JP3491076B2 - Blood pressure measurement device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention recognizes Korotkoff sounds (hereinafter abbreviated as "K sounds") to measure blood pressure, and enables accurate blood pressure measurement even when the measurement environment is not good, especially during exercise. The present invention relates to a blood pressure measurement device that can be performed.

[0002]

2. Description of the Related Art In a blood pressure measuring method based on K-sound recognition, after the arm girdle is worn on the upper arm or the like, the pressure of the arm girth is controlled to recognize the K sound and the maximum and minimum blood pressures are obtained. However, the level of the K sound is low, and if there is a disturbance such as body movement, it is affected by the disturbance, and it is difficult to identify it. Recently, exercise stress tests have been attracting attention for the purpose of evaluating circulatory function and other purposes. However, since the cardiac activity dynamically changes during exercise and there is a lot of noise due to body movements, etc. Was difficult.

Various measures have been taken to solve such problems. Heartbeat-synchronous type sphygmomanometer is intended that pulse wave from the electrocardiogram signal generator after a predetermined time has paying attention to that occurring, JP 61-85922, only a certain period of generation of the pulse wave is expected vibration Is to reduce the influence of noise. It omits about another invention contained in this invention. Japanese Patent Application Laid-Open No. 59-160437 has almost the same contents. However, in these inventions, it is described that the signal is measured for a certain period after a certain period of time from the generation of the electrocardiographic signal, but no specific description about the certain period and the certain period is made. In addition, JP-A-62-181
In 029, the vibration is measured for a certain period in which the blood vessel vibration is expected, and the K sound is measured in synchronization with the blood vessel vibration for a certain period in which the K sound is expected to be generated. It can be considered that this is an improvement of the above-mentioned Japanese Patent Laid-Open No. 61-85922. Since the fixed time and the fixed period are proportional to the cycle of the electrocardiographic signal, even if the cycle of the electrocardiographic signal changes a little. You can follow it and measure. However, it does not describe a method to follow the fluctuation of the electrocardiographic signal cycle, and basically it can be applied only when the cycle of the electrocardiographic signal is almost constant, and is not applicable to dynamic changes such as exercise load. I can't follow. Further, in these inventions, noise generated during the measurement period cannot be removed.

Japanese Patent Laid-Open No. 62-295647 discloses a time at which a K sound is generated by measuring a delay time between the generation of an electrocardiographic signal and blood flow sound and a delay time between the electrocardiographic signal and K sound. To measure the K sound. The purpose of this invention is to measure blood pressure during exercise.
The sound generation time can be predicted to some extent. However, since blood flow sound measurement is premised, blood pressure measurement cannot be performed when blood flow sound measurement is difficult, that is, when noise is superimposed, it is difficult to identify it. Further, since two sensors for K sound detection and blood flow sound detection are used, the structure is complicated unlike the present invention. Furthermore, the method of predicting the K sound occurrence time differs from that of the present invention.

According to Japanese Patent Publication No. 5-61929, a K sound is first identified by a pattern recognition method, and further, the K sound is generated during the rising period of the pulse wave, and the signals generated in other periods are noise, and the noise is removed. There are also things to try. However, also in this case, when noise is superimposed on the K sound, pattern recognition itself becomes difficult.

Japanese Patent Publication No. 5-56897 relates to a sphygmomanometer based on a vibration method, which is different from the method based on the K-sound recognition of the present invention, but detects vascular vibration and frequency-analyzes it to determine a specific frequency. Focusing on, the pressure when the electric power changes greatly is determined as the maximum or minimum blood pressure. This is also difficult to identify because the power for a specified frequency changes when there is noise.

During exercise, the vibration detection microphone may be displaced from the mounting position, and the signal may not be detected. Conventionally, no sphygmomanometer intended for measurement during exercise incorporates means for solving this problem. However, in the tonometry method that adapts to the radial artery and keeps the volume constant, the sensitivity of the sensor becomes a problem because the measurement signal is weak, and multiple sensors are arranged, and the largest output among them is Some choose a sensor. Fair fair 5-4641
3 is this. However, in this invention, the sensor with the largest output is selected using the sensor output as an index, so if there is noise, the output may be the largest due to noise, and the optimum sensor is selected to extract the signal. There are things you can't do. Further, the sensitivities of the sensors vary individually, and when using a plurality of sensors, it is necessary to select the sensors or separately perform sensitivity correction. Further tonometry method intended group Dzu rather completely different principle and means the K sound method, purpose are devised another field of the time of the monitor rest, it is impossible to apply this invention to the blood pressure measurement during exercise .

[0008]

Recently, as the importance of the evaluation of the cardiovascular system by the exercise stress test has been widely recognized, the need for blood pressure measurement not only at rest but also during exercise is increasing. In the blood pressure measurement in the exercise test, first, in a rest state before the test, then repeat the measurement at fixed time intervals while giving an exercise load using a treadmill or an ergometer, and then recover after the exercise test is completed. Rest at intervals and measure at regular time intervals. In the exercise stress test, cardiac activity dynamically changes, and along with that, the generation timing of the electrocardiographic signal and K sound also greatly changes. In addition, noise due to body movements and the like occurs during the entire measurement period. Therefore, it is difficult to identify K sound and pulse sound by the conventional method, and it is difficult to measure blood pressure accurately.
The present invention accurately predicts the K sound generation time, reduces the influence of noise, enhances the K sound discrimination ability, and solves the above-mentioned problems. This enables accurate blood pressure measurement. The blood pressure measurement method is a pressurization method in which the blood pressure is measured while gradually increasing the pressure according to the procedure of pressure control, and conversely, the blood pressure is first increased to a value higher than the maximum blood pressure value, and then the pressure is gradually decreased. There is a step-down method. The present invention can be applied to either method.
However, the boosting method will be described here for convenience.

[0009]

According to the present invention, a pressurizing means for applying a pressure to a blood vessel, a pressure detecting means for detecting a pressure applied to the blood vessel, and a vibration detecting means for detecting a vibration generated in the blood vessel. An electrocardiographic detection means for detecting an electrocardiographic signal,
The present invention relates to a heartbeat-synchronized blood pressure measuring device, which has a signal processing means for processing a detected signal, measures K sound from the vibration and measures blood pressure, and which can be used even during exercise.

In order to solve the above-mentioned problems, first, the signal is measured only during the period when K sound is expected to be generated to reduce the influence of noise. When an electrocardiographic signal is generated, vibration of blood vessels occurs after a certain time delay. The vibration is only the pulse wave at the pressure below the minimum blood pressure, and when the pressurization progresses to reach the minimum blood pressure, K
Sound is generated by being superimposed on the pulse wave. When the pressure is further increased, a plurality of pulse waves in which the K sound is superimposed are generated, and when the systolic blood pressure is reached, the K sound disappears, and thereafter, only the pulse wave vibrates. The timing of K sound generation changes depending on the pressure applied to the blood vessel and the heart rate (electrocardiographic signal generation cycle) at that time. In order to predict the K sound occurrence time, it is necessary to consider such points. A first aspect of the present invention is to intuition proposed the influence of said pressure.

The delay time td from the electrocardiographic signal generation time to the K-sound generation time is affected by the armband pressure even if the electrocardiographic signal generation cycle is constant. When the pressure changes from the maximum blood pressure to the minimum blood pressure by about 50 mmHg, the delay time td is 100 m.
Change about S. Therefore, in order to accurately predict the K sound generation time, it is necessary to consider the influence of pressure. Therefore, in the invention of claim 1, advance to create a prediction equation of lag time td as a function of the pressure P applied to the vessel, by measuring the pressure P and time at that every time the electrocardiographic signal is generated, this The delay time td with respect to the pressure P is obtained using the above-mentioned prediction formula,
This delay time td is added to the generation time of the electrocardiographic signal to obtain the predicted time t1 of K sound generation, and the vibration signal is measured during the period T1 before and after the time t1. In addition, the blood pressure measurement, the relationship between the pressure P and the delay time td at that time every time detecting an electrocardiographic signal was measured and adapted to learn and correct the prediction equation. The updated prediction formula was used for the next blood pressure measurement. Conventionally, K
There is nothing to predict the occurrence time of the sound and the pulse wave, but the present invention so to claim 1, intended to account for the influence of the pressure of the cuff, but also you learn-correcting the prediction equation every time the measurement of Did not exist.

[0012] More to the first aspect of the invention, K-sound generating time
Can be predicted more accurately than before, so the vibration measurement period can be set to K
Since it can be shortened to the sound generation period, the influence of noise can be reduced. Further, the present invention can be applied to the case where the pulsation of the heart dynamically changes during exercise. Therefore, accurate blood pressure measurement is possible.

Even if the K-sound occurrence time is accurately predicted and the K-sound is detected from the vibration signal, if there is a lot of noise, it is necessary to distinguish whether it is the K-sound or the noise. Therefore, claim 2
In the described invention, frequency analysis is performed every time K sound is measured, a digital filter is created using this frequency characteristic, and the vibration signal is measured through this filter. Moreover, even for the same subject, the frequency characteristics of the K sound will change if the pressure of the arm girdle or the blood pressure value changes.
An adaptive filter is used to analyze the frequency characteristic every time the K sound is measured to learn the change in the frequency characteristic and correct the characteristic of the digital filter. Conventionally, some K sound detection filters have been devised, but a digital filter is created by utilizing the frequency characteristics of K sound as in the present claim, and further, K
There has been no method for learning the frequency characteristic of each sound and modifying the digital filter to identify the K sound by using the adaptive filter.

The signal measured by the inventions of claims 1 and 2 is K
Although it has a high probability of being a sound, if there is noise similar to the frequency characteristic of the K sound, it is erroneously recognized as a K sound. Therefore, the K sound is always generated by overlapping with the pulse wave, and the vibration component includes the pulse wave component and the K sound component by a predetermined amount, which is utilized to distinguish between the K sound and noise. In this invention according to claim 3, wherein the vibration signal by frequency analysis determined the power ratio of the pulse wave and K sound, the value of this ratio is K sound if Dere within a certain range,
If it is out of the range, it is determined to be noise. As a result, whether the signal passed through the digital filter for detecting K sound according to claim 2 is K sound or noise that accidentally passed,
Can be identified. In the past, there were those that paid attention to the change in the power of the K sound. The above-mentioned prior art / Japanese Patent Publication No. 5-56897 is to identify a K sound by analyzing a frequency of a signal and observing a change in power of a specific frequency component. However, the present invention judges that the K sound is generated or disappears when the value of the electric power of the specific frequency changes significantly, which is clearly different from the invention of claim 3 . Conventionally, there has been no method for identifying the K sound by the method of the present invention.

[0015] The invention of claim 4, wherein is intended to detect a signal only to suppress the noise. A plurality of sensors for detecting vibration are arranged, each sensor measures a signal in a vibration measurement period TA and a period TB other than that, and a ratio is obtained. The sensors M1 and M2 having the maximum and minimum ratios are selected. , The main input sensor and the reference input sensor, respectively, the output signal of the sensor M2 is processed by the filter H (jω), the difference between the output of the sensor M1 and the output of the filter H (jω) is taken as the output S0, and the output S0 is The noise is suppressed by feeding back to the filter H (jω) and modifying the coefficient of the filter H (jω) so that the output S0 is minimized. The LMS method used in the field of communication may be used as the algorithm for correcting the filter coefficient. However, the coefficient correction algorithm may use any means. Since there is a correlation between the noise included in the signal detected by the sensor M1 and the noise detected by the sensor M2, this adaptation processing is possible. This algorithm is always executed during measurement, and if the sensor mounting position shifts,
The sensor at the optimum position is selected again so that it can be used. The TA may use the measurement period T1 described in claim 1 or 2, and the TB may use the period in which no vibration occurs.

Conventionally, as described in Jpn. Pat. Appln. KOKAI-46413, there are some which use a plurality of sensors.
However, in this invention, the sensor with the largest output is selected using the output of the sensor as an index, so it is not possible to determine whether the sensor with the largest output is due to a signal or due to noise, and noise cannot be suppressed. . Further, the sensitivities of the sensors vary individually, and when using a plurality of sensors, it is necessary to select or perform sensitivity correction, which complicates the use. Further, the present invention relates to a device of an application field different from the invention of the present claim called the tonometry method, and has different purposes, means, actions and effects. Always select the most suitable sensor as in the invention of this claim
However, there has been no method of suppressing noise by the adaptive processing in the past.

The K sound just before disappearing is weak and difficult to recognize, which causes an error in blood pressure measurement. Therefore, in the invention of claim 5, wherein in order to solve this problem was to identify the vanishing point of the K sound from a different perspective than the K sound that the pulse wave of the phase. That is, an algorithm for sequentially measuring the phase of vibration with the vibration detector 3 during blood pressure measurement and determining that the K sound disappeared when the phase was inverted was added. Conventionally, there is no document that mentions that the phase of the pulse wave is inverted when the K sound disappears.

[0018] even when blood pressure exercise test changes, always allow efficient short time blood pressure measurement, in the invention of claim 6 wherein <br/>, low constant value than the diastolic blood pressure value to be expected The pressure P1 and the pressure P2, which is higher than the systolic blood pressure by a constant value, are set, and pressurization or depressurization is performed in the low-speed measurement mode within the range of P1 to P2, and rapid pressurization or depressurization is performed outside the range. I chose As the predicted blood pressure value, the previously measured value, the blood pressure value predicted from the measurement result up to the previous time, the heart rate, or the like can be used. Further, it is a feature of the present invention that P1 and P2 are updated each time measurement is performed so as to cope with changes in blood pressure. As a result, the blood pressure can be measured in a short time, and when the blood pressure value changes during the operation, the pressures P1 and P2 are changed accordingly, so that it can be used during exercise. Some conventional resting sphygmomanometers perform rapid pressurization and depressurization outside the blood pressure measurement range, but they can only control within a fixed range, and when blood pressure fluctuates as in an exercise test, it follows it. Then, there is no one that can change the range of P1 and P2.

[0019]

[Function] Conventionally, there have been those that predict the time of occurrence of vibration to measure blood pressure, but since the influence of the pressure on the arm girdle was not taken into consideration, a large measurement period must be taken,
Therefore, there was a high probability that noise was mixed. In the invention of claim 1 wherein <br/>, predicts the K sound generation time in consideration of the pressure of the cuff
And, also, the prediction type of lag time because they are learned and corrected in each measurement can be applied to vary the period of the electrocardiographic signal such as during exercise.

[0020] According to the second aspect of the invention, the subject uppermost
A digital filter having a frequency characteristic of a new K tone is created and a signal is processed through this filter. Each time K sound is measured, frequency analysis is performed to learn the frequency characteristics, the characteristics of the digital filter are corrected, and the result is used for the next K sound analysis. Therefore, the K sound can be identified more accurately than before, and even if the frequency characteristic of the K sound changes due to a change in the armband or the blood pressure value, the accurate K sound identification can be performed correspondingly.

[0021] According to the third aspect of the invention, obtains the power ratio of the pulse wave and K sound, it is determined that the K sounds are present if the value of the power ratio is within a predetermined range. Therefore, noise having a frequency characteristic similar to K sound can be identified, and even if noise is superimposed to some extent, K sound can be identified.

According to the invention described in claim 4 , noise can be suppressed by using the reference input signal having a high correlation with the noise component for the measurement signal having a poor SN ratio. If the mounting position of the sensor deviates due to body movement or the like, the optimum sensor is selected again at that time, noise is similarly suppressed, and vibration is measured. Therefore, it is possible to always perform measurement in good condition even in an exercise load test in which there is a lot of noise and the sensor mounting position may shift.

[0023] According to the fifth aspect of the invention, the K sound that pulse wave vibration of the phase at another indicator so to recognize the presence of the K sound, maximum or if K sound near the diastolic blood pressure is weak,
The occurrence or disappearance can be accurately determined.

[0024] According to a sixth aspect of the present invention, within the set pressure range to measure the vibration with pressure or vacuum at a low speed, the outside setting range perform rapid pressurization and pressure reduction. Further, the set range is changed according to the actually measured blood pressure value. Therefore, according to the invention of this claim, even if the blood pressure value fluctuates greatly, it is possible to follow it and perform efficient and short-time measurement. Also, in the exercise stress test, blood pressure fluctuates in a short time.
It is necessary to make the measurement time for each measurement as short as possible. Also from this point of view, accurate measurement is possible in the present invention. Further, since the blood pressure measurement is repeatedly performed in the exercise load test, the physical load on the subject can be reduced because the measurement time for one measurement is short. Conventionally, there were those that perform rapid pressurization / depressurization within an almost fixed range, but by following the changes in the latest measured maximum / minimum blood pressure values, the most appropriate blood pressure value can be predicted from the previous measurement value. However, there is no one that performs rapid pressurization / depressurization to this vicinity.

Although the exercise load test based on the K-sound recognition method has been mainly described above, any of the inventions can be applied to a resting blood pressure monitor .

[0026]

EXAMPLE An example of application to an exercise test by a pressurizing method of measuring blood pressure while increasing the pressure applied to the arm band of a sphygmomanometer will be described with reference to the drawings. Figure 1
1 is a configuration diagram of the present invention, in which 1 is an arm band that applies pressure to a blood vessel, 2 is a pressure gauge that detects pressure applied to the blood vessel, that is, pressure of the arm band, and 3 is vibration detection that detects vibration generated in the blood vessel. In the present invention, a plurality of microphones are arranged as a vibration detection sensor in the present invention, 4 is a pump for sending air to the armband to pressurize it, and 5, 6, 7 are valves for opening and closing to control the flow of air. Among these, the valve 7 is a valve for low-speed decompression by blood pressure measurement by the blood pressure reduction method, 8 is a chamber for smoothing the pressure applied to the arm girdle, 9 is the pump 4, the valves 5-7, etc. A CPU including an I / O port and a device driver that reads a signal from a vibration detector and performs data processing, 10 is a display for displaying measurement results, 11 is a control panel for controlling the device, and 12 is an electrocardiogram. No. detection section, A. The electrocardiographic signal detection unit 12 may be an electrocardiograph or a port for taking in signals from an external electrocardiograph.

When the measurement is started, the valve 5 is opened, the valves 6 and 7 are closed, the pump 4 is turned on, and air is sent.
The air sent from the pump is smoothed in the chamber 8 and sent into the arm girdle at a constant speed to pressurize the blood vessel. In the present invention, rapid pressurization is performed up to the set pressure P1. This will be described in detail in the description of the invention of claim 7. From P1 to the set value P2, blood pressure is measured while pressurizing at a constant low speed.

During the measurement, the electrocardiographic signal, the vibration, and the pressure are measured by the electrocardiographic signal detector 12, the vibration detector 3, and the pressure gauge 2, respectively. The K sound is generated a certain time after the electrocardiographic signal is generated. Its delay time td has it been known that depend on blood pressure, also subject affects the pressure applied to the vessel. According to the first aspect of the present invention, the K sound generation time is predicted in consideration of the influence of the pressure P, and the vibration signal is measured .

In the invention according to claim 1 , the electrocardiographic signal is
Delay time td until the Korotkoff sound is generated
A prediction equation as a function of the pressure applied to the vessel.
When the electrocardiographic signal is detected by the electrocardiographic signal detection unit 12, the pressure P at that time is measured by the pressure gauge 2 and the delay time td of K sound generation with respect to this pressure P is obtained from the prediction formula. ,
The obtained td is added to the electrocardiographic signal generation time to obtain the K sound generation predicted time t1, and the vibration is measured by the vibration detector 12 in the period T1 before and after the time t1. FIG. 2 shows this situation. As shown in FIG. 4A, when an electrocardiographic signal is generated, a K sound is generated with a certain delay from this point. This delay time is affected by pressure. When the electrocardiographic signal is detected, the pressure P at that time is measured, the delay time td with respect to the pressure P is calculated from the prediction formula of FIG. 7B, and this td is added to the electrocardiographic signal generation time to obtain t1. K sound is expected to occur. When this t1 is obtained, the vibration is measured in the period T1 before and after that. Further, in the invention of this claim, at the time of measuring the blood pressure, the K sound occurrence time is predicted to measure the vibration, and at the same time, the pressure P and the delay time td are actually measured, and the result is used to calculate the prediction formula. Learn and modify to use in the next blood pressure measurement. The prediction formula of the delay time td is created as follows. That is, the prediction formula can be generally described as a function of the pressure P as follows: td = f (p) ... (1)

However, the formula (1) cannot be uniquely determined because it varies depending on the subject, and even the same subject changes depending on the condition such as blood pressure at the time of measurement. Therefore, in the present invention, at the time of blood pressure measurement, the pressure P and the delay time td at that time are actually measured every time an electrocardiographic signal is generated, and td = P * A + B ... (2) P is the pressure of the armband, and A and B are constants. Is linearly regressed and used as a prediction formula for the K sound occurrence time. The broken line in FIG. 2B is the measured data, and the solid line is the regression line. In addition to this, the prediction formula is various, such as an actual measurement value, a regression of the actual measurement value other than the formula (2), a formula (1) specified from the characteristics of the subject, or a formula in which these are corrected by the heart rate. There are various types, but the type does not matter. However, since it has not yet been applied to an individual in the first blood pressure measurement, the constant of the prediction formula (2) has not been determined and cannot be used as it is. Therefore, in the present invention, A = 1.0 and B = 100, which are considered statistically appropriate from the experimental results, are set and used in the first measurement. It has been confirmed that even with this, it is possible to measure more than the conventional heart rate reference blood pressure monitor. Also in the exercise test, the first measurement is performed in a resting state before the test, and thus the prediction formula may not be used at first, and the measurement may be performed in the same manner as a conventional blood pressure monitor. Also in this case, the relationship between the pressure P and the delay time td is actually measured, and a prediction formula is created for the next measurement.

When the K sound generation time t1 is predicted as described above, the vibration is measured during the period T1 before and after the prediction. This may be measured during the period of T1 by the gate means, but in the invention of this claim, the probability density function shown in FIG. 2C-1 is used to further suppress the influence of noise. . The function in the figure has a probability of 1 in the section of T10 and a sine wave in the section of T11. The interval T10 is associated so that the probability of K sound generation is statistically within the range of 3σ. Specifically, T10 is 100 mS, T11 is 50
Although it is set to about mS, if the prediction of K sound generation is performed more accurately than in equation (2), both T10 and T11 can be reduced, and if noise is low or noise is improved in terms of hardware. If possible, it may be larger.
As a result, the signal is detected as 100% in the period of T10 and attenuated and detected in the period of T11. By doing so, most vibration signals can be detected during the period of T10, and even if a signal occurs at T11 with a small probability, the vibration signal can be detected because it is strong. On the other hand, the noise is measured as it is during the period of T10, but when it is generated at T11, it is usually weaker than the vibration signal, and thus can be suppressed. The probability density function may be learned and determined for each measurement, or may be obtained by statistical processing from many measurement results. Moreover, the function as shown in FIG. 2 (c-2) or (c-3) may be used. The function expression does not matter. The present invention can be applied to methods other than the K sound recognition method such as the vibration method.

[0032] As described above, Ri by <br/> the inventions of claim 1, the measurement period T1 can be narrowly limited to about pulse generation period, enabling small measure influenced therefor noise Become. But because during exercise a lot of noise mixed, measurement period
It is not possible to determine whether the signal measured during the interval T1 is K sound, noise, or noise superimposed on K sound. Therefore, the K sound is identified by the following procedure. In the second aspect of the present invention, the vibration detecting meter 3 measures the vibration signal of the subject frequency analysis, to create a digital filter with the frequency characteristics of the K sound components therein in the measurement period T1, This filter is used to process the vibration signal. That is, the signal is analyzed by the digital filter having the K sound frequency characteristic peculiar to the subject. Furthermore, since the frequency characteristic of the K sound changes due to changes in blood pressure, pressure of the arm band, etc., the frequency characteristic of the K sound is learned every time vibration is measured, and the characteristic of the digital filter is corrected. ing.

FIG. 3 shows how the digital filter is produced. FIG. 3 (a) is a frequency analysis of the vibration when the K sound is generated, and the pulse wave component in the low frequency region is
The K sound components are distributed in the higher frequency region. The frequency f at which the power becomes half-value by extracting the K sound component from this
L and fH are cut-off frequencies in the low band and high band, respectively, and a difference Δf between the frequencies is a bandwidth, and the digital filter shown in FIG. From the experimental results, the ratio of the power of all vibration signals to the power of K sound is usually about 20 to 30% on average. Depending on the subject, it may not be possible to separate the K sound as shown in the figure, but in this case, for example, the frequency at which the power of the high frequency component is 20 to 30% with respect to all vibrations is set to The low cutoff frequency is fL. Here, the K-sound component power is set to 20 to 30% of the total vibration, but this is a value determined for convenience by the K-sound detection sensitivity. However, since it is only necessary to be able to detect the K sound, the value of the ratio may be set to 20% or less when weaker power may be used.
The K sound component may be set to 0% or more so as to partially include the pulse wave component.

Although the signal passed through the digital filter according to claim 2 is highly likely to be K sound, it may be noise having the same frequency characteristic as K sound. The invention according to claim 3 is an invention for identifying this. That is,
Since K sound always occurs is superimposed on the pulse wave, the vibration includes a proportion of the power of the pulse wave and K sound, attention is paid to the point that, the pulse wave or full oscillation power and K sound Power of
Then, the power ratio of the two was calculated, and if this value was within a certain range, there was K sound, and if it was outside the range, it was judged that there was no K sound. This is shown in FIG. 4 , where FIG. 4 (a) is a frequency analysis of the entire vibration signal, where A is the pulse wave component, B is the K sound component, and C is the noise component in the higher range. is there. The boundary between the regions in the figure is set to the low and high cutoff frequencies of the digital filter according to the second aspect . FIG. 6B shows a frequency analysis of a signal that has passed through the digital filter, that is, K sound, and its power is D.

In the invention of this claim, the power ratio D / A between the K sound and the pulse wave is obtained, and if this value is within a certain range, it is determined that the K sound exists. As described in the embodiment of claim 2 , the value of the ratio has been experimentally determined to be about 20 to 30%, so a range including this, for example, 40% is set to a constant value. This value depends on the desired identification accuracy.
Can be changed. Besides this, the power ratio is D / (A + B +
C), D / (A + B), D / (A + C), etc., or B / A, B / (A + B + C), B / (A + B), from only FIG. B
You may use / (A + C) etc. Any equation may be used as long as it shows the power relationship between the pulse wave and the K sound. However, the range of determination changes depending on which of the above formulas is used. Since the K sound is always generated by being superimposed on the pulse wave (low frequency component), according to the invention described in this claim, noise with a small amount of low frequency components such as a quick sound of the armband and body movement is mistakenly regarded as the K sound. Discrimination is eliminated, and K-tone discrimination ability is improved.

[0036] As described above, by accurately predicting the K-sound generating time in the invention of claim 1 Symbol placement and vibration signal measured as narrow as possible period, the K sound characteristics of the subject in the invention of claim 2, wherein The K filter is detected by a digital filter provided, and further,
In the invention described in 3, the K sound is identified from the power ratio between the vibration and the K sound. By combining these inventions, accurate blood pressure measurement is possible even in an exercise test in which there is much noise and the electrocardiographic signal changes rapidly.

The invention according to claim 4, is the also you detect only the vibration by suppressing the noise included in the signal. Most of the conventional blood pressure measuring devices use one microphone as a sensor of the vibration detector 3 . Therefore, if there is a lot of noise or the sensor mounting position is displaced due to body movement, measurement may not be possible. Therefore, in the invention of this claim, the vibration detecting meter 3 Sen as shown in FIG. 5 (a)
Used by arranging a plurality of microphones to support, by mounting across the blood vessel, the sensor is able to detect the vibration in one of the microphones be slightly shifted.

Further, the adaptation processing is performed as follows.
As a result, noise is suppressed. That is,
Without each sensor, vibration period TA and other period T
The signal is measured at B and the signals measured at the periods TA and TB are
Select sensors M1 and M2 with maximum and minimum ratio. Figure Five
(B) shows the state of the signal measured by each sensor.
In the example of this figure, S1 is selected for M1 and S1 is selected for M2.
It The sensor M1 detects the blood vessel vibration best, and the sensor M2 detects most
Only noise is detectedis doing. The se
The output of sensor M1 is SM1 and the output of M2 is SM2,
As shown in FIG. 5C, the signal SM2 is filtered by the filter H (jω).
Output from the sensor M1 and the output of the filter H (jω).
The force difference is calculated, and the output S0 of the system is filtered by the filter H (j
ω) to minimize the output S0
The coefficient of the filter H (jω) is changed. this
To determine the coefficient, the properties of the data are learned adaptively.
Standard LMS algorithm can be used, but coefficient
The type of determining means does not matter. Included in sensors M1 and M2
Noise is highly correlated, use the system in Fig. 5 (c).
By appropriately determining the coefficient of the filter H (jω)
Then, it is possible to suppress the noise and detect only the vibration signal.
it can. In the above example, the system of FIG.
Noise is suppressed by applying adaptation processing, but it is easier
As a method, the signal from the output SM1 to SM2 of the M1 is
A method of subtracting may be used. This is the function H (j
ω) is 1 and is an approximate method. Besides this, the period T
Select the sensor M1 with the maximum signal ratio of A and TB,
May be measured. This sets the function H (jω) to 0
Corresponds to the case. This TA is T1 of claim 1 or a claim
T2 of Term 2 and TB use other periods
Just do it. This algorithm is always checked during measurement
If it is not properly attached, select the appropriate sensor again,
Take a measurement. The invention of this claim is suitable for other than the K-sound recognition method.
Can be used.

However, since the K sound signal is weak near the maximum and minimum blood pressures, this causes a measurement error. Therefore, in the invention of claim 5, wherein the vibration of the phase is focused on that inverted boundary vanishing point of K sound, vibration measured by the vibration detecting meter 3 during blood pressure measurement, and detects the phase , CP when K sound disappears before the point where the phase is reversed
Judgment is made at U9, and it is used as an aid in blood pressure determination. Figure 6
Represents this, and the phase of the vibration signal is reversed before and after the K sound is extinguished during the measurement, indicating that the K sound is extinguished before that. In the past, there was no sphygmomanometer that makes such a judgment, so K
In many cases, it was difficult to recognize the sound disappearance, but when the invention of this claim is used, the K sound disappearance point can be detected from a completely different angle of the phase different from the K sound, and the blood pressure measurement error. Is less. The invention of this claim can be applied not only to the K-sound recognition method but also to any blood pressure measurement method as long as it detects a pulse wave.

The invention according to claim 6 relates to reduction of measurement time. When the measurement is started, rapid pressurization is performed up to the set pressure P1. P1 is set to a value lower by a constant value p1 than the lowest blood pressure value measured last time.
The constant value p1 is set to about 20 mmHg, but can be changed. Initially, the minimum blood pressure of the subject is unknown, so P1 is set to about 50 mmHg, which is considered to be lower than the general minimum blood pressure value. This can also be changed depending on the purpose and case. If the subject's lowest blood pressure is 50 mmH
If it is about g or less, P1 is automatically reset to a lower value of p1 and the measurement is performed again. In the above embodiment, P1 is set to be a value lower than the previously measured diastolic blood pressure by a constant value p1, but it may be set to a value lower than the expected diastolic blood pressure. Therefore, instead of the previous lowest blood pressure value, a (moving) average value of the measured lowest blood pressures or a value predicted from a change in the electrocardiographic signal cycle may be used. P1
Is updated at each measurement with the newly measured blood pressure value. In the pressure range from P1 to P2, the pump 4 applies a constant amount of low speed pressurization to measure the blood pressure.

When the pressure is increased to the set value P2, rapid depressurization is performed thereafter. P2 is set to be higher than the systolic blood pressure value measured last time by a constant value p2. The constant value p2 is 20 mm
Although it is set to about Hg, it can be changed. At first, the systolic blood pressure of the subject is unknown, so P2 is set to 170 mmHg, which is considered to be higher than the general systolic blood pressure value. This is also a value that can be changed. If the systolic blood pressure is higher than the initial set value of 170 mmHg, the value is automatically set again to a value higher by the constant value p2 and the measurement is performed again.
P2 is updated at each measurement. In the above-described embodiment, P2 is set to a value higher than the previously measured systolic blood pressure by a constant value p2, but it may be set to a value higher than the expected systolic blood pressure value. Therefore, instead of the previous systolic blood pressure value, a (moving) average value of the measured systolic blood pressure or a value predicted from a change in the electrocardiographic signal cycle may be used. FIG. 7 shows the above pressurization and depressurization. In the same figure, (a) is a pressurization curve of the step-up method and (b) is a pressurization curve of the step-down method. The invention described in this claim can be applied not only to the K-sound recognition method but also to all blood pressure measuring devices.

Although the pressure increasing method has been described above, the pressure decreasing method in which the K sound is detected after gradually increasing the pressure to the highest blood pressure or higher and gradually decreasing the pressure can also be used. In the step-down method, when the measurement starts, the valve 5 is opened, the valves 6 and 7 are closed, and the pump 4 is operated to rapidly pressurize to the set value P2. When the pressure reaches the set value P2, the valves 5 and 6 are closed, the valve 7 is opened, the constant pressure is exhausted to reduce the pressure, and the K sound is detected during that time to determine the maximum and minimum blood pressures. When the set pressure P1 is reached, the valve 5 is opened to perform rapid depressurization. Further, in the above description, the configuration of FIG. 1 is used to explain both the step-up method and the step-down method, but a device limited to the step-up method or step-down method only needs to have the necessary requirements in FIG. .

[0043]

According to the first aspect of the present invention, since the K sound generation time is predicted in consideration of the influence of the pressure of the arm band, the K sound generation can be predicted more accurately than before. Therefore, the measurement period T1 can be shortened as compared with the conventional case, and the influence of noise can be reduced. Also, the prediction formula of the delay time td from the generation of the electrocardiographic signal to the generation of the K sound is learned for each measurement.
Since it is corrected, it can be used even when the heart rate, that is, the electrocardiographic signal generation cycle changes abruptly. Therefore, accurate blood pressure measurement is possible even in a noisy exercise test.

[0044] In this method of et al., Even if there is a K sound that could not be recognized in the middle, to recognize retroactively from then recognized K sound, it can also be referred to. As a result, accurate blood pressure measurement is possible even in a noisy exercise test.

[0045] According to the second aspect of the invention, the subject of the K
Since a digital filter having a sound frequency characteristic is created and a signal is analyzed through the filter, theoretically K
Can it to detect the sound only. In addition, the frequency characteristic of the digital filter is updated and used according to the K sound frequency characteristic that changes depending on the arm cord pressure or blood pressure. Therefore, it is possible to identify the K sound and noise more accurately than that using a conventional general filter, and the accuracy of blood pressure measurement is improved.

[0046] According to the third aspect of the invention, using the property that the K sound always occurs is superimposed on the pulse wave, determined power ratio of the pulse wave component and K sound components, it any, within a predetermined range If so, the signal is judged to be K sound. When a noise having a frequency component similar to the K sound was measured, it was conventionally determined to be the K sound. However, according to the invention of this claim, since such noise does not have a pulse wave component, the noise is Is recognized. In other words, noise with a frequency component similar to K sound is mistakenly K
It will not be distinguished from sound. Also, near the K sound and K
Even when noise is superimposed on the sound, the K sound can be identified, and the blood pressure can be measured accurately. Therefore, an accurate blood pressure measurement is possible even in an exercise load test that is greatly affected by noise.

According to the invention described in claim 4 , the K sound can be effectively extracted from the noisy signal. Further, even if the sensor is displaced due to body movement or the like, the sensor at the optimum position can always be selected. Therefore, it is possible to accurately measure blood pressure even in an exercise load test under poor measurement conditions.

[0048] According to a fifth aspect of the present invention, even if the conventional method is identified weak K sound whether generated or extinguished difficult, incorporating identifying indicia that did not exist prior called pulse wave phase As a result, the range in which the K sound is generated can be identified, so that more accurate blood pressure measurement is possible.

[0049] According to a sixth aspect of the present invention, a fixed value lower pressure P1 than the minimum blood pressure to be expected, than the maximal blood pressure expected to set a constant value higher pressure P2, the pressure P1 and P
Within the range of 2, pressure is applied or reduced at a low speed for measurement, and outside the range of pressures P1 and P2, pressure is increased or reduced rapidly.
Moreover, each time measurement is performed, P1 and P2 are sequentially updated using the latest measurement result having the highest correlation with the blood pressure to be measured. Therefore, it becomes possible to measure blood pressure more efficiently in a short time and even in an exercise test in which blood pressure changes rapidly. Some conventional sphygmomanometers perform rapid pressurization / depressurization, but they cannot be used when blood pressure fluctuates because they have a fixed range that covers the range of maximum and minimum blood pressures at rest. It was In the exercise stress test, the blood pressure also changes in a short time, so it is better to measure the blood pressure in the shortest possible time in order to perform accurate blood pressure measurement. Also in this sense, the invention of the present claim enables more accurate blood pressure measurement than ever before. Further, in the exercise load test, the blood pressure is repeatedly measured while applying a severe exercise load, so that the physical load on the subject is large. According to the invention of this claim, the measurement time can be shorter than that of the conventional method, and the physical burden on the subject can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of claim 1 , in which (a) predicts a K sound generation time from a pressure P when an electrocardiographic signal is generated, and a period T before and after that is predicted.
1 shows the timing of measuring the vibration, the broken line in (b) shows the measured values of the pressure P and the delay time td, the solid line shows the predictive equation in which the measured values are linearly regressed by the least squares method, and (c) shows the period T1. The respective probability density functions used in the measurement are shown.

FIG. 3 shows a procedure for producing a digital filter for detecting Korotkoff sounds according to claim 2. (A) is a result of frequency analysis of the measurement signal, (b) is shows the digital filters created based on the K sound component of (a).

FIG. 4 is a signal used in the invention according to claim 3 ,
(A) is the result of frequency analysis of the vibration signal containing K sound,
A, B, and C are a pulse wave component, a K sound component, and high frequency noise, respectively. (B) is a diagram of a result of frequency analysis of K sound.

[5] according to claim 4, wherein, (a) is a vibration detection sensor, (b) the period TA and TB each sensor has detected
FIG. 4C is a diagram of the signal strength of FIG. 4C, and FIG. 7C is a configuration diagram of noise suppression by the adaptation processing.

FIG. 6 is a real-time axis waveform of a pulse wave according to a fifth aspect of the present invention, where it is determined that the Korotkoff sound has disappeared at the point where the phase of the pulse wave is inverted.

FIG. 7 is a diagram showing a process of pressurization and depressurization during blood pressure measurement according to claim 6 ; (A) is a diagram for the step-up method and (b) is a diagram for the step-down method. P1 and P2 are target set values for pressurization / depressurization speed control.

[Explanation of symbols]

In FIG. 1, 1 is an arm band that applies pressure to a blood vessel, 2 is a pressure gauge that detects the pressure applied to the blood vessel, 3 is a vibration detector that detects blood vessel vibration, 4 is a pressurizing pump, 5 and 6 and 7 are A valve that controls the flow of air, 8 is a chamber that smoothes the pressure applied to the arm girdle, 9 that controls the pump, valve, etc., reads the signals of the pressure gauge and vibration detector, and performs data processing C
PU, 10 is a display for displaying measurement results, 11 is a control panel for controlling the apparatus, and 12 is an electrocardiographic signal detection unit. E and K in FIG. 2A are the electrocardiographic signal and K sound , t
1 and T1 are the K sound occurrence time and the measurement period predicted in the invention of claim 1. FL, fH, and Δf in FIG. 3 are the low cutoff frequency, the high cutoff frequency, and the frequency band of the filter, respectively. Figure 4
A, B, C and D are pulse wave, K sound, high frequency noise, K
Power value of sound. In FIG. 5 , S1, S2, S3, S4 and S5 are vibration detection sensors, and TA and TB are signal measurement periods. M1 and M2 are main input sensor and reference input sensor, SM1 and SM2
Is the output of the sensors M1 and M2, H (jω) is the adaptive filter, and S0 is the output of the system.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) A61B 5/022

Claims (6)

(57) [Claims] 1. A pressurizing means for applying a pressure to a blood vessel, a pressure detecting means for detecting a pressure applied to the blood vessel, a vibration detecting means for detecting a vibration generated in the blood vessel, and a heart for detecting an electrocardiographic signal. The detection time of the Korotkoff sound generated in synchronism with the electrocardiographic signal
Forecast and Korotkoff sound generation
The vibration of the blood vessel including the noise is measured and the measured vibration is filtered.
In a blood pressure measurement device that recognizes Korotkoff sounds and measures blood pressure, a delay time td until the electrocardiographic signal is generated and Korotkoff sounds are generated, and a prediction formula is created as a function of pressure applied to the blood vessel. Every time an electrocardiographic signal is generated during measurement, the delay time td is calculated using the prediction formula by referring to the pressure applied to the blood vessel, and this td is added to the electrocardiographic signal generation time. Then, the Korotkoff sound generation time t1 is predicted, and the vibration is measured during a period T1 before and after the time t1, and the pressure P and the delay time t are repeated each time the measurement is repeated.
A blood pressure measurement device having an algorithm for measuring d and learning / correcting the prediction formula. 2. The digital vibration is selected from the blood vessel vibrations measured during the period T1.
Extract the Korotkoff sound using the digital filter
The Korotkoff sounds with a frequency analysis, to create a digital filter with the frequency characteristics of the Korotkoff sounds, so as to process the blood vessel vibration signal generated next using the digital filter, further rollers every time the measurement is repeated
Frequency analysis of tokoff sound and update digital filter
The blood pressure measurement device according to claim 1, configured as described above . 3. Vascular vibration and Korotkoff measured during period T1
Determine the respective power of sound determines the power ratio of the vascular vibration and Korotkoff sounds, having an algorithm that determines Korotkoff sounds or miscellaneous <br/> sound by the value of the ratio, according to claim 1 or請
Blood pressure measurement device of Motomeko 2 wherein. Wherein the plurality of sensors for detecting a vibration period of generation of the vibration at each of the sensors TA and other periods T
The vibration is measured at B, the ratio of the signals measured during the period of TA and TB is taken, and the sensor M1 having the maximum ratio and the sensor M2 having the minimum ratio are selected as the main input sensor and the reference input sensor, respectively. The output signal of M2 is filtered by the filter H (jω)
Processing, the difference between the output of the sensor M1 and the output of the filter H (jω) is taken as the output S0, and the output S0 is used as the filter H.
Fed back to (j [omega]), claim the output S0 has an algorithm to suppress noise by an adaptive process to correct the coefficients of the filter H (j [omega]) so as to minimize, always to repeat this algorithm during measurement 1 to contract
The blood pressure measurement device according to any one of claim 3 . 5. detects the phase of a blood vessel vibration, Korotkoff sounds when the phase is inverted with a decision algorithm that has disappeared, <br/> blood pressure measuring device as claimed in any one of claims 1 to 4 . 6. Next measurement from the measured maximum blood pressure and minimum blood pressure
The maximum blood pressure and the minimum blood pressure at time are predicted, and a pressure P1 that is a constant value lower than the predicted minimum blood pressure value and a pressure P2 that is a constant value higher than the predicted maximum blood pressure are set, and P1 and P2 are set.
Within the range of the blood pressure was measured by pressure or vacuum at a low speed, performs rapidly elevated or reduced in the range other than that, the set value P1 and P2 have an algorithm for updating every measurement, claim The blood pressure measurement device according to any one of claims 1 to 5 .