JPH0349684Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a blood pressure measuring device that automatically measures the blood pressure of a subject, and particularly relates to a blood pressure measuring device that measures blood pressure based on the Korotkoff sounds generated from the arteries as a result of compression by a cuff. This paper relates to improvements in measuring devices.

Prior Art A cuff for compressing a part of a living body and a microphone attached to the cuff to detect KOROTOKOFF sounds are used. Specifically, blood pressure measuring devices have been widely known that measure blood pressure by using the cuff pressure when Korotkoff sounds occur and disappear due to changes in cuff compression pressure as systolic blood pressure values and diastolic blood pressure values.

On the other hand, since blood pressure is an important index representing the state of physical health and is one of the basic information for medical judgment, high reliability is required of the measuring device. For this reason, a second microphone is disposed in a portion of the cuff located upstream of the artery from the microphone, and detects the arterial sound generated from the artery in synchronization with the heart beat. Based on this arterial sound, the passage time of the signal representing the Korotkoff sound detected by the microphone is limited to a certain period during which the Korotkoff sound is expected to occur, thereby preventing the contamination of noise, etc. A blood pressure measuring device that can measure blood pressure with high accuracy has been proposed. For example, the apparatus described in Japanese Patent Application No. 59-220136 previously filed by the applicant of the present application is one example.

Problems that the invention aims to solve However, in this type of blood pressure measuring device,
Since the microphone that detects Korotkoff sounds is predetermined, when wrapping the cuff prior to blood pressure measurement, the microphone must be positioned downstream of the artery, making its handling difficult. It was troublesome. Furthermore, when measuring blood pressure during exercise, for example, it is desirable to arrange piping or the like for supplying pressure fluid to the cuff above.
This is in the opposite direction to the direction in which the cuff is wound when measuring blood pressure, so in such cases a special cuff with two microphones placed in opposite directions must be used. There was a problem.

Means for Solving the Problems The present invention was made to solve the above problems, and its main points are (a) a cuff that compresses a part of the living body, and (b) an artery. (c) a pair of microphones disposed on the cuff so as to be located above the cuff, each detecting arterial sound generated from two positions on the artery and outputting a pulse sound signal representing the arterial sound; (d) a discriminating means for discriminating the positional relationship of the pair of microphones on the artery based on a difference in arterial sounds; and (d) a micro that is determined by the discriminating means to be located on the upstream side of the artery. (e) gate means for limiting the passage time of the pulse sound signal output from the other microphone based on the pulse sound signal output from the microphone; and (e) the pulse sound signal inputted through the gate means represents The blood pressure measuring device is configured to include a blood pressure determining means for determining a blood pressure value using an arterial sound as a Korotkoff sound.

Function and Effects of the Invention In such a blood pressure measuring device, arterial sounds generated from two positions on the artery are detected by a pair of microphones disposed in the cuff, and the discrimination means is used to distinguish between the arterial sounds. The positional relationship between the pair of microphones is determined based on the difference in the generation state and waveform of the arterial sound, and the pulse output from the microphone determined by the determining means to be located on the upstream side of the artery is determined. Based on the sound signal, the gate means is opened for a certain period of time during which arterial sound is expected to occur at the position where the other (downstream) microphone is installed, and a pulse sound signal is output from the other microphone. is allowed to pass. Then, only the pulse sound signals that have passed through the gate means within this fixed period are processed as signals representing Korotkoff sounds, and based on this, blood pressure values such as the systolic blood pressure value and the diastolic blood pressure value are determined by the blood pressure determining means. Ru.

Therefore, according to the blood pressure measuring device of the present invention, even if noise or the like is mixed into the pulse sound signal output from the microphone located on the downstream side of the artery, the noise can be removed by the gate means. Therefore, highly accurate blood pressure measurement can be performed. Furthermore, the positional relationship between the pair of microphones disposed on the cuff is determined based on the difference in the arterial sounds detected by them, so when winding the cuff, Either of the pair of microphons can be positioned upstream of the artery, making the cuff easier to handle, and there is also the advantage of being able to freely select the winding direction as needed. .

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

In FIG. 1, reference numeral 10 denotes a rubber bag-shaped cuff that is wrapped around the upper arm of the subject. An electric pump 14 that supplies gas and increases its pressure, and an exhaust valve device 16 that exhausts the gas in the cuff 10 to lower the pressure of the cuff 10.
is connected. The exhaust valve device 16 is composed of, for example, a rapid exhaust opening/closing valve and a slow exhaust opening/closing valve equipped with a throttle, and is in a closed state to prevent gas from being discharged from the cuff 10 and in a closed state to prevent gas from being discharged from the cuff 10 for blood pressure measurement. It is designed to be switchable between three states: a slow evacuation state in which gas is gradually ejected, and a rapid evacuation state in which gas within the cuff 10 is rapidly ejected. Moreover, the pressure sensor 12 is configured with an amplifier, and after amplifying the detected pressure, a pressure signal representing the pressure is generated.
SP is supplied to the low pass filter 18. The low-pass filter 18 removes vibration components such as pulse waves from the supplied pressure signal SP, and then transmits it to the A/D.
It is supplied to the converter 20.

A pair of microphones 22 and 24 are also disposed on the cuff 10 at a portion located above the artery when the cuff 10 is wrapped around the upper arm or the like. The microphones 22 and 24 both detect arterial sounds generated from the arteries as the heart beats, and output pulse sound signals SS1 and SS2 representing the arterial sounds. , SS2
are amplified by amplifiers 26 and 28, respectively, and then
The signal is supplied to bandpass filters 30 and 32. The band pass filters 30 and 32 are for removing vibration components caused by body movements other than arterial sounds and noises such as electric scalpels from the pulse sound signals SS1 and SS2.
Only vibration components related to arterial sound (for example, vibration components of about 10 to 150 Hz) are allowed to pass through, and each of them is supplied to the A/D converter 20.

The A/D converter 20 converts the supplied pressure signal SP and pulse sound signals SS1 and SS2 into digital signals, respectively, and supplies the digital signals to the I/O port 34. The I/O port 34 is also supplied with an activation signal SA from a push button PB.
This I/O port 34 is connected to a CPU 36, which constitutes a microcomputer, via a data bus line.
Connected to RAM38 and ROM40,
The CPU 36 performs signal processing according to a program stored in advance in the ROM 40 while utilizing the temporary storage function of the RAM 38, and outputs a drive signal MP for operating the electric pump 14 and a drive signal MV for switching the exhaust valve device 16 through I/O, respectively. Output from port 34. Further, a display signal DD is supplied to the display device 42 to display the measured systolic blood pressure value and diastolic blood pressure value numerically. Note that the CPU 36 is supplied with a pulse signal CK of a predetermined frequency from a clock signal source 44.

Next, the operation of this embodiment will be explained based on the flowchart of FIG.

First, when a power switch (not shown) is turned on, an initialization step is performed and step S1 is executed.
It is determined whether the push button PB has been operated, in other words, whether the activation signal SA is being supplied to the I/O port 34. When the activation signal SA is supplied,
Next, step S2 is executed and the exhaust valve device 16 is
is closed, the electric pump 14 is activated, and the pressure is increased until the actual pressure in the cuff 10 represented by the pressure signal SP reaches a predetermined target pressure higher than the subject's systolic blood pressure value.

Next, step S3 is executed and the pulse sound signal SS
Based on the difference in the arterial sounds expressed by SS1 and SS2,
The positional relationship of the microphones 22 and 24 on the artery is determined. This is because when an artery is compressed by the cuff 10, the flow of blood within the artery is obstructed, so the arterial sound detected upstream and the arterial sound detected downstream are As shown in Figure 3, the generation situation with respect to the cuff pressure is different, and the frequency of the upstream arterial sound is lower than that of the downstream arterial sound, and the width of the waveform is wider than that of the upstream arterial sound. Since there are differences such that the arterial sound is wider, the positional relationship between the microphones 22 and 24 can be determined based on these differences. In addition,
The downstream arterial sound means the Korotkoff sound, and in Figure 3, the cuff pressures P ₁ and P ₂ when the downstream arterial sound occurs or disappears represent the systolic blood pressure value and the diastolic blood pressure value, respectively. ing.

In this embodiment, step S3 is executed when the pressure of the cuff 10 is increased to a target pressure higher than the systolic blood pressure value of the subject, that is, when the pressure of the cuff is in the range of P1 _or more in FIG. Therefore, at this time, the flow of the subject's blood is completely blocked by the cuff 10, and no arterial sound can be detected downstream from the cuff 10. Therefore, for example, the positional relationship between the microphones 22 and 24 can be easily determined based on the presence or absence of this arterial sound. The positional relationship between the microphones 22 and 24 can be determined more accurately by determining whether the width of the waveform is lower than the predetermined value or whether the width of the waveform is larger than a predetermined constant value. This step
S3 and the CPU 36, RAM 38 and ROM 40 that execute it are connected to the microphones 22 and 2.
This constitutes a discriminating means for discriminating the positional relationship on the artery of No. 4.

In the above manner, the microphones 22 and 2 are
4 is determined, then step S4
The K sound detection routine is executed periodically every time an arterial sound is detected by the upstream microphone, followed by the blood pressure determination routine at step S5, and then at step S6.
In step 1, it is determined whether blood pressure measurement has been completed. The K sound detection routine in step S4 detects the pulse sound signal SS1 or SS2 output from the microphone 22 or 24 determined to be located on the upstream side in step S3. This function limits the passage time of the pulse sound signal SS1 or SS2 output from 22 or 24, and the CPU 36 and RAM that execute this
38 and ROM 40, forming a gate means,
For example, it is composed of the steps shown in FIG.

That is, first, in step R1, the microphone 2 determined to be located on the upstream side
The arterial sound detected by 2 or 24 is defined as the first arterial sound, and it is determined whether or not this first arterial sound has been detected. Step R1 is repeated while the first artery sound is not detected, but when the first artery sound is detected, step R2 is executed next. Time t ₁ in FIG. 5 shows the state at this time. At this time, the counting time T of the timer that counts the pulse signal CK supplied from the clock signal source 44 is reset.

In step R2, the time Tmin. from when the first arterial sound is detected until the gate is opened is calculated. This Tmin. is calculated by setting the arterial sound detected by the microphone 22 or 24 determined to be located downstream in step S3 as the second arterial sound, and the detected first arterial sound and the second arterial sound. Calculate the time difference Δt _o-1 with the arterial sound, schedule this time as the delay time from when the first arterial sound is detected until the second arterial sound occurs, and calculate the fixed time from that time difference Δt _o-1. (Half the gate opening time, e.g.
It is calculated by subtracting about 150msec). In this case, while the compression pressure of the cuff 10 is high and the second artery sound is not detected, the time difference between the previous first artery sound and the second artery sound cannot be calculated. The set value is used.

Subsequently, step R3 is executed, and it is determined whether the timer counting time T has reached the above-mentioned Tmin. Step until counting time T reaches Tmin.
The execution of R3 is repeated, but the counting time T is
When Tmin. is reached, step R4 is executed, the gate is opened, and the pulse sound signal SS1 or SS2 output from the microphone 22 or 24 determined to be located on the downstream side is allowed to pass. Time t ₂ in FIG. 4 shows the state at this time.

Next, step R5 is executed, and it is determined whether a second arterial sound (i.e., Korotkoff sound) has been detected based on the pulse sound signal SS1 or SS2 that has passed through the gate. If a second pulse sound is detected, then step R7 is executed and the gate is closed to prevent the passage of the pulse sound signal SS1 or SS2, but immediately after the gate is opened, the second pulse sound signal No arterial sounds are detected, so the step
R6 is executed and it is determined whether the timer count T has reached Tmax. This Tmax.
It corresponds to the time difference Δt _o-1 plus a certain time (half the gate opening time, for example, about 150 msec), and steps R5 and R6 are repeated while the counting time T is less than Tmax. The gate will be opened. Therefore, the gate that restricts the passage of the pulse sound signal SS1 or SS2 output from the downstream microphone 22 or 24 is as follows:
It is opened only for a certain period of time (approximately 150 msec) before and after the time when the second artery sound is expected to occur, and normally the second artery sound is detected during this period and is described later. This is used as sampling data for determining blood pressure values.
Time _t3 in FIG. 4 shows the state at this time.
Incidentally, in the unlikely event that the second arterial sound cannot be detected, the gate is closed at time _t4 in FIG. 4 when the counting time T of the timer exceeds Tmax. In addition, the actual time difference Δt _o between the first artery sound and the second artery sound this time is the delay time Δt _{o -} from when the first arterial sound is detected next until the second arterial sound occurs in step R8. ₁ and will be used as a reference for calculating the next gate opening/closing time. Note that, although the above gate is a time gate in software, a known gate circuit that allows input of a signal between the above Tmin. and Tmax. may be provided.

On the other hand, in the blood pressure value determination routine of step S5, the exhaust valve device 16 is first switched to a slow exhaust state to gradually lower the pressure in the cuff 10, and during this pressure lowering process, the pulse passing through the gate is The sound signal SS1 or SS2 is read as sampling data, and the blood pressure value is determined using the second artery sound represented by the pulse sound signal SS1 or SS2 as the Korotkoff sound. That is, when the pressure in the cuff 10 decreases and the hemostasis in the artery is gradually released, blood begins to flow through the artery, and along with this, the second artery sound is also detected at the microphone 24 on the downstream side. The pressure signal SP at the time when the first second artery sound is detected is
While the pressure of the cuff 10 represented by is taken as the systolic blood pressure value,
Cuff 1 represented by the pressure signal SP when the pressure of the cuff 10 further decreases, the compression state by the cuff 10 is relieved, and the second artery sound can no longer be detected.
The pressure of 0 is determined as the diastolic blood pressure value.
This blood pressure value determination routine and its execution
The CPU 36, RAM 38, ROM 40, pressure sensor 12, etc. constitute blood pressure determining means for determining the blood pressure value.

If both the systolic blood pressure value and the diastolic blood pressure value are not determined in the blood pressure value determination routine, the determination in step S6 is negative, so steps S4 and S5 are repeatedly executed, but the determination in step S6 is affirmed. Then step S7
and S8 are executed, the exhaust valve device 16 is switched to the rapid exhaust state, the gas in the cuff 10 is rapidly exhausted, and the systolic blood pressure value and the diastolic blood pressure value are numerically displayed on the display device 42.

In such a blood pressure measuring device, by executing a K sound detection routine including a gate means, the pulse sound signal SS1 outputted from the downstream microphone 22 or 24 only for a certain period during which the second arterial sound is expected to occur. Alternatively, the passage of SS2 is allowed, and only the second artery sound represented by the pulse sound signal SS1 or SS2 that has passed during that time is used as sampling data for determining the blood pressure value. Even if noise N due to body movement, electric scalpel, etc. is mixed in, it is removed by a gate provided in the K sound detection routine. Therefore, there is no risk that the blood pressure value will be erroneously determined due to such noise N, and blood pressure measurement can be performed with high accuracy.

Moreover, this K sound detection routine is performed using a time difference Δt _o-1 between the previously detected first artery sound and the second artery sound.
is calculated and this time is used as the time when the second artery sound is expected to occur. Therefore, due to individual differences between subjects and changes in the pressure of the cuff 10, the second artery sound may be detected after the first artery sound is detected. Even if the time until the arterial sound is generated changes, the scheduled time for the second arterial sound to occur will change accordingly, so the gate opening period can be shortened and measurement accuracy can be further improved. There is.

On the other hand, in the blood pressure measuring device of this embodiment, the positional relationship between the pair of microphones 22 and 24 disposed in the cuff 10 is determined based on the generation status and waveform difference of the arterial sounds detected by them. Since this is determined in advance in step S3 prior to blood pressure measurement, which of the pair of microphones 22 and 24 is positioned on the upstream side of the artery when winding the cuff 10 is determined in advance. The cuff 10 can be easily handled without any problem, and there is an advantage that the winding direction can be freely selected as required.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, the positional relationship between the microphones 22 and 24 is determined when the pressure in the cuff 10 is increased to a target pressure higher than the systolic blood pressure value of the subject.
It is also possible to determine the positional relationship based on differences in the amplitude of arterial sounds during the process of increasing or decreasing the pressure.

In addition, in the above embodiment, the gate opening/closing times Tmin. and Tmax. by the K sound detection routine are calculated from the previous time difference Δt _o-1 , but due to individual differences among the subjects, etc. It is also possible to take this into account and set it to a constant value in advance. In this case, the set value may be corrected depending on the blood flow velocity of the artery or the pressure of the cuff 10.

Furthermore, in the embodiment described above, the blood pressure value is measured during the blood pressure lowering process of the cuff 10;
It is also possible to configure the blood pressure value to be measured during the pressurization process of the cuff 10.

Furthermore, in the embodiment described above, the gate is opened and closed in synchronization with the generation of the first arterial sound, but the gate may be opened and closed in synchronization with the disappearance of the first arterial sound.

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the configuration of a blood pressure measuring device that is an embodiment of the present invention. FIG. 2 is a flowchart illustrating the operation of the apparatus shown in FIG. FIG. 3 is a graph showing the general relationship between cuff pressure and arterial sounds detected upstream and downstream thereof. Figure 4 shows K in Figure 2.
3 is a flowchart illustrating a sound detection routine. FIG. 5 is a time chart showing the opening and closing of the gate in accordance with the execution of the flowchart of FIG. 4, together with the occurrence of the first arterial sound and the second arterial sound. 10: Cuff, 12: Pressure sensor, 22, 24:
Microphone, 36: CPU, 38: RAM, 4
0: ROM, SS1, SS2: Pulse signal, step
S3: Discrimination means, Step S4: Gate means, Step S5: Blood pressure determination means.

Claims (1)

[Claims for Utility Model Registration] A blood pressure measuring device that measures blood pressure based on Korotkoff sounds generated from an artery by compressing a part of a living body, comprising: a cuff that compresses the part of the living body; and the artery. a pair of microphones disposed on the cuff so as to be located above the artery, each detecting arterial sounds generated from two positions on the artery and outputting a pulse sound signal representing the arterial sound; a determining means for determining the positional relationship of the pair of microphones on the artery based on a difference; and a pulse output from the microphone determined by the determining means to be located on the upstream side of the artery. gate means for limiting the passage time of the pulse sound signal output from the other microphone based on the sound signal; and arterial sound represented by the pulse sound signal inputted through the gate means as the Korotkoff sound and a blood pressure value. A blood pressure measuring device characterized by having a blood pressure determining means for determining.