 is provided to separate an upper atmospheric chamber 70 from a lower liquid chamber 72, with the atmospheric chamber 70 communicating with the atmosphere. In this case, there is no problem even if the tube changes its internal volume in response to bending.

Further, in the embodiment described above, the liquid 22 has the same specific gravity as blood, but it may be a liquid such as water that has a specific gravity different from blood. In this case, in order to match the fluid pressure at the same height position as the cuff 10 and the amount of variation in blood pressure value due to the difference in height position, the systolic blood pressure value H and the diastolic blood pressure value L are multiplied by the specific gravity of the blood. It is necessary to provide a process for correcting the

Further, in the above embodiment, the atmospheric pressure receiving unit 24 is arranged at approximately the same height as the heart of the subject, but it is also possible to For example, the atmospheric pressure receiving section 24 may be placed at a height position that differs from the heart level by a predetermined constant dimension. In this case, the measured systolic blood pressure value H and diastolic blood pressure value L are corrected taking into account the predetermined constant dimensions.

Further, in the above embodiments, the present invention is applied to a blood pressure measuring device that continuously measures blood pressure values, but the present invention can also be applied to a blood pressure measuring device that measures blood pressure values only once. Of course.

Further, in the above embodiment, the blood pressure value is measured using an oscillometric method during the process of lowering the cuff pressure, but other blood pressure measurement methods such as a microphone method or an ultrasonic method may also be employed.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a blood pressure measuring device which is an embodiment of the present invention. Figure 2 is the first
FIG. 3 is an enlarged sectional view of the atmospheric pressure receiving section in the figure. Third
The figure is an enlarged cross-sectional view of the main part of the differential pressure sensor in FIG. 1. FIG. 4 is a flowchart illustrating the operation of one embodiment of the present invention. Figure 5 shows
FIG. 3 is a schematic diagram showing main parts of another embodiment of the present invention. 10: Cuff, 12: Differential pressure sensor, 20: Tube (flexible tube), 22: Liquid, 24: Atmospheric pressure receiving section, Step S3: Blood pressure measurement routine (blood pressure determining means).

Claims (1)

[Scope of Claims] 1. A blood pressure measuring device that measures the blood pressure of a living body by compressing a part of the living body located at a different height from the heart with a cuff, which contains a liquid and has one end. A flexible tube having an atmospheric pressure receiving part in which the liquid receives atmospheric pressure, and arranged so that the atmospheric pressure receiving part is at a height position that is in a constant relationship with the height position of the heart of the living body. a flexible tube connected to the cuff and the other end of the flexible tube to detect a pressure difference between the pressure inside the flexible tube and the pressure inside the cuff at the same height as the cuff. A blood pressure measuring device comprising: a differential pressure sensor; and a blood pressure value determining means for determining a blood pressure value of the living body based on the pressure detected by the differential pressure sensor.