JPH0763452B2 - Electronic blood pressure monitor - Google Patents

Description

The present invention relates to an electronic sphygmomanometer, and more particularly to an electronic sphygmomanometer that measures blood pressure by the Korotkoff method during pressurization.

[Prior Art] Conventionally, in order to measure Korotkoff sound at the time of pressurization, valve noise, diaphragm drive sound, pulsation sound, and air blow sound generated by driving an air feeding pump must be input to a Korotkoff sound sensor. Need to prevent. To deal with this, either insert a mechanical filter with a fluid resistance and a buffer tank between the air pump and the cuff, or store compressed air in the buffer tank to boost the pressure using this air, or use a CFC gas cylinder without an air pump. A method of pressurizing using a carbon dioxide gas cylinder is adopted.

In addition, noises generated from the cuff such as rubbing of the cuff cloth and peeling of the fusner that occur during the process of bulging the cuff have been dealt with by improving the cuff.

Furthermore, for artefacts that occur due to pulsation of the cuff central side after ischemic state where the pulse is strong due to hyperactivity, etc., no specific measures have been taken, and when pressure is raised to a pressure higher than one's expected blood pressure. Has manually pressed the pressurization stop switch or the device stop switch to stop the pressurization.

[Problems to be Solved by the Invention] However, due to abnormal pressurization or acceleration due to misidentification of noise generated by cloth jamming or Fusner peeling (such as magic tape) generated in the process of swelling of the cuff as Korotkoff sound. The abnormal pressurization caused by the artefact due to the pulsation of the central side of the cuff when the pulse is abnormally strong increases the burden on the patient and reduces the safety of the sphygmomanometer, and at the same time causes the measurement accuracy to decrease due to measurement error. There is.

The present invention provides an electronic sphygmomanometer that eliminates the above-mentioned conventional drawbacks, prevents abnormal blood pressure, and enhances measurement accuracy.

[Means for Solving the Problem] In order to solve this problem, the electronic sphygmomanometer of the present invention measures a blood pressure by pressing a part of a living body with a cuff and detecting the occurrence or disappearance of Korotkoff sounds. An electronic blood pressure monitor
It has two types of bandpass filters with different frequency bands that pass the signal from the Korotkoff sound sensor, and determines whether boosting is stopped based on the relativity of the output of the signals that have passed through the two types of bandpass filters. It is characterized by comprising a determining means and a boosting stopping means for stopping boosting based on the determination result of the determining means.

The determination means further calculates a systolic blood pressure value generally predicted from the diastolic blood pressure value and the mean blood pressure value measured during pressurization, and a value obtained by adding the maximum variation of the expected value to the value is taken as the pressurization limit value. If the pressure is set and the pressure reaches this limit value, the boosting stop is determined. Also,
The determination means further has a threshold value obtained by multiplying the maximum magnitude of the cuff vibration arterial wave detected in synchronization with the Korotkoff sound at the time of pressurization by a value smaller than 1 determined by the measurement system including the cuff of the sphygmomanometer. Is provided, and it is determined that the pressurization is stopped under the condition that the cuff vibration arterial wave detected after the detection of the average blood pressure is continuously lower than the threshold value for two or more beats. Further, the determination means further determines the boost stop based on the phase relationship of the cuff vibration arterial wave detected in synchronization with the Korotkoff sound at the time of pressurization.

[Operation] With such a configuration, abnormal pressure rise caused by erroneously recognizing noise generated by cloth misalignment or Fusner peeling (such as magic tape) generated in the process of swelling of the cuff as Korotkoff sound, or abnormal pulse pulse When it is strong, it prevents abnormal pressurization caused by artefact due to pulsation of the cuff center side and enhances measurement accuracy.

Embodiments Embodiments will be described in detail below with reference to the drawings.

<Principle of Preventing Abnormal Boosting> First, the principle of preventing abnormal boosting will be described.

Method using different band pass filters Generally, the frequency band included in the Korotkoff sound signal has many 40 to 60 Hz components near systolic blood pressure (near the first point of swan) and 60 to 60 Hz near diastolic blood pressure (near the fifth point of swan). 120Hz
Contains a lot of ingredients, up to systolic blood pressure contains 40-120Hz component. On the other hand, the noise generated from the cuff is
It does not always contain 40 to 120 Hz uniformly, it may mainly contain 40 to 60 Hz, or it may mainly contain 60 to 120, and also the artefact caused by the pulsation on the cuff center side. Mainly includes low signals below 40Hz, 40-120Hz
The signal is detected by the detector only intermittently, not continuously.

Therefore, the signals from the Korotkoff sound sensor are provided with two types of band pass filters with different frequency bands, these are passed, and the relative levels of the signals output from each are observed. When it is repeated once or more, it is judged as noise due to the pulsation of the central side of the cuff and noise generated by the cuff, and the boosting is stopped.

Specifically, 40-120Hz bandpass filter and 60-120Hz
A bandpass filter of Hz is provided, and a signal of a certain threshold level (a level recognized as K sound) or higher appears as a pair, and the former signal is only within 4 beats. If it disappears after being continuously detected, it is normal.On the contrary, only the latter signal is continuously detected, or only the former signal is detected and then the latter signal is detected. When it is detected that both signals are not detected in pairs four times, it is judged as abnormal and boosting is stopped to prevent abnormal boosting.

Method based on blood pressure value during pressurization Generally, the relationship between systolic blood pressure, mean blood pressure and diastolic blood pressure is systolic blood pressure value−mean blood pressure value = 2 × (mean blood pressure value−minimum blood pressure value). Abnormal boosting is prevented by checking the variation inherent in the measurement system including the cuff and setting the value including the variation as the boost limit value.

Specifically, from the diastolic blood pressure (P _D ) and the mean blood pressure (P _M ) measured at the time of pressurization, the generally expected diastolic blood pressure value is calculated as P _M + 2 × (P _M −P _D ). Then, the systolic blood pressure and the true systolic blood pressure value obtained by this calculation are statistically examined using the device and the cuff, and the maximum variation in the difference, for example, 30 mmHg.
If the cuff pressure was Itatsu to a value obtained by adding the _{(P L) P L = 30} + P M +2 (P M -P D), stops the boost as a boost abnormal.

Method based on cuff oscillating arterial waves The change in blood vessel volume under the cuff in the ischemic state is different from that in the non-ischemic state. It seems that the volume of the blood vessel volume under the cuff at the time is about 50% of the volume at which the change becomes large. Therefore, it is expected that the size of the cuff oscillating arterial wave that changes with the volume of the blood vessel below the cuff will be smaller than half the size of the mean blood pressure point. A value including an error of the measurement system is set to this value, and when the magnitude of the pulse wave is 2 beats or more below this value, the boosting is stopped to prevent abnormal boosting due to noise.

Specifically, a Korotkoff sound detection unit and a pulse wave detection unit that separately detects the cuff vibration arterial wave superimposed on the cuff pressure are provided,
Observe the magnitude of the pulse wave from this pulse wave detection unit that is detected in synchronization with Korotkoff sound, and use the pulse wave detection unit and the cuff used for this blood pressure monitor to statistically reach a pressure higher than the systolic blood pressure. When the pulse wave size in the case of the above is measured, it is obtained by investigating a fraction of the pulse wave size of the mean blood pressure point, for example, 0.
When the pulse wave detected below the value obtained by multiplying the value of 3 is continued for 2 consecutive beats, the pressurization is stopped as an abnormal pressurization.

Method based on the phase relationship between the K sound and the cuff vibration arterial wave The phase relationship between the Korotkoff signal and the cuff vibration arterial wave is generally that at the lowest blood pressure point, the Korotkoff sound is generated at the rising portion of the cuff vibration arterial wave, and As it approaches the hypertension point, it moves to the peak point side of the cuff vibration arterial wave, and at the systolic blood pressure point, it is a part after the peak point of the normal cuff vibration arterial wave. On the other hand, the cuff noise is generated without the phase constant with the Korotkoff sound. Further, the influence of the pulsation on the central side of the cuff, which occurs when the pulse is strong such as in the hyperactive state, occurs at the rising point of the cuff vibration arterial wave.

Therefore, if the phase difference between the Korotkoff sound signal and the cuff vibration arterial wave signal is detected, and if the signal is above the Korotkoff sound recognition level for two or more consecutive beats when the phase relationship is not appropriate for systolic blood pressure, , The boost is stopped as a boost abnormality.

<Example of Configuration of Electronic Sphygmomanometer> FIG. 1 is a block diagram showing the configuration of the electronic sphygmomanometer of the present embodiment.

The cuff 1 that compresses a part of the living body and the Korotkoff sensor 2 on the cuff peripheral side are provided, and the signal from the Korotkoff sound sensor 2 is input to the Korotkoff sound detection unit 10 and amplified by the amplifier 11, for example, 40 to 120 Hz and 60 Through two kinds of band pass filters 12 and 13 of up to 120 Hz, comparators 14 and 15 that recognize the output of each filter as a Korotkoff sound when it is above a certain threshold from the threshold circuit 16 are connected. The outputs of the comparators 14 and 15 are connected to the microcomputer 50.

On the other hand, the signal from the pressure sensor 21 connected to the cuff 1 is amplified by the amplifier 22 of the pressure detection unit 20 and connected to the A / D converter 33, and its digital output is connected to the micro computer 50 to detect the pressure of the cuff. Is being detected. Also, pressure sensor 21
After amplifying the signal from the pulse wave detector 30, the pulse wave detector 30 removes the DC component and passes through a bandpass filter 31 for canceling noise, and then again amplified by the amplifier 32 and connected to the A / D converter 33, and the digital signal The output is connected to the microcomputer 50 to detect the cuff vibration arterial wave signal superimposed on the pressure signal.

The cuff pressure is controlled by the motor / valve drive unit 41 from the microcomputer 50, and the air supply pump 42 capable of controlling the rotation speed and the air supply pump 42 between the air supply pump 42 and the cuff 1 at the time of pressurization. It has a pulsation prevention filter 46 consisting of a fluid resistance 46b and a surge tank 46a that prevents the valve noise diaphragm drive sound and pulsation generated by the air pump 42 and enables detection of Korotkoff sound, and is parallel to this filter 46. In addition, it has a bypass valve 45 for bypassing air when unnecessary, and also has a rapid exhaust valve 43 and a constant speed exhaust valve 47.

The microcomputer 50 operates by receiving power supply from the power supply unit 60, and has an arithmetic / operation unit having a counter 51a and a flag 51b.
CPU51 for control, ROM52 which stores a control program,
The RAM 53 includes a point storage unit 53a for auxiliary storage, which stores points of systolic blood pressure, average blood pressure, and diastolic blood pressure, and a maximum value storage unit 53b for storing the maximum pulse wave value.
Further, an LCD display unit 70 for displaying a blood pressure value is connected to the microcomputer 50, and this display unit has an abnormal pressurization indicator 71 for notifying an abnormal pressurization.

This electronic sphygmomanometer recognizes the Korotkoff sound at the time of pressurization and confirms its continuity, thereby recognizing the occurrence point as the lowest blood pressure point and the disappearance point as the highest blood pressure point, while measuring the peak value of the pulse wave peak value. The point is set as the average blood pressure point, and after the maximum blood pressure is recognized, rapid decompression is performed to a pressure slightly higher than the average blood pressure point, and then the accuracy is high again at the decompression speed of the pressure change slower than when measuring the minimum blood pressure during pressurization. Operates to measure the lowest blood pressure.

FIG. 2 is a diagram for explaining the concept of the operation of the electronic blood pressure monitor.

After performing rapid pressurization up to cuff pressure of 20 mmHg, it becomes medium speed pressurization, the time when the Korotkoff sound signal appears from the comparator 15 is the minimum blood pressure point during pressurization, the maximum value of the cuff swing arterial wave is the average blood pressure point, The time when both outputs of the comparators 14 and 15 disappear, the systolic blood pressure point, and the comparator 15
The last time point when the output of is disappeared is the diastolic blood pressure point.

At the time of recognizing the systolic blood pressure, the following control is performed corresponding to each of the above pressure increase prevention methods.

Method using different band pass filters Observing the outputs of the two filters for detecting Korotkoff sounds described above, except for the case where the outputs of only the filter 12 as shown in Figs. 3A to 3D are within 4 consecutive beats, for example, When the outputs of the filters 12 and 13 do not form a pair as shown in FIGS. 4A to 4C when four times are counted from the average blood pressure point,
As an abnormality, the pressurization is stopped, and the timing at which the last Korotkoff sound is detected is displayed as the systolic blood pressure. In addition, this abnormality at this time may be displayed by blinking or another indicator.

Method based on blood pressure value during pressurization The expected systolic blood pressure obtained by the formula given earlier than the minimum blood pressure and average blood pressure obtained during pressurization during confirmation of this systolic blood pressure should be considered as variations in this measurement system. For example
A pressure value 30 mmHg higher is set as the boost limit value, and if it is detected that the cuff pressure value exceeds this value, it is judged as a boost and the boost is stopped. At this time, this abnormality is displayed by an indicator or the like.

Method based on cuff vibration arterial wave The pulse wave detection unit detects the magnitude of the cuff vibration arterial wave detected in synchronization with Korotkoff sound at the time of this systolic blood pressure recognition, and the magnitude is the peak value of the pulse wave at the mean blood pressure point. If, for example, 30% or less of two consecutive beats (indicated by A in FIG. 2) is reached, it is determined that the true systolic blood pressure point has been passed, and the pressurization is stopped. At this time, this abnormality is displayed by an indicator or the like. .

Method based on the phase relationship between the K sound and the cuff vibration arterial wave When observing this systolic blood pressure, observe the phase relationship between the Korotkoff sound and the pulse wave detected by the pulse wave detection unit, and check the Korotkoff sound at or after the peak point of the pulse wave. If the Korotkoff signal appears continuously for two or more beats at other timings, it is judged as abnormal, the boost is stopped, and the last Korotkoff sound of the phase relationship that is valid is detected. Recognize and display points as systolic blood pressure points. Alternatively, it is dealt with by displaying only the indicator as an abnormality or by performing both.

<Processing Procedure of Electronic Sphygmomanometer> FIG. 5 and FIGS. 6A to 6D show a flow chart showing the processing procedure of the electronic sphygmomanometer.

FIG. 5 is a main flow. First, at step S11, the counter i, the flag E, and the pressure value are initialized to zero values. Perform rapid pressurization up to 20 mmHg with steps S12 and S13, and
After 0mmHg, switch to medium speed pressurization and check continuous Korotkoff sounds at step S15. At step S16, the point where this Korotkoff sound is generated is stored as the diastolic blood pressure point. Next, in step S17, the maximum value of the pulse wave crest value is checked, and in step S18, the maximum value and the point thereof are stored as the average blood pressure point.

After the mean blood pressure, in step S19, switching to low speed pressurization is performed, and in step S20, elimination of Korotkoff sound is checked. Since abnormal boosting may occur at this point, if the Korotkoff sound does not disappear, the process proceeds to step S28 to check whether the boosting is abnormal. If there is abnormality, step S2
The process proceeds from 9 to S30, the pressure is rapidly reduced in step S30, and the abnormal pressure increase indicator is set in step S31. If the pressure is not abnormally increased, the process returns to step S20 and the Korotkoff sound disappearance check is repeated.

If there is disappearance of Korotkoff sound, proceed from step S20 to step S21 and memorize this point as the systolic blood pressure point,
In steps S22 and S23, the pressure is rapidly reduced to mean blood pressure + α (α ≈ 10 mmHg). At step S24, switch to low-speed decompression, and at step S25 check the disappearance of Korotkoff sounds, and at step S26
The point disappeared by is stored as the minimum blood pressure point during decompression, and the maximum blood pressure during pressure increase and the minimum blood pressure during pressure reduction are displayed in step S27.

FIGS. 6A to 6D are a flow chart showing the above-described four examples of the routine of the abnormal boost check in step S28.

In FIG. 6A, first, in step S41, it is checked whether the Korotkoff sounds that have passed through the different band pass filters 12 and 13 are a pair, and if they are a pair, the process directly returns. If they are not a pair, and if there are four types of patterns shown in FIGS. 3A to 3D in step S42, the process directly returns. If the pattern is not of four types, the counter i is counted up by one in step S43, and it is checked in step S44 whether i is 4 or not. In the case of 4, the process proceeds to step S45 to set the flag E of abnormal pressure rise and returns.

In FIG. 6B, in step S51, the average blood pressure value P _M and the minimum blood pressure value P _M
By calculating the _{P M +2 (P M -P D} ) +30 from _D take this into P _L. In step S52, it is checked whether or not the current pressure value P is larger than P _{L, and} if not, the process directly returns. If it is larger, the routine proceeds to step S53, where the abnormal pressure rising flag E is set and the routine returns.

In Fig. 6C, the maximum value A of the pulse wave is 0.3 × A at step S61.
Calculate and put it in A ₀ . In step S62, it is checked whether or not the current crest value of the pulse wave is smaller than A _{0. If} it is not smaller, i = 0 is set in step S66 and the process returns. If it is smaller, the counter i is counted up at step S63, and i =
If not 2, return as it is. When i = 2, the process proceeds to step S65 to set the abnormal pressure rising flag E and return.

In Fig. 6D, the phase of the Korotkoff sound and the pulse wave is compared in step S71, and in step S72, the Korotkoff sound is output from the bottom point of the pulse wave to the middle of the rising point and the peak point of the pulse wave as shown in Fig. 7. It is checked whether or not it is within the range (R). If it is not within the range, i =
Set 0 and return. If there is Nutep S73 counter i
Is counted up, and in step S74 it is checked whether i = 2. If i = 2 is not satisfied, the process directly returns. i =
In the case of 2, the flag E of abnormal boosting is set in step S75 and the process returns.

In this example, FIGS. 6A to 6D are independent abnormal boosting checks, but by combining these, the abnormal boosting check can be performed more correctly.

[Effects of the Invention] According to the present invention, it is possible to provide an electronic blood pressure monitor that prevents abnormal blood pressure and improves measurement accuracy.

In other words, the abnormal increase in pressure due to the cuff noise such as cloth shift and fusner peeling that occurs during pressure increase can be prevented, so that the safety for the patient is secured and the burden is reduced. Moreover, the measurement error due to the generation of this kind of noise can be prevented, and the accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the electronic sphygmomanometer of the present embodiment, FIG. 2 is a diagram showing the principle of blood pressure measurement with the electronic sphygmomanometer of the present embodiment, and FIGS. 3A to 3D show abnormal pressurization. FIG. 4A to FIG. 4C are diagrams showing pattern examples of abnormal pressurization, FIG. 5 is a flow chart showing the processing procedure of the electronic sphygmomanometer of the present embodiment, and FIGS. 6A to 6D are FIG. 7 is a flow chart showing an example of the routine of the abnormal boosting check, and FIG. 7 is a diagram showing the phases of the Korotkoff sound and the pulse wave. In the figure, 1 ... Cuff, 2 ... Korotkoff sensor, 10 ... Korotkoff sound detector. 11 …… Amplifier, 12 …… Bandpass filter (40 to 120Hz), 13 …… Bandpass filter (60
~ 120Hz), 14,15 …… Comparator, 16 …… Threshold circuit, 20 …… Pressure detector, 21 …… Pressure sensor, 22 …… Amplifier, 30 …… Pulse wave detector, 31 …… Band pass Filter, 32
...... Amplifier, 33 …… A / D converter, 41 …… Motor / valve drive, 42 …… Air pump, 43 …… Rapid exhaust valve, 45 …… Bypass valve, 46 …… Pulsation prevention filter,
46a …… Surge tank, 46b …… Fluid resistance, 47 …… Constant speed exhaust valve, 50 …… Microcomputer, 51 …… CPU, 5
1a …… Counter i, 51b …… Flag E, 52 …… ROM53 ……
RAM, 53a ... Point storage section, 53b ... Maximum value storage section, 6
0: Power supply, 70: LCD display, 71: Abnormal boost indicator.

Claims (4)

[Claims] 1. An electronic sphygmomanometer for measuring blood pressure by pressing a part of a living body with a cuff to detect the occurrence or disappearance of Korotkoff sounds, and having different frequency bands for passing signals from the Korotkoff sound sensor. Based on the relativity of the output of the signal that has passed through the two types of bandpass filters, a determination unit that determines whether boosting is stopped, and a determination result of the determination unit An electronic sphygmomanometer, which is provided with a boosting stop means for stopping boosting. 2. The judgment means further calculates a systolic blood pressure value generally predicted from the diastolic blood pressure value and the mean blood pressure value measured at the time of pressurization, and adds the maximum variation of the predicted value to the calculated systolic blood pressure value. 2. The electronic sphygmomanometer according to claim 1, wherein the boosting limit value is set as, and the boosting stop is determined on condition that the pressure reaches this limit value. 3. The determination means further sets a maximum value of the cuff vibration arterial wave detected in synchronization with the Korotkoff sound at the time of pressurization to a value smaller than 1 determined by the measurement system including the cuff of the sphygmomanometer. A step of stopping the pressurization is performed under the condition that a threshold value is set and the cuff vibration arterial wave detected after detection of the average blood pressure is continuously lower than the threshold value for two or more beats. The electronic blood pressure monitor according to item 1 or 2. 4. The determination means further determines whether boosting is stopped based on the phase relationship of the cuff vibration arterial wave detected in synchronization with Korotkoff sound at the time of boosting. An electronic blood pressure monitor according to any one of 1.