KR101646529B1 - Apparatus and method for automatic detection of arterial blood pressure - Google Patents

Abstract

The present invention relates to a blood pressure waveform detecting apparatus and a blood pressure waveform detecting method using the same. The present invention detects a peak of a waveform from a blood pressure waveform sensed by a body to a sensor, divides the blood pressure waveform into period units, and then calibrates the unit of the blood pressure waveform using information of the blood pressure separately measured from the blood pressure waveform The present invention also provides a blood pressure waveform detecting apparatus for robustly detecting a blood pressure waveform and calibrating a blood pressure unit even for an atrial fibrillation patient having an unstable pulse due to an irregular heart beat, and provides a blood pressure waveform detection and correction method using the same .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an automatic blood pressure waveform detecting apparatus,

The present invention relates to an apparatus and a method for detecting a blood pressure waveform.

The heart of the body periodically beats and sends blood to the entire body from the heart to peripheral blood vessels. The pressure on the blood vessel wall in the process of blood flowing along the blood vessel is called blood pressure. In addition, the heart repeats contraction and relaxation while pulsating. The systolic blood pressure is called the systolic blood pressure when the heart's ventricle contracts and the blood is pushed into the artery. It is called the systolic blood pressure because it is the highest systolic blood pressure. The diastolic blood pressure is called the diastolic blood pressure and the lowest blood pressure is also called the diastolic blood pressure.

As the heart periodically pulses, the blood pressure changes periodically between the systolic and diastolic blood pressure, and the periodic fluctuation of the blood pressure is referred to as a pulse, and the waveform is referred to as a pulse wave or a blood pressure waveform. The blood pressure waveform according to the change of the pulse is affected by the pulsating force of the heart, the beating state, the elasticity of the blood vessel, the viscosity of the blood, and has different sizes and shapes depending on the positions of the arteries, veins and capillaries.

As a method of measuring blood pressure, there is an invasive method of measuring blood pressure with a pressure gauge by inserting a measuring device into a blood vessel, and a non-invasive method of measuring blood pressure by sensing blood flow from a sensor outside the body. Noninvasive blood pressure measurement methods generally use a method of measuring the changing blood pressure as the upper arm compresses with pressure and relaxes. In order to measure the pulse more precisely, the blood pressure is measured by a non-invasive method by bringing the tonometry into contact with the passing skin of the blood vessel and measuring the vibration according to the change of the blood pressure in the blood vessel.

Conventional blood pressure measuring apparatuses measure systolic blood pressure and diastolic blood pressure, but can not measure a fine waveform of a pulse or detect minute waveforms of a pulse non-invasively, so that a blood pressure unit of a waveform can not be measured. In addition, there is a blood pressure waveform measuring device for calibrating a blood pressure unit after detecting a fine waveform of a pulse, but the conventional device can not reliably detect a heartbeat cycle for a blood pressure waveform of an atrial fibrillation patient having an irregular heartbeat , And the blood pressure unit can not be corrected correctly due to irregular pulse changes. In addition, since the existing apparatus can measure only at a specific position such as a finger or a wrist, there is a problem that accuracy of the blood vessel is degraded when the blood vessel to be detected is changed.

A problem to be solved by the present invention is to detect a peak of a waveform from a blood pressure waveform detected by a sensor in a body and to divide the blood pressure waveform into cycle units and then use the separately measured blood pressure information to calculate a unit of the blood pressure waveform The present invention also provides a device for detecting a blood pressure waveform and correcting a blood pressure unit even in an atrial fibrillation patient having an unstable pulse due to irregular heartbeat and providing a blood pressure waveform detection and correction method using the same will be.

According to one aspect of the present invention, there is provided a blood pressure waveform detecting apparatus comprising: a low pass filter unit for receiving a pulse wave and filtering the pulse wave with a low pass filter to obtain a low frequency signal; And a pulse wave peak detector for detecting a peak of the pulse wave using the low frequency signal obtained by the low pass filter.

According to one embodiment, the low-pass filter unit may be capable of variably controlling a filter coefficient of the low-pass filter.

According to an embodiment of the present invention, the pulse-wave peak detector detects a peak of a low-frequency signal obtained by the low-pass filter, and detects a peak of the pulse wave within a predetermined time interval from a peak of the detected low- can do.

According to an embodiment, the pulse wave peak detector may further include: a differential section for differentiating the low-frequency signal obtained by the low-pass filter section; A zero crossing point detecting unit for detecting the zero crossing point of the differentiated signal in the differential unit; And a local maximum point detecting unit for detecting a maximum point of the pulse wave within a predetermined time interval based on the zero crossing point detected by the zero crossing point detecting unit.

The blood pressure waveform detecting apparatus may further include a filter coefficient adjusting unit for adaptively calculating a filter coefficient value of the low-pass filter according to the characteristics of the pulse wave.

According to an embodiment, the filter coefficient adjustment unit may include a heart rate calculation unit for calculating an average heart rate during a predetermined time of the pulse wave; And a filter coefficient calculator for calculating a filter coefficient value of the low pass filter based on the average heart rate value, wherein when the average heart rate value fluctuates, the filter coefficient value of the low pass filter is set to the average heart rate And adjusts it in accordance with the adjustment.

According to an embodiment of the present invention, the heart rate calculation unit may analyze the frequency domain signal of the pulse wave to calculate an average heart rate during a predetermined time.

According to an embodiment, the heart rate calculation unit may include a linear tendency remover to obtain a signal from which a linear trend, which is a linear component having a constant slope, is removed from the signal of the pulse wave; A window function applying unit that obtains a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the signal obtained in the linear tendency remover; A frequency domain transformer for transforming the signal obtained by the window function application unit into a frequency domain signal; And a signal analyzer for analyzing the signal in the converted frequency domain to calculate an average heart rate of the pulse wave for a predetermined time.

According to an embodiment, the filter coefficient calculator may calculate a filter coefficient value of the low-pass filter having a predetermined multiple of the average heart rate calculated by the heart rate calculator as a cut-off frequency.

The blood pressure waveform detecting apparatus may further include a cycle unit pulse wave detecting unit for detecting the pulse wave divided by the cycle unit using the peak information of the pulse wave detected by the pulse wave peak detecting unit.

The blood pressure waveform detecting apparatus may further comprise a pulse wave measuring unit for measuring a pulse of the blood vessel of the body to measure a pulse, amplifying the measured pulse signal, and removing noise of the amplified pulse signal to obtain the pulse wave .

According to another aspect of the present invention, there is provided an apparatus for detecting a blood pressure waveform, comprising: a blood pressure detecting unit for detecting a blood pressure of a body blood vessel to measure a pulse, amplifying the pulse signal, and removing noise of the amplified pulse signal, A pulse wave measuring unit; A low-pass filter unit receiving the pulse wave and filtering the pulse wave with a low-pass filter to obtain a low-frequency signal; A filter coefficient adjuster for adaptively calculating a filter coefficient value of the low pass filter according to characteristics of the pulse wave; A pulse wave peak detector for detecting a peak of the pulse wave using the low frequency signal obtained by the low pass filter; A periodic unit pulse wave detector for detecting the pulse wave divided by a cycle unit using the pulse wave peak information of the pulse wave detected by the pulse wave peak detector; A pulse-wave specifying unit that receives blood pressure information including blood pressure and blood pressure measurement time point information of a specific part of the body and pulse waves measured separately from the blood pressure information, and specifies a cycle of the pulse wave corresponding to the blood pressure measurement time; And a pulse-wave unit calibration unit for calibrating the unit of the pulse wave of the specified period using the blood pressure information.

According to an embodiment of the present invention, the pulse-wave specifying unit detects a starting point of each cycle of the pulse wave, analyzes the blood pressure information, and specifies the pulse wave of one cycle occurring after a certain period at the time of measuring the blood pressure .

According to one embodiment, the pulse-wave specifying unit makes a tangent line around the highest point of the first-order differential signal of the pulse wave, creates a horizontal line connecting the lowest points of the pulse wave, And the start point of each pulse of the pulse wave is detected using an intersecting tangent method, which is a method of determining the start point of the pulse wave.

According to an embodiment, the pulse-wave unit calibration unit may calibrate the pulse-wave unit of one cycle specified by the pulse-wave specifying unit on the basis of the blood pressure, And calibrating the unit of the pulse wave.

The blood pressure waveform detecting apparatus may further include a blood pressure measuring unit for measuring the blood pressure information.

According to one embodiment, the blood pressure measuring unit includes a sensor unit for measuring a blood pressure while pressing and relaxing a specific part of the body; A sensor driver for driving the sensor unit; An amplifying unit for amplifying the blood pressure signal measured by the sensor unit; A noise removal filter unit for removing noise of the blood pressure signal amplified by the amplification unit through filtering; And a blood pressure information calculation unit for analyzing the blood pressure signal from which noise has been removed from the noise canceling filter unit and calculating the blood pressure information including the blood pressure and the blood pressure measurement time point information.

According to an embodiment of the present invention, the low-pass filter unit may variably adjust a filter coefficient of the low-pass filter, and the filter coefficient adjuster may adjust the filter coefficient of the low- A rate calculator; And a filter coefficient calculator for calculating a filter coefficient value of the low pass filter based on the average heart rate value, wherein when the average heart rate value fluctuates, the filter coefficient value of the low pass filter is set to the average heart rate Wherein the pulse wave peak detecting unit comprises: a differentiating unit for differentiating the low-frequency signal obtained by the low-pass filter unit; A zero crossing point detecting unit for detecting the zero crossing point of the differentiated signal in the differential unit; And a local maximum point detecting unit for detecting a maximum point of the pulse wave within a predetermined time interval based on the zero crossing point detected by the zero crossing point detecting unit, wherein the peak detecting unit detects the peak of the low frequency signal obtained by the low pass filter unit, And the peak of the pulse wave is detected within a predetermined time interval from the peak of the low-frequency signal.

According to an embodiment, the heart rate calculation unit may include a linear tendency remover that obtains a signal from which a linear trend, which is a linear component having a constant slope, is removed from the signal of the pulse wave; A window function applying unit that obtains a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the signal obtained in the linear tendency remover; A frequency domain transformer for transforming the signal obtained by the window function application unit into a frequency domain signal; And a signal analyzer for analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time, wherein the filter coefficient calculator calculates the average heart rate of the pulse wave And a filter coefficient value of the low-pass filter having a predetermined multiple of the cut-off frequency as the cut-off frequency.

According to another aspect of the present invention, there is provided a blood pressure waveform detecting method comprising: a pulse wave measuring step of detecting a blood pressure of a body vessel, amplifying a signal of the detected blood pressure, and removing noise to measure a pulse wave; Filtering the measured pulse wave with a low pass filter capable of variable adjustment of a filter coefficient; Detecting a peak of the pulse wave using a signal filtered by the low-pass filter; And detecting the pulse wave divided in a cycle unit by using the detected peak information.

In one embodiment, detecting the peak of the pulse wave includes: differentiating the signal filtered by the low-pass filter; Detecting a position of a zero crossing point of the differentiated signal; And detecting a peak of the pulse wave within a predetermined time interval based on the detected zero crossing point.

The blood pressure waveform detection method may further include analyzing a frequency domain signal of the pulse wave to calculate an average heart rate during a predetermined period of time and outputting the average pulse rate of the low pass filter to the low pass And a filter coefficient adjusting step of adaptively adjusting the filter coefficient of the filter.

In one embodiment, the adjusting the filter coefficient includes: obtaining a signal from which a linear trend, which is a linear component having a constant slope, is removed from the signal of the pulse wave; Obtaining a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the linearly removed signal; Converting the signal defined by the predetermined length into a frequency domain signal; Analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time; And adaptively adjusting the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated heart rate.

According to another aspect of the present invention, there is provided a blood pressure waveform detecting method comprising: a pulse wave measuring step of detecting a blood pressure of a body vessel, amplifying a signal of the detected blood pressure, and removing noise to measure a pulse wave; Wherein the controller calculates the average heart rate for a predetermined time by analyzing the frequency domain signal of the pulse wave and adjusts the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated average heart rate. A filter coefficient adjustment step of adjusting the filter coefficient; Filtering the measured pulse wave with the low-pass filter having the adjusted filter coefficient; Detecting a peak of the pulse wave using a signal filtered by the low-pass filter; Detecting the pulse wave divided in a cycle unit by using the detected peak information; Measuring blood pressure information including a blood pressure of a specific part of the body and blood pressure measurement time point information; Identifying a starting point of each cycle of the pulse wave and analyzing the measured blood pressure information to identify the pulse wave of one cycle occurring after a certain period of time at the time of measuring the blood pressure among the input pulse waves; And calibrating the specified unit of the pulse wave based on the blood pressure and calibrating the unit of the pulse wave of the remaining periods based on the calibrated pulse wave of one period .

In one embodiment, the step of detecting the peak of the pulse wave includes: differentiating a signal filtered by the low-pass filter; Detecting a position of a zero crossing point of the differentiated signal; And detecting a peak of the pulse wave within a predetermined time interval based on the detected zero crossing point, wherein the filter coefficient adjusting step comprises: Obtaining a signal from which a linear trend is removed; Obtaining a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the linearly removed signal; Converting the signal defined by the predetermined length into a frequency domain signal; Analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time; And adaptively adjusting the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated average heart rate.

In one embodiment, measuring the blood pressure information comprises: measuring blood pressure while pressing and relaxing a specific part of the body; Amplifying the measured blood pressure signal; Removing noise of the amplified blood pressure signal through filtering; And analyzing the noise-removed blood pressure signal and calculating the blood pressure information including the blood pressure and the blood pressure measurement time point information.

The apparatus and method for detecting a blood pressure waveform according to the present invention have an effect of detecting a blood pressure waveform and correcting a blood pressure unit even for an atrial fibrillation patient having a pulse that is not stable due to irregular heart beat. In addition, there is an effect of detecting a blood pressure waveform and calibrating a blood pressure unit even for a person having a stable pulse of a normal form.

1 is a block diagram showing a blood pressure waveform detecting apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a filter coefficient adjustment unit according to an embodiment of the present invention.
3A is a reference view showing a frequency response characteristic of a low-pass filter of a low-pass filter according to an embodiment of the present invention.
FIG. 3B is a reference view showing pulse waveforms of peripheral blood vessels before and after filtering by a low-pass filter according to an embodiment of the present invention.
FIG. 3C is a reference view showing pulse waveforms of the aorta and the aorta by comparing the pulse waveforms before and after filtering by the low-pass filter according to an embodiment of the present invention.
4 is a block diagram illustrating a pulse wave peak detector according to an embodiment of the present invention.
FIG. 5 is a reference view showing a process of detecting a peak of a pulse wave by a low-pass filter and a pulse-wave peak detector according to an embodiment of the present invention.
6 is a block diagram showing a blood pressure measuring unit according to an embodiment of the present invention.
7A is a reference diagram showing a peripheral blood pressure waveform in a normal state.
FIG. 7B is a reference diagram showing a waveform in which peripheral blood pressure waveforms in a steady state of several cycles are superimposed. FIG.
7C is a reference diagram showing a peripheral blood pressure waveform in an atrial fibrillation patient having irregular heartbeat.
FIG. 7D shows waveforms of peripheral blood pressure waveforms of various periods shown in FIG. 7C, averaged peripheral blood pressure waveforms (a thick gray line) when the waveforms are averaged, an average of systolic blood pressure values of each cycle Line).
FIG. 7E is a graph showing the relationship between the pulse wave of the first period (bold gray line) and the systolic blood pressure value of the pulse wave of the first cycle (blue line) ) As a reference.
8 is a flowchart of a blood pressure waveform detection method according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the preferred embodiments of the present invention will be described below, but it is needless to say that the technical idea of the present invention is not limited thereto and can be variously modified by those skilled in the art.

1 is a block diagram showing a blood pressure waveform detecting apparatus according to an embodiment of the present invention. The blood pressure waveform detecting apparatus according to the present embodiment includes a pulse wave measuring unit 100, a low pass filter unit 200, a filter coefficient adjusting unit 300, a pulse wave peak detecting unit 400, a periodic pulse wave detecting unit 500, (600), a pulse-wave specifying unit (700), and a pulse-wave unit calibrating unit (800). The above embodiment is an optimal embodiment of the present invention. Another embodiment of the present invention may include a low pass filter unit 200 and a filter coefficient adjuster 300 and may further include a pulse wave measuring unit 100, a pulse wave peak detecting unit 400, 500). Another embodiment of the present invention includes a pulse wave measuring unit 100, a low pass filter unit 200, a filter coefficient adjusting unit 300, a pulse wave peak detecting unit 400, a periodic pulse wave detecting unit 500, 700, and a pulse wave unit calibration unit 800, and may further include a blood pressure measurement unit 600 as needed.

Hereinafter, each part of the blood pressure waveform detecting apparatus will be described in detail with respect to the above-described optimum embodiment.

The pulse-wave measuring unit 100 detects a blood pressure of a blood vessel of a body to measure a pulse, amplifies the measured pulse signal, removes noise of the amplified pulse signal, and acquires a pulse wave according to the amplified pulse signal do. At this time, it is preferable that the body blood vessel measuring the pulse is a radial artery, and the blood pressure change can be measured in a non-invasive manner by contacting a highly accurate tonometry with a point on the wrist passing through the radial artery. In the signal measured by the above-mentioned torque meter, the noise inserted in the measurement process can be filtered out to acquire the pulse wave of the radial artery. The pulse wave measured by the pulse wave measuring unit 100 is a signal having no unit, and the unit can be calibrated by the pulse wave unit calibration unit 800 to be described later. The pulse wave thus obtained may be input to the low-pass filter unit 200.

The low-pass filter unit 200 receives the pulse wave from the pulse-wave measuring unit 100 and then filters the low-pass-filtered signal to obtain a low-frequency signal. At this time, the low-pass filter can adjust the frequency response characteristic of the filter by variably controlling the filter coefficient. The filter coefficient may be adjusted adaptively according to the value of the filter coefficient calculated by the filter coefficient adjusting unit 300 to be described later.

The filter coefficient adjustment unit 300 adaptively calculates the filter coefficient value of the low-pass filter of the low-pass filter unit 200 according to the characteristics of the pulse wave. The filter coefficient adjusting unit 300 adjusts the filter coefficient according to the characteristics of the pulse wave to adjust the cutoff frequency of the low pass filter so that the pulse wave peak detecting unit 400 to be described later is optimized in accordance with the characteristics of the pulse wave, So that the peak can be detected. The configuration and operation of the filter coefficient adjusting unit 300 and the low-pass filter unit 200 will be described in more detail with reference to FIGS. 2, 3A, 3B, 3C and 5.

The pulse wave peak detector 400 detects the peak of the pulse wave using the low frequency signal obtained by the low pass filter 200. At this time, the pulse wave peak detector 400 preferably detects the peak of the low frequency signal and detects the peak of the pulse wave within a predetermined time interval from the peak of the detected low frequency signal. By detecting the highest point of the low frequency signal as described above, it is possible to grasp the overall flow of the blood pressure excluding the high frequency component of the pulse wave, and to grasp the approximate interval in which the peak of the pulse wave occurs. By detecting the coordinates of the pulse wave having the maximum magnitude value within a predetermined time interval from the highest point of the detected low frequency signal as described above, it is possible to detect the local peak, which is likely to occur locally due to noise, as the systolic blood pressure, The peak of the pulse wave corresponding to the point can be correctly detected. The configuration and operation of the pulse wave peak detector 400 will be described in more detail with reference to FIGS. 4 and 5. FIG.

The periodic pulse wave detecting unit 500 detects the pulse wave classified in a cycle unit by using the peak information of the pulse wave detected by the pulse wave peak detecting unit 400. For example, the periodic pulse wave detector 500 can detect the pulse wave classified in a cycle unit by dividing one cycle of the pulse wave based on the highest point of the pulse wave detected by the pulse wave peak detector 400. [ The pulse wave detected by the periodic pulse wave detector 500 is divided into the pulse wave and the pulse wave.

The blood pressure measuring unit 600 measures blood pressure information including a blood pressure of a specific part of the body and a time point at which the blood pressure is measured. Preferably, the blood pressure measuring unit 600 can measure the blood pressure of the brachial artery of the body. The configuration and operation of the blood pressure measuring unit 600 will be described in more detail with reference to FIG.

The pulse wave identifying unit 700 receives the blood pressure information measured by the blood pressure measuring unit 600 and receives the detected pulse wave divided into cycle units obtained by the cycle unit pulse wave detecting unit 500, And specifies the period of the pulse wave corresponding to the time point at which the blood pressure is measured.

At this time, the pulse-wave specifying unit 700 preferably detects the start point of each cycle of the input pulse wave using an intersecting tangent method. The Intersecting Tangent Method is a method used to detect the starting point of a pulse wave. This method first sets a certain ratio of the pulse wave size to the threshold, and in the lower range, the pulse wave changes from a negative slope to a positive slope A tangent line is formed around the first differential peak point of each pulse wave when the detected lowest points exist within a predetermined time unit from each other and a horizontal line connecting the lowest point of each detected pulse wave is made, And the horizontal line is determined as the starting point of each cycle of the pulse wave.

The pulse-wave specifying unit 700 analyzes the blood pressure information and specifies the pulse wave of one period occurring after a predetermined period at the time when the blood pressure is measured. Here, the predetermined period is one cycle, It is preferable that the pulse wave of the first cycle occurring after the measured point is specified.

The pulse-wave unit calibration unit 800 calibrates a unit of one-cycle pulse wave specified by the pulse-wave specifying unit 700 using the blood pressure information received from the blood pressure measuring unit 600. [ At this time, the pulse-wave unit calibration unit 800 calibrates the unit of the pulse wave of one period specified by the pulse-wave specifying unit 700 on the basis of the magnitude of the blood pressure inputted from the blood pressure measuring unit 600, The units of the pulse wave of the remaining periods can be corrected on the basis of the pulse wave of one period whose unit is calibrated. The operation of the pulse-wave specifying unit 700 and the pulse-wave unit calibrating unit 800 will be described in more detail with reference to FIG.

For example, in the blood pressure waveform detecting apparatus, when the pulse wave measuring unit 600 measures blood pressure in the brachial artery and sends information on the blood pressure and the time of measurement thereof to the pulse-wave specifying unit 700, Pulse wave peak detecting unit 400 and periodic pulse wave detecting unit 500 after being measured in the radial artery by the ultrasonic wave measuring unit 100 and receiving the detected pulse wave divided periodically while passing through the low pass filter unit 200, The pulse wave unit calibration unit 800 specifies the pulse wave amplitude of the pulse wave of the specified one period in the pulse wave specifying unit 700, The unit of the blood pressure of the brachial artery measured may be calibrated and the unit of blood pressure of the pulse wave of the remaining period may be calibrated in accordance with the blood pressure of the pulse wave of the calibrated unit.

2 is a block diagram showing a filter coefficient adjustment unit 300 according to an embodiment of the present invention. The filter coefficient adjustment unit 300 may include a heart rate calculation unit 310 and a filter coefficient calculation unit 320.

The heart rate calculating unit 310 calculates an average heart rate during a predetermined time of the pulse wave and analyzes the frequency domain signal of the pulse wave to calculate an average heart rate during a predetermined time. For this, the heart rate calculation unit 310 may include a linear tendency remover 311, a window function application unit 312, a frequency domain transform unit 313, and a signal analysis unit 314.

The linear tendency remover 311 obtains a signal in which the linear trend is removed from the signal of the pulse wave. The linear tendency of the signal means that the signal has a fixed offset value or has a linear component such as a constant slope in a certain section. The removal of the linear tendency means that the offset Which means to extract and remove components.

 The window function applying unit 312 applies a window function to the signal obtained by the linear tendency remover 311 to acquire a signal limited to a predetermined length. This is a preprocessing step for performing frequency domain transformation in the frequency domain transformer 313. The window function is a function having a specific value only within a predetermined period of a finite length, and various kinds of window functions exist depending on the type of the function. Preferably, the Hanning Window Function may be a window function.

The frequency domain transforming unit 313 transforms the signal obtained by the window function applying unit 312 into a frequency domain signal. Preferably, a Fast Fourier Transform (FFT) method can be applied as a frequency domain transform method of a signal.

The signal analyzer 314 analyzes the converted signal in the frequency domain to calculate the average heart rate of the pulse wave for a predetermined time. The average heart rate of the pulse wave may be a frequency value corresponding to a signal having the largest magnitude in the converted frequency domain signal.

The filter coefficient calculating section 320 calculates the filter coefficient value of the low pass filter section 200 based on the heart rate value calculated by the heart rate calculating section 310. [ At this time, the filter coefficient calculator 320 may calculate the filter coefficient value such that the cut-off frequency of the low-pass filter of the low-pass filter 200 is a predetermined multiple of the heart rate. Preferably, the filter coefficient calculator 320 calculates a filter coefficient so that the low-pass filter of the low-pass filter unit 200 is a finite impulse response (FIR) low-pass filter having a cutoff frequency of 1.8 times the calculated heart rate. The coefficient value can be calculated. As the blood pressure waveform progresses to the periphery, the harmonic component of the second order or less increases in the waveform, and the frequency component of the blood pressure waveform shifts as the heartbeat changes. Therefore, in order to minimize the error of the blood pressure waveform according to the position of the blood vessel and the change of the heartbeat, the filter coefficient calculator 320 calculates a value of 1.8 times the heart rate, which is a value immediately before the second harmonic component in the waveform, It is preferable to set the cut-off frequency of the pass filter. However, the value of the cutoff frequency above can be modified as necessary.

As described above, the filter coefficient calculator 320 adjusts the filter coefficient value of the low pass filter 200 according to the heart rate of the pulse wave so that the cutoff frequency of the low pass filter is a predetermined multiple of the heart rate, Although the waveform of the pulse wave varies according to the heart rate, the low-pass filter unit 200 may receive a sawtooth-shaped low-frequency signal from which a pulse wave having various heart rate values is input and the inflection point is removed.

3A is a reference view showing a frequency response characteristic of the low-pass filter of the low-pass filter 200 according to an embodiment of the present invention. As shown in the drawing, the low-pass filter of the low-pass filter unit 200 increases the cutoff frequency value by a predetermined multiple as the heartbeat rate of the pulse wave increases.

FIG. 3B is a view showing a comparison of the shapes of the pulse waves before and after filtering the peripheral blood vessels by the low-pass filter unit 200. FIG. 3C is a graph showing the relationship between the pulse waves of the aortic blood vessels before and after filtering by the low- Of the present invention. As shown in the drawing, the pulse waves are filtered by the low-pass filter unit 200, and then become a sawtooth-shaped low-frequency signal in which inflection points are stably removed.

4 is a block diagram illustrating a pulse wave peak detector 400 according to an embodiment of the present invention. The pulse wave peak detecting unit 400 may include a differentiating unit 410, a zero crossing point detecting unit 420, and a local peak detecting unit 430.

The differentiating unit 410 first differentiates the low-frequency signal received from the low-pass filter unit 200. [ As described above, the differentiating unit 410 differentiates the low-frequency signal as described above, and can detect the peak position of the pulse wave, that is, the approximate position of the point corresponding to the systolic blood pressure.

The zero crossing point detector 420 detects the position of the zero crossing point of the non-divided signal at the differentiating unit 410. At this time, the position of the zero crossing point where the non-divided signal changes from a positive value to a negative value and becomes zero is the highest point of the low frequency signal.

The local peak detecting unit 430 detects the peak of the pulse wave within a predetermined time interval based on the zero crossing point detected by the zero crossing point detecting unit 420. The local peak detector 430 compares size information of the pulse wave within a predetermined time interval with reference to the time when the zero crossing point occurs, and determines the point having the largest value as the peak of the pulse wave. Preferably, the peak of the pulse wave can be detected within a time interval of 100 ms before the zero crossing point. Here, the 100 ms search region is set in order to consider the effect of group delay due to the filtering of the signal through the low pass filter unit 200, and the length of the search region may be changed if necessary.

The pulse wave peak detector 400 may also operate as an apparatus for detecting the lowest point of the pulse wave. In the same principle, when the zero pulse detector 420 detects that the non-divided signal changes from a negative value to a positive value, Detecting a lowest point of the low-frequency signal and detecting a lowest point of the pulse wave within a predetermined time interval based on the lowest point of the detected low-frequency signal, thereby detecting a lowest point corresponding to the diastolic blood pressure of the pulse wave Can be detected. The blood pressure waveform can be detected on the same principle by using the lowest point detected as above instead of the peak of the pulse wave detected in the present invention.

FIG. 5 is a reference view showing a process of detecting the peak of the pulse wave by the low-pass filter 200 and the pulse-wave peak detector 400 according to an embodiment of the present invention.

6 is a block diagram showing a blood pressure measuring unit 600 according to an embodiment of the present invention. The blood pressure measuring unit 600 may include a sensor unit 610, an amplifying unit 620, a noise removing filter unit 630, a blood pressure information calculating unit 640, and a sensor driving unit 650.

The sensor unit 610 measures blood pressure while compressing and relaxing a specific part of the body. Preferably, the brachial artery pressure can be measured while the upper arm is squeezed under pressure and relaxed.

The amplification unit 620 amplifies the measured blood pressure signal.

The noise removing filter unit 630 removes the noise of the amplified blood pressure signal through filtering.

The blood pressure information calculating unit 640 analyzes the blood pressure signal from which the noise is removed, and calculates the blood pressure information including the blood pressure and the blood pressure measurement time point information.

The sensor driver 650 drives the sensor unit 610 by adjusting the air pressure of a pushing pad provided on the sensor unit 610.

According to the blood pressure waveform detecting apparatus of the present invention as described above, a low-pass filter adaptively changing its frequency response characteristic according to various pulse wave states is designed, and a low-frequency signal in which an inflection point is removed is used And detects the peak of the pulse wave within a predetermined time interval by using the peak information of the low frequency signal. By detecting the peak of the pulse wave in the pulse wave of the atrial fibrillation patient having irregular heartbeat characteristic, The pulse wave can be detected.

According to the blood pressure waveform detecting apparatus of the present invention as described above, the unit of the pulse wave of the first cycle occurring nearest to the measurement time of the brachial artery blood pressure is corrected to the measured blood pressure, Since the unit is calibrated on the basis of the pulse wave of the first period, even if the heart rate changes irregularly after the measurement point of the blood pressure, the pulse wave can be calibrated to have the correct unit value. The conventional blood pressure waveform detecting apparatus calibrates the unit by superimposing the waveform of the pulse wave for a predetermined time to derive the averaged waveform and then substituting the measured blood pressure into the waveform of the averaged pulse wave to correct the unit, It is difficult for the atrial fibrillation patient having the normal blood pressure waveform to have a steady state, which is assumed by the existing blood pressure waveform detecting apparatus. Therefore, the conventional blood pressure waveform detecting apparatus can not correct the blood pressure unit correctly There is a problem. However, the apparatus for detecting a blood pressure waveform according to an embodiment of the present invention corrects a blood pressure unit of a pulse wave based on a pulse wave of a first cycle that occurs closest to the measured blood pressure, so that the blood pressure unit can be robustly corrected even in the case of irregular pulse have. The improvement effect of the blood pressure waveform detecting apparatus according to the present invention when compared with the existing apparatus can be confirmed by reference figures of FIGS. 7A, 7B, 7C, 7D and 7E.

7A is a reference diagram showing a peripheral blood pressure waveform in a normal state.

FIG. 7B is a reference diagram showing a waveform in which peripheral blood pressure waveforms in a steady state of several cycles are superimposed. FIG.

7C is a reference diagram showing a peripheral blood pressure waveform in an atrial fibrillation patient having irregular heartbeat.

FIG. 7D shows waveforms of peripheral blood pressure waveforms of various periods shown in FIG. 8C, averaged peripheral blood pressure waveforms (a thick gray line) when these waveforms are averaged, and an average of systolic blood pressure values of each cycle Line).

FIG. 7E is a graph showing the relationship between a pulse wave of a first period (a bold gray line) and a pulse wave of the first period when the pulse-wave-unit identifying unit 700 and the pulse-wave-unit calibrating unit 800 according to an embodiment of the present invention are applied. (Blue line) of the systolic blood pressure of the subject.

When the blood pressure waveform of an image fibrillation patient is detected using an existing apparatus, the starting point is not correctly detected and the unit is not corrected as shown in FIG. 7D. However, when the blood pressure is detected using the blood pressure waveform detecting apparatus according to the present invention, The starting point is detected correctly and the unit is corrected.

8 is a flowchart of a blood pressure waveform detection method according to another embodiment of the present invention. Each step of FIG. 8 is a process of operating the blood pressure waveform detecting apparatus according to the first embodiment of the present invention. Therefore, the parts of the blood pressure waveform detecting apparatus which overlap with those described above in the process of the above-described description of FIGs. 1 to 7 will be briefly described.

In step S1, the blood pressure of the body blood vessel is sensed, the signal of the sensed blood pressure is amplified, and noise is removed to measure the pulse wave. At this time, it is preferable to measure the pulse wave of the radial artery above the wrist using a high-precision torque meter.

In step S2, an average heart rate is calculated for a predetermined time by analyzing a frequency domain signal of the pulse wave, and a filter coefficient is calculated so that a cutoff frequency of the low pass filter in step S3 is a predetermined multiple of the calculated heart rate Adaptively adjust. At this time, in step S2, a signal obtained by removing a linear trend from a signal of the pulse wave is acquired, a signal defined by a predetermined length is obtained by applying a window function to the signal of which the linear tendency is removed, Wherein the controller is configured to convert a signal limited to a predetermined length into a signal in a frequency domain, analyze the signal in the converted frequency domain to calculate an average heart rate of the pulse wave for a predetermined time, The filter coefficient of the low-pass filter can be adaptively adjusted so as to have a constant multiple of the rate. At this time, the window function is preferably a Hanning Window function, and the cutoff frequency is preferably 1.8 times the measured heart rate.

In step S3, the measured pulse wave is filtered by a low-pass filter having a filter coefficient value adjusted in step S2 of the filter coefficient.

In step S4, the peak of the pulse wave is detected using the signal filtered by the low-pass filter. At this time, in step S4, the signal filtered by the low-pass filter is differentiated, the position of the zero crossing point of the differentiated signal is detected, and the highest point of the pulse wave is detected within a predetermined time interval based on the detected zero crossing point . At this time, it is preferable that the predetermined time interval for finding the peak of the pulse wave is within 100 ms from the zero crossing point.

In step S5, the pulse wave divided by the period is detected using the detected peak information. In step S5, the detected pulse wave is obtained by dividing the pulse wave on a cycle basis.

In step S6, the blood pressure information including the blood pressure of the specific part of the body and the blood pressure measurement time point information is measured. At this time, in step S6, the blood pressure is measured while pressing and loosening a specific part of the body, the amplified blood pressure signal is amplified, the noise of the amplified blood pressure signal is removed by filtering, and the noise- And the blood pressure information including the blood pressure and the blood pressure measurement time point information can be measured. At this time, it is preferable that the specific part of the body for measuring the blood pressure information is the upper arm.

In step S7, the start point of each cycle of the pulse wave is detected, and the measured blood pressure information is analyzed to identify the pulse wave of one cycle occurring after a certain period of time from the pulse pressure measurement time of the pulse wave.

In step S8, the specified unit of the pulse wave of one cycle is calibrated based on the blood pressure, and the unit of the pulse wave of the remaining cycles is calibrated based on the calibrated pulse wave of one period.

It is to be understood that the present invention is not limited to these embodiments, and all elements constituting the embodiment of the present invention described above are described as being combined or operated in one operation. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them.

In addition, although all of the components may be implemented as one independent hardware, some or all of the components may be selectively combined to perform a part or all of the functions in one or a plurality of hardware. As shown in FIG. In addition, such a computer program may be stored in a computer readable medium such as a USB memory, a CD disk, a flash memory, etc., and read and executed by a computer to implement an embodiment of the present invention. As the recording medium of the computer program, a magnetic recording medium, an optical recording medium, a carrier wave medium, and the like can be included.

Furthermore, all terms including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined in the Detailed Description. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: a pulse wave measuring unit
200: Low pass filter section
300: Filter coefficient adjustment section
310: heart rate calculation unit
311: linear tendency remover
312: Window function application part
313: Frequency domain transform unit
314:
320: Filter coefficient calculation unit
400: pulse wave peak detection unit
410:
420: Zero crossing point detecting section
430: Local peak detector
500: Periodic pulse wave detector
600: blood pressure measuring unit
610:
620:
630: Noise reduction filter section
640: blood pressure information calculation unit
650:
700: pulse wave specific part
800: pulse wave unit calibration unit

Claims (26)

A blood pressure waveform detecting apparatus comprising:
A low-pass filter unit that receives a pulse wave and filters the pulse wave with a low-pass filter to obtain a low-frequency signal;
A pulse wave peak detector for detecting a peak of the pulse wave using the low frequency signal obtained by the low pass filter; And
A filter coefficient adjusting unit adapted to adaptively adjust a filter coefficient value of the low pass filter according to an average heart rate during a predetermined time of the pulse wave while calculating a filter coefficient value of the low pass filter adaptively according to characteristics of the pulse wave;
And the blood pressure waveform detecting device. The method according to claim 1,
Wherein the low-pass filter unit variably adjusts a filter coefficient of the low-pass filter. The method according to claim 1,
Wherein the pulse-wave peak detecting unit detects a peak of the low-frequency signal obtained by the low-pass filter unit and detects a peak of the pulse wave within a predetermined time period from a peak of the detected low-frequency signal. The blood pressure monitor according to claim 3,
A differential section for differentiating the low-frequency signal obtained by the low-pass filter section;
A zero crossing point detecting unit for detecting the zero crossing point of the differentiated signal in the differential unit; And
And a local peak detecting unit for detecting a peak of the pulse wave within a predetermined time interval based on the zero crossing point detected by the zero crossing point detecting unit. delete 2. The apparatus according to claim 1,
A heart rate calculation unit for calculating the average heart rate during a predetermined time of the pulse wave; And
And a filter coefficient calculating section for calculating a filter coefficient value of the low pass filter based on the average heart rate value,
Wherein the controller adjusts the filter coefficient value of the low pass filter according to the average heart rate when the average heart rate value fluctuates. The method according to claim 6,
Wherein the heart rate calculation unit analyzes the frequency domain signal of the pulse wave to calculate an average heart rate during a predetermined time. 8. The apparatus according to claim 7, wherein the heart rate-
A linear tendency remover that obtains a signal from which a linear trend, which is a linear component having a constant slope, is removed from the signal of the pulse wave;
A window function applying unit that obtains a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the signal obtained in the linear tendency remover;
A frequency domain transformer for transforming the signal obtained by the window function application unit into a frequency domain signal; And
And a signal analyzer for analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined period of time. The blood pressure detecting apparatus according to claim 6, wherein the filter coefficient calculating section calculates a filter coefficient value of the low-pass filter having a cutoff frequency that is a predetermined multiple of an average heart rate calculated by the heart rate calculating section . The method according to claim 1,
And a periodic unit pulse wave detecting unit for detecting the pulse wave separated in a cycle unit by using the peak information of the pulse wave detected by the pulse wave peak detecting unit. The method according to claim 1,
Further comprising a pulse wave measuring unit for amplifying a pulse signal obtained by measuring a blood pressure of a body vessel to measure a pulse and removing the noise of the amplified pulse signal to obtain the pulse wave. A blood pressure waveform detecting apparatus comprising:
A pulse wave measuring unit for obtaining a pulse wave by removing a noise of the amplified pulse signal by amplifying a pulse signal obtained by measuring a blood pressure of a body blood vessel and measuring a pulse;
A low-pass filter unit receiving the pulse wave and filtering the pulse wave with a low-pass filter to obtain a low-frequency signal;
A filter coefficient adjuster for adaptively calculating a filter coefficient value of the low pass filter according to characteristics of the pulse wave;
A pulse wave peak detector for detecting a peak of the pulse wave using the low frequency signal obtained by the low pass filter;
A periodic unit pulse wave detector for detecting the pulse wave divided by a cycle unit using the pulse wave peak information of the pulse wave detected by the pulse wave peak detector;
A pulse-wave specifying unit that receives blood pressure information including blood pressure and blood pressure measurement time point information of a specific part of the body and pulse waves measured separately from the blood pressure information, and specifies a cycle of the pulse wave corresponding to the blood pressure measurement time; And
And a pulse-wave unit calibration unit for calibrating the unit of the pulse wave of the specified period using the blood pressure information. 13. The method of claim 12,
Wherein the pulse-wave specifying unit detects a starting point of each cycle of the pulse wave, analyzes the blood pressure information, and specifies the pulse wave of one cycle occurring after a certain period of time at the time of measuring the blood pressure. 14. The method of claim 13,
The pulse-wave specifying unit makes a tangent line around the highest point of the first-order differential signal of the pulse wave, creates a horizontal line connecting the lowest points of the pulse wave, and determines an intersection of the tangent line and the horizontal line as a starting point of each cycle of the pulse wave Wherein a start point of each cycle of the pulse wave is detected using an intersecting tangent method. 13. The method of claim 12,
The pulse-wave unit calibration unit calibrates the pulse-wave unit of one cycle specified by the pulse-wave specifying unit on the basis of the blood pressure and calibrates the unit of the pulse wave of the remaining cycles based on the calibrated pulse wave of one period And the blood pressure waveform detecting device. 13. The method of claim 12,
And a blood pressure measuring unit for measuring the blood pressure information. 17. The blood pressure monitor according to claim 16,
A sensor unit for measuring a blood pressure while pressing and relaxing a specific part of the body;
A sensor driver for driving the sensor unit;
An amplifying unit for amplifying the blood pressure signal measured by the sensor unit;
A noise removal filter unit for removing noise of the blood pressure signal amplified by the amplification unit through filtering; And
And a blood pressure information calculation unit for analyzing the blood pressure signal from which noise has been removed by the noise elimination filter unit and calculating the blood pressure information including the blood pressure and the blood pressure measurement time point information. 13. The method of claim 12,
Wherein the low-pass filter unit is capable of variably controlling a filter coefficient of the low-pass filter,
Wherein the filter coefficient adjustment unit comprises:
A heart rate calculation unit for calculating an average heart rate during a predetermined time of the pulse wave; And
And a filter coefficient calculation unit for calculating a filter coefficient value of the low pass filter based on the average heart rate value, wherein when the average heart rate value fluctuates, a filter coefficient value of the low pass filter is changed according to the average heart rate And adjusts it by adaptation,
Wherein the pulse wave peak-
A differential section for differentiating the low-frequency signal obtained by the low-pass filter section;
A zero crossing point detecting unit for detecting the zero crossing point of the differentiated signal in the differential unit; And
And a local maximum point detecting unit for detecting a maximum point of the pulse wave within a predetermined time interval based on the zero crossing point detected by the zero crossing point detecting unit and detects a peak of the low frequency signal obtained by the low pass filter unit, And detects the peak of the pulse wave within a predetermined time interval from the highest point of the low-frequency signal. 19. The method of claim 18,
Wherein the heart rate-
A linear tendency remover that obtains a signal from which a linear trend, which is a linear component having a constant slope, is removed from the signal of the pulse wave;
A window function applying unit that obtains a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the signal obtained in the linear tendency remover;
A frequency domain transformer for transforming the signal obtained by the window function application unit into a frequency domain signal; And
And a signal analyzer for analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time,
Wherein the filter coefficient calculator calculates the filter coefficient value of the low pass filter having a predetermined multiple of the average heart rate calculated by the heart rate calculator as a cutoff frequency. A blood pressure waveform detecting method comprising:
A pulse wave measuring step of detecting a blood pressure of a body blood vessel, amplifying a signal of the detected blood pressure, and removing noise to measure a pulse wave;
Wherein the filter coefficient value of the low pass filter adaptively adjusting the filter coefficient according to the characteristic of the pulse wave is calculated by adapting the filter coefficient value of the low pass filter according to the average heart rate of the pulse wave Adjusting a filter coefficient;
Filtering the measured pulse wave with the low-pass filter;
Detecting a peak of the pulse wave using a signal filtered by the low-pass filter; And
And detecting the pulse wave divided in a cycle unit by using the detected peak information. 21. The method of claim 20, wherein detecting the peak of the pulse wave comprises:
Differentiating the signal filtered by the low-pass filter;
Detecting a position of a zero crossing point of the differentiated signal; And
And detecting a peak of the pulse wave within a predetermined time interval based on the detected zero crossing point. 21. The method of claim 20,
Wherein the filter coefficient adjustment step comprises calculating a mean heart rate for a predetermined time by analyzing a frequency domain signal of the pulse wave and calculating a mean heart rate for a predetermined time by using the low pass Wherein the filter coefficient of the filter is adjusted adaptively. 23. The method of claim 22,
Obtaining a signal from which a linear trend is removed from a signal of the pulse wave;
Obtaining a signal defined by a predetermined length by applying a window function to the linearly removed signal;
Converting the signal defined by the predetermined length into a frequency domain signal;
Analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time; And
And adaptively adjusting the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated average heart rate. A blood pressure waveform detecting method comprising:
A pulse wave measuring step of detecting a blood pressure of a body blood vessel, amplifying a signal of the detected blood pressure, and removing noise to measure a pulse wave;
Wherein the controller calculates the average heart rate for a predetermined time by analyzing the frequency domain signal of the pulse wave and adjusts the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated average heart rate. A filter coefficient adjustment step of adjusting the filter coefficient;
Filtering the measured pulse wave with the low-pass filter having the adjusted filter coefficient;
Detecting a peak of the pulse wave using a signal filtered by the low-pass filter;
Detecting the pulse wave divided in a cycle unit by using the detected peak information;
Measuring blood pressure information including a blood pressure of a specific part of the body and blood pressure measurement time point information;
Receiving a pulse wave of a body;
Detecting a starting point of each cycle of the pulse wave and identifying the pulse wave of one cycle occurring after a certain period of time from the pulse wave measuring time point of the pulse wave; And
And calibrating the unit of the specified one cycle of the pulse wave with reference to the blood pressure and calibrating the unit of the pulse wave of the remaining cycles based on the corrected one cycle of the pulse wave, Detection method. 25. The method of claim 24,
Wherein the step of detecting the peak of the pulse wave includes:
Differentiating the signal filtered by the low-pass filter;
Detecting a position of a zero crossing point of the differentiated signal; And
And detecting a peak of the pulse wave within a predetermined time interval based on the detected zero crossing point,
Wherein the filter coefficient adjustment step comprises:
Obtaining a signal from which a linear trend, which is a linear component having a constant slope, is removed from a signal of the pulse wave;
Obtaining a signal defined by a predetermined length by applying a window function that is a function having a specific value only within a predetermined period of a finite length to the linearly removed signal;
Converting the signal defined by the predetermined length into a frequency domain signal;
Analyzing the converted signal in the frequency domain to calculate an average heart rate of the pulse wave for a predetermined time; And
And adaptively adjusting the filter coefficient of the low pass filter so that the cutoff frequency of the low pass filter has a predetermined multiple of the calculated average heart rate. 25. The method of claim 24, wherein measuring blood pressure information comprises:
Measuring blood pressure while pressing and relaxing a specific part of the body;
Amplifying the measured blood pressure signal;
Removing noise of the amplified blood pressure signal through filtering; And
And analyzing the noise-removed blood pressure signal to calculate the blood pressure information including the blood pressure and the blood pressure measurement time point information.

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