KR100648414B1 - Electric Blood Pressure Measurement System With A Compensation Device of Error Rate - Google Patents

Abstract

The present invention relates to an electronic blood pressure measurement system having an error correction unit.

In recent years, the medical industry is urging the elimination of mercury use, and an electronic sphygmomanometer is generally used as a substitute for mercury sphygmomanometers in hospitals and homes. Most electronic blood pressure monitors use an oscillometric method, which itself has a high error rate, and is particularly affected by cuff and arterial hardness. In order to compensate for the error in such a conventional electronic blood pressure meter, the present invention provides a blood pressure measurement system having an accuracy by placing an error correction unit. In the electronic blood pressure measurement system having an error correction unit of the present invention, the error correction unit corrects an error by extracting a variable related to hardness of blood vessels using a tactile sensor.

Electronic Blood Pressure Gauge, Error Correction, Tactile Sensor

Description

Electric Blood Pressure Measurement System With A Compensation Device of Error Rate

1 is a schematic block diagram for explaining an error correction unit according to an embodiment of the electronic blood pressure measurement system of the present invention.

2 is a schematic flowchart of an operation processor of FIG. 1.

3A is a measurement error diagram of an electronic blood pressure monitor in systolic blood pressure.

3B is a measurement error diagram of an electronic sphygmomanometer in diastolic blood pressure.

FIG. 4A is a time delay (dT) correlation diagram of a direct wave and a reflected wave in a volume pulse wave respectively measured by a photoplethysography (SpO 2) and a tactile sensor (Tactile).

FIG. 4B is a correlation diagram of an index (SI) indicating the hardness of the aorta when the photoplethysography (SpO 2) and the tactile sensor (Tactile) are used, respectively.

Figure 5a is a comparison of the error rate of the electronic blood pressure measuring system of the present invention and the conventional electronic blood pressure monitor in systolic blood pressure.

Figure 5b is a comparison of the error rate of the electronic blood pressure measuring system and the conventional electronic blood pressure monitor of the present invention in diastolic blood pressure.

The present invention relates to an electronic blood pressure measurement system having an error correction unit.

Cardiovascular disease is the leading cause of death, and hypertension is a major risk factor for cardiovascular disease, and accurate blood pressure measurement is of paramount importance.

Blood pressure is caused by the contraction of the ventricles so that some of the blood that has been ejected into the aorta is moved through the arteries to the periphery, but large amounts of blood are not transported to the periphery and are temporarily contained within the aorta and arteries, where the vasculature expands because of its elasticity. This causes pressure in these vessels because the aorta and arteries receive more blood than their volume, which is arterial pressure, or blood pressure. Average arterial pressure refers to the average blood pressure during one cardiac cycle, which is obtained using systolic pressure and diastolic pressure. Systolic blood pressure is obtained when blood in the ventricles is ejected into the aorta by contraction of the myocardium. Is the maximum pressure in the blood vessels of the blood vessels, and the diastolic blood pressure is the pressure in the blood vessels when the blood temporarily stored in the systolic aorta flows into the peripheral vessels and then expands.

As a method of measuring blood pressure, it is largely classified into a direct method and an indirect method.

Direct method is to measure the pressure in the blood vessel by inserting a catheter (catheter) in the blood vessel is a high risk and expensive and is used only in the intensive care unit.

Indirect method is a non-invasive measurement of blood pressure, and indirect method includes Auscultatory measurement, Palpatory measurement, Flush measurement, Oscillometric measurement, Doppler Ultrasound measurement , Volume-oscillometric measurement, pulse wave velocity measurement, and the like, and among them, a standard of blood pressure measurement is a stethoscope which is measured using a mercury sphygmomanometer. However, in recent years, the medical industry is urging the elimination of mercury use, and electronic blood pressure monitors are generally used as a substitute for mercury blood pressure monitors in hospitals and homes. Most electronic sphygmomanometers use an oscillometric method. The oscillometric method does not measure blood pressure directly, but empirically determines the characteristic ratio that has a constant proportion to the vibration width, assuming that the maximum vibration width in the cuff is the average arterial pressure. At this time, since the pressure is calculated by the systolic and diastolic blood pressures, there are various error generating factors, and thus the error rate is high, and the cuff and artery stiffness are greatly affected.

In other words, it is very difficult for an electronic sphygmomanometer to pinpoint the maximum amplitude of vibration occurring in a cuff, and the characteristic rate varies by 10-20% from person to person, which is the cuff volume, arterial compliance, cardiac cycle and pulse wave. It is influenced by SF (Systolic Fraction) which indicates the ratio of the delay time. Using a cuff volume normalized to the arterial volume does not have a significant effect on the characterization ratio, but using a cuff with a cuff volume of 100 or less can cause accuracy problems. In general, when the cuff volume is constant, the characteristic ratio changes according to SF. SF is the most important factor in accurately estimating the average arterial pressure, and SF is the most important factor to correct the error of the electronic sphygmomanometer. have. In addition, the characteristic ratio is influenced by the dynamic factors of arterial vessel wall and the peak to peak size of arterial pressure. As a person ages, the vascular wall hardness increases and thus the arterial pressure peak size may increase, leading to a significant increase in the systolic characteristics ratio, resulting in severe overestimation of diastolic, mean arterial pressure, and systolic blood pressure. Will result. In order not to commit such a diagnostic error, a method of assessing the condition of the arterial wall should be accompanied.

In order to evaluate the arterial wall condition, the arterial hardness can be calculated by using photoplethysmography on the finger, but the optical sensor used here can be inserted into an electronic sphygmomanometer to create an integrated sphygmomanometer in many ways. Inadequate

Therefore, the conventional electronic sphygmomanometer is required to increase the accuracy by complementing the error, and further development of the more accurate electronic blood pressure measurement equipment for the replacement of the mercury sphygmomanometer is urgent.

The technical problem to be achieved by the present invention is to provide a blood pressure measurement system having an increased accuracy by providing an error correction.

In order to achieve the above technical problem, in the electronic blood pressure measurement system having an error correction unit of the present invention, the error correction unit is a tactile sensor, a tactile sensor driver for driving the tactile sensor, the frequency signal detected from the tactile sensor as a voltage A frequency-voltage converter for converting, an A / D converter for converting the output signal of the frequency-voltage converter into a digital signal, and an arithmetic processing unit for receiving the output signal of the A / D converter and extracting variables related to hardness of blood vessels; It is characterized by.

The operation processor may include a preprocessor for removing noise from an output signal of the A / D converter, a peak detector for detecting peaks from an output signal of the preprocessor, and a first peak and a second largest peak among peaks detected by the peak detector. And a time difference detector for detecting a time difference between the second peaks.

The preprocessing unit includes an average waveform extraction unit for removing a noise from an output signal of the A / D converter and determining a template and obtaining an average waveform.

The peak detection unit includes first differential means for differentiating the output signal of the preprocessing unit, and second differential means for differentiating the output of the first differential means again, and if the second peak does not exist, output of the second differential means. An inflection point close to zero after the first peak generation point in the signal is referred to as the second peak.

In addition, in the electronic blood pressure measurement method having an error correction step of the present invention, the error correction step is a frequency-voltage conversion step of converting the frequency signal detected by the tactile sensor into a voltage, the signal obtained from the frequency-voltage conversion step And an arithmetic processing step of extracting a hardness index of blood vessels from the signal obtained from the A / D conversion step of converting the digital signal to the A / D conversion step.

The operation processing step may include a preprocessing step of removing noise from an output signal of an A / D converter, a peak detection step of detecting a peak from a signal obtained from the preprocessing step, and a first largest peak among peaks detected in the peak detection step. And detecting a time difference between the peak and the second largest second peak.

In addition, in the electronic blood pressure measurement system having an error correction unit of the present invention, the error correction unit is a frequency-voltage converter for converting the frequency signal detected by the tactile sensor, the tactile sensor into a voltage, the output signal of the frequency-voltage converter An A / D conversion unit for converting the digital signal, and an arithmetic processing unit for receiving the output signal of the A / D conversion unit and extracting the arterial hardness index; The calculation processing unit may include a correction unit for correcting the blood pressure value measured by the electronic blood pressure monitor, the hardness index of the artery measured by the electronic blood pressure monitor, the tactile sensor, and the average arterial pressure.

Hereinafter, the configuration and operation of an electronic blood pressure measurement system having an error correction unit according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram for explaining an error correction unit according to an embodiment of the electronic blood pressure measurement system of the present invention, a tactile sensor 100, a tactile sensor driver 200, a frequency-voltage converter 300 ), An A / D conversion unit 400, and an arithmetic processing unit 500.

The tactile sensor 100 is a sensor for extracting a hardness related signal of a blood vessel mounted at a place where a pulse runs, and is composed of two piezoelectric ceramic transducers in the shape of a plate, and one side of the sensor is an ultrasonic transducer. It is an ultrasonic transducer, and the other is designed to be used as a vibration pickup.

The tactile sensor driver 200 includes an amplifier and a phase shifter. The vibration detector of the tactile sensor detects vibration, converts it into a voltage, passes through the amplifier and the phase shifter, and is fed back to another piezoelectric element of the tactile sensor. The feedback signal is output to the frequency-voltage converter 300 as an output signal of the tactile sensor.

The frequency-voltage converter 300 converts the output signal of the tactile sensor, which is a frequency signal, into a voltage signal.

 The A / D converter 400 converts the output signal of the frequency-voltage converter 300 into a digital signal.

The calculation processor 500 receives the output signal of the A / D converter and extracts a variable related to the hardness of blood vessels. The calculation processor 500 includes a preprocessor 520, a peak detector 540, a time difference detector 560, and a corrector 580.

The preprocessor 520 removes noise from the output signal of the A / D converter, determines a template, and obtains an average waveform.

The peak detector 540 detects peaks from the output signal of the preprocessor, and includes first differential means for differentiating the output signal of the preprocessor and second differential means for differentiating the output of the first differential means again. When the second peak does not exist, an inflection point close to zero after the first peak occurrence point in the output signal of the second differential means is set as the second peak.

The time difference detector 560 detects the time difference between the largest first peak and the second largest second peak among the peaks detected by the peak detector. In general, the index indicating the hardness of the aorta (Stiffness Index (SI)) is derived by dividing the height (key) by the time delay of the direct wave and the reflected wave in the digital volume pulse (DVP), the time difference of the present invention The time difference between the first peak and the second peak obtained by the detector 560 corresponds to the time delay of the direct wave and the reflected wave in the volume pulse wave.

The correction unit 580 corrects the blood pressure value measured by the electronic sphygmomanometer using the blood pressure value measured by the electronic sphygmomanometer, the hardness index of the artery measured by the tactile sensor, and the average arterial pressure.

2 is a schematic flowchart of an operation processor of FIG. 1.

After removing noise from the output signal of the A / D converter 400 (S100), the template is determined (S200), and the peak value is obtained by performing cross correlation with the waveform (S300). The waveform is cut out at each cycle to obtain an average waveform (S400). The average waveform thus obtained is first-differentiated (S500) to find a zero point intersection point to obtain a first peak and a second peak (S600). If the number of zero crossings is smaller than three (S700), since the second peak does not occur (S800), the second derivative is performed (S800), and the point near zero is found to be the second peak (S900). . The time difference between the first peak and the second peak is obtained (S950), and the time difference between the first peak, the second peak, and the first peak and the second peak is stored in the memory (S1000).

3A and 3B are measurement error diagrams of an electronic blood pressure monitor, in which three pairs of auscultation data and three pairs of electronic blood pressure data measured by each subject were compared. All these comparisons were performed on 121 subjects. FIG. 3A is a measurement error diagram of an electronic sphygmomanometer in systolic blood pressure, and FIG. 3B is a measurement error diagram of an electronic sphygmomanometer in diastolic blood pressure. The mean blood pressure error for 121 subjects was 4.6 ± 9.4 mmHg for systolic blood pressure and 14.4 ± 9.6 mmHg for diastolic blood pressure. It is based on the American National Standard Institute (hereinafter referred to as ANSI) and the American Association for the Advancement of Medical Instrumentation (hereinafter referred to as AAMI). The measured level is less than 5 ± 8mmHg determined by SP10.

4A and 4B are data comparison diagrams of photoplethysmography and tactile sensors. FIG. 4A shows the correlation between the time delay (dT) of the direct wave and the reflected wave in the volume pulse wave measured by the photoplethysography (SpO2) and the tactile sensor (Tactile), respectively. The correlation coefficient (r) at this time is 0.695 (p <0.0001). ), It can be seen that the values obtained with the photoplethysography and the tactile sensor are correlated and statistically significant. 4B is a correlation diagram of the index (SI) indicating the hardness of the aorta when the photoplethysography (SpO2) and the tactile sensor (Tactile) are used, respectively, and the correlation coefficient (r) at this time is 0.617 (p <0.0001). As a result, it can be seen that the values obtained by the photoplethysography and the tactile sensor are correlated and statistically significant. That is, the error correction unit of the present invention measures the hardness of the artery, and it can be seen that the measured value is not different from the value measured by photoplesis morphography.

Photoplethysography can also calculate the hardness of arteries in the finger, but the optical sensor used here is in many ways inadequate for inserting into an electronic sphygmomanometer to form an integrated sphygmomanometer. However, the tactile sensor of the error correction unit of the present invention can be measured anywhere the vibration of the pulse, it can be inserted into the electronic sphygmomanometer to configure an integrated blood pressure monitor provided with an error correction unit.

The error rate correction of the present invention is made through regression analysis. Correction of the error rate of systolic blood pressure is based on the systolic blood pressure value ( SBP _Auscultatory ) measured by auscultation method, and the systolic blood pressure value ( SBP _{Oscillometric} ) measured by an electronic sphygmomanometer and the arterial hardness _index ( SI _Tactile ) measured by a tactile sensor. ) And average arterial pressure ( MAP ) as a predictor. This is the same as Equation 1.

SBP _Auscultatory = 12.6 + 0.851 SBP _{Oscillometric} + 1.12SI _Tactile + 0.020MAP
Where SBP _Auscultatory is systolic blood pressure measured by auscultation method, SBP _{Oscillometric} is systolic blood pressure measured by an electronic sphygmomanometer, SI _Tactile is the hardness index of artery measured by tactile sensor, and MAP is mean arterial pressure. Equation 1 is obtained through regression analysis. That is, Equation 1 shows the following.
Systolic blood pressure measured by the audit method = 12.6 + 0.851 × systolic blood pressure measured by an electronic sphygmomanometer + 1.12 × arterial hardness index + 0.020 × average arterial pressure

Correction of the error rate of diastolic blood pressure is based on the systolic blood pressure ( DBP _Auscultatory ) measured by auscultation method, and the diastolic blood pressure value ( DBP _{Oscillometric} ) measured by an electronic sphygmomanometer and the arterial hardness index ( SI _Tactile ) measured by a tactile sensor. The mean arterial pressure ( MAP ) is a predictor. This is the same as Equation 2.

DBP _Auscultatory = 16.9-0.444 DBF _{Oscillometric} + 1.13SI _Tactile + 1.01MAP
Where DBP _Auscultatory is the systolic blood pressure value measured by auscultation method, DBF _{Oscillometric} is the diastolic blood pressure value measured by the electronic sphygmomanometer, SI _Tactile is the hardness index of the artery measured by the tactile sensor, and MAP is the average arterial pressure. Equation 2 is obtained through regression analysis. That is, Equation 2 shows the following.
[Diastolic blood pressure measured by the audit method] = 16.9-0.444 × [diastolic blood pressure measured by an electronic sphygmomanometer] + 1.13 × [hardness index of arteries measured by a tactile sensor] + 1.01 × [average arterial pressure]

5A and 5B are diagrams illustrating an error rate comparison between an electronic blood pressure measuring system having an error correcting unit and a conventional electronic blood pressure monitor according to an exemplary embodiment of the present invention. FIG. 5A is a conventional electronic blood pressure measuring system of the present invention in systolic blood pressure. Fig. 5b is a comparison of error rates between the electronic blood pressure measuring system of the present invention and the conventional electronic blood pressure monitor in the diastolic blood pressure. 5A and 5B, the X axis represents the average systolic or diastolic blood pressure measured by auscultation method (Aus SBP Ave, Aus DBP Ave), and the Y axis represents the blood pressure value measured by the electronic blood pressure measuring system and the conventional electronic blood pressure monitor of the present invention. The error of the blood pressure value measured by auscultation method is shown, and in FIG. 5A and FIG. 5B, (circle) shows the value measured with the electronic blood pressure measuring system by this invention, + shows the value measured with the conventional electronic blood pressure monitor. 5A and 5B were performed through a total of 121 subjects. As can be seen from Figure 5a, Figure 5b, the electronic blood pressure measurement system with an error correction unit according to the present invention is less error. Through this, it can be seen that the electronic blood pressure measurement system having an error correction unit has improved accuracy.

The present invention is not limited to the above described and illustrated in the drawings, and of course, more modifications and variations are possible to those skilled in the art within the scope of the following claims.

As described above, the electronic blood pressure measurement system of the present invention greatly improves accuracy by providing error correction. In addition, the error correction unit of the present invention measures the hardness of the artery by using a tactile sensor, which can be measured anywhere the vibration of the pulse, it is inserted into the electronic sphygmomanometer to construct an integrated blood pressure monitor with an error correction unit It is convenient.

Claims (7)

An electronic blood pressure measurement system having an error correction unit, wherein the error correction unit A tactile sensor comprising two ceramic piezoelectric sensors; A tactile sensor driver for driving the tactile sensor; A frequency-voltage converter converting the frequency signal detected by the tactile sensor into a voltage; An A / D converter converting the output signal of the frequency-voltage converter into a digital signal; Receiving the output signal of the A / D converter, extracting the hardness index of the artery, and correcting the blood pressure value measured by the electronic sphygmomanometer with the blood pressure value measured by the electronic sphygmomanometer, the hardness index of the artery measured by the tactile sensor and the average arterial pressure Electronic blood pressure measurement system comprising a calculation processing unit. According to claim 1, wherein said processing unit A preprocessor to remove noise from an output signal of the A / D converter; A peak detector detecting a peak from an output signal of the preprocessor; And a time difference detection unit for detecting a time difference between the largest first peak and the second largest second peak among the peaks detected by the peak detection unit. The method of claim 2, wherein the pretreatment unit And an average waveform extracting unit for removing a noise from an output signal of the A / D converter and determining a template and obtaining an average waveform. The method of claim 2, wherein the peak detection unit First differential means for differentiating the output signal of the preprocessing unit, and second differential means for differentiating the output of the first differential means again, And an inflection point close to zero after the first peak occurrence point in the output signal of the second differential means as the second peak, if the second peak does not exist. The hardness of blood vessels from the signal obtained from the frequency-voltage conversion step of converting the frequency signal detected by the tactile sensor into voltage, the A / D conversion step of converting the signal obtained from the frequency-voltage conversion step into a digital signal, and the A / D conversion step. An electronic blood pressure measurement method comprising an error correction step including an operation processing step of extracting an index, Error rate correction of systolic blood pressure SBP _Auscultatory = 12.6 + 0.851 SBP _{Oscillometric} + 1.12SI _Tactile + 0.020MAP (SBP _Auscultatory is the systolic blood pressure measured by auscultation method, SBP _{Oscillometric} is the systolic blood pressure measured by an electronic sphygmomanometer, SI _Tactile is the hardness index of the artery measured by the tactile sensor, and MAP is the average arterial pressure.) Done by Error rate correction of diastolic blood pressure DBP _Auscultatory = 16.9-0.444 DBF _{Oscillometric} + 1.13SI _Tactile + 1.01MAP (Where DBP _Auscultatory is the systolic blood pressure measured by auscultation method, DBF _{Oscillometric} is the diastolic blood pressure measured by an electronic sphygmomanometer, SI _Tactile is the hardness index of the artery measured by the tactile sensor, and MAP is the average arterial pressure.) Electronic blood pressure measurement method characterized in that carried out by. The method of claim 5, wherein the operation processing step A preprocessing step of removing noise from an output signal of the A / D converter; A peak detection step of detecting a peak from the signal obtained from the preprocessing step; And a time difference detecting step of detecting a time difference between the largest first peak and the second largest second peak among the peaks detected in the peak detection step. In the electronic blood pressure measurement system having an error correction unit, The error compensator is a tactile sensor consisting of two piezoelectric ceramic transducers bonded together, a frequency-voltage converter converting a frequency signal detected from the tactile sensor into a voltage, and a digital output signal of the frequency-voltage converter. A / D conversion unit for converting the signal, A / D conversion unit for receiving the output signal and calculating the arterial hardness index, The calculation processing unit includes a correction unit for correcting the blood pressure value measured by the electronic blood pressure monitor, the hardness index of the artery measured by the electronic blood pressure monitor, the tactile sensor, and the average arterial pressure. Systolic blood pressure in the correction unit SBP _Auscultatory = 12.6 + 0.851 SBP _{Oscillometric} + 1.12SI _Tactile + 0.020MAP (SBP _Auscultatory is the systolic blood pressure measured by auscultation method, SBP _{Oscillometric} is the systolic blood pressure measured by an electronic sphygmomanometer, SI _Tactile is the hardness index of the artery measured by the tactile sensor, and MAP is the average arterial pressure.) Corrected by The diastolic blood pressure in the correction unit DBP _Auscultatory = 16.9-0.444 DBF _{Oscillometric} + 1.13SI _Tactile + 1.01MAP (Where DBP _Auscultatory is the systolic blood pressure measured by auscultation method, DBF _{Oscillometric} is the diastolic blood pressure measured by an electronic sphygmomanometer, SI _Tactile is the hardness index of the artery measured by the tactile sensor, and MAP is the average arterial pressure.) Electronic blood pressure measurement system, characterized in that for correcting by.

Images