JP2001008908A - Electric sphygmomanometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of sphgmomanometry and precisely measure blood pressure even if moving strength is high by improving detective accuracy of a pulse wave. SOLUTION: There are provided a photoelectric sensor for detecting pulse wave 10 and an acceleration sensor for detecting noise 11 on a cuff 1. A noise component which is generated by physical movement which is superposed on a pulse wave signal which is obtained by the photoelectric sensor 10 is decreased by using a signal that is obtained by the acceleration sensor 11 and blood pressure is calculated by using the pulse wave signal which decreases the noise component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic sphygmomanometer which is hardly affected by noise and artistic factors caused by body movement.

[0002]

2. Description of the Related Art Conventionally, sphygmomanometers designed to measure blood pressure during body movement include sphygmomanometers for exercise load tests and 24 sphygmomanometers.
There is a time portable sphygmomanometer and the like. These sphygmomanometers measure blood pressure by an auscultation method, an oscillometric method, or a combination of both methods, which measures Korotkoff sounds.

[0003]

However, in the conventional sphygmomanometer described above, i) In the oscillometric method, the pressure noise caused by body movement largely overlaps the pressure pulse wave. ii) In the auscultation method for measuring Korotkoff sounds, noise caused by body motion is erroneously recognized as Korotkoff sounds. Therefore, there are the following problems. The detection accuracy of the pulse wave decreases, and it becomes difficult to determine the blood pressure value, or the accuracy of determining the blood pressure decreases. Even if an electrocardiogram synchronization function that enhances body movement tolerance is used in the Korotkoff method, if the exercise intensity is high, noise becomes continuous, making it difficult to detect a pulse wave.

Accordingly, the present invention addresses such problems,
It is an object of the present invention to provide an electronic sphygmomanometer capable of improving blood pressure measurement accuracy by increasing pulse wave detection accuracy and performing accurate blood pressure measurement even when exercise intensity is high.

[0005]

In order to achieve the above object, an electronic sphygmomanometer according to claim 1 of the present invention provides a cuff for pressing a measurement site of a living body, and pressurizes and depressurizes the inside of the cuff. A pressure control means, a pressure detection means for detecting a pressure in the cuff, and a blood pressure calculation means for calculating a blood pressure from a signal obtained by the pressure detection means; At least one pulse wave detecting means for detecting a wave, at least one noise detecting means provided on the cuff for detecting noise due to body movement from a measurement site, and a pulse wave signal obtained by the pulse wave detecting means. Noise component reducing means for reducing a noise component due to superimposed body motion using a signal obtained by the noise detecting means, wherein the blood pressure calculating means calculates a blood pressure using a pulse wave signal with the reduced noise component. To do And butterflies.

This electronic sphygmomanometer uses the body movement component (noise component due to body movement) detected by the noise detection unit to extract only the noise component from the pulse wave signal of the pulse wave detection unit on which the noise component is superimposed by the body movement. It is to reduce. An advantage of using a pulse wave instead of a Korotkoff sound in measuring blood pressure during body movement is that a pulse wave (a photoelectric pulse wave, a pressure pulse wave, or the like) is not easily affected by noise noise. In a system using an acoustic sensor such as the Korotkoff sound system, it is difficult to reduce noise noise. On the other hand, almost no noise is superimposed on the pulse wave during body motion, but only a noise component due to body motion is superimposed. Therefore, if a noise component due to body motion can be removed from the pulse wave, an accurate pulse wave can be reproduced.
In addition, since noise due to body motion has less difference in characteristics depending on the position than acoustic noise, if the noise detection unit is located around the pulse wave detection unit, the influence of the body movement will be the noise detection unit and the pulse wave detection unit. Acts almost equally. Therefore, the process of reducing noise due to body motion is easier than in the case of acoustic noise.

In addition, since pulse wave and body motion noise are in a frequency lower region than Korotkoff sound and acoustic noise, even if digital signal processing is performed, it is possible to cope with a relatively low sampling frequency. is there. In addition,
In the present invention, a cuff pressure sensor, a photoelectric pulse wave sensor, an impedance sensor, a strain sensor, or the like may be used as the pulse wave detecting means.

[0008] In the case of measuring the noise by converting the movement of a living body into a physical quantity, the noise detecting means includes a speed sensor, an acceleration sensor, a position sensor, a displacement sensor, an angle sensor, an azimuth sensor, and a tilt sensor. In the case of measuring biomass (for example, blood volume) that changes depending on
A photoelectric sensor or the like may be used. The noise component reduction means includes a differential operation process after matching the phase and amplitude of the pulse wave signal and the noise signal due to body motion, or an adaptive filter process. Note that signal processing after noise reduction is the same as that of a conventional blood pressure monitor.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a block diagram showing the configuration of the electronic sphygmomanometer according to the first embodiment. This electronic sphygmomanometer includes a cuff 1 for compressing a measurement site of a living body, a pressure pump (pressure control means) 2 for pressurizing the inside of the cuff 1, and an exhaust valve (pressure control means) 3 for reducing the pressure in the cuff 1 And a pressure sensor (pressure detecting means) 4 for detecting the pressure in the cuff 1, a display 5 for displaying the calculated blood pressure value and the like, a pressurizing pump 2, an exhaust valve 3, a display 5 and the like. A CPU 6, an amplifier 7 for amplifying an output from the pressure sensor 4, and an A for converting an analog signal from the amplifier 7 into a digital signal and inputting the digital signal to the CPU 6.
/ D converter 8. However, the configuration so far is the same as that of a conventional sphygmomanometer.

This electronic sphygmomanometer is provided on the cuff 1 and at least one photoelectric sensor 10 as pulse wave detecting means for detecting a pulse wave from a measurement site. And an acceleration sensor 11 as at least one noise detecting means for detecting noise due to the body motion. A noise component due to body movement superimposed on the pulse wave signal obtained by the CPU 6 by the CPU 6 is obtained by the acceleration sensor 11. A noise component reduction function that reduces using a signal,
It has a blood pressure calculation function of calculating a blood pressure using a pulse wave signal with reduced noise components.

The pulse wave signal of the photoelectric sensor 10 and the body motion signal of the acceleration sensor 11 are respectively amplified by an amplifier 12, converted into digital signals by an A / D converter 8, and input to the CPU 6. The electronic sphygmomanometer according to the second embodiment shown in FIG. 2 uses one photoelectric sensor 13 instead of the acceleration sensor 11 as a noise detection unit. Other configurations are the same as those of the electronic sphygmomanometer of the first embodiment.

Electronic sphygmomanometer of the first embodiment (see FIG. 1)
3 is a schematic cross-sectional view of the cuff 1 (cross-sectional view in the transverse direction of the upper arm), and FIG. 5 is a schematic cross-sectional view in another direction (cross-sectional view of the upper arm in the longitudinal direction). 3 and 5 show a state in which the cuff 1 is attached to the upper arm 40, for example.
Inside, a bone 41 and an artery 42 extend. Here, the photoelectric sensor 10 for detecting the pulse wave and the acceleration sensor 11 for detecting the noise are mounted close to a predetermined portion of the cuff 1 and at different positions in the circumferential direction of the cuff 1 (the transverse direction of the upper arm 40). Are located. The photoelectric sensor 10 includes a light emitting element and a light receiving element.
The light is radiated to the artery 42 inside, and the reflected light is received by the light receiving element. In addition, noise due to body movement generated in the upper arm 40 is detected by the acceleration sensor 11.

An electronic sphygmomanometer according to a second embodiment (see FIG. 2)
FIG. 4 shows a schematic cross-sectional view (cross-sectional view in the transverse direction of the upper arm) of the cuff 1 in FIG. In FIG. 4, the photoelectric sensor 13 for noise detection is not composed of a light emitting element and a light receiving element. The light emitting element is common to the light emitting element 20 of the photoelectric sensor 10 for pulse wave detection, and only the light receiving element 31 for noise detection is used. Are disposed on the opposite side of the light emitting element 20 from the light receiving element 21 for detecting a pulse wave. Note that the distance between the light emitting element 20 and the light receiving element 21 and the distance between the light emitting element 20 and the light receiving element 31 are not necessarily the same, but both the pulse wave signal and the body motion signal are the same. If acquired by a light receiving element located at the same distance from the body, since the amount of change in biomass, which is a body motion component, acts in the same manner on the pulse wave signal and the body motion signal, the body motion component superimposed on the pulse wave signal A highly correlated body motion signal can be obtained, and the noise removal efficiency is further improved.

Next, the first and second components configured as described above are used.
The operation of the electronic sphygmomanometer according to the embodiment will be described with reference to the flowchart of FIG. FIG. 6 shows a case where the blood pressure is measured in the process of depressurizing the cuff. When blood pressure measurement is performed during the depressurization process of the cuff, the cuff is once pressurized above the systolic blood pressure, and then depressurized at a constant pressure. The point is the diastolic blood pressure. As another method, a method of determining a blood pressure value with a threshold value of a predetermined ratio to the maximum value of the pulse wave amplitude may be used.

First, in step (hereinafter abbreviated as ST) 1, after all variables are initialized, pressurization of the cuff is started (ST2). When the internal pressure of the cuff reaches or exceeds the systolic blood pressure, decompression at a constant pressure is started (ST3), and the measurement of the cuff pressure, the pulse wave signal, and the measurement of the body motion signal are performed in the depressurization process (ST4). The noise component due to body movement is removed from the pulse wave signal based on the measurement result (ST5). Thereafter, the systolic blood pressure and the diastolic blood pressure are calculated using the pulse wave signal with the reduced noise component (ST6), and the obtained blood pressure values are displayed (ST7).

Note that the flowchart of FIG.
Although the processing up to T7 is performed during the depressurization process of the cuff, these processes may be performed during the pressurization process of the cuff. Next, noise component removal processing (ST5) in the flowchart of FIG.
A specific method will be described. As described above, as the noise component reduction processing, there is a differential operation processing after matching the phase and the amplitude of the pulse wave signal and the noise signal due to the body motion, or an adaptive filter processing. The noise component removal processing is as shown in FIG.

First, when the decompression of the cuff is started (ST1)
1. Corresponding to ST3 in FIG. 6), a correlation operation is performed between a pulse wave signal obtained by a pulse wave detection sensor and a body motion signal obtained by a noise detection sensor to obtain a phase difference and an amplitude ratio. (ST12). For the body motion signal, delay processing and gain change are performed using the phase difference and the amplitude ratio obtained by the correlation operation (ST13), and the difference between the body motion signal and the pulse wave signal after the processing in ST13 is obtained. Performing dynamic operation processing (ST1
According to 4), a noise component due to body movement can be reduced from the pulse wave signal. This differential operation process is continued until the decompression is completed (ST15).

The reason why the noise component can be reduced by the differential operation processing is as follows. In normal blood pressure measurement, the measurement site of the living body is pressurized with a cuff above the systolic blood pressure,
Thereafter, the pressure is reduced at a predetermined speed. However, when the pressure is increased to the maximum blood pressure or higher, the artery is completely occluded and the pulsation is stopped. At this time, only the noise due to body movement exists in the signal of the sensor for pulse wave detection. Therefore, FIG.
The cuff pressure is certain to be higher than the systolic blood pressure (can be estimated by referring to the resting systolic blood pressure or the previous systolic blood pressure value). The correlation between the pulse wave signal (ST21) on which the body motion noise is superimposed and the body motion signal (ST22) obtained by the noise detection sensor is obtained to determine the phase difference and the amplitude ratio (ST23). Differential arithmetic processing is performed on the body motion signal and the pulse wave signal that have been subjected to the gain adjustment using the obtained phase difference and amplitude ratio (ST24).
Is performed, it is possible to reduce noise components due to body movement in the pulse wave signal.

That is, as shown in FIG. 11, when the cuff pressure is between the systolic blood pressure and the diastolic blood pressure, the artery pulsates. Is detected. Since the phase difference and the amplitude ratio between the two signals obtained when the blood pressure is equal to or higher than the systolic blood pressure are kept substantially equal in the body motion signal (see FIG. 12), the difference between the two signals is obtained using the phase difference and the amplitude ratio. By performing the motion calculation process, the noise component due to the body motion is reduced, and the pulse wave component remains (see FIG. 13). Therefore, only the body motion noise can be reduced from the pulse wave signal mixed with the noise due to the body motion.

On the other hand, the noise component removal processing using an adaptive filter uses an adaptive filter instead of the correlation operation processing (ST12 in FIG. 7). As the adaptive filter, a lattice type adaptive filter, a transversal type adaptive filter is used. Filters can be used. Further, as a specific configuration of the adaptive algorithm, a configuration such as LMS, RLS, and LSL can be used. Then, the adaptive filter performs the adaptive operation from the time of the cuff pressure, which is certain to be higher than the systolic blood pressure, and obtains the pulse wave detection sensor using the body motion signal obtained by the noise detection sensor. A noise component due to body movement is removed from the obtained pulse wave signal. The adaptive filter filters the body motion signal and outputs a signal corresponding to a body motion noise component superimposed on the pulse wave signal. Then, the adaptive operation is performed by updating the filter coefficient of the filtering of the body motion signal so that the output of the differential operation processing is minimized by the adaptive algorithm. Since the adaptive filter has a high degree of freedom in adjustment, noise due to body movement can be removed more accurately than in the differential operation processing.

In addition, the configuration using the above adaptive filter may be partially used. This noise component removal processing is as shown in FIG. First, when depressurization of the cuff is started (ST31, corresponding to ST3 in FIG. 6), the adaptive operation of the adaptive filter is performed when the cuff pressure is certain to be higher than the systolic blood pressure (ST32). It is determined whether or not the coefficients have converged (ST33). When the filter coefficients have converged, the updating of the filter coefficients is stopped (ST34), and the filter operation and the differential operation are performed with the filter coefficients fixed (ST35). The filter operation and the differential operation process are continued until the pressure reduction ends (ST36).

That is, in FIG. 10, the body motion signal (ST
42, see FIG. 15), the adaptive filter (ST43)
, An adaptive operation is performed in accordance with an adaptive algorithm (ST44), and a differential operation process (ST44) is performed on the body motion signal after the adaptive operation and the pulse wave signal on which the body motion signal is superimposed (see FIG. 14).
By performing 45), noise components due to body movement can be reduced from the pulse wave signal (see FIG. 16). The adaptive operation by the adaptive filter and the differential operation processing are performed until the decompression is completed.

The reason why the noise component can be reduced by the adaptive filter processing is as follows. Since the relationship between the pulse wave detection sensor and the noise detection sensor obtained when the blood pressure is equal to or higher than the systolic blood pressure is maintained substantially the same in the body motion signal, even if the updating of the filter coefficient is stopped, Only the noise component due to the pulse wave is reduced, and the pulse wave component remains. This method is effective when the frequency component of the noise due to body motion approaches or overlaps the frequency component of the pulse wave. In such a case, if the update of the filter coefficient is continued as described above, the adaptive filter updates the filter coefficient so as to reduce the pulse wave component similarly to the noise due to body motion,
The pulse wave component will not remain in the output signal after the noise component removal processing. However, by stopping the update of the filter coefficient, it is possible to prevent a problem that the pulse wave is removed.

[0024]

The electronic sphygmomanometer of the present invention has the following effects because it is configured as described above. (1) In blood pressure measurement during body movement, a pulse wave signal with less noise component due to body movement can be obtained, and a highly accurate blood pressure value can be calculated. Therefore, accurate blood pressure measurement can be performed even when exercise intensity is high. (2) The electrocardiogram gating lead, which has been conventionally required when measuring blood pressure during body movement, becomes unnecessary, so that not only the number of parts can be reduced, but also the attachment of the living body to the measurement site becomes simple. (3) According to the configuration of the third aspect, the pulse wave signal and the body motion signal can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electronic sphygmomanometer according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of an electronic sphygmomanometer according to a second embodiment.

FIG. 3 is a schematic cross-sectional view (cross-sectional view in the transverse direction of the upper arm) of the cuff in the electronic sphygmomanometer according to the first embodiment.

FIG. 4 is a schematic sectional view (a sectional view in a transverse direction of an upper arm) of a cuff in an electronic sphygmomanometer according to a second embodiment.

FIG. 5 is a schematic cross-sectional view (a cross-sectional view in the longitudinal direction of the upper arm) of the cuff in the electronic sphygmomanometer according to the first embodiment in another direction.

FIG. 6 is a flowchart showing an example of the operation of the electronic sphygmomanometer of the embodiment.

FIG. 7 is a flowchart illustrating a differential operation process as an example of a specific method of the noise component removal process in the flowchart of FIG. 6;

FIG. 8 is a functional flowchart for explaining a main part of the flowchart of FIG. 7;

9 is a flowchart showing adaptive filter processing as another example of a specific method of the noise component removal processing in the flowchart of FIG. 6;

FIG. 10 is a functional flowchart for explaining a main part of the flowchart of FIG. 9;

FIG. 11 is a waveform diagram illustrating a pulse wave signal obtained by a sensor for detecting a pulse wave when a differential operation process is used as a noise component removal process.

FIG. 12 is a waveform diagram illustrating a body motion signal obtained by a noise detection sensor when a differential operation process is used as the noise component removal process.

FIG. 13 is an output waveform diagram after differential operation processing when differential operation processing is used as noise component removal processing.

FIG. 14 is a waveform diagram showing a pulse wave signal obtained by a sensor for detecting a pulse wave when adaptive filter processing is used as noise component removal processing.

FIG. 15 is a waveform diagram showing a body motion signal obtained by a noise detection sensor when adaptive filter processing is used as noise component removal processing.

FIG. 16 is an output waveform diagram after adaptive filter processing when adaptive filter processing is used as noise component removal processing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cuff 2 Pressurizing pump (pressure control means) 3 Exhaust valve (pressure control means) 4 Pressure sensor (pressure detection means) 6 CPU (blood pressure calculation means, noise component reduction means) 10 Photoelectric sensor (pulse wave) for pulse wave detection Detection means) 11 acceleration sensor for noise detection (noise detection means) 13 photoelectric sensor for noise detection (noise detection means)

Claims (11)

[Claims] 1. A cuff for compressing a measurement site of a living body,
In an electronic sphygmomanometer including a pressure control unit that pressurizes and depressurizes the inside of the cuff, a pressure detection unit that detects a pressure in the cuff, and a blood pressure calculation unit that calculates a blood pressure from a signal obtained by the pressure detection unit, At least one pulse wave detecting means provided on the cuff for detecting a pulse wave from a measurement site; at least one noise detection device provided on the cuff for detecting noise due to body movement from the measurement region; Noise component reduction means for reducing a noise component due to body movement superimposed on the pulse wave signal obtained by the detection means using the signal obtained by the noise detection means, wherein the blood pressure calculation means reduces the noise component. An electronic sphygmomanometer, which calculates a blood pressure by using the obtained pulse wave signal. 2. The electronic sphygmomanometer according to claim 1, wherein said pulse wave detecting means measures volume oscillation of an artery as a pulse wave. 3. The pulse wave detecting means and the noise detecting means,
The electronic sphygmomanometer according to claim 1 or 2, wherein the electronic sphygmomanometer is arranged at different positions in a circumferential direction of the cuff. 4. The pulse wave detecting means and the noise detecting means,
The electronic sphygmomanometer according to claim 1, wherein the electronic sphygmomanometer has an equivalent detection mechanism. 5. The pulse wave detecting means and the noise detecting means,
5. The electronic sphygmomanometer according to claim 4, wherein each of the active sphygmomanometers is active detection means for irradiating the body with physical energy, and also serves as physical energy for detection of the active detection means. 6. The electronic sphygmomanometer according to claim 1, wherein said pulse wave detecting means uses a photoelectric pulse wave as a pulse wave. 7. The noise component reducing means specifies and identifies a difference between characteristics of body motion noise superimposed on signals obtained by the pulse wave detecting means and the noise detecting means, respectively, and determines a characteristic difference of the specified and identified noise. 7. The electronic sphygmomanometer according to claim 1, wherein the noise component is reduced by using. 8. The noise component reducing means performs correlation calculation of signals obtained by the pulse wave detecting means and the noise detecting means when the cuff internal pressure is equal to or higher than the systolic blood pressure, thereby obtaining a difference in the characteristic of body motion noise. The electronic sphygmomanometer according to claim 7, wherein the electronic blood pressure monitor is specified and identified. 9. The noise component reducing unit specifies and identifies a difference in characteristics of body motion noise by performing adaptive filter processing on signals obtained by the pulse wave detecting unit and the noise detecting unit, respectively. The electronic sphygmomanometer according to claim 7, wherein 10. The noise component reducing means adjusts a phase difference and an amplitude ratio reflecting a correlation calculation result of signals obtained by the pulse wave detecting means and the noise detecting means when the cuff internal pressure is equal to or higher than the systolic blood pressure. 9. The electronic sphygmomanometer according to claim 8, wherein the noise component is reduced by performing a differential operation process on the two signals after the adjustment, thereby using a characteristic difference of the specified and identified noise. 11. The noise component reducing means uses an adaptive filter coefficient converged by adaptive filter processing of signals obtained by the pulse wave detecting means and the noise detecting means when the cuff internal pressure is equal to or higher than the systolic blood pressure. Filtering the signal obtained by the noise detecting means when the internal pressure is equal to or lower than the systolic blood pressure, and differentially processing the signal obtained by the filtering processing and the signal obtained by the pulse wave detecting means, thereby identifying and identifying the identified noise. 10. The electronic sphygmomanometer according to claim 9, wherein a noise component is reduced using the characteristic difference.