JPS6373934A - Blood pressure measuring apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an improvement in a blood pressure measuring device that automatically measures the blood pressure of a living body.

Prior Art Korotkoff sound detection means detects Korotkoff sounds generated from a living body as pressure changes in a cuff wound around a part of the living body and outputs a Korotkoff sound signal representing the Korotkoff sounds; A blood pressure measuring device is known that includes a blood pressure value determining means that determines a blood pressure value based on occurrence and extinction.

Such blood pressure measuring devices are usually provided with a noise removal means such as a hand-pass filter, which eliminates vibrations with frequency components different from Korotkoff sounds, such as noises generated due to body movements of living organisms, etc. It is designed to remove.

However, even in a device equipped with such a noise removal means, it is not possible to remove noise that approximates the frequency component of the Korotkoff sound, and as a result, blood pressure values may be determined incorrectly.

For this reason, conventionally, a heartbeat detecting means is provided that outputs an electrocardiographic signal synchronized with the heartbeat, and after a predetermined period of time has elapsed from the generation of the electrocardiogram signal, a period of a predetermined time width based on the heartbeat cycle is detected. A gate is provided and the Korotkoff sound signal is collected through this time gate. However, the time from the generation of the electrocardiogram 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 period, so even if the pulsation period decreases, the systolic blood pressure value decreases. In the case of people who do not use this method, the time range of the time gate may be insufficient to reliably collect Korotkoff sounds.

On the other hand, the applicant filed the earlier patent application No. 1
No. 39048 provides a blood pressure measuring device in which a gate means is opened and closed based on the DI time and the like in the previous blood pressure measuring cycle of the same subject. In this device, since the gate means is opened and closed accurately in response to individual differences among the subjects, it has the advantage that Korotkoff sounds can be collected more reliably.

Problems to be Solved by the Invention However, such devices still have problems to be solved. That is, in such a device, the gate means is opened and closed based on the previous blood pressure measurement, so depending on the previous blood pressure measurement, the gate means may not be opened or closed accurately. be. That is, it is sufficient if the previously measured blood pressure value is sufficiently reliable, but if the blood pressure value is erroneously measured due to noise or the like, there is a problem in that the accuracy of the current blood pressure measurement is impaired.

Means for Solving the Problems The present invention was made against the background of the above circumstances, and its gist is to detect the heartbeat of a living body and output an electrocardiographic signal synchronized with the heartbeat. A heartbeat detection means, a Korotkoff sound detection means for detecting Korotkoff sounds generated from a living body in response to changes in pressure of a cuff wrapped around a part of the living body, and outputting a Korotkoff sound signal representing the Korotkoff sounds; A blood pressure measuring device comprising: (a) generation of the Korotkoff sound signal from generation of the electrocardiogram signal in a previous blood pressure measurement cycle; (b) determining a first opening time after a predetermined time has elapsed from the generation time of the electrocardiographic signal, and determining a first closing time after a predetermined time from the first opening time; (C) a second opening/closing time determining means for determining a second opening time and a second closing time, respectively, based on the DI time detected by the DI time detecting means; (dll Time for collecting the Korotkoff sound signal from the earlier of the first and second opening times to the later of the first and second closing times. and gate means.

As described above, in the blood pressure measuring device of the present invention, as shown in the claim correspondence diagram of FIG. 6, the DI time from the generation of the electrocardiogram signal to the generation of the Korotkoff sound signal in the previous blood pressure measurement cycle is At the same time as being detected by the detection means, the first opening/closing time determining means determines the first opening time after a predetermined time has elapsed from the generation time of the electrocardiographic signal, and the first closing time is determined after a predetermined time from the first opening time. Meanwhile, a second opening time and a second closing time are respectively determined based on the DI time by the second opening/closing time determining means. Then, the time gate means starts the first opening time from the earlier of the first opening time and the second opening time.
The Korotkoff sound signal is collected up to the later of the closing time and the second closing time, and the blood pressure value is determined by the blood positive value determining means based on the generation and extinction of the Korotkoff sound represented by this Korotkoff sound signal. is determined.

Effects of the Invention As described above, according to the blood pressure measuring device of the present invention, the time gate consisting of the first opening time and the first closing time determined based on the generation time of the electrocardiographic signal and the time gate of the same subject A time gate means is used that has a maximum time width that is the sum of the two time gates, the time gate consisting of the second opening time and the second closing time determined based on the D1 time in the previous blood pressure measurement cycle. Therefore, compared to the conventional case that uses only a gate method based on the pulsation period,
Korotkoff sound signals can be collected more reliably without being influenced by individual differences among subjects.

Furthermore, even if the second opening time and second closing time based on the DI time were not determined accurately 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 as follows, it is possible to effectively prevent the accuracy of the current blood pressure measurement from being impaired due to the previous blood pressure measurement.

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

In FIG. 1, numeral 10 is a rubber bag-shaped cuff that is wrapped around the upper arm or the like of the subject. The cuff lO has cuff 1
A pressure sensor 12 that detects zero pressure, an electric pump 14 that supplies gas into the cuff 10 and increases the pressure. And an exhaust valve device 16 is connected to exhaust the gas inside the cuff 10 to lower the pressure of the cuff 10. The exhaust valve device 16 is composed of, for example, an on-off valve for rapid evacuation, a throttle valve for constant-speed evacuation, and an on-off valve. The cuff 10 can be switched between three states: a constant speed 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, supplies a pressure signal SP representing the pressure to the low-pass filter 18. The low-pass filter 18 removes vibration components such as pulse waves from the pressure signal SP, and removes the cuff pressure signal S representing the static pressure of the cuff 10.
C is supplied to the A/D converter 20.

The cuff 10 has microphones 22 and 24 disposed at its upstream and downstream ends, respectively, in a portion that is located above the artery when it is wrapped around the upper arm or the like. These microphones 22.
24 detects the vibration sound generated by blood flow from the artery and outputs sound signals SSI and SS2 representing the vibration sound, and the output sound signals SSI and SS2 are sent to amplifiers 26 and 28, respectively. After being amplified at , the signal is supplied to bandpass filters 30 and 32. Bandpass filter 3
0 extracts only the blood flow sound component (for example, a vibration component of about 10 to 150 Hz) that occurs with the pulsation of the artery from the sound signal SS1, and removes the other vibration components. The blood flow sound signal SB representing λ/D convert 2
Supply to 0. Furthermore, the bandpass filter 32 filters a so-called Korotkoff sound component (for example, 30
The microphone 2
4 and the amplifier 28 constitute the Korotkoff sound detecting means of this embodiment, and detect a click sound signal S representing the Korotkoff sound.
K is supplied to the A/D converter 20.

The A/D converter 20 receives the supplied cuff pressure signal S.
C. After converting the blood flow sound signal SB and Korotkoff sound signal SK into digitally encoded cuff pressure signal SCD, blood flow sound signal SBD, and Korotkoff sound signal SKD,
They are supplied to the CPU 34 according to timing No. 18 ST. The CPU 34 connects to I10 via the data bus line.
The I10 boat 36 is connected to the port 36, and the I10 boat 36 is connected to the electrocardiograph 40, which is equipped with an electrode 38 attached to the chest of the subject and detects the heartbeat electrically. An electrocardiographic signal SH representing pulsation is supplied. These electrodes 38 and electrocardiograph 40 constitute the heartbeat detection means of this embodiment.

In addition, the I10 boat 36 has a start signal S from the push button PB.
A is now supplied.

The CPU 34 constitutes a so-called microcomputer together with the RAM 42 and the ROM 44, and processes signals supplied according to a program stored in the ROM 44 in advance while utilizing the primary storage function of the RAM 42, and generates a drive signal MP for operating the electric pump 14. , and exhaust valve device 1
The drive signal M V for switching the I10 port '36 is outputted from each of the I10 ports '36, and the timing signal S
T is supplied to the A/D converter 20. In addition, display 4
6 to supply the display signal DD from the I10 boat 36,
The systolic blood pressure value and diastolic blood pressure value are displayed numerically. Note that the CPU 34 is supplied with a pulse signal CK of a predetermined frequency from a clock signal source 48.

Next, the operation of this embodiment will be explained based on the flowcharts shown in FIGS. 2 and 3 and the time charts shown in FIGS. 4 and 5.

In FIG. 2, when a power switch (not shown) is turned on, step S1 is executed after an initialization step (not shown), and whether or not the push button PB has been operated, in other words, the start signal SA is sent to the I10 boat 36. It is determined whether or not it is supplied. When the activation signal SA is supplied, step S2 is then executed, in which the exhaust valve device 16 is closed and the electric pump 14 is activated, so that the actual pressure in the cuff 10 represented by the cuff pressure signal SCD is predetermined. The pressure is increased until the target pressure is reached, which is higher than the patient's systolic blood pressure value. When the pressure of the cuff lO reaches the target pressure, the electric pump 14
is stopped, the exhaust valve device 16 is switched to a constant rate exhaust state, and the pressure in the cuff 10 is lowered at a constant rate. During this process, a blood pressure value determination routine in step S3, which is the blood pressure value determination means of this embodiment, 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 well-known blood pressure is determined based on the Korotkoff sound signals SKD sequentially collected during the blood pressure lowering process of the cuff 10. A systolic blood pressure value and a diastolic blood pressure value are determined according to a value determination algorithm.

Next, by executing steps s4 and s5, the exhaust valve device 16 is switched to the rapid exhaust state, and the gas in the cuff 1o is rapidly exhausted, and the indicator 4
6 displays the systolic blood pressure (a and the diastolic blood pressure value).

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

In the above interrupt routine, first, in step R1, the electrocardiographic signal SI is read, and in the subsequent step R2, the R wave indicating the strongest peak of the heart beats represented by the electrocardiographic signal SH is detected. If the determination in step R2 is negative, the interrupt routine is terminated without going through the following steps, but if it is determined that an R wave has been detected, the subsequent step At R3, the counting content t of the timer that counts the pulse signal CK supplied from the clock signal source 4 is reset, and the heartbeat period T1 of the subject's heart is calculated.Time in FIG. 1o indicates the state at this time.The pulsation period T1 is specifically the time T, -+ (4th (see figure) is used.Also, the heartbeat is normally P.

It consists of five wave waves: Q, R, S, and T, but of these, the R wave shows the strongest peak, so there is no risk of the R wave being mistakenly detected due to external noise. .

In the subsequent step R4, the blood flow sound signal SBD is calculated only when the count content t of the timer is within the range of the following equation (1).
Allow reading of.

0.1T+ <t<0.3T, ...(1) In other words, the count content is still 0. If I T + has not been reached, step R4 is repeated, but when the count content t is 0. When IT is reached, steps R5 and R
6 is executed, the blood flow sound signal SBD is loaded, and it is determined whether or not blood flow sound has been detected based on the blood flow sound signal SBD. The time range in equation (1) above is set based on the pulsation period T1 because the delay time (P1 time) from when the R wave is detected to when the occurrence of blood flow sound is detected is measured. This is based on the fact that when a person's pulsation cycle is short, the time range in which blood flow sounds are expected to occur is also narrowed accordingly.

If blood flow sound is not detected in step R6, the steps from step R4 onwards are repeated, but if blood flow sound is detected, reading of the blood flow sound signal SBD ends at that point, and step R7 is executed. Ru. Time 1 in Figure 4. is the time when the blood flow sound was detected in step R6. Normally, the blood flow sound is detected by the time the count content of the timer reaches 0.3T, but if the count content t reaches 0.3T without detecting the blood flow sound, at that point At this point, the reading of the blood flow sound signal SBD is stopped, and the interrupt routine ends.

In step R7, the PI waiting time is read, and the ratio between the current P1 time and the P1 time read in the previous blood pressure measurement cycle is calculated. In the subsequent step R8, the longest 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, is determined. Three consecutive DI times around the hypertension value DI□+DIS□
.

DIs3 and three consecutive D1 times around the diastolic blood pressure value D
I□, DI, □, and DId3 are respectively read, and their DI times DI□, DI. 2. D
Average value of l, 3 and D1 time DIa+, Dlaz, D
The difference ΔD■ from the average value of la:+ is determined from the following equation (2). Therefore, this step S8 is D in this embodiment.
This corresponds to I time determining means.

(2) In this way, by using the average value of three consecutive DI times, ΔDr is made stable regardless of the occurrence of arrhythmia or the like. FIG. 5 shows the delay time between the occurrence of blood flow sound detected by the microphone 22 attached on the upstream side of the artery and the occurrence of Korotkoff sound detected by the microphone 24 attached on the downstream side, That is, D.I.
This shows the difference between the time and 21 hours with respect to the cuff pressure.As can be seen from the figure, the difference between the DI time around the diastolic blood pressure value and the P1 time is relatively small, and the difference between the DI time around the systolic blood pressure value and the P1 time is relatively small.
The difference between I time and P1 time is relatively large. Therefore, ΔDI is the difference between the DI time from the onset of a heartbeat to the occurrence of the earliest scheduled Korotkoff sound and the D'1 time from the occurrence of the last scheduled Korotkoff sound, i.e., the scheduled time. It corresponds to the time from the generation of the first Korotkoff sound to the generation of the last Korotkoff sound. In addition, DI=+, DI-2, DI-3 and Dl, ++,
DId□, Dl, +i do not include the DI time of the systolic blood pressure value itself and the DI time of the diastolic blood pressure value itself, respectively. This is because, as shown in FIG. 5, values near the systolic and diastolic blood pressure values other than the systolic blood pressure value itself and the diastolic blood pressure value themselves are relatively stable.

Next, by executing step R9, the following equation (3
) and (4), time T2 corresponding to the second opening time and time T3 corresponding to the second closing time of this embodiment are determined based on the P1 time ratio and ΔDI. Therefore, these times T z and T s are determined in accordance with individual differences among the subjects.

...(3) T:1=T2+ΔDIX1.75 ...
(4) However, P■: P in this blood pressure measurement cycle
1 hour PIp: When step RIO is executed during the PI waiting time in the previous blood pressure measurement cycle, time T4 corresponding to the first opening time and time T corresponding to the first closing time of this embodiment are the same as the above-mentioned pulse. It is determined based on the motion period T1.

That is, in this embodiment, time T4 is 0. I
T + D and time T S are determined at 0.6 T + , respectively. The time range defined by both times T4 and T is set to be larger than the time range in step R4. The reason for this is that the generation time of the blood flow sound is not affected by the pressure of the cuff 10, but the generation time of the Korotkoff sound is not affected by the pressure of the cuff 10.
Based on being influenced by pressure. In this embodiment, step R9 causes the second opening/closing time determining means to
10 corresponds to the first opening/closing time determining means.

In the next step R11, it is determined whether time T2 is smaller than time T4. If this judgment is affirmed, the time T2 is set to the opening side T0 of the time gate means of this embodiment in the subsequent step R12, while if the judgment in step R12 is negative, step R13
is executed, and time T4 is the opening side T. It is said that Next, in step R14, it is determined whether time T3 is smaller than time T. If this judgment is affirmed, the time T3 is set to the closing side Te of the time gate means of this embodiment in the subsequent step R15, while if the judgment in step R14 is negative, step R1
6 is executed, and time T5 is set as the closing side Te.

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 'l'0<t<Te. Therefore, this step R17 corresponds to the time gate means of this embodiment. In step R17, the count content t is still T. If the count has not reached To, step R17 is repeatedly executed, but if the count reaches To and does not exceed Te, steps R18 and R19 are executed,
The Korotkoff sound signal SKD is read, and it is determined based on the Korotkoff sound signal SKD whether or not a Korotkoff sound has been detected.

When the Korotkoff sound is detected by repeatedly executing the judgments from step R17 onwards, the reading of the Korotkoff sound signal SKD is completed at that point, the gate means is closed, and the interrupt routine is also completed. Time t2 in FIG. 4 is the time when the Korotkoff sound is detected in step R19 and the gate means is closed. Normally, the Korotkoff sound is detected before the timer count t reaches Te, but if the count exceeds Te without the Korotkoff sound being detected, the gate means is closed and the interrupt routine is executed. be terminated. Time L3 in FIG. 4 is the time when the gate means is closed in this manner.

The Korotkoff sounds detected in this interrupt routine are 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 predetermined time intervals, but the pulsation period T is updated every time an R wave is detected, and when the next interrupt routine is executed, the pulsation period T is Time T (see FIG. 4) is used as T.

As described above, in the blood pressure measuring device of this embodiment, in step R9, the PI time and DI time, which change depending on the individual differences of the subjects, and the pr time ratio, which changes for each blood pressure measurement cycle, are , the second opening time and the second
Times T2 and T3 corresponding to the closing time are determined, and times T4 and T corresponding to the first opening time and the first closing time are respectively determined based on the pulsation cycle T1 in Ste-Knob RIO. On the other hand,
In the time gate means of step R17, the opening side T
The earlier time of T2 and T4 is the open side T0, and the later time of the close side T3 and T5 is the closed side T. It is said that As a result, compared to the conventional case in which only the time gate based on the pulsation period is used, it is possible to substantially expand the time rQ range of the time gate means by an amount corresponding to individual differences among the subjects. For example, in the case of a person whose systolic blood pressure value does not decrease even if the pulsation period decreases, even if the Korotkoff sound is at the time T4 (0, I
T,) even if it occurred before the Korotkoff sound signal SK
D can be collected more reliably.

Furthermore, according to this embodiment, even if it is desired to accurately determine the second opening/closing time based on the D1 time depending on the previous blood pressure measurement, the time gate can be determined based on the first opening/closing time based on the pulsation cycle. Therefore, 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 addition, in the above embodiment, the time 'rz, T3 is
DI time and PI in the previous blood pressure measurement cycle
Although it is determined based on the time ratio, it is not necessary to do so, and the microphones 2, 2, the amplifier 26, and the bandpass filter 30 are deleted, steps R4 to R7 of the interrupt routine are deleted, and step R is determined based on the time ratio.
9, the determination may be made based only on the DI time. Even in this case, a certain effect of the present invention can be obtained.

Furthermore, in the above embodiment, when calculating ΔDI, the DI time around the systolic blood pressure value and the DI time around the diastolic blood pressure value in the previous blood pressure measurement cycle were used; ΔDI obtained in this way
The average value of ΔDI and ΔDI obtained in the immediately previous blood pressure measurement cycle may be used.

Further, in the above embodiment, the heartbeat cycle Tl, as well as the first opening time T4 and the first closing time T, etc. are updated every time an R wave is detected, but they do not have to be updated. .

Further, in the above embodiment, the R wave with the largest peak behind the heart beat is detected, but the heart beat may be detected using other waves such as Q waves and S waves. It doesn't matter if you do that.

Further, in the above embodiments, the gate means is constituted by software using a microcomputer, but this gate means may also be constituted by a hard logic circuit.

Further, in the above embodiment, the blood pressure value is measured during the blood pressure lowering process of the cuff 10, but the blood pressure value is measured during the blood pressure raising process of the cuff 10. S can also be created.

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

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the configuration of a blood pressure measuring device that is an embodiment of the present invention. 2 and 3 are flowcharts for explaining the operation of the apparatus shown in FIG. 1. FIG. 4 is a time chart showing the opening and closing of the gate means in accordance with the execution of the flowchart in FIG. 3, together with the occurrence of pulsation, blood flow sounds, and Korotkoff sounds. FIG. 5 is a diagram showing the relationships used in the flowchart of FIG. 3. FIG. 6 is a complaint correspondence diagram. 10: Cuff 24: Microphone 28: Amplifier 32: Hand pass filter 38: Electrode 40: Electrocardiograph SK, SKD: Korotkoff sound signal SH: Electrocardiogram signal Step R8: DI time determining means Step R9: Second opening/closing time determining means Step RIO: First opening/closing time determining means Step R17
: Time gate means applicant: Nippon Korin-ku Co., Ltd. N'j Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A heartbeat detecting means for detecting the heartbeat of a living body and outputting an electrocardiographic signal synchronized with the heartbeat, and a heartbeat detecting means for detecting the heartbeat of a living body and outputting an electrocardiographic signal synchronized with the heartbeat, A blood pressure measuring device comprising a Korotkoff sound detection means for detecting a Korotkoff sound and outputting a Korotkoff sound signal representing the Korotkoff sound, and a blood pressure value determining means for determining a blood pressure value based on the generation and extinction of the Korotkoff sound. DI time detection means for detecting a DI time from generation of the electrocardiogram signal to generation of the Korotkoff sound signal in the previous blood pressure measurement cycle; a first opening/closing time determining means for determining a time and a first closing time a predetermined time after the first opening time; and a second opening time and a second opening time based on the DI time detected by the DI time detecting means. second opening/closing time determining means for determining second closing times; and
and time gate means for collecting the Korotkoff sound signal from the earlier of the opening times to the later of the first closing time and the second closing time. Blood pressure measuring device.