JPH0687841B2 - Blood pressure measurement device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a blood pressure measurement device that automatically measures blood pressure of a living body.

Prior art Korotkoff sound detection means for detecting the Korotkoff sound generated from the living body due to the pressure change of the cuff wound around a part of the living body and outputting a Korotkoff sound signal representing the Korotkoff sound, and the Korotkoff sound detection means. There is known a blood pressure measurement device including a blood pressure value determining unit that determines a blood pressure value based on occurrence and disappearance.

In such a blood pressure measuring device, a noise removing means such as a bandpass filter is usually provided, whereby a vibration of a frequency component different from the Korotkoff sound, for example, noise generated due to body movement of a living body, etc. Is designed to be removed. 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.

For this reason, conventionally, a heartbeat detecting means for outputting an electrocardiographic signal synchronized with the pulsation of the heart is provided, and a predetermined time width based on the pulsation cycle of the heart after a lapse of a predetermined time from the generation of the electrocardiographic signal. A gate is provided and the Korotkoff sound signal is collected through this time gate. However, the time from the generation of the electrocardiographic signal to the generation of the Korotkoff sound signal (DI time) is considered to be a function of the systolic blood pressure value rather than the pulsation cycle, so the systolic blood pressure value decreases even if the pulsation cycle decreases. In the case of a person who does not do so, there is a case where the Korotkoff sound cannot be reliably collected because the time range of the time gate is insufficient.

On the other hand, the applicant of the present invention filed Japanese Patent Application No. 61-1390
In No. 48, there is provided a blood pressure measurement device in which the gate means is opened and closed based on the DI time or the like in the previous blood pressure measurement cycle of the same subject. In this device,
Since the gate means is opened / closed appropriately according to the individual difference of the person to be measured, there is an advantage that the Korotkoff sound can be more reliably collected.

Problems to be Solved by the Invention However, such a device still has problems to be solved. That is, in such a device, since the gate means is opened and closed based on the previous blood pressure measurement, it may not be possible to accurately open and close the gate means depending on the previous blood pressure measurement. That is, the blood pressure value of the previous measurement may be sufficiently reliable, but if it is erroneously measured due to noise or the like, the accuracy of the blood pressure measurement of this time is impaired.

Means for Solving Problems The present invention has been made in view of the above circumstances, and its gist is to detect a heartbeat of a living body and output an electrocardiographic signal synchronized with the heartbeat. Heartbeat detection means,
The Korotkoff sound detection means for detecting the Korotkoff sound generated from the living body according to the pressure change of the cuff wound around the part of the living body and outputting the Korotkoff sound signal representing the Korotkoff sound, and the generation of the Korotkoff sound and In a blood pressure measurement device provided with a blood pressure value determination means for determining a blood pressure value based on disappearance, (a) in a previous blood pressure measurement cycle,
DI time detection means for detecting a DI time from the generation of the electrocardiographic signal to the generation of the Korotkoff sound signal, and (b) determining the first open time after a predetermined time has elapsed from the generation time of the electrocardiographic signal, The first time after a predetermined time from the first opening time
First opening / closing time determining means for determining a closing time, and (c) the above
Second opening / closing time determining means for respectively determining a second opening time and a second closing time based on the DI time detected by the DI time detecting means; and (d) the first opening time and the second opening time. Time gate means for collecting the Korotkoff sound signal from the earlier time to the later one of the first closing time and the second closing time.

As described above, in the blood pressure measurement device of the present invention, as shown in the claim correspondence diagram of FIG. 6, the DI time from the generation of the electrocardiographic signal to the generation of the Korotkoff sound signal in the previous blood pressure measurement cycle is DI time. In addition to being detected by the detection means, the first opening / closing time determination means determines the first opening time after a predetermined time has elapsed from the generation time of the electrocardiographic signal and determines the first closing time after a predetermined time from the first opening time. On the other hand, the second opening / closing time determination means determines the second opening time and the second closing time based on the DI time.
Then, the time gate means outputs the Korotkoff sound signal from the earlier one of the first opening time and the second opening time to the later one of the first closing time and the second closing time. The blood pressure value is determined by the blood pressure value determination means based on the occurrence and disappearance of the Korotkoff sound represented by the Korotkoff sound signal.

Effect of the Invention As described above, according to the blood pressure measurement device of the present invention, the time gate of the first open time and the first closed time determined with reference to the generation time of the electrocardiographic signal and that of the same subject. The time gate means having the maximum time width of the two time gates, that is, the time gate having the second opening time and the second closing time determined based on the DI time in the previous blood pressure measurement cycle, is used. Therefore, the Korotkoff sound signal can be more reliably collected without being relatively affected by the individual difference of the person to be measured, as compared with the conventional case in which only the gate means based on the pulsation cycle is used.

In addition, even when the second opening time and the second closing time based on the DI time are not accurately determined due to the previous blood pressure measurement, the first opening time and the first closing time based on the pulsation cycle. Since the time gate means can be configured by the above, it is possible to effectively prevent the accuracy of the present blood pressure measurement from being impaired due to how the previous blood pressure measurement was performed.

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

In FIG. 1, reference numeral 10 is a rubber bag-like cuff that is wound around the upper arm of the subject. The cuff 10 has a pressure sensor 12 that detects the pressure of the cuff 10, an electric pump 14 that supplies gas into the cuff 10 to raise the pressure, and discharges gas from the cuff 10 to reduce the pressure of the cuff 10. An exhaust valve device 16 is connected. The exhaust valve device 16 includes, for example, a rapid exhaust on-off valve, a constant-speed exhaust throttle valve and an on-off valve.
There are three states: a closed state that blocks the discharge of gas from the cuff 10, a constant-speed exhaust state that gradually discharges the gas in the cuff 10 for blood pressure measurement, and a rapid exhaust state that rapidly discharges the gas in the cuff 10. It can be switched to the state. Further, the pressure sensor 12 is configured to include an amplifier, amplifies the detected pressure, and then applies a low-pass filter to the pressure signal SP representing the pressure.
Supply to 18. The low-pass filter 18 removes a vibration component such as a pulse wave from the pressure signal SP, and supplies a cuff pressure signal SC representing the static pressure of the cuff 10 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. Each of these microphones 22 and 24 detects the vibration sound generated from the artery with blood flow,
Sound signals SS1 and SS2 representing the vibration sound are output, and the output sound signals SS1 and SS2 are amplified by amplifiers 26 and 28, respectively, and then supplied to bandpass filters 30 and 32. The bandpass filter 30 extracts only the blood flow sound component (for example, a vibration component of about 10 to 150 Hz) generated with the pulsation of the artery from the sound signal SS1, and removes other vibration components. The blood flow sound signal SB representing the blood flow sound is supplied to the A / D converter 20. Further, the bandpass filter 32 is a so-called Korotkoff sound component (for example, 30 to 80 Hz) that is generated in synchronization with the pulsation of the artery accompanying the compression of the cuff 10 from the sound signal SS2.
The microphone 24 and the amplifier are used to remove only the vibration component) and remove the other vibration components.
28 together with the Korotkoff sound detecting means of the present embodiment, and outputs the Korotkoff sound signal SK representing the Korotkoff sound to the A / D converter 2
Supply to 0.

The A / D converter 20 converts the supplied cuff pressure signal SC, blood flow sound signal SB and Korotkoff sound signal SK into digitally coded cuff pressure signal SCD, blood flow sound signal SBD and Korotkoff sound signal SKD, respectively. , And supplies them to the CPU 34 according to the timing signal ST. The CPU 34 is connected to the I / O port 36 via the data bus line, and the I / O port 36
Is supplied with an electrocardiographic signal SH representing the heart beat from an electrocardiograph 40 that is equipped with an electrode 38 that is adhered to the chest of the person to be measured and that electrically detects the heart beat. It has become. The electrode 38 and the electrocardiograph 40 constitute the heartbeat detecting means of this embodiment. The I / O port 36 also has a pushbutton PB.
The activation signal SA is supplied from.

The CPU 34 constitutes a so-called microcomputer together with the RAM 42 and the ROM 44.The CPU 34 processes a signal supplied according to a program previously stored in the ROM 44 while utilizing the primary storage function of the RAM 42, and drives the electric pump 14 with a driving signal MP. , And the drive signal MV for switching the exhaust valve device 16 is output from the I / O port 36, and the timing signal ST is supplied to the A / D converter 20. Further, the display device 46 is made to supply the display signal DD from the I / O port 36 so that the maximum blood pressure value and the minimum blood pressure value are numerically displayed. 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 charts of FIGS. 4 and 5.

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 or not the push button PB has been operated, in other words, a start signal.
It is determined whether SA is being supplied to I / O port 36. 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 activated to increase the actual pressure of the cuff 10 represented by the cuff pressure signal SCD until it reaches a target pressure higher than a predetermined systolic blood pressure value of the subject. 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 the constant speed exhaust state, and the pressure in the cuff 10 is decreased at a constant speed. In this process, the blood pressure value determination routine of step S3, which is the blood pressure value determination means of this embodiment, is executed.

In the blood pressure value determination routine, the hemostatic state of the artery is released by gradually relieving the compression state by the cuff 10, and the well-known blood pressure based on the Korotkoff sound signal SKD sequentially collected during the process of reducing the pressure of the cuff 10. A systolic blood pressure value and a diastolic blood pressure value are determined according to a value determination algorithm. Then, by performing steps S4 and S5, the exhaust valve device 16 is switched to the rapid exhaust state, the gas in the cuff 10 is rapidly exhausted, and the maximum blood pressure value and the minimum blood pressure value are displayed on the display 46. Is displayed.

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 in step R2 that is subsequently executed, the R wave having the strongest peak of the heart beats represented by the electrocardiographic signal SH is detected. It is determined whether or not. If the determination in step R2 is negative, the interrupt routine is terminated without going through the following steps. However, if it is determined that the R wave is detected, the interrupt signal is supplied from the clock signal source 48 in the following step R3. Pulse signal
The count content t of the timer for counting CK is reset and the pulsation cycle T ₁ of the subject's heart is calculated. Fourth
Time t _{0 in the} figure indicates the state at this time. In addition, as the pulsation cycle T ₁ , specifically, a time T _n−1 (see FIG. 4) from when the R wave is detected last time until when the R wave is detected this time is used. Also, the heart beat is usually composed of five spike waves of P, Q, R, S, and T. Of these, the R wave shows the strongest peak, and the R wave is caused by noise from the outside. There is no risk of false detection of waves.

The subsequent step R4 permits the reading of the blood flow sound signal SBD only when the count content t of the timer is within the range of the following expression (1), for example.

_{0.1T 1 <t <0.3T 1 ····} (1) In other words, although the execution of step R4 is repeated when the counting contents t has not yet reached the 0.1 T _1, counting content t is
When 0.1T ₁ is reached, steps R5 and R6 are executed, the blood flow sound signal SBD is read, and the blood flow sound signal SBD is read.
Based on the above, it is determined whether or not the blood flow sound is detected. The time range of the above equation (1) is set based on the pulsation period T _{1 because} the delay time (PI time) from the detection of the R wave to the detection of the generation of blood flow sound is This is based on the fact that the shorter the pulsation cycle of the measurer, the shorter the pulsation cycle, and the narrower the time range in which the blood flow sound is scheduled to be generated.

If the blood flow sound is not detected in step R6, the execution of steps R4 and below is repeated, but when the blood flow sound is detected, the reading of the blood flow sound signal SBD ends at that time,
Step R7 is executed. The time t ₁ in FIG. 4 is the step
This is the time when the blood flow sound was detected at R6. Normally, the blood flow sound is detected until the count content t of the timer reaches 0.3T ₁ , but the count content t is 0.3T without the blood flow sound being detected.
_When the number reaches ₁ , the reading of the blood flow sound signal SBD is stopped at that point and the interrupt routine ends.

In step R7, the PI time is read, and the ratio between this PI time and the PI time read in the previous blood pressure measurement cycle is calculated. In the subsequent step R8, the DI time in the previous blood pressure measurement cycle of the same subject, that is, the delay time from the occurrence of the heart beat to the occurrence of the Korotkoff sound detected by the downstream microphone 24, 3 near high blood pressure
Three consecutive DI times DI _S1 , DI _S2 , DI _S3 and three consecutive DI times DI _d1 , DI _d2 , Dl _d3 near the diastolic blood pressure value are read, respectively, and these DI times DI _S1 , DI _S2 , DI are read. The difference ΔDI between the average value of _{S3 and} the average value of DI times DI _d1 , DI _d2 , DI _d3 is determined from the following equation (2). Therefore, this step S8 corresponds to the DI time determining means of this embodiment.

Thus, by using the average value of three consecutive DI times, ΔDI is made stable regardless of the occurrence of arrhythmia. FIG. 5 is a delay time between the generation of blood flow sound detected by the microphone 22 mounted on the upstream side of the artery and the generation of Korotkoff sound detected by the microphone 24 mounted on the downstream side, That is, the difference between the DI time and the PI time is shown with respect to the cuff pressure.As can be seen from the figure, the difference between the DI time near the diastolic blood pressure value and the PI time is relatively small, and the DI near the systolic blood pressure value is relatively small. The difference between time and PI time is relatively large. Therefore, ΔDI is the difference between the DI time from the occurrence of the heart beat to the earliest scheduled Korotkoff sound generation and the DI time from the scheduled final Korotkoff sound occurrence, that is, the earliest scheduled time. It corresponds to the time from the generation of the Korotkoff sound of to the generation of the final Korotkoff sound. DI _S1 , DI _S2 , DI _S3 and DI _d1 , D
I _d2 and DI _d3 do not include the DI time of the systolic blood pressure value itself and the DI time of the diastolic blood pressure value itself. This is because, as shown in FIG. 5, values other than the systolic blood pressure value itself and the diastolic blood pressure value itself, values near the diastolic and diastolic blood pressure values are relatively stable.

Next, by executing step R9, the following equation (3)
And based on the DI time ratio and ΔDI from (4),
Time T _3, which corresponds to the time T ₂ and a second closed time corresponding to the second opening time of this embodiment is determined. Therefore, the times T ₂ and T ₃ are determined in accordance with the individual difference of the person to be measured.

T ₃ = T ₂ + ΔDI × 1.75 (4) However, PI: PI time in the current blood pressure measurement cycle PI _p : PI time in the previous blood pressure measurement cycle Subsequently, when step R10 is executed, First of example
The time T ₄ corresponding to the opening time and the time T ₅ corresponding to the first closing time are determined based on the pulsation cycle T ₁ . That is, in this embodiment, the time T ₄ is 0.1T ₁ and the time T ₅ is
It is decided to be 0.6T ₁ . Time range by both time T ₄ and T ₅ is set to be larger than the time range in step R4. The reason for this is that the time of blood flow
Although not affected by the pressure of 10, the Korotkoff sound generation time is based on the effect of the pressure of the cuff 10. In this embodiment, step R9 corresponds to the second opening / closing time determining means, and step R10 corresponds to the first opening / closing time determining means.

In the next step R11, it is determined whether or not the time T ₂ is smaller than the time T ₄ . If the determination is affirmative, the time T ₂ is set to the opening time T ₀ of the time gate means of the present embodiment in the subsequent step R12, while if the determination in step R12 is negative, the step R13 is performed. Running,
The time T ₄ is set to the opening time T ₀ . Next, in step R14, the time T ₃ is a time T ₅ is smaller than or not is determined. If this determination is positive, the subsequent step R15
At time T ₃ is the closing time Te of the time gate means of this embodiment.
While that is, when the determination in step R14 is negative, in step R16 is executed, the time T ₅ is the closed time Te
It is said that

Next, when step R17 is executed, reading of the Korotkoff sound signal SKD is started only when the count content t of the timer is within the range of T ₀ <t <Te. Therefore, this step R17 corresponds to the time gate means of this embodiment. In step R17, if the count content t has not yet reached T ₀ , step R17 is repeatedly executed, but if the count content t reaches T ₀ and does not exceed Te, step R18 is performed.
And R19 are executed, the Korotkoff sound signal SKD is read, and it is judged whether the Korotkoff sound is detected or not based on the Korotkoff sound signal SKD.
When the Korotkoff sound is detected by repeatedly executing the determinations in and after step R17, the reading of the Korotkoff sound signal SKD ends at that point, the gate means is closed, and the interrupt routine is also ended. Time t _{2 in} Fig. 4
Is the time when the Korotkoff sound was detected in step R19 and the gate means was closed. Normally, the Korotkoff sound is detected before the count content t of the timer reaches Te. However, if the count content t exceeds Te without detecting the Korotkoff sound, the gate means is closed and the interrupt routine is executed. Can be terminated. The time t _{3 in} FIG. 4 is the time when the gate means is closed in this way.

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 in step S3. Note that such an interrupt routine is repeatedly executed at a predetermined time interval, but the pulsation cycle T ₁ is updated each time an R wave is detected, and the pulsation cycle will be executed at the next execution of the interrupt routine. The time T _n (see FIG. 4) is used as T ₁ .

Thus, in the blood pressure measurement device of the present embodiment, in step R9, based on the PI time and DI time that changes according to the individual difference of the person to be measured, the PI time ratio that changes for each blood pressure measurement cycle. , T ₂ and T ₃ corresponding to the second opening time and the second closing time are determined, respectively, and at step R10, the times T ₄ and T ₅ corresponding to the first opening time and the first closing time are determined. While each is determined based on the pulsation cycle T ₁ , in the time gate means of step R17, the earlier one of the opening times T ₂ and T ₄ is set as the opening time T ₀ and the closing time T _3. The later one of T ₅ and T ₅ is the closing time T _e . As a result, it is possible to substantially widen the time range of the time gate means by the amount corresponding to the individual difference of the person to be measured, as compared with the conventional case where only the time gate based on the pulsation cycle is used. In the case of a person whose systolic blood pressure does not decrease even if the pulsation cycle decreases, even if the Korotkoff sound is generated at the time T ₄
(0.1T ₁ ) Korotkoff sound signal S, even if it occurs before
KD can be collected more reliably.

Further, according to the present embodiment, even if the second opening / closing time based on the DI time was desired to be accurately determined by the previous blood pressure measurement, the first based on the pulsation cycle is used.
Since the time gate means can be configured by the opening / closing time, it is possible to effectively prevent the accuracy of the current blood pressure measurement from being impaired due to the previous blood pressure measurement.

In the above embodiment, the times T ₂ and T ₃ are determined based on the DI time in the previous blood pressure measurement cycle and the PI time ratio, but this is not always necessary, and the microphone 22 and the amplifier 26 are not necessarily required. , And the bandpass filter 30 may be deleted, steps R4 to R7 of the interrupt routine may be deleted, and the determination may be made based on only the DI time in step R9. Even in this case, the temporary effect of the present invention can be obtained.

Further, in the above-mentioned example, when obtaining ΔDI, the DI time near the systolic blood pressure value and the DI time near the diastolic blood pressure value in the previous blood pressure measurement cycle were used. The average value of ΔDI thus obtained and ΔDI obtained in the immediately preceding blood pressure measurement cycle may be used.

Further, in the above-described embodiment, the heartbeat period T ₁ , and thus the first
The opening time T ₄ and the first closing time T ₅ are updated each time the R wave is detected, but they may not be updated.

Further, in the above-described embodiment, the R wave having the largest peak among the heart beats is detected, but the beat of the heart may be detected by using other spike waves such as Q wave and S wave. But it doesn't matter.

Further, in the above-mentioned embodiment, the gate means is constituted by the software of the microcomputer, but the gate means may be constituted by the hard logic circuit.

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

The above description is merely one embodiment of the present invention, and the present invention can be variously modified 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 for explaining the operation of the apparatus shown in FIG. FIG. 4 is a time chart showing the opening and closing of the gate means in accordance with the execution of the flowchart of FIG. 3 together with the occurrence states of pulsation, blood flow sound and Korotkoff sound. FIG. 5 is a diagram showing the relationships used in the flowchart of FIG. FIG. 6 is a claim correspondence diagram. 10: Cuff 24: Microphone 28: Amplifier 32: Bandpass filter 38: Electrode 40: Electrocardiograph SK, SKD: Korotkoff sound signal SH: Electrocardiographic signal Step R8: DI time determining means Step R9: Second opening / closing time determining means Step R10: First opening / closing time determining means Step R17: Time gate means

Claims (1)

[Claims] 1. A heartbeat detecting means for detecting a heartbeat of a living body and outputting an electrocardiographic signal in synchronism with the heartbeat, and a heartbeat detecting means which is generated from the living body according to a pressure change of a cuff wound around a part of the living body. In a blood pressure measuring device comprising Korotkoff sound detecting means for detecting Korotkoff sound and outputting a Korotkoff sound signal representing the Korotkoff sound, and blood pressure value determining means for determining a blood pressure value based on occurrence and disappearance of the Korotkoff sound , A DI time detecting means for detecting a DI time from the generation of the electrocardiographic signal to the generation of the Korotkoff sound signal in the previous blood pressure measurement cycle, and a first opening time after a predetermined time has elapsed from the generation time of the electrocardiographic signal And a first opening / closing time determining means for determining a first closing time after a predetermined time from the first opening time, and a second opening time based on the DI time detected by the DI time detecting means. And second opening / closing time determining means for respectively determining a second closing time, and a later one of the first closing time and the second closing time from the earlier one of the first opening time and the second opening time. And a time gate means for collecting the Korotkoff sound signal up to that time.