JPH03121045A - Electronic hemadynamometer - Google Patents

Abstract

PURPOSE:To obtain an electronic hemadynamometer for preventing the abnormal blood pressure with high precision by suspending the boosting on the basis of the result of the judgment of a judging means for judging the predetermined boosting suspension condition. CONSTITUTION:The signal supplied from a Korotkoff sound sensor 2 is allowed to pass by installing two band-pass filters 12 and 13 having two kinds of different frequency bands, i.e., the band-pass filter 12 having a frequency band of 40-60Hz and the band-pass filter 13 having a frequency band of 60-120Hz. It is judged normal when the signals over a certain thresh level (level recognized as Korotkoff sound) from the both band-pass filters, in view of the both relativity appear in pair, and only the former signals are continuously detected within four beats, and then vanishes. On the contrary, when the case where the both signals are not detected in pair continues four times except the above-described, for example when only the latter signals are detected continuously or only the latter signals are detected after only the former signals are detected, it is judged that the case is abnormal, and the abnormal rise of pressure is prevented by suspending boosting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic sphygmomanometer, and particularly to an electronic sphygmomanometer that measures blood pressure using the Korotkoff method during pressure increase.

[Prior art] Conventionally, in order to measure Korotkoff sound during pressurization, valve noise generated by driving an air pump, diaphragm drive sound, pulsation sound, and air supply sound are input to a Korotkoff sound sensor. It is necessary to prevent To deal with this, you can either insert a mechanical filter with a fluid resistance and a buffer tank between the air pump and the cuff, store compressed air in the buffer tank and use this air to increase the pressure, or It uses a method of pressurizing using gas cylinders or carbon dioxide gas cylinders.

Additionally, noise generated from the cuff, such as rubbing of the cuff cloth and peeling of the zipper, which occurs during the inflation process of the cuff, has been addressed by improving the cuff.

Furthermore, special measures are taken to prevent artifacts caused by pulsations on the central side of the cuff after a state of ischemia where the pulse is strong due to increased blood pressure. The pressurization was stopped by manually pressing the pressurization stop switch or device stop switch.

[Problems to be Solved by the Invention] However, abnormal pressure rise or increased pressure occurs when the noise generated by cloth rubbing or peeling of a zipper (of Velcro, etc.) that occurs during the cuff inflation process is mistaken as Korotkoff sound. Abnormal blood pressure increases caused by artifacts caused by pulsations on the central side of the cuff when the pulse is abnormally strong due to blood pressure increases the burden on the patient, reduces the safety of the blood pressure monitor, and at the same time causes a decrease in measurement accuracy due to measurement errors. There is.

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

[Means for Solving the Problem] In order to solve this problem, the electronic blood pressure monitor of the present invention measures blood pressure by applying pressure with a cuff that is a part of a living body and detecting the occurrence or disappearance of Korotkoff sounds. The electronic sphygmomanometer includes a determining means for determining a predetermined pressurization stop condition, and a pressurizing stop means for stopping pressurization based on the determination result.

Here, the determination means passes the signal from the Korotkoff sound sensor through two types of band-pass filters with different frequency bands and observes the relativity of the output. A first determining means is provided for determining whether a state in which more noise is generated is present.

Further, the determination means calculates a systolic blood pressure value that is generally predicted from the diastolic blood pressure value and the average blood pressure value measured during pressure increase,
A value obtained by adding the expected maximum variation of values to that value is set as a pressure increase limit value, and a second determining means is provided for determining whether the pressure has reached this limit value.

Further, the determination means determines a threshold value obtained by multiplying the maximum magnitude of the cuff oscillation artery wave detected in synchronization with the Korotkoff sound during pressurization by a value smaller than l determined by the measurement system including the cuff of the blood pressure monitor. and third discriminating means for discriminating when the cuff oscillation arterial wave detected after the mean blood pressure is detected falls below the threshold value for two or more consecutive beats.

Further, the determining means includes a fourth determining means for determining the increase in pressure by discriminating between the Korotkoff sound and noise using the phase relationship of the cuff oscillation artery wave detected in synchronization with the Korotkoff sound during the increase in pressure. Equipped with

[Function] With this configuration, noise caused by cloth rubbing or peeling of a zipper (such as Velcro) that occurs during the cuff inflation process is mistakenly recognized as Korotkoff sound, resulting in abnormal pressure increase or abnormal pulse due to an accelerated state. This prevents abnormal pressure rise caused by artifacts caused by pulsations on the central side of the cuff when the pressure is strong, and improves measurement accuracy.

[Example code] Hereinafter, embodiments will be described in detail according to the drawings.

<Principle of preventing abnormal pressure rise> First, the principle of preventing abnormal pressure increase will be explained.

■ Method using different bandpass filters The frequency band included in the Korotkoff sound signal generally has many 40 to 60H2 components near the systolic blood pressure (near the first point of the Swan), and 60 to 60H2 components near the diastolic blood pressure (near the fifth point of the Swan). Contains a lot of ~120H2 component, and the frequency up to systolic blood pressure is 40~120Hz
Contains ingredients. On the other hand, the noise generated from the cuff does not always uniformly include the 40 to 120 Hz range;
If it mainly contains 0 to 60 Hz, or 60 to 120 Hz
In addition, artifacts caused by pulsations on the central side of the cuff mainly include low signals below 40H2, and signals between 40H2 and 60H2 are detected by the detection unit only intermittently, not continuously. Not done.

Therefore, the signal from the Korotkoff sound sensor is passed through two types of band-pass filters with different frequency bands, and the relative level of the signal output from each is observed. When this is repeated, it is determined that the noise is due to the pulsation on the central side of the cuff and noise generated from the cuff, and the pressurization is stopped.

Specifically, a 40-60H2 bandpass filter and 6
A band pass filter of 0 to 120 Hz is provided, and by looking at the relativity of both, signals above a certain threshold level (level recognized as a K sound) appear in pairs, and then 4
If only the former signal is detected continuously within a beat and then disappears, it is considered normal; conversely, only the latter signal is detected continuously, or only the former signal is detected, then only the latter signal is detected. Abnormal boosting of voltage is prevented by determining that an abnormality has occurred and stopping boosting when both signals are bare and not detected four times in addition to the above.

■Method based on blood pressure value during pressurization In general, the relationship between systolic blood pressure, mean blood pressure, and diastolic blood pressure is systolic blood pressure - mean blood pressure = 2 x (mean blood pressure - diastolic blood pressure), and this relationship is used to In addition, abnormal pressure rise can be prevented by checking the inherent variations in the measurement system including the cuff and setting the pressure increase limit value as a value including the variations.

Specifically, from the diastolic blood pressure (Po) and mean blood pressure (PM) measured during pressurization, the expected systolic blood pressure value on board the ship is calculated as p, +2x (Pu-po), and this calculation is added to this. The systolic blood pressure obtained by If cuff pressure is reached, pressurization is stopped as an abnormality.

■ Method based on cuff oscillation arterial waves Changes in blood vessel volume under the cuff in an ischemic state are different from those in a non-ischemic state, and in a state where the cuff is barely ischemic, the blood vessel volume is ischemic at the center of the cuff, and the average It is thought that the volume is about 50% of the volume at which the change in blood vessel volume under the cuff becomes the largest during blood pressure. Therefore, it is expected that the magnitude of the cuff oscillation arterial wave, which changes depending on the blood vessel volume under the cuff, will also be smaller than half the magnitude of the average blood pressure point.

Abnormal pressure increase due to noise can be prevented by setting a value that includes the error of the measurement system, and stopping pressure increase when the pulse wave size becomes two or more beats below this value.

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 detector, which is detected in synchronization with the Korotkoff sounds, and use the pulse wave detector and the cuff used in this sphygmomanometer to determine if the pressure is statistically higher than the systolic blood pressure. For example, 0
．． If the detected pulse wave is below the value multiplied by the value 3 for two consecutive beats, the pressure increase is determined to be abnormal and the pressure increase is stopped.

■ How to determine the phase relationship between the sound and the cuff oscillation arterial wave The phase relationship between the Korotkoff signal and the cuff oscillation artery wave is -M-wise, at the diastolic blood pressure point, the Korotkoff sound occurs at the rising edge of the cuff oscillation arterial wave; As it approaches the systolic blood pressure point, it moves toward the peak point of the cuff oscillation arterial wave, and at the systolic blood pressure point, it is usually a portion after the peak point of the cuff oscillation arterial wave. On the other hand, cuff noise occurs with an inconsistent phase with Korotkoff sound. In addition, the influence of the pulsation on the cuff central side, which occurs when the pulse is strong in the photoadvanced state, occurs at the rising point of the cuff oscillating arterial wave.

Therefore, the phase difference between the Korotkoff sound signal and the cuff vibration arterial wave signal is detected, and if a signal equal to or higher than the Korotkoff sound recognition level is input for two or more consecutive beats when the phase relationship is not appropriate for systolic blood pressure, Stop pressurization due to abnormal pressurization.

Configuration Example of Electronic Blood Pressure Monitor> FIG. 1 is a block diagram showing the configuration of the electronic blood pressure monitor of this embodiment.

A Korotkoff sensor 2 is provided on the distal side of the cafe and cuff that presses a part of the living body, and the signal from the Korotkoff sound sensor 2 is input to the Korotkoff sound detection unit 10 and amplified by an amplifier 11. The output of each filter is passed through two types of band-pass filters 12 and 13 with a frequency of 120 Hz, and the output of each filter is connected to comparators 14 and 15, which recognize the sound as Korotkoff sound when the frequency exceeds a certain threshold value from the threshold circuit 16. The outputs of 14° and 15 are connected to a microcomputer 50.

On the other hand, the signal from the pressure sensor 21 connected to the cuff 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 microcomputer 5o to measure the cuff pressure. Detected. or,
After amplifying the signal from the pressure sensor 21, the pulse wave detection unit 3
The pressure signal is passed through a band-pass filter 31 for eliminating DC components of 0 and canceling noise, amplified again by an amplifier 32 and connected to an A/D converter 33, and its digital output is connected to a microcomputer 5o. Detects the cuff vibration arterial wave signal superimposed on the

The cuff pressure is controlled by a motor from the microcomputer 50.
Air supply pump 42 and air supply pump 4 whose rotational speed can be controlled via valve drive unit 41
A pulsation prevention device consisting of a fluid resistance 46b and a surge tank 46a is provided between the air pump 42 and the cuff 2 to prevent valve noise, diaphragm drive noise, and pulsation generated by the air pump 42 during pressurization, thereby enabling the detection of Korotkoff sounds. A bypass valve 45 for bypassing air when unnecessary is provided in parallel with the filter 46, and a rapid exhaust valve 43 and a constant speed exhaust valve 47.

The microcomputer 50 operates by receiving power supply from a power supply section 60, and includes a CPU 51 for calculation and control which has a counter 51a and a flag 51b, a ROM 52 for storing control programs, and an auxiliary memory for storing systolic blood pressure and average blood pressure. , a point storage unit 53a that stores points of diastolic blood pressure.
and a maximum value storage section 53b that stores the maximum pulse wave value. Further, an LCD display section 70 for displaying blood pressure values is connected to the microcomputer 50, and this display section has an abnormal pressure increase indicator 71 for reporting abnormal pressure increase.

This electronic sphygmomanometer detects Korotkoff sounds during pressurization and confirms their continuity, thereby recognizing the point at which they occur as the diastolic blood pressure point and the point at which they disappear as the systolic blood pressure point. The point is taken as the average blood pressure point, and after recognizing the systolic blood pressure, rapid depressurization is performed to a pressure slightly higher than the average blood pressure point l-, and then the accuracy is again determined at a decompression speed with a slower pressure change than when measuring the diastolic blood pressure during pressurization. Operates to measure high diastolic blood pressure.

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

Rapid inflation is performed until the cuff pressure reaches 20 mmHg, followed by medium-speed inflation, and the diastolic pressure point at the time when the Korotkoff sound signal appears from the comparator 15 is the diastolic blood pressure point, the maximum value of the cuff oscillation arterial wave is the average blood pressure point, The point in time when both the outputs of the comparators 14 and 15 disappear is the systolic blood pressure point 1. The last point in time when the output of the comparator 15 disappears during pressure reduction is defined as the diastolic blood pressure point during pressure reduction.

At this point in time when the systolic blood pressure is recognized, the following control is performed corresponding to each of the above-mentioned pressure increase prevention methods.

■ Method using different bandpass filters Observe the outputs of the two filters for Korotkoff sound detection described above, and unless the output of only the filter 12 is within 4 consecutive beats as shown in Figures 3A to 3D, For example, if the outputs of the filters 12 and 13 do not form a pair four times, counting from the average blood pressure point, as shown in FIGS. 4A to 4C,
The pressure increase is stopped as an abnormality, and the timing at which the last Korotkoff sound is detected is displayed as the systolic blood pressure. Further, this abnormality at this time may be displayed by blinking or other indicators.

■Method based on blood pressure value during pressurization When confirming systolic blood pressure recognition, the expected systolic blood pressure obtained from the formula shown earlier should be considered as a variation in the diastolic blood pressure and mean blood pressure obtained during pressurization in this measurement system. , for example 3
A pressure value 0 mmHg higher is set as the pressure increase limit value, and if it is detected that the cuff pressure value exceeds this value, the pressure increase is determined to be abnormal and the pressure increase is stopped. At this time, this abnormality is displayed with an indicator or the like.

■Method based on cuff oscillation arterial waves During this systolic blood pressure recognition, the pulse wave detection unit detects the magnitude of the cuff oscillation arterial waves detected in synchronization with the Korotkoff sounds, and the magnitude is the pulse wave at the mean blood pressure point. If the high value (indicated by A in Figure 2) falls below, for example, 30% for two consecutive beats, it is determined that the true systolic blood pressure point has been passed and pressure increase is stopped, and this abnormality is displayed on an indicator, etc. do.

■A method based on the phase relationship between the sound and the cuff vibration arterial wave When recognizing the systolic blood pressure, the phase relationship between the Korotkoff sound and the pulse wave detected by the pulse wave detector is observed, and the Korotkoff sound is detected at or after the peak point of the pulse wave. When the Korotkoff signal appears, continue measurement, and if the Korotkoff signal appears for two or more consecutive beats at any other timing, it is determined to be abnormal, and the boost is stopped.The last Korotkoff sound detection point in the phase relationship is determined to be appropriate. is recognized as the systolic blood pressure point and displayed.

Alternatively, the problem can be dealt with by simply displaying it on the indicator as an abnormality, or by doing both.

<Processing Procedure of Electronic Sphygmomanometer> Fig. 5 and Figs. 6A to 6D are flowcharts showing the processing procedure of the electronic sphygmomanometer.

FIG. 5 shows the main flow. First, in step Sll, the counter i, the flag E, and the pressure value are initialized to zero. Steps S12 and S13 perform rapid pressurization up to 20 mmHg, and after 20 mmHg, switch to medium speed pressurization, and check for continuous Korotkoff sounds in step S15. In step S16, the point at which this Korotkoff sound occurs is stored as the diastolic blood pressure point during pressurization. Next, in step S17, the maximum value of the pulse wave height value is checked, and in step S18, the maximum value and its point are stored as an average blood pressure point.

After the average blood pressure, the pressure is switched to low-speed pressurization in step S19, and the disappearance of Korotkoff sounds is checked in step S20. Since there is a possibility that an abnormal pressure increase may occur at this point, if the Korotkoff sound does not disappear, the process advances to step S28 to check whether there is an abnormal pressure increase. If there is an abnormality, the process proceeds from step S29 to S30, where the pressure is suddenly reduced in step S30, and an abnormal pressure increase indicator is set in step S31. If there is no abnormal pressure increase, the process returns to step S20 and the check for Korotkoff sound disappearance is repeated.

If the Korotkoff sound disappears, steps S20 to S32
Step S22.1 stores this point as the systolic blood pressure point. In S23, the average blood pressure child 〇 (041
Rapidly reduce pressure to 0 mmHg). In step S24, the mode is switched to low-speed decompression, in step S25 it is checked whether the Korotkoff sound has disappeared, in step S26 the point where it disappeared is stored as the diastolic blood pressure point during decompression, and in step S27 the systolic blood pressure during pressurization and the diastolic blood pressure during depressurization are determined. Display.

FIGS. 6A to 6D are flowcharts showing the above-mentioned four examples of the abnormal pressure increase check routine in step S28.

In FIG. 6A, first, in step S41, it is checked whether the Korotkoff sound passed through different bandpass filters 12, 13 is bare or not, and if it is bare, the process returns directly. If it is not bear, and if it is one of the four patterns shown in FIGS. 3A to 3D in step S42, the process returns directly. If the pattern is not 4 types, step S4
3, the counter i is incremented by one, and step S4
At step 4, check whether i is 4 or not, and if it is not 4, simply return. In the case of 4, the process proceeds to step S45, sets the abnormal pressure increase flag E, and returns.

In FIG. 6B, the mean blood pressure value PM and the diastolic blood pressure value P are determined in step S51. From P. Calculate +2(Pv Po)+30 and enter this into Pa. In step S52, it is checked whether the current pressure value P is greater than Pa, and if it is not greater, the process returns directly. If larger, step S
Proceed to step 3, set flag E for abnormal pressure increase, and return.

In FIG. 6C, from the maximum value A of the pulse wave to 0 in step S61.
．． Calculate 3XA and put it in AO.

In step S62, it is checked whether the current pulse wave height value is less than 80, and if it is not, it is set to i20 in step S66 and the process returns. If it is smaller, step S63
Count up the counter i, and if i is not 2, return directly. If i=2, the process advances to step S65, sets the abnormal pressure increase flag E, and returns.

In FIG. 6D, in step S71 the phase of the Korotkoff sound and the pulse wave is compared, and in step S72 it is checked whether the Korotkoff sound is in front of the pulse wave as shown in FIG. 7A. If not, in step S76 = 0 and return. If so, count up the counter i in step S73,
In step S74, it is checked whether f=2 or not, and if i=2, the process returns directly. If i=2, a flag E for abnormal pressure increase is set in step S75, and the process returns.

In this example, although FIGS. 6A to 6D are used as independent abnormal pressure increase checks, by combining these, a more accurate abnormal pressure increase check can be performed.

[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.

That is, it is possible to prevent abnormal pressurization and decrease due to cuff noise that occurs during pressurization, such as cuff cloth shifting and zipper peeling, thereby ensuring safety for the patient and reducing the burden on the patient. In addition, measurement errors due to the occurrence of this type of noise were prevented, and accuracy was improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the electronic sphygmomanometer of this embodiment, Fig. 2 is a diagram showing the principle of blood pressure measurement with the electronic sphygmomanometer of this embodiment, and Figs. 3A to 3D show abnormal pressure increase and Figures 4A to 4C are diagrams showing examples of abnormal pressure increase patterns. Figure 5 is a flowchart showing the processing procedure of the electronic blood pressure monitor of this embodiment. Figures 6A to 6D are diagrams showing abnormal pressure rise patterns. A flowchart showing an example of the boost check routine, FIGS. 7A and 7B are diagrams showing the phases of Korotkoff sounds and pulse waves. In the figure, ■...Cuff, 2...Korotkoff sensor, 10
...Korotkoff sound detection section. 11...Amplifier, 12.
・Band pass filter (40~120H2) 1
3...Band pass filter (60-120Hz)
14.15... Comparator, 16... Threshold circuit, 20... Pressure detection section, 21... Pressure sensor,
22... Amplifier, 30... Pulse wave detection unit, 31...
Bandpass filter, 32...Amplifier, 33...A
/D converter, 41... motor/valve drive section, 4
2...Air supply pump, 43...Rapid exhaust valve, 45
...Bypass valve, 46...Anti-pulsation filter,
46a...Surge tank, 46b...Fluid resistance, 4
7... Constant speed exhaust valve, 50... Microcomputer, 51... CPU, 51a... Counter i, 5
1b...Flag E152...ROM53...RA
M, 53a... Point storage section, 53b... Maximum value storage section, 60... Power supply section, 70... LCD display section,
71... Abnormal boost indicator.

Claims (5)

[Claims] (1) An electronic sphygmomanometer that measures blood pressure by compressing a part of a living body with a cuff and detecting the occurrence or disappearance of Korotkoff sounds, comprising a determination means for determining a predetermined pressor stop condition; An electronic sphygmomanometer characterized by comprising a pressure increase stop means for stopping pressure increase based on a determination result. (2) The determination means passes the signal from the Korotkoff sound sensor through two types of bandpass filters with different frequency bands and observes the relativity of the output. 2. The electronic blood pressure monitor according to claim 1, further comprising a first determining means for determining whether noise is occurring. (3) The determination means calculates the systolic blood pressure value that is generally predicted from the diastolic blood pressure value and the mean blood pressure value measured during pressurization, and calculates the value obtained by adding the expected maximum variation of the value to the pressure increase limit value. 3. The electronic sphygmomanometer according to claim 1, further comprising second determining means for determining whether the pressure has reached this limit value. (4) The determination means determines a threshold value obtained by multiplying the maximum magnitude of the cuff oscillation arterial wave detected in synchronization with the Korotkoff sound during pressurization by a value smaller than 1 determined by the measurement system including the cuff of the blood pressure monitor. Claim 1, further comprising a third determining means that sets a value and determines when the cuff oscillation arterial wave detected after the mean blood pressure is detected falls below the threshold value for two or more consecutive beats.
The electronic blood pressure monitor according to any one of Items 3 to 3. (5) The determination means performs a fourth discrimination for determining a pressurization by discriminating between the Korotkoff sound and noise using the phase relationship of the cuff oscillation artery wave detected in synchronization with the Korotkoff sound during pressurization. The electronic blood pressure monitor according to any one of claims 1 to 4, characterized in that the electronic blood pressure monitor comprises means.