JP2002224061A - Electronic sphygmomanometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure blood pressure even at a body movement. SOLUTION: A frequency is respectively analyzed on a pulse wave signal by superimposing noise caused by the body movement and the noise content by the body movement, and is converted into time series data [(b) and (f) of Fig.5]. These frequency series data are compared, and a frequency component of the pulse wave signal is determined. An area other than a frequency area of the pulse wave signal is removed from the frequency series data on the pulse wave signal. The pulse wave signal after removing the area other than this frequency area is converted into the time series data from the frequency series data, and the pulse wave signal is reproduced [(c) of the drawing 5]. The reproduced pulse wave signal is used as a trigger signal [(d) of Fig.5]. The noise content is removed from a Korotkoff sound signal [(e) of Fig.5], and blood pressure is calculated on the basis of a noise-removed Korotkoff sound.

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 can measure even during body movement.

[0002]

2. Description of the Related Art Conventional blood pressure monitors designed for measuring blood pressure during body movement include a blood pressure monitor for an exercise load test and a 24
There is a time portable blood pressure monitor and the like. These sphygmomanometers measure blood pressure by the Korotkoff sound method, the oscillometric method, or a combination of both methods.

However, in this type of electronic sphygmomanometer, in the oscillometric method, pressure noise caused by body motion or the like largely overlaps with the pressure pulse wave, and in the Korotkoff sound method, noise caused by body motion or the like is generated. There is a problem that it is erroneously recognized as a Korotkoff sound. Therefore, the conventional method has a problem in that the detection accuracy of the pulse wave and the Korotkoff sound decreases, and it becomes difficult to determine the blood pressure value, and the accuracy of the blood pressure value decreases.

Therefore, in order to solve this problem, conventionally, in an oscillometric blood pressure monitor, a predetermined logic is used to monitor a cuff pressure pulse wave and determine the presence or absence of noise due to body movement and the like. A measurement error occurs when it is determined that there is noise. Alternatively, information indicating that noise was generated during the measurement is added, and in a Korotkoff sound type blood pressure monitor, an electrocardiographic electrode is provided in addition to the Korotkoff sound sensor in order to increase resistance to noise due to body movement and the like. There is a method of determining the blood pressure value using only the signal of the Korotkoff sound sensor only in a short section (Korotokoff sound evaluation period) where it is considered that a Korotkoff sound will appear, with the ECG signal as a trigger signal. .

As a technique for reducing noise due to body movement, noise caused by body movement is transmitted to the sensor directly by transmitting air from the outside, transmitted to the body, or held by the sensor. Such as those transmitted from the cuff
Since there are various noise sources, a method of preparing a large number of sensors for each noise factor and performing signal processing may be considered in order to reduce noise for each individual factor.

[0006]

The conventional oscillometric method for countermeasures against noise caused by body movement or the like is a method for eliminating or invalidating blood pressure measurement during body movement. It does not make it measurable.

In the above-mentioned countermeasure against noise caused by body movement in the Korotkoff sound method, the output of the Korotkoff sound sensor due to noise caused by body movement or the like during a period in which the Korotkoff sound is unlikely to appear is determined. Since it is possible to prevent erroneous recognition as a Korotkoff sound, it is effective when exercise intensity is relatively weak. However, in situations where noise due to body motion etc. occurs continuously, for example, when exercise intensity is high, even during periods when cuff pressure is high and Korotkoff sounds do not appear originally, Korotkoff sound evaluation using electrocardiogram signals as trigger signals Noise caused by body movements and the like enters the period, making it difficult to determine the Korotkoff sound appearance time and disappearance time, which are important factors in determining the systolic blood pressure and the diastolic blood pressure, making it difficult to determine the blood pressure value.

Furthermore, in the above-described method for reducing noise caused by body movement, the device configuration and signal processing become complicated,
It is difficult to achieve with reasonable pricing. Therefore, a method is often adopted in which the difference between the frequency components of noise and Korotkoff sound is used to collectively reduce the noise with a filter. However, of the noise, noise that overlaps the Korotkoff sound with the frequency domain cannot be completely removed.

The present invention has been made in view of the above problems, and has as its object to provide an electronic sphygmomanometer capable of accurately measuring blood pressure even during body movement.

[0010]

An electronic sphygmomanometer according to the present invention comprises a cuff, control means for increasing / decreasing the pressure in the cuff, detecting means for detecting the pressure in the cuff, and an output of the detecting means. A pulse wave detecting means for detecting a pulse wave signal from a cuff pressure, a means for detecting a noise signal caused by at least one or more body movements, and a blood pressure calculating means; Each of the signals is subjected to frequency analysis, data conversion means for converting time-series data to frequency-series data, and a means for comparing the frequency-series data to determine a frequency component of the pulse-wave signal, from the frequency-series data of the pulse-wave signal, Means for removing the frequency band other than the pulse wave signal, converting the frequency sequence data of the pulse wave signal after removing the frequency band other than the pulse wave signal into time series data, and reproducing the pulse wave signal; Trigger signal As, and means for removing noise from the input Korotkoff sound signals, based on the Korotkoff sound which is noise reduction, and to calculate the blood pressure.

In this electronic sphygmomanometer, a cuff pressure sensor, a photoelectric pulse wave sensor, an impedance sensor, a strain sensor, or the like may be used as a means for detecting a pulse wave signal. In addition, as means for detecting a noise signal due to body movement,
In the case of a sensor that measures the movement of a living body by converting the movement into a physical quantity, a speed sensor, an acceleration sensor, a position sensor, a displacement sensor, an angle sensor, an azimuth sensor, a tilt sensor, and the like are used as a biological quantity (for example, blood) For example, a photoelectric sensor or the like may be used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a block diagram showing a configuration of an electronic sphygmomanometer according to one embodiment of the present invention.
The electronic sphygmomanometer according to this embodiment includes a cuff 1 for pressurizing a measurement site of a living body, a pressurizing pump (pressure control means) 2 for pressurizing the inside of the cuff 1, and an exhaust valve (pressure control means) for reducing the pressure inside the cuff 1 3), a pressure sensor (pressure detecting means) 4 for detecting the pressure in the cuff 1, a Korotkoff sound detecting sensor (Korotkoff sound detecting means) 5 for detecting Korotkoff sound, and a display for displaying the calculated blood pressure value and the like. , A CPU 7 for controlling the pressure pump 2, the exhaust valve 3, the display 6, etc., an amplifier 8 for amplifying the output of the pressure sensor 4, an amplifier 9 for amplifying the output of the Korotkoff sound detection sensor 5, and an amplifier. 8, a filter 10 for removing noise from the output of the pressure sensor 4,
A / D converter 11 which converts an analog signal from Korotkoff sound detection sensor 5 into a digital signal and inputs it to CPU 6
And However, the above configuration is the same as that of a conventional electronic sphygmomanometer.

The electronic sphygmomanometer according to this embodiment includes an acceleration sensor 12 provided as a noise signal detecting means provided in the cuff 1 as a noise signal due to body movement and the like, and an amplifier 13 for amplifying the output of the acceleration sensor 12. The noise signal obtained by the acceleration sensor 12 and the frequency analysis and comparison of the pulse wave signal extracted from the pressure signal obtained by the pressure sensor 4 are used to remove noise components caused by body movement and the like from the pulse wave signal. The feature is that the pulse wave signal after noise removal is used as a trigger signal for Korotkoff sound, noise is removed from the input Korotkoff sound, and blood pressure is determined.

The blood pressure determining means determines a systolic blood pressure and a diastolic blood pressure by applying a predetermined algorithm to the cuff pressure signal and the Korotkoff sound signal taken into the CPU 7.

Next, a processing operation of blood pressure measurement including noise removal of the electronic blood pressure monitor of this embodiment will be described with reference to a flowchart shown in FIG. First, in step ST1, all variables are initialized. Then, turn on the pressure pump 2
Then, pressurization of the cuff 1 is started (step ST2). When the internal pressure of the cuff 1 exceeds the systolic blood pressure, the pressurizing pump 2
FF is performed, and the slow depressurization at a constant pressure in the cuff 1 is started (step ST3).

During the depressurization process, the measurement of the cuff pressure signal, the measurement of the Korotkoff sound signal, the measurement of the pulse wave signal, and the measurement of the noise signal are performed (step ST4). The resulting noise is removed (step ST5). Using the pulse wave signal from which noise has been removed as a trigger signal, noise is removed from the input Korotkoff sound signal (step ST6), the systolic blood pressure and the diastolic blood pressure are determined (step ST7), and the obtained blood pressure value is displayed on the display 6 (Step ST8).

The method of removing noise from the input Korotkoff sound signal is as follows. First, noise caused by body motion or the like is removed from the input pulse wave signal.

The measured pulse wave signal and noise signal are taken into the CPU 7 as time-series data. The pulse wave signal and the noise signal are subjected to frequency analysis and converted into frequency sequence data. As a means for frequency analysis, for example, a fast Fourier transform is used.

FIGS. 3 and 4 show examples (power spectra) of the frequency analysis results of the pulse wave signal and the noise signal. When there is no noise due to body motion or the like, only the spectrum of the frequency component of the pulse wave exists in the power spectrum of the pulse wave signal as shown in FIG. As shown in FIG. 3B, there is no characteristic spectrum. When there is noise due to body movement, etc., the power spectrum of the pulse wave signal
As shown in FIG. 4A, both the spectrum of the frequency component of the pulse wave and the spectrum of the frequency component of the body motion exist, and the power spectrum of the noise signal has the body spectrum as shown in FIG. Only the spectrum of the motion frequency component exists.
Therefore, the frequency component of the pulse wave is extracted by comparing the two. The extraction is performed, for example, based on the difference between the power spectrum of the pulse wave signal and the power spectrum of the body motion signal.

Next, noise removal from the Korotkoff sound signal after extracting only the frequency component of the pulse wave will be described with reference to FIG.

After extracting only the frequency component of the pulse wave, the frequency sequence data of the pulse wave signal (see FIG. 5B) is removed except for the frequency range of the pulse wave signal, and the frequency sequence data is converted to the time series data. [Refer to FIG. 5C.] In this case, an inverse fast Fourier or the like is used.

As a result, only the waveform of the pulse wave component is reproduced from the data converted into the time-series data, and a pulse wave signal from which noise due to body movement or the like has been removed can be obtained.

Here, the frequency component of the pulse wave is extracted, the frequency components other than the frequency range are removed, and the frequency series data is converted into time series data to reproduce the waveform. Determines whether the original waveform can be faithfully reproduced.

However, in determining the blood pressure, the blood pressure value can be determined only by the amplitude information of the original waveform, and if a result proportional to the amplitude is obtained, the blood pressure value can be determined even if the waveform information is slightly lost. Has no effect. Therefore, when the waveform is reproduced, even if the frequency components other than the fundamental frequency range of the pulse wave are removed and the waveform is reproduced, the accuracy of the final blood pressure value is not affected.

Here, the advantage of performing waveform reproduction using only the fundamental frequency range is that the power spectrum of the fundamental frequency is strong and extraction is easy.

The pulse wave signal thus obtained is synchronized with the Korotkoff sound. Thus, using this pulse wave signal as a trigger signal (see FIG. 5D), it is possible to remove noise from the input Korotkoff sound signal [see FIG. 5E].

The amplitude of the reproduced pulse wave signal is small at a cuff pressure equal to or higher than the systolic blood pressure and at a cuff pressure equal to or lower than the diastolic blood pressure. This is apparent from the fact that the signal used in the oscillometric method is reproduced. Therefore, if the amplitude value of the pulse wave signal used as the trigger signal is determined in advance by the threshold value, the noise existing in the cuff pressure equal to or higher than the systolic blood pressure or equal to or lower than the diastolic blood pressure is not erroneously recognized as the Korotkoff sound. When ECG is used as a trigger signal, noise present in cuff pressures higher than systolic blood pressure or lower than diastolic blood pressure may be erroneously recognized as Korotkoff sounds because the electrocardiographic signal appears constantly regardless of blood pressure. was there. It can be said that the electronic sphygmomanometer according to this embodiment can measure with high accuracy also from this point.

As described above, by using the method of the present invention,
The blood pressure can be determined with high accuracy regardless of the presence or absence of noise due to body motion or the like. In the above embodiment,
Although the detection means of the noise signal caused by body motion and the like is an acceleration sensor, instead of this, a speed sensor, a position sensor, a displacement sensor, an angle sensor, an azimuth sensor, a tilt sensor, etc.
A sensor that converts the movement of the measurement unit into a physical quantity for measurement, or a photoelectric sensor that measures a biomass (for example, blood volume) that changes due to the movement of the measurement unit may be used.

FIG. 6 shows another embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an electronic sphygmomanometer using a photoelectric sensor 14 as a means for detecting a noise signal caused by body movement.

In the electronic sphygmomanometer shown in FIG. 1, the pulse wave signal for determining the blood pressure is a pulse wave signal extracted from the cuff pressure signal by a filter. Pulse waves may be detected using an impedance sensor or a strain sensor.

FIG. 7 shows another embodiment of the present invention.
FIG. 4 is a block diagram illustrating a configuration of an electronic sphygmomanometer using a photoelectric sensor 15 as a pulse wave signal detecting unit.

FIG. 8 shows another embodiment of the present invention in which a photoelectric sensor 15 is used as a pulse wave signal detecting means, an amplifier 16 and a photoelectric sensor 14 is used as a means for detecting a noise signal caused by body movement and the like. It is a block diagram which shows the structure of the electronic blood pressure monitor which was used.

[0033]

According to the present invention, a pulse wave signal and a noise signal caused by body movement are detected, a frequency of the pulse wave signal is obtained, and a component other than the frequency range of the pulse wave component is obtained from the pulse wave signal. Remove. Since the pulse wave signal after removal is used as a trigger signal of Korotkoff sound, highly accurate blood pressure determination can be performed even under the condition that noise such as body motion is mixed. Further, it is not necessary to attach an electrocardiographic electrode to obtain a trigger signal. If turned over, electrocardiographic information can be used as separate information.

[Brief description of the drawings]

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

FIG. 2 is a flowchart for explaining a processing operation of blood pressure measurement including noise removal of the electronic blood pressure monitor of the embodiment.

FIG. 3 is a diagram showing frequency sequence data of a pulse wave component and a body motion signal at the time of measurement under rest in the electronic blood pressure monitor of the embodiment.

FIG. 4 is a diagram showing frequency sequence data of a pulse wave component and a body motion signal during measurement during body motion in the electronic blood pressure monitor of the embodiment.

FIG. 5 is a waveform diagram for explaining a process of obtaining a Korotkoff sound signal in which noise has been removed from an input signal on which noise due to body movement has been superimposed in the electronic blood pressure monitor of the embodiment.

FIG. 6 is a block diagram showing a configuration of an electronic sphygmomanometer according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an electronic sphygmomanometer according to still another embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an electronic sphygmomanometer according to still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 cuff 2 pressure pump 3 exhaust valve 4 pressure sensor 5 Korotkoff sound sensor, 6 display 7 CPU 8, 9, 13, 16 amplifier 10 filter 11 A / D converter 12 acceleration sensor 14, 15 photoelectric sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noboru Ohama 801 Minami-Fudo-do, Higashi-iri, Higashikawa, Shiokoji-dori, Shimogyo-ku, Kyoto Inside the OMRON Life Science Laboratory Co., Ltd. 801 Higashiiri Minami Fudodoucho OMRON Life Science Laboratory Co., Ltd. F-term (reference) 4C017 AA08 AA09 AB01 AC26 AC32 BC16 BC17 BD05

Claims (5)

[Claims] 1. A cuff, a control means for increasing / decreasing a pressure in the cuff, a means for detecting a pressure in the cuff, and a pulse wave detection for detecting a pulse wave signal from a cuff pressure output from the detection means. Means for detecting a noise signal caused by at least one or more body movements, and a blood pressure calculating means, wherein the pulse wave signal and the noise signal are each subjected to frequency analysis to obtain time-series data. Data conversion means for converting the pulse sequence signal into frequency sequence data; means for comparing the frequency sequence data to obtain a frequency component of the pulse wave signal; A means for converting the frequency series data of the pulse wave signal after removing the frequency band other than the pulse wave signal into time series data and reproducing the pulse wave signal, and using the reproduced pulse wave signal as a trigger signal. Korotkoff sound An electronic sphygmomanometer comprising: means for removing noise from a signal; and calculating blood pressure based on the Korotkoff sound from which noise has been removed. 2. The method according to claim 1, wherein only the fundamental frequency is obtained from the frequency components of the pulse wave signal, and all frequency bands other than the fundamental frequency range of the pulse wave signal are removed from the frequency sequence data of the pulse wave signal. 2. The method according to claim 1, further comprising: converting frequency sequence data of the pulse wave signal from which all have been removed to time-series data, reproducing the pulse wave signal, and calculating the blood pressure based on the reproduced pulse wave signal. Electronic blood pressure monitor as described. 3. The electronic sphygmomanometer according to claim 1, wherein the means for detecting the noise signal is a sensor for converting a body motion or the like into a physical quantity and measuring the physical quantity. 4. The electronic sphygmomanometer according to claim 1, wherein the means for detecting the noise signal is a sensor for measuring a biomass that changes due to body movement or the like. 5. The electronic sphygmomanometer according to claim 1, wherein the means for detecting the pulse wave signal is a sensor for measuring a volume vibration of an artery as a pulse wave.