JPH0467449B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a blood pressure measuring device that automatically measures the blood pressure of a subject, and particularly to a blood pressure measuring device that measures the blood pressure based on the Korotkoff sounds generated from the arteries as a result of compression by a cuff. This invention relates to improvements in blood pressure measuring devices.

Prior art A cuff for compressing a part of a living body and a Korotkoff sound sensor installed on the cuff to detect Korotkoff sounds, which are generated in synchronization with the generation of pulse waves from arteries as a result of compression by the cuff. A blood pressure measuring device that measures blood pressure based on Korotkoff sounds includes a pulse wave sensor that detects pulse waves generated from an artery, and a pulse wave sensor that detects pulse waves generated from an artery, and a pulse wave sensor that detects pulse waves generated from an artery by opening and closing the Korotkoff sound sensor for a certain period of time during which Korotkoff sounds are expected to occur. An automatic device comprising: a gate means for allowing the detected signal to pass; and a gate control means for switching the gate means to an open state when the pulse wave signal detected by the pulse wave sensor exceeds a predetermined level. Blood pressure measuring devices are known. for example,
This is the one described in Japanese Patent Application Laid-Open No. 55-52736. According to such an automatic blood pressure measuring device,
Of the signals from the Korotkoff sound sensor, only signals that occur during a certain period during which the Korotkoff sound is expected to occur are detected as true Korotkoff sounds, so they cannot be removed by noise removal means such as a bandpass filter. There is an advantage that the noise that is close to the frequency component of the Korotkoff sound, which could not be detected, is reliably removed outside the above-mentioned fixed period, so that the blood pressure value can be obtained accurately.

Problems to be Solved by the Invention However, in the blood pressure measuring device as described above, the gate means is switched to the open state when the pulse wave signal exceeds a predetermined level or when the pulse wave signal rises. It's getting old. Therefore, considering that the time point at which the Korotkoff sound occurs in relation to the pulse wave varies depending on the individual differences and blood pressure values of the subject, it is possible to narrow the time interval for switching the gate means to the open state. The open period of the means had to be set relatively wide, and a sufficient noise removal effect could not necessarily be obtained.

The present invention has been made against the background of the above circumstances, and its purpose is to provide an automatic blood pressure system that can appropriately remove noise with its high noise removal ability, regardless of the individual differences and blood pressure values of the subject. We may provide measuring equipment.

Problems to be Solved by the Invention In order to achieve the above object, the gist of the present invention is to provide a cuff for compressing a part of a living body, and a Korotkoff sound sensor provided on the cuff to detect Korotkoff sounds. A blood pressure measuring device that measures blood pressure based on Korotkoff sounds generated from an artery as a result of compression by a cuff, comprising: (a) a pulse wave sensor that detects a pulse wave generated from the artery;
(b) gate means that opens and closes to allow passage of the signal detected by the Korotkoff sound sensor for a certain period during which the Korotkoff sound is expected to occur; and (c) the signal detected by the pulse wave sensor. delay time determining means for determining the delay time for switching the gate means to the current open state based on the time difference between the rising point of the previous pulse wave and the previous Korotkoff sound detected by the Korotkoff sound sensor; ) gate control means for switching the gate means to an open state and operating the gate means after the delay time has elapsed after the current pulse wave rising point is detected by the pulse wave sensor;

Effect: By doing this, the delay time determining means
The delay time for switching the gate means to the current open state is determined based on the time difference between the rising point of the previous pulse wave detected by the pulse wave sensor and the previous Korotkoff sound detected by the Korotkoff sound sensor. At the same time, the gate control means switches the gate means to the open state after the delay time has elapsed from the rising point of the current pulse wave, and the signal from the Korotkoff sound sensor is switched to the open state for a certain period during which the Korotkoff sound is expected to occur. is allowed to pass. and,
Only the signals that have passed within the certain period are subjected to signal processing, and based on this, the systolic blood pressure value and the diastolic blood pressure value are determined.

Effects of the Invention As described above, the automatic blood pressure measuring device of the present invention has the following features:
Since the gate is switched to the open state based on the time difference from the rising point of the previous pulse wave to the point at which the previous Korotkoff sound occurred, the actual Korotkoff sound relative to the rising point of the pulse wave during blood pressure measurement is The gate is reliably switched to the open state at necessary and sufficient time intervals to cover the occurrence point. Therefore, according to the present automatic blood pressure measurement device, noise can be sufficiently removed due to its high noise removal ability, regardless of the individual differences and blood pressure values of the subjects.
High reliability of blood pressure values can be obtained.

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

FIG. 2 is a block diagram showing an example of an automatic blood pressure measuring device according to the present invention. In the figure, 10
1 is a rubber bag-shaped cuff that is wrapped around the upper arm of the subject, and the cuff 10 includes a pressure sensor 12 that detects the pressure of the cuff 10, and a pressure sensor 12 that supplies gas to the cuff 10. An electric pump 14 that increases the pressure of the cuff 10 and an exhaust valve device 16 that exhausts the gas inside the cuff 10 to lower the pressure of the cuff 10 are connected. The exhaust valve device 16 is composed of, for example, an on-off valve for rapid evacuation, a throttle valve for slow evacuation, and an on-off valve. The cuff 10 can be switched between three states: a slow evacuation state in which the gas in the cuff 10 is gradually ejected, and a rapid evacuation state in which the gas in the cuff 10 is rapidly ejected. Further, the pressure sensor 12 is configured with an amplifier, and after amplifying the detected pressure, a pressure signal SP representing the pressure is sent to the low-pass filter 1.
Supply to 8. Low pass filter 18 is a pressure signal
Removes vibration components such as pulse waves from the SP, and
A cuff pressure signal SC representing the static pressure of is supplied to the A/D converter 20.

The cuff 10 has a part that is located on the artery when it is wrapped around the upper arm, etc.
A microphone 50 is disposed at the downstream end thereof. The microphone 50 detects the vibration sound generated from the artery and outputs a sound signal SS3 representing the vibration sound, but it can also detect not only audible sound but also vibration sound with a lower frequency. A type microphone, an acceleration type microphone, etc. are preferably used. The output sound signal SS3 is amplified by an amplifier 52 and then supplied to bandpass filters 54 and 56. The band pass filter 54 extracts only the pulse wave component (for example, a vibration component of about 10 to 50 Hz) generated in conjunction with the pulsation of the artery from the sound signal SS3, and removes the other vibration components. A pulse wave sensor is configured together with the microphone 50 and the amplifier 52, and a pulse wave signal SM representing a pulse wave is supplied to the A/D converter 20. Moreover, the bandpass filter 56
It extracts only the Korotkoff sound component generated as the cuff 10 is compressed from the SS3, and together with the microphone 50 and amplifier 52, it constitutes a Korotkoff sound sensor, and a K sound signal representing the Korotkoff sound is used.
SK is supplied to the A/D converter 20. and,
Cuff pressure signal supplied to A/D converter 20
SC, pulse wave signal SM, and K sound signal SK are converted into digitally coded cuff pressure signal SCD, pulse wave signal SMD, and K sound signal SKD, respectively, and then output to the I/O port 34. ,I/
An activation signal SA is supplied to the O port 34 from the push button PB.

The I/O port 34 connects a CPU 36, which constitutes a microcomputer, via a data bus line.
Connected to RAM38 and ROM40,
The CPU 36 processes the supplied signals according to a program stored in the ROM 40 in advance while utilizing the temporary storage function of the RAM 38, and generates a drive signal MP for operating the electric pump 14 and a drive signal MV for switching the exhaust valve device 16. I/O port 3
Output from 4. In addition, a display signal is displayed on the display device 42.
DD is supplied and the systolic and diastolic blood pressure values are displayed numerically. In addition, CPU3
6 is supplied with a pulse signal CK of a predetermined frequency from a clock signal source 44.

Next, the operation of the automatic blood pressure measuring device configured as described above will be explained based on the flowcharts of FIGS. 3 and 4 and the time chart of FIG. 5.

In FIG. 3, first, when a power switch (not shown) is turned on, step S1 is executed after an initialization step (not shown), and it is determined whether the push button PB has been operated or not, in other words, the activation signal SA is sent to the I/O port 34. It is determined whether or not it is supplied. When the activation signal SA is supplied, step S2 is executed next, the exhaust valve device 16 is closed, the electric pump 14 is activated, and the cuff pressure signal is
The pressure is increased until the actual pressure in the cuff 10 represented by the SCD reaches or exceeds a predetermined target pressure that is higher than the subject's systolic blood pressure value. When the pressure in the cuff 10 reaches the target pressure, the electric pump 14 is stopped, the exhaust valve device 16 is switched to a slow exhaust state, and the pressure in the cuff 10 gradually drops. During this process, a blood pressure value determination routine in step S3 is executed.

In the blood pressure value determination routine, the state of hemostasis in the artery is released by gradually relaxing the compression state by the cuff 10, and the cuff pressure signal at the time when the Korotkoff sound was first detected is determined based on the K sound signal SKD. While the pressure of the cuff 10 represented by SDC is taken as the systolic blood pressure value, the pressure of the cuff 10 further decreases, the compression state by the cuff 10 is relieved, and the K sound signal is generated.
Cuff 1 represented by cuff pressure signal SCD when Korotkoff sounds can no longer be detected based on SKD
A pressure of 0 is determined as the diastolic blood pressure value. and,
When both the systolic blood pressure value and the diastolic blood pressure value are determined in the blood pressure value determination routine, then step S4
and S6 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.

On the other hand, in parallel with the blood pressure value determination routine in step S3 above, the interrupt routine shown in FIG. By opening and closing the gate based on
Passage of SKD is becoming acceptable.

That is, first, in step R1, it is determined based on the pulse wave signal SMD whether the rising point of the pulse wave has been detected. When detecting the rising point of this pulse wave, for example, as disclosed in Utility Application No. 15595-1980, which the present applicant previously filed, a certain range is limited to the front side of the maximum inclination angle portion of the pulse wave. ,
In the waveform within this range, a portion having a preset inclination angle within the range of 45 to 85 degrees may be detected as a rising point. If the rising point of the pulse wave is not detected in step R1, this step is repeatedly executed, but if the rising point is detected,
Next step R2 is executed. Time t ₁ in Figure 5
indicates the state at this time. Furthermore, 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 switching delay time from when the rising point of the pulse wave is detected until the gate is opened is
Calculate Tmin. This Tmin. is calculated by calculating the time difference Δt _o-1 between the rising point of the pulse wave detected last time and the Korotkoff sound. The delay time is scheduled as the _delay time of
It is calculated by subtracting about 150 msec). That is, this step R2 corresponds to the delay time determining means of the present invention. In this case, while the compression pressure of the cuff 10 is high and no Korotkoff sounds are detected, the time difference between the rise point of the previous pulse wave and the Korotkoff sounds cannot be calculated, so the predetermined setting as Tmin. 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 R until counting time Tmin.
3 is repeated, but the counting time T is Tmin.
When it reaches step R4, the gate is opened and the K sound signal SKD is allowed to pass. Fifth
Time _t2 in the figure shows the state at this time. In this embodiment, step R3 corresponds to gate control means, and step R4 and step R7, which will be described later, correspond to gate means.

Next, step R5 is executed and the K sound signal SKD is
Based on this, it is determined whether a Korotkoff sound is detected. If the Korotkoff sound is detected, step R7 is subsequently executed, and the gate is closed to prevent the passage of the K sound signal SKD. However, since the Korotkoff sound is usually not detected immediately after the gate is opened, Step R6 is executed to determine whether the timer count T has reached Tmax. This Tmax. is determined by adding a certain amount of time ( _half of the gate opening time, for example 150
When the counting time T is less than or equal to Tmax., the above step R5 is executed.
The execution of R6 is repeated and the gate is opened.

Therefore, the gate that restricts the passage of the K-sound signal SKD is set for a certain period of time (150 m) before and after the time when the Korotkoff sound is expected to occur.
It is opened only for a certain period of time with a width of about 1.5 seconds), and Korotkoff sounds are usually detected during this period and used as sampling data for determining blood pressure values. Time _t3 in FIG. 5 shows the state at this time. In addition, in the unlikely event that the Korotkoff sound cannot be detected, the counting time T of the timer is
At time _t4 in FIG. 5, which exceeds Tmax, the gate is closed. The actual time difference Δt _o between the current pulse wave rising point and the Korotkoff sound is the delay time Δt _o-1 from when the next pulse wave rising point is detected until the Korotkoff sound occurs in step R8. This data will be used as a reference for calculating the next gate switching delay time.

As described above, according to the blood pressure measuring device of the present embodiment, the current gate is switched to the open state based on the time difference Δt _o-1 from the rising point of the previous pulse wave to the previous Korotkoff sound generation point. Therefore, the gate can be reliably switched to the open state at necessary and sufficient time intervals to cover the actual occurrence point of the Korotkoff sound relative to the rising point of the pulse wave during blood pressure measurement. Therefore, according to the automatic blood pressure measurement device of this embodiment, noise can be sufficiently removed by the high noise removal ability regardless of the fixed difference or blood pressure value of the subject, and high reliability of the blood pressure value can be obtained. For example, as shown by the dashed line in FIG. 5, even if noise N that approximates Korotkoff sound caused by body movement etc. is mixed into the K sound signal SKD, it will not be signal processed as Korotkoff sound.
There is no risk that the blood pressure value will be erroneously determined due to such noise N, and the reliability of the blood pressure measuring device is improved.

In addition, in the blood pressure measuring device of this example, 1
Since pulse waves and Korotkoff sounds are both detected by each microphone 50, there is an advantage that the apparatus can be easily configured.

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

For example, in the above-mentioned embodiment, the gate means and the gate control means are incorporated into the microcomputer as _{an interrupt} routine. A gate circuit that allows passage of the K sound signal SKD for a certain period during which the Korotkoff sound is expected to occur after the switching delay time of the gate to the open state has elapsed is connected to the bandpass filter 56 and the A/
It is also possible to configure the gate means with hard logic, such as by providing it between the D converter 20 and the D converter 20.

Further, in the above-described embodiment, the blood pressure value is measured during the step of lowering the blood pressure of the cuff 10, but the blood pressure value may be measured during the step of increasing the pressure of the cuff 10.

Further, in the above embodiment, one microphone 5
Although the pulse wave and the Korotkoff sound are both detected at 0, it is also possible to provide a microphone for detecting the pulse wave separately from the microphone 50, or the pressure sensor 12 detects the pulse wave. It is also possible to detect pulse waves from pressure vibrations of the cuff 10 or from vibrations of the arterial surface wall using an ultrasonic interferometer.

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 drawings]

FIG. 1 is a diagram corresponding to claims of the present invention. Second
The figure is a block diagram illustrating the configuration of a blood pressure measuring device that is an embodiment of the present invention. 3 and 4 are flowcharts illustrating the operation of the apparatus of FIG. 2. 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 rising point of the pulse wave and the occurrence of Korotkoff sounds. 10: Cuff, 50: Microphone, 52: Amplifier (pulse wave sensor), 54: Bandpass filter,
50: Microphone, 52: Amplifier (Korotkoff sound sensor), 56: Bandpass filter, Step R2: Delay time determining means, Step R3: Gate control means, Steps R4 and R7: Gate means.

Claims (1)

[Claims] 1. A cuff for compressing a part of a living body, and a Korotkoff sound sensor provided on the cuff for detecting Korotkoff sounds, which detects Korotkoff sounds generated from arteries due to compression by the cuff. A blood pressure measuring device that measures blood pressure based on the following: a pulse wave sensor that detects a pulse wave generated from the artery; and a pulse wave sensor that detects a pulse wave generated from the artery; and a pulse wave sensor that detects a pulse wave generated from the artery; a gate means for allowing the detected signal to pass; and a gate means for allowing the detected signal to pass, based on the time difference between the rising point of the previous pulse wave detected by the pulse wave sensor and the previous Korotkoff sound detected by the Korotkoff sound sensor. a delay time determining means for determining a delay time for switching the means to the current open state; and switching the gate means to the open state after the delay time has elapsed after the rising point of the current pulse wave is detected by the pulse wave sensor. A blood pressure measuring device characterized by comprising: a gate control means for activating the gate;