JPH0628634B2 - Blood pressure measurement device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a blood pressure measuring device for automatically measuring the blood pressure of a subject, and in particular, blood pressure for measuring blood pressure based on Korotkoff sounds generated from an artery due to compression by a cuff. The present invention relates to improvement of a measuring device.

BACKGROUND ART A cuff for compressing a part of a living body, and a KOROTOKOFF sound provided in the cuff to detect a sound,
With a Korotkoff sound sensor that outputs a Korotkoff sound signal that represents that Korotkoff sound, based on the Korotkoff sound that is generated from the artery when the cuff is pressed, specifically, the Korotkoff sound that is generated when the pressure of the cuff is changed. 2. Description of the Related Art A blood pressure measuring device that measures blood pressure by using the cuff pressure at the time of disappearance as the maximum blood pressure value and the minimum blood pressure value has been widely known from the past.

By the way, since blood pressure is an important indicator of physical health and is one of the basic information for medical judgment,
High reliability is required for the measuring device. On the other hand, in the blood pressure measurement device, usually, a noise removal means such as a bandpass filter is provided, and vibration of a frequency component different from the Korotkoff sound, for example, noise generated due to body movement of the measurement subject or the like. And so on. However, even a device provided with such noise removing means cannot remove even noise that is close to the frequency component of Korotkoff sounds, and due to this, the blood pressure value may be erroneously determined.

On the other hand, as described in Japanese Utility Model Laid-Open No. 59-147502 and Japanese Patent Laid-Open No. 59-108537, a heartbeat synchronizing pulse having a constant time width from the generation of an electrocardiographic signal and a pressure generated in the cuff. It has been proposed to provide a gate means for collecting the Korotkoff sound detected by the microphone only during the period when the signal indicating the pulse pressure, which is the vibration, is simultaneously generated. According to this, there is an advantage that the noise can be removed during the period other than the constant time width from the generation of the electrocardiographic signal or the period other than the generation time width of the signal indicating the pulse pressure.

Further, as described in Japanese Patent Laid-Open No. 59-64024, a gate is generated by generating a pulse having a certain time width after a certain delay time after a sound is detected by an upstream microphone mounted on the upstream side of a cuff. A device has been proposed that allows the Korotkoff sound to pass through when the Korotkoff sound is detected after the gate is opened by a downstream microphone attached to the downstream side of the cuff. According to this, the external factor noise detected at the same time in the upstream microphone and the downstream microphone is removed, but the Korotkoff sound of the internal factor generated from the artery has a time difference detected in each microphone. It has the advantage of being detected through the gate as a normal Korotkoff sound.

Problems to be Solved by the Invention However, the above-mentioned Japanese Utility Model Application Laid-Open No. 59-147502,
In the device described in Japanese Patent Laid-Open No. 59-108537, which opens the gate for a certain period of time based on the time when the electrocardiographic signal is generated, the variation is considered in consideration of individual differences and changes in pulse rate. The gate opening period must be set relatively long, and the signal indicating the pulse pressure, which is another condition for opening the gate, is detected by a microphone because the pressure sensor detects changes in cuff pressure. The time width is larger than that of the generated pulse sound, and the effect of eliminating the noise mixed in the Korotkoff sound is not always sufficiently obtained.

Further, in the device of the type in which the gate is opened and closed by the upstream microphone mounted on the upstream side of the cuff as described in JP-A-59-64024, contact noise of the cuff and ambient noise are generated. There is an inconvenience that the gate is inadvertently opened in response to external noise such as ambient noise.

The present invention has been made in the background of the above circumstances,
It is an object of the present invention to provide a blood pressure measurement device capable of removing variations in pulse rate and external noise as much as possible when collecting Korotkoff sounds.

Means for Solving the Problems The gist of the present invention for achieving such an object is to provide a cuff for compressing a part of a living body and a cuff provided downstream of the cuff and compressed by the cuff. A Korotkoff sound sensor that outputs a Korotkoff sound signal that detects the Korotkoff sound that is generated from the downstream portion of the artery and whose occurrence and disappearance are related to the systolic blood pressure value and the diastolic blood pressure value, and outputs the Korotkoff sound signal In the blood pressure measuring device for measuring the blood pressure based on the Korotkoff sound generated from the artery with the pressure by the cuff, (a) an electrocardiographic signal representing the pulsation of the heart of the living body is detected. An electrocardiographic sensor that outputs (b) a blood flow representing the blood flow sound by detecting the blood flow sound generated from the upstream side part of the artery that is provided on the upstream side of the artery of the cuff and is compressed by the cuff. Message Blood flow sound sensor that outputs a signal, and (c) allows the currency of the blood flow sound signal for a period that is synchronized with the pulsation of the heart represented by the electrocardiographic signal and is determined based on the cycle of the pulsation. First gate means, and (d) the passage of the Korotkoff sound signal for a period that is synchronized with the blood flow sound represented by the blood flow sound signal that has passed through the first gate means and is determined based on the cycle of the pulsation. The second gate means for permitting is provided.

In the blood pressure measuring device configured as described above, first, when the heartbeat is detected by the electrocardiographic sensor, only the first gate is synchronized with the heartbeat and is determined based on the cycle of the heartbeat. The means are opened to allow passage of the blood flow sound signal. Then, the second gate means is opened for a period in synchronization with the blood flow sound signal and determined based on the cycle of the pulsation to allow passage of the Korotkoff sound signal.

EFFECTS OF THE INVENTION As described above, the first gate means is opened and the blood flow sound is passed for a period which is synchronized with the pulsation of the heart and is determined based on the pulsation cycle. Regardless of the occurrence of the difference or change, the first gate means is controlled to open for a necessary and sufficiently short period, so that noise can be mixed into the blood flow sound detected by the blood flow sound sensor. Can be prevented. Therefore, it is possible to reduce the accidental opening of the second gate means in response to external noise such as cuff contact noise or ambient noise generated around. Moreover, since the period during which the Korotkoff sound is allowed to pass by the second gate means is also synchronized with the blood flow sound and is determined based on the pulsation cycle, the open period of the second gate means is also possible. It is preferable to prevent the noise from being mixed into the Korotkoff sound for a short time. In this way, accidental opening of the second gate means in response to external noise is reduced, and moreover, noise is suitably suppressed from mixing in the Korotkoff sound passing through the second gate means. The erroneous measurement of the blood pressure is effectively prevented regardless of the individual difference or variation in the pulse rate of the measurement subject.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a rubber bag-shaped cuff that is wound around the upper arm of the subject. The cuff 10 has a cuff 1
A pressure sensor 12 for detecting the pressure of 0, an electric pump 14 for supplying gas into the cuff 10 to increase the pressure thereof, and an exhaust valve device 16 for discharging the gas in the cuff 10 to reduce the pressure of the cuff 10 are connected. Has been done. The exhaust valve device 16 includes, for example, an on-off valve for rapid exhaust, a throttle valve for slow exhaust, and an on-off valve, and a closed state that prevents discharge of gas from the cuff 10 and a gas in the cuff 10 for blood pressure measurement. Can be switched to three states, that is, a slow exhaustion state in which the gas in the cuff 10 is gradually discharged and a rapid exhaustion state in which the gas in the cuff 10 is rapidly discharged. Further, the pressure sensor 12 includes an amplifier, amplifies the detected pressure, and then supplies a pressure signal SP representing the pressure to the low pass filter 18. The low-pass filter 18 removes a vibration component such as a pulse wave from the pressure signal SP and outputs a cuff pressure signal SC representing the static pressure of the cuff 10.
Is supplied to the A / D converter 20.

The cuff 10 is a portion located on the artery in a state in which the cuff 10 is wound around the upper arm and the like, and microphones 22 and 24 are provided at the upstream end and the downstream end thereof, respectively. . These microphones 2
Numerals 2 and 24 each detect a vibration sound generated from an artery with blood flow, and output sound signals SS1 and SS2 representing the vibration sound. The output sound signals SS1 and SS2 are amplifier 26 respectively. , 28 and then supplied to bandpass filters 30 and 32. The bandpass filter 30 extracts only a blood flow sound component (for example, a vibration component of about 10 to 150 Hz) generated with the pulsation of an artery from the sound signal SS1 and removes other vibration components. A blood flow sound sensor is configured with the microphone 22 and the amplifier 26, and the blood flow sound signal SB representing the blood flow sound is supplied to the A / D converter 20. In addition, the bandpass filter 32 extracts only a so-called Korotkoff sound component (for example, a vibration component of about 10 to 150 Hz) that is generated in synchronization with the pulsation of the artery due to compression of the cuff 10 from the sound signal SS2, The other vibration components are removed, and a Korotkoff sound sensor is configured with the microphone 24 and the amplifier 28, and the Korotkoff sound signal SK representing the Korotkoff sound is supplied to the A / D converter 20.

Then, the A / D converter receives the supplied cuff pressure signal S
C, blood flow sound signal SB, and Korotkoff sound signal SK are converted into digitally coded cuff pressure signal SCD, blood flow sound signal SBD, and Korotkoff sound signal SKD, respectively,
They are supplied to the CPU 34 according to the timing signal ST. The CPU 34 is connected to an I / O port 36 via a data bus line, and the I / O port 36 is provided with an electrode 38 attached to the chest or the like of the subject to electrically measure the heartbeat. An electrocardiographic signal SH representing the pulsation of the heart is supplied from an electrocardiograph 40 as an electrocardiographic sensor for detecting the heartbeat. Further, the activation signal SA is supplied to the I / O port 36 from the push button PB.

The CPU 34 constitutes a microcomputer together with the RAM 42 and the ROM 44, and uses the temporary storage function of the RAM 42 to process the signal supplied in accordance with the program stored in the ROM 44 in advance, and the electric pump 1
4 and the drive signal MV for switching the exhaust valve device 16 are respectively output from the I / O port 36, and the timing signal ST is A / D.
It is supplied to the converter 20. Further, the display signal DD is supplied to the display device 46 so that the maximum blood pressure value and the minimum blood pressure value are displayed numerically. The CPU 34 is supplied with a pulse signal CK having a predetermined frequency from the clock signal source 48.

Next, the operation of this embodiment will be described based on the flowcharts of FIGS. 2 and 3 and the time chart of FIG.

In FIG. 2, when a power switch (not shown) is turned on, step S1 is executed through an initialization step (not shown) to determine whether the push button PB has been operated, in other words, the activation signal SA is supplied to the I / O port 36. It is determined whether or not it has been done. When the activation signal SA is supplied, step S2 is executed next, the exhaust valve device 16 is closed and the electric pump 14 is operated, and the actual pressure of the cuff 10 represented by the cuff pressure signal SCD is predetermined. The pressure is increased until a target pressure higher than the systolic blood pressure value of the subject is reached. When the pressure of the cuff 10 reaches the target pressure, the electric pump 1
4 is stopped, the exhaust valve device 16 is switched to the slow exhaust state, and the pressure of the cuff 10 is gradually decreased. In this process, the blood pressure value determination routine of step S3 is executed.

In the blood pressure value determination routine, the hemostasis state of the artery is released by gradually relieving the compressed state by the cuff 10, and the cuff pressure signal SCD at the time when the Korotkoff sound is first detected based on the Korotkoff sound signal SKD The pressure of the cuff 10 represented is set as the systolic blood pressure value, while the pressure of the cuff 10 further decreases to relieve the compressed state of the cuff 10 and the Korotkoff sound cannot be detected based on the Korotkoff sound signal SKD. The pressure in the cuff 10 represented by the signal SCD is determined as the minimum blood pressure value. Then, when both the systolic blood pressure value and the diastolic blood pressure value are determined in the blood pressure value determination routine, steps S4 and S5 are executed next, the exhaust valve device 16 is switched to the rapid exhaust state, and the gas in the cuff 10 is rapidly exhausted. The maximum blood pressure value and the minimum blood pressure value are numerically displayed on the display 46 while being discharged.

On the other hand, in parallel with the blood pressure value determination routine of step S3, the interrupt routine shown in FIG. 3 is periodically executed at predetermined time intervals.

In the interrupt routine, first, the electrocardiographic signal SH is read in step R1, and subsequently in step R2, the R wave representing the strongest peak of the heart beats represented by the electrocardiographic signal SH is detected. Is determined.
When the R wave is detected in step R2, the count content t of the timer for counting the pulse signal CK supplied from the clock signal source 48 is reset, and subsequently step R3 is executed. Time t _{0 in} FIG. 4 shows the state at this time. The heart beat is usually P,
It is composed of five spike waves of Q, R, S, and T. Of these, the R wave shows the strongest peak, and there is no risk of false detection of the R wave due to external noise. .

Step R3 corresponds to the first gate means, and when the counting content t of the timer is T, where the pulsation cycle of the heart of the subject is T, the following equation 0.1T <t <0.3T. Only when it is within the range of 1), read the blood flow sound signal SBD. That is, when the count content t has not yet reached 0.1T, the execution of step R3 is repeated, but when the coefficient content t reaches 0.1T, steps R4 and R5 are executed and the blood flow sound signal SBD is changed. While being read, it is determined whether or not the blood flow sound is detected based on the blood flow sound signal SBD. Time t _{1 in} FIG.
Indicates that the count content t of the timer reaches 0.1T and the step R
4 and R5 is the time when execution started.

When the blood flow sound is not detected in step R5, the execution of step R3 and thereafter is repeated. When the blood flow sound is detected, the reading of the blood flow sound signal SBD ends at that time, and the first gate means Is closed and step R6 is executed. The time t ₂ in FIG.
5, the time when the blood flow sound is detected and the first gate means is closed. Normally, the count content t of the timer is 0.3
Blood flow sound is detected before reaching T, but when the count content t reaches 0.3 T without blood flow sound being detected,
At that point, the reading of the blood flow sound signal SBD is stopped, the first gate means is closed, and the interrupt routine ends. The time t _{3 in} FIG. 4 is the time when the first gate means is closed in this way.

Here, the time range of the above formula (1), that is, the permissible passage period of the blood flow sound by the first gate means is the time range in which the blood flow sound is scheduled to be generated, and the pulsation R
It corresponds to the delay time until the blood flow sound is generated at the site where the microphone 22 is arranged after the wave is detected, and is set with a certain width in consideration of the individual difference of the person to be measured. -ing Further, the reason why the time range is set based on the pulsation cycle T is that the delay time becomes short when the pulsation cycle of the measurement subject is short, and the blood flow sound is planned to be generated accordingly. Based on the narrow time range. Therefore, for example, if the pulsation period T is about 1000 ms which is a normal value, the time range of the above formula (1) is about 200 ms, but if the pulsation period T is about 500 ms during exercise, The time range of the above equation (1) is shortened to about 100 ms. In addition, since the generation time of the blood flow sound is not affected by the pressure change of the cuff 10, the time range in which the blood flow sound signal SBD is read is set in comparison with the case of detecting the Korotkoff sound affected by the pressure change of the cuff 10. There is no problem even if it is set within a narrow time range as in the above formula (1). As the pulsation cycle T, specifically, a time T _n-1 (see FIG. 4) from when the R wave is detected last time to when the R wave is detected this time is used.

In step R6, the Korotkoff sound signal SKD is read, and in step R7, which is subsequently executed, it is determined whether the Korotkoff sound is detected based on the read Korotkoff sound signal SKD. If not detected, step R8 is executed. This step R8 constitutes the second gate means together with step R5, and the counted content t of the timer is expressed by the following equation t <0.5T. It is determined whether or not (2) is satisfied, and if it is satisfied, the above-mentioned steps R6 and thereafter are repeated to allow the reading of the Korotkoff sound signal SKD.

When the Korotkoff sound is detected by repeating the execution of step R6 and thereafter, the reading of the Korotkoff sound signal SKD ends at that point, the second gate means is closed, and the interrupt routine is also ended. Time t in FIG.
₄ , the Korotkoff sound is detected in step R7,
It is the time when the second gate means is closed. Normally, the Korotkoff sound is detected by the time the count content t of the timer reaches 0.5T, but if the count content t reaches 0.5T without the Korotkoff sound being detected, the Korotkoff sound signal is obtained at that time. The reading of SKD is stopped, the second gate means is closed, and the interrupt routine is terminated. The time t _{5 in} FIG. 4 is the time when the second gate means is closed in this way.

Here, the time of the above formula (2), that is, the final time of the passage permission period of the Korotkoff sound signal by the second gate means, corresponds to the end time of the period in which the Korotkoff sound is scheduled to be generated. Is the pulse cycle T of the subject's heart
Is set on the basis of when the R-wave is detected in step R2 and the Korotkoff sound is generated at the portion where the microphone 24 is arranged when the pulsation cycle of the measurement subject is short. Based on becoming shorter. Therefore, for example, if the pulsation cycle T of the person to be measured is about 1000 ms, the blood flow sound is detected during the permissible passage period of the Korotkoff sound signal SKD by the second gate means (when the Korotkoff sound is not detected). After that, it is a period until the counted content t of the timer reaches about 500 ms, specifically, a period within a range of 200 to 400 ms. Further, when the pulsation period T is about 500 ms during exercise or the like, it is a period until the count content t of the timer reaches about 250 ms after the blood flow sound is detected, specifically, 100 to 200 ms. The period is within the range of.

Although the final time for which the reading of the Korotkoff sound signal SKD is permitted is set with reference to the time of detecting the R wave in step R2, the reading start time is the same as the detection of the blood flow sound in step R5. Therefore, the Korotkoff sound signal SKD is based on the time when the R wave is detected.
The start time is slower than when the read start time is set, and the period in which the Korotkoff sound signal SKD is allowed to be read is short.

The Korotkoff sound detected in this interrupt routine is used as sampling data for determining the blood pressure value in the blood pressure value determination routine of step S3. Note that such an interrupt routine is repeatedly executed at a predetermined time interval, but the pulsation cycle T is updated each time an R wave is detected, and the pulsation cycle T is re-executed at the next execution of the interrupt routine. The time T _n (see FIG. 4) is used as

As described above, in the blood pressure measurement device according to the present embodiment, the reading of the Korotkoff sound signal SKD for determining the blood pressure value is started at the same time when the blood flow sound is detected in step R5. The period during which the signal SKD is allowed to be read is relatively short. Moreover, since the blood flow sound is detected based on the blood flow sound signal SBD which is allowed to be read for a fixed time in synchronization with the detection of the R wave in step R2, noise is mixed in the blood flow sound signal SBD. However, it is hardly detected as bloodstream sound, and reading of the Korotkoff sound signal SKD is rarely started by mistake. Therefore, the Korotkoff sound signal SKD is
The occurrence is read only for a relatively short fixed period, which is more effective in preventing erroneous measurement of the blood pressure value due to the mixing of noise, as compared with the conventional blood pressure measurement device.

Further, both the period during which the blood flow sound signal SBD is allowed to be read based on step R3 and the final time when the Korotkoff sound signal SKD is allowed to be read based on step R8 are both pulsations of the heart of the subject. Since it is determined based on the cycle T, the period during which the signals SBD and SKD can be read is a shorter period according to the pulse cycle T of the measurement subject, and the pulse rate of the measurement subject is individual. Despite the difference and the variation due to the change during the measurement, the measurement accuracy of the blood pressure value is further improved.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above-described embodiment, the reading of the Korotkoff sound signal SKD is started at the same time as the detection of the blood flow sound and is ended when the count content t of the timer reaches 0.5T, but the blood flow sound is detected. It is also possible to start reading after a certain time has passed from the start.

Further, the pulsation cycle T does not necessarily need to be updated every time the R wave is detected.

Further, although the blood pressure value is measured in the process of lowering the pressure of the cuff 10 in the above-described embodiment, the blood pressure value may be measured in the process of raising the pressure of the cuff 10.

Further, in the above-mentioned embodiment, the first and second gate means are constituted by software of the microcomputer, but these gate means may be constituted by a hard logic circuit.

Further, in the above-described embodiment, the R wave having the largest peak among the heart beats is detected, but the other heartbeats such as the Q wave and the S wave may be used to detect the heart beat. But it doesn't matter.

Although not illustrated one by one, the present invention can be carried out in variously modified and improved modes based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the configuration of a blood pressure measurement device that is an embodiment of the present invention. 2 and 3 are flow charts illustrating the operation of the device of FIG. FIG. 4 is a time chart showing opening / closing of the first and second gate means in association with the execution of the flowchart of FIG. 3 together with the occurrence states of pulsation, blood flow sound and Korotkoff sound. 10: Cuff 22: Microphone (blood flow sound sensor) 26: Amplifier (blood flow sound sensor) 30: Band pass filter (blood flow sound sensor) 24: Microphone (Korotokov sound sensor) 28: Amplifier (Korotokov sound sensor) 30: Band pass filter (Korotokov sound sensor) 34: CPU, 40: Electrocardiograph (electrocardiographic sensor) 42: RAM, 44: ROM SB, SBD: Blood flow sound signal SK, SKD: Korotkoff sound signal SH: Electrocardiographic signal step R3: First gate means Steps R5, R8: Second gate means

Claims (2)

[Claims] 1. A sound generated from a cuff for compressing a part of a living body and a downstream side portion of an artery which is provided on the downstream side of the cuff and is compressed by the cuff, the generation and disappearance of which are the maximum. Detecting Korotkoff sounds associated with the high blood pressure value and the minimum blood pressure value, and a Korotkoff sound sensor that outputs a Korotkoff sound signal representing the Korotkoff sound, and based on the Korotkoff sound generated from the artery with pressure by the cuff. In a blood pressure measuring device for measuring blood pressure, an electrocardiographic sensor that detects a pulsation of the heart of the living body and outputs an electrocardiographic signal representing the pulsation, and is provided on the upstream side of the artery of the cuff, A blood flow sound sensor that detects a blood flow sound generated from an upstream region of an artery to be compressed and outputs a blood flow sound signal that represents the blood flow sound; and a blood flow sound sensor that synchronizes with the heart beat represented by the electrocardiographic signal. And of the pulsation First gate means for allowing passage of the blood flow sound signal only for a period set based on the period, and the pulsation synchronized with the blood flow sound represented by the blood flow sound signal passing through the first gate means. And a second gate means for allowing passage of the Korotkoff sound signal only for a period set based on the cycle. 2. A period T _{g1 in} which blood flow sound is allowed to pass by the first gate means, where T is the pulsation period, is determined according to the following equation: 0.1T <T _g1 <0.3T The blood pressure measurement device according to claim 1, wherein the period T _g2 during which the second gate means allows the passage of Korotkoff sounds is determined according to the following equation: 0 <T _g2 <0.5T.