CN101229058A - Initial calibration device for measuring arterial blood pressure by pulse wave transmission time method - Google Patents

Abstract

The invention discloses an initial calibration device for measuring arterial blood pressure by a pulse wave transmission time method, which is characterized by comprising the following steps: the control unit is used for providing control signals to enable all the functional units to operate in a coordinated mode; a pressure unit for applying an applied pressure to the artery; the detection unit is used for detecting the arterial blood pressure and the pulse wave transmission time of the detected person under different applied pressures; and the fitting unit is used for receiving the detected values of the arterial blood pressure and the pulse wave transmission time under different pressures output by the detection unit, forming a sampling point by the corresponding arterial blood pressure and the corresponding pulse wave transmission time, fitting the obtained group of sampling points, and outputting the obtained fitting curve as a calibration curve of the relationship between the pulse wave transmission time and the arterial blood pressure. The device can obtain more accurate calibration results, the process is continuous and rapid, and the initial calibration efficiency and precision of measuring the arterial blood pressure by the pulse wave transmission time method can be greatly improved.

Description

Initial Calibration Device for Measuring Arterial Blood Pressure by Pulse Wave Transit Time Method

technical field

The invention relates to a calibration technique for measuring arterial blood pressure, in particular to an initial calibration device for measuring arterial blood pressure with a pulse wave transit time method.

Background technique

Measuring blood pressure is a basic method for understanding health conditions and observing conditions, especially for middle-aged and elderly people suffering from cardiovascular diseases.

At present, blood pressure measuring devices are mainly divided into two categories: invasive measuring devices and non-invasive measuring devices. The invasive measurement device adopts the direct measurement method. When measuring arterial blood pressure, a catheter is inserted into the artery, and the arterial pressure is measured through a transducer connected with a fluid column. This method needs to be operated by professional medical personnel, the cost is high, and it is easy to cause bacterial infection.

The non-invasive measuring device adopts an indirect measuring method, which is safe, convenient and comfortable to use, and is currently a commonly used blood pressure measuring method in hospitals. This method is also used at home by many patients who require long-term monitoring of blood pressure. Among them, the most commonly used indirect measurement device is a cuff-type blood pressure measurement device. This measuring device is widely used in clinical practice, wherein the arterial blood pressure value obtained by auscultating the blood pressure measuring device has been used as a standard value for blood pressure measurement.

The use of cuff type blood pressure measuring devices has the following disadvantages.

First, the cuff can cause discomfort to the user. If the cuff is used frequently, the tissues and blood vessels beneath the cuff may be damaged due to frequent compression.

Secondly, since it takes a certain amount of time to inflate and deflate, the cuff-type device takes a long time to complete a measurement, so they cannot achieve continuous measurement of blood pressure.

Third, there are certain problems in the accuracy of this measuring device. First of all, since inflation and deflation will affect the tension of blood vessels, the accuracy of measurement will be affected. In addition, the size of the cuff will also affect the blood pressure measurement results.

For the above reasons, cuff-type blood pressure measuring devices are not suitable for people who need to measure blood pressure frequently, especially people who need to monitor blood pressure continuously for a long time. At the same time, the impact on measurement accuracy due to the use of the cuff also needs to be improved.

Due to the above reasons, the use of non-invasive, cuffless blood pressure measuring devices has become the development direction of blood pressure measurement technology. This device uses pulse wave-related characteristic quantities, such as pulse wave velocity (Pulse wave velocity, PWV), to measure blood pressure. The pulse wave transmission velocity refers to the speed at which the pulse wave travels along the artery. As early as 1922, Bramwell and Hill discovered the relationship between pulse wave velocity and vascular volume elasticity. Since then, many different research results have shown that pulse wave velocity is related to blood pressure, and this correlation is subject-dependent. That is, there is a definite relationship between the pulse wave transmission velocity and blood pressure of each individual. Further research also shows that the relationship between each individual's pulse wave transmission velocity and arterial blood pressure can be roughly described in the form of a linear equation. Therefore, the first-order equation of the relationship between the pulse wave transmission velocity and arterial blood pressure of each individual can be found out, and then the arterial blood pressure value can be obtained indirectly by using the pulse wave transmission velocity. Since the pulse wave transmission speed is not easy to measure directly, in practice, the pulse wave transmission time (PTT) is often measured indirectly, that is, the time required for the pulse wave to travel between two points on the artery, to obtain the pulse wave transmission speed indirectly. Thus the arterial blood pressure value is obtained.

Based on the above measurement principles, US Patents 5,649,513, 5,865,755 and 6,599,251, European Patent 0413267, and Chinese Patents CN1293913A and CN1127939C all disclose methods or devices for measuring blood pressure using pulse wave transit time or pulse wave transit velocity. The pulse wave transit time can be determined by using the reference point on the electrocardiographic signal and the reference point on the pulse wave detected on the peripheral artery in the same cardiac cycle. Pulse waves can be detected using photoplethysmography. Photoplethysmography is to shine light on the body tissue and measure the reflected light, transmitted light or scattered light of the tissue. The light received by the photodetector characterizes the change of blood flow under the tissue. In addition, there are other methods of detecting pulse wave signals, such as the use of pressure sensors and impedance plethysmography.

The advantage of using pulse wave transit time to measure blood pressure is that it does not require the use of a cuff, thus providing a fast and comfortable long-term measurement. This measurement can be performed frequently and continuously without causing any damage to the tissue or blood vessels at the measurement site.

However, the measurement of blood pressure using the pulse wave transit time should be calibrated for each user, that is, the relationship between the pulse wave transit time and the blood pressure of the subject to be measured must be accurately established, otherwise, the measurement results will be unreliable. Therefore, before measuring blood pressure using pulse wave transit time, an initial calibration should be performed first.

For sphygmomanometers using the pulse wave transit time measurement principle, the initial calibration steps generally include: firstly use a standard sphygmomanometer to measure blood pressure, and then input the measured value to the control unit of the cuffless device to establish the relationship between blood pressure and pulse wave transit time. relation. For example, US Pat. No. 6,603,329 discloses a multifunctional sphygmomanometer employing a method of measuring blood pressure by measuring pulse wave transit time. The device includes an input unit for entering blood pressure values required for initial calibration. Japanese Patent No. 2002-172094 discloses a blood pressure measurement system comprising a general-purpose device for measuring blood pressure (usually based on a cuff-type method) and an electronic wrist watch sphygmomanometer based on pulse transmission theory. The main feature of the invention is that the blood pressure value measured by the universal blood pressure measuring device can be automatically transmitted to the electronic wrist watch blood pressure meter for its initial calibration, so the user does not need to manually input the calibration data. Once the calibration is completed, the electronic wrist watch blood pressure monitor can use the detected ECG signal and the detected pulse wave signal to calculate the pulse wave transit time to estimate the user's blood pressure value.

When performing the above initial calibration, it is difficult to obtain accurate measurement results if only a few sampling points obtained by measurement are used to establish the relationship between the pulse wave transit time and arterial blood pressure. In fact, it is necessary to obtain multiple sampling points composed of pulse wave transit time and corresponding arterial blood pressure in different states, and to fit these sampling points, and finally obtain a more accurate calibration curve and achieve accurate calibration. Specifically, within a certain variation range of the arterial blood pressure, a group of sampling points is obtained, and these sampling points are fitted to finally obtain a fitting curve describing the relationship between the pulse wave transit time and the arterial blood pressure. Since the relationship between pulse wave transit time and arterial blood pressure can be fitted with a primary curve, the equation describing the primary curve can be further obtained, and the measured pulse wave transit time can be brought into the equation to obtain a more accurate calculation. arterial blood pressure value. It can be seen that the key to performing the initial calibration is to obtain a group of sampling points of the subject under different arterial blood pressures.

In order to obtain the sampling points under different arterial blood pressures, Chinese patent document CN 1127939C proposes to use the different pulse wave transit times and arterial blood pressure values measured when the palm is placed on the heart level and away from the heart level to determine the calibration equation. However, European Patent No. 0875200 proposes to measure the different pulse wave transit times and arterial blood pressure at rest and during exercise to obtain the relationship between the two. US Patent No. 5,649,513 proposes to measure different blood pressure values when lying down and sitting up to calibrate the blood pressure measurement equation.

Several initial calibration measures for measuring blood pressure by the pulse transit time method have been provided in the above-mentioned prior art. The calibration process of these measures all adopts the method of keeping the measured person in different physical states to obtain the pulse wave transmission of different blood pressure values. The measurement values of time and blood pressure, after obtaining these measurement results, use this group of measurement results as sampling points to realize initial calibration.

The main problem of the above-mentioned prior art is that the initial calibration process cannot be carried out continuously, which makes the initial calibration time too long and difficult to realize. In addition, the blood pressure values corresponding to the sampling points obtained by the above method have a large dispersion, and the fitting line obtained based on these sampling points deviates greatly from the actual situation, making the initial calibration results unreliable. With the widespread use of the method of measuring arterial blood pressure by pulse transit time, a convenient and reliable initial calibration device is urgently needed to quickly and accurately perform initial calibration on sphygmomanometers that measure blood pressure by pulse transit time.

Contents of the invention

In view of the above-mentioned defects, the technical problem to be solved by the present invention is to provide an initial calibration device for a device for measuring arterial blood pressure by the pulse wave transit time method.

The present invention provides an initial calibration device for a device for measuring arterial blood pressure by the pulse wave transit time method, comprising:

The control unit is used to provide control signals to coordinate the operation of each functional unit;

a pressure unit for applying external pressure to the artery;

The detection unit is used to detect the arterial blood pressure and pulse wave transit time of the subject under different applied pressures;

The fitting unit receives the detected values of arterial blood pressure and pulse wave transit time under different pressures output by the detection unit, and forms a sampling point with the corresponding arterial blood pressure and pulse wave transit time, and samples the obtained set of Points are fitted, and the obtained fitting curve is output as a calibration curve of the relationship between pulse wave transit time and arterial blood pressure.

Preferably, the detection unit includes the following subunits:

The arterial blood pressure detection unit is used to detect the arterial blood pressure corresponding to different pressures during the pressurization process of the pressure unit;

The pulse wave transit time measurement unit is used to measure the pulse wave transit time; under the control of the control unit, the unit obtains the pulse wave transmission under a certain pressure while the arterial blood pressure detection unit detects the arterial blood pressure under the pressure time.

Preferably, the arterial blood pressure output by the arterial blood pressure detection unit is specifically the equivalent arterial blood pressure corresponding to different cuff pressures, and the unit includes:

A cuff-type sphygmomanometer is used to detect mean arterial pressure, systolic pressure and diastolic pressure; and, the cuff of the sphygmomanometer simultaneously serves as the pressure unit;

Cuff pressure sensor for detecting cuff pressure;

The arterial blood pressure calculation unit is used to receive the detection value output by the cuff sphygmomanometer and the cuff pressure sensor, and calculate the equivalent arterial blood pressure corresponding to different cuff pressures using the following equation:

${\mathrm{<span\; class="notranslate">\; BP</span>}}_{\mathrm{<span\; class="notranslate">\; eq</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="A20071000291700181.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="A20071000291700181.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}$

Wherein, BP _eq is the equivalent arterial blood pressure; P ₀ , P _s and P _d are the arterial mean pressure, systolic pressure and diastolic pressure measured by the cuff sphygmomanometer respectively, and L ₁ and L ₂ are the cuff width and the length from the end of the cuff to the finger; P _c is the cuff pressure value detected by the cuff pressure sensor, and k is a constant.

Preferably, the arterial blood pressure detection unit further includes:

Finger pressure sensor, which is used to detect the pressure on the finger;

The constant k calculation unit is used to receive the pressure at the finger detected by the finger pressure sensor, the blood pressure detection value output by the cuff type sphygmomanometer, and the cuff pressure detection value output by the cuff pressure sensor, and according to the following The formula calculates the constant k:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; fc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}$

Wherein, P ₀ is the average arterial pressure obtained by the current measurement of the cuff-type sphygmomanometer, P _fc is the pressure at the finger of the current measurement measured by the finger pressure sensor; P _c [t _m ] is During the process of cuff pressure change, the cuff pressure value measured by the cuff pressure sensor when the amplitude of the photoplethysmography signal reaches the maximum value; P _s and P _d are the systolic and diastolic blood pressure measured by the cuff sphygmomanometer, respectively.

Preferably, the pulse wave transit time measuring unit includes:

An electrocardiographic signal detection unit for detecting the electrocardiographic signal of the subject;

The photoplethysmography signal detection unit is used to detect the photoplethysmography signal of the subject;

A preprocessing unit, configured to receive the electrocardiographic signal output by the electrocardiographic signal detection unit and the photoplethysmographic signal output by the photoplethysmographic signal detection unit, and filter and amplify the above signals;

A vertex detection unit, configured to receive the filtered and amplified signal output by the preprocessing unit, and detect and obtain the vertex of the R-wave of the ECG signal and the vertex, bottom point or middle point of the photoplethysmography signal;

The pulse wave transit time calculation unit is used to receive the apex, bottom point or intermediate point of the R-wave apex of the electrocardiographic signal output by the apex detection unit and the apex, bottom point or middle point of the photoplethysmography signal, and use the above-mentioned special signal point as a reference point, and The time difference between the reference point on the electrical signal and the reference point on the photoplethysmographic signal in the same period is used to calculate the pulse wave transit time.

Preferably, the fitting of the sampling points by the fitting unit specifically adopts a first-order curve for fitting.

Preferably, a calculation unit is also included, which calculates the coefficient a and the constant b in the equation PTT=a·BP _eq +b=a·BP+b representing the primary curve according to the primary curve obtained by the fitting unit and Output, the sphygmomanometer using the pulse wave transit time method to measure arterial blood pressure can use the above coefficients and constants to obtain the above linear curve equation to realize the calibration of blood pressure measurement.

The present invention provides a new initial calibration device aiming at the problem that the initial calibration process of measuring blood pressure by pulse transit time is too complicated and the calibration result is not reliable enough in the prior art. After the device applies an external force on the artery, the blood pressure will change regularly, and a set of arterial blood pressure corresponding to different applied pressures will be obtained. At the same time, the pulse wave transmission time corresponding to each applied pressure will be measured, and the obtained pulse wave will be obtained. The transit time and arterial blood pressure were used as sampling points for fitting, and a calibration curve of the relationship between pulse wave transit time and arterial blood pressure was obtained. Since when the external pressure is applied to the artery, different continuous arterial blood pressure values can be obtained through the continuous change of the pressure, therefore, the device can obtain more accurate calibration results. The more obvious advantage of this device is that different blood pressure values can be obtained without using complex methods of changing the physiological state of the subject, and the process is continuous and rapid, which can greatly improve the efficiency of initial calibration.

In a preferred embodiment of the present invention, the cuff is used to apply the external pressure, and combined with the cuff method to measure blood pressure, the required data under different external pressures can be obtained naturally during the cuff blood pressure measurement, so that the calibration process and The blood pressure measurement process is closely integrated to achieve convenient and rapid results.

Description of drawings

Fig. 1 is a unit block diagram of the first embodiment of the present invention;

Fig. 2 is the change curve of the pulse wave transit time during the cuff pressure raising process;

Fig. 3 is an example of the distribution of sampling points on the coordinate axis with the pulse wave transit time as the vertical axis and the equivalent blood pressure as the horizontal axis in the first embodiment of the present invention.

Detailed ways

The following first embodiment is a preferred embodiment of the initial calibration device for measuring arterial blood pressure by the blood pressure pulse wave transit time method provided by the present invention. The block diagram of the device is shown in Figure 1.

It should first be explained that the relationship between pulse transit time and arterial blood pressure can be roughly fitted by a linear curve, and the equation corresponding to the fitted curve is as follows:

PTT=a·BP _eq +b=a·BP+b

Among them, PTT represents the pulse wave transit time; BP _eq is the equivalent arterial blood pressure; BP is the measured arterial blood pressure required. The equivalent blood pressure is defined as the weighted average of blood pressure values at various places on the pulse wave propagation path, and the equivalent blood pressure can be used as the blood pressure measurement value. In the initial calibration device provided in this embodiment, due to the cuff pressure, the arterial blood pressure varies everywhere, so the weighted average equivalent blood pressure needs to be used as the blood pressure measurement value. When this formula is used for calibration, the blood pressure value obtained is the desired arterial blood pressure measurement.

The function of this calibration device is to obtain an accurate fitting curve between pulse transit time and arterial blood pressure, or to represent the coefficient a and constant b of the straight line equation of the fitting curve, and output the above results to the pulse wave transit time Methods In sphygmomanometers that measure arterial blood pressure, these sphygmomanometers calibrate the measurement results accordingly, so that accurate blood pressure measurement results can be obtained.

In order to obtain the coefficients a and b in the linear equation of the above-mentioned relationship between pulse wave transit time and equivalent blood pressure, it is necessary to obtain a set of pulse wave transit time and corresponding arterial blood pressure, and then, through this set of corresponding values, obtain the described coefficient a and constant b. In the prior art, a set of sampling point values including corresponding pulse wave transit time and equivalent blood pressure is obtained by using different body positions or exercise conditions, and these values are used for straight line fitting to obtain the required coefficient a and constant b. In this embodiment, changes in arterial blood pressure generated during cuff pressurization and decompression in the cuff blood pressure measurement method are used. Since cuff pressurization or decompression will cause a pressure difference in the blood pressure of the arterial part wrapped by the cuff, and the pressure difference will change due to the change of the cuff pressure, therefore, the cuff pressure will affect the arterial blood pressure value, which can be A set of pulse wave transit time under different arterial blood pressures is obtained during the cuff pressure change, and the required fitting curve can be obtained by using this set of data, or the parameters a and b in the fitting formula can be obtained.

Fig. 2 shows the change of the pulse wave transit time during the cuff pressure increase. Wherein, when the external pressure generated by the cuff pressure is equal to the internal pressure of the arterial blood pressure, the pulse wave transit time reaches the maximum value. Using the relationship between the cuff pressure and the arterial blood pressure, a set of data related to arterial blood pressure and pulse wave transit time can be obtained.

Therefore, through the cuff pressure change process, a set of pulse wave transit time is obtained, and at the same time, the cuff pressure is measured by a sensor to obtain the cuff pressure corresponding to the pulse wave transit time, and then the relationship between the cuff pressure and blood pressure is used to obtain Corresponding arterial blood pressure value (actually equivalent arterial blood pressure value). Using this set of values, a fitting curve between pulse transit time and equivalent arterial blood pressure can be obtained.

Considering that the pressure of the cuff makes blood pressures in different parts of the artery different, the arterial blood pressure specifically adopts the equivalent arterial blood pressure, so that the change of the arterial blood pressure caused by the pressure of the cuff can be calculated, so as to perform effective calibration.

Since cuff pressurization and decompression are inevitable processes in the cuff blood pressure measurement method, the required set of data can be obtained only by using sensors to measure some relevant parameters during the blood pressure measurement process. This makes the calibration method simpler and more effective than those provided by the prior art.

According to the above calibration distance, the following first embodiment provides a blood pressure calibration device that uses the above principle for initial calibration. The calibration device collects relevant measurement values of the subject to be measured, and after calculation is performed based on these measurement values, a calibrated fitting line or a linear equation is obtained and output to the sphygmomanometer, thereby realizing initial calibration of blood pressure measurement. Figure 1 shows a block diagram of such a device.

As shown in FIG. 1 , the blood pressure calibration device includes a control unit 11 , a pressure unit 12 , a detection unit 13 , a fitting unit 14 , and a calculation unit 15 .

The control unit 11 is used to provide control signals to make other functional units operate in coordination.

The pressure unit 12 is used for applying external pressure to the artery of the subject to be detected. Preferably, the pressure unit 12 uses a cuff of a cuff-type sphygmomanometer to apply pressure to the subject's artery. The advantage of choosing a cuff for a cuff-type sphygmomanometer is that it is easy to obtain and can be conveniently combined with the blood pressure detection process.

The detection unit 13 is used to detect the arterial blood pressure and pulse wave transit time of the subject under different applied pressures. In this embodiment, the detection unit 13 includes an arterial blood pressure detection unit 131 and a pulse wave transit time measurement unit 132 .

The arterial blood pressure detection unit 131 is configured to detect the arterial blood pressure corresponding to different pressures during the pressing process of the pressure unit 12 . The arterial blood pressure output by the unit is specifically the equivalent arterial blood pressure corresponding to different cuff pressures. In this embodiment, preferably, the unit further includes a cuff sphygmomanometer 1311 , a cuff pressure sensor 1312 , an arterial blood pressure calculation unit 1313 , a finger pressure sensor 1314 , and a constant k calculation unit 1315 .

The cuff-type sphygmomanometer 1311 is a commonly used medical device in the field, and is used to detect mean arterial pressure, systolic pressure and diastolic pressure; and the cuff of the sphygmomanometer serves as the pressure unit 12 at the same time.

The present invention uses the blood pressure measured by the cuff-type sphygmomanometer 1311 as the standard blood pressure. The cuff sphygmomanometer 1311 can easily obtain relatively accurate blood pressure values, which are generally used as standard values in the medical field, and can be compared with blood pressure values obtained by measuring pulse wave transit time to achieve calibration of the latter. During the measurement, the cuff of the cuff-type sphygmomanometer 1311 is wrapped around a certain part of the body of the subject whose blood pressure is to be measured, such as the upper arm, and inflated. During this process, an external pressure will be generated on the artery. The relationship between pressure and arterial blood pressure measures blood pressure. In this embodiment, during the cuff pressurization or decompression process of the cuff-type sphygmomanometer, it is also used to measure and obtain a set of sampling points under different external pressures. In order to make the distribution of sampling points uniform, the cuff pressurization or decompression process should be continuous and uniform, so as to make the applied pressure on the artery uniform and change continuously.

It should be noted that the final result of the blood pressure measured by the cuff sphygmomanometer is the mean arterial pressure, systolic blood pressure, and diastolic blood pressure. However, during the cuff pressurization and decompression process, the arterial blood pressure is affected by the cuff pressure. , under different cuff pressures, the arterial blood pressure is different; at the same time, due to the influence of the cuff pressure, the blood pressures of the arteries are also different. This device is to obtain the relationship between the arterial blood pressure value and the pulse wave transmission time under different pressures. Therefore, the average arterial pressure, systolic pressure, and diastolic pressure obtained by using a cuff-type sphygmomanometer in this device are calculated to correspond to different cuffs. Actual blood pressure under stress. Since the arterial blood pressure varies from place to place under the action of the cuff pressure, the blood pressure is specifically the equivalent arterial blood pressure. The equivalent arterial blood pressure refers to the weighted average value of the arterial blood pressure in various places, which can be calculated by formula according to the specific cuff pressure obtained from the measurement, and the mean arterial pressure, systolic pressure and diastolic pressure obtained from this measurement. The equivalent arterial blood pressure and the pulse wave transit time measured at the cuff pressure can then be used to form a required sampling point.

The cuff pressure sensor 1312 is used to detect the cuff pressure. Specifically, various types of pressure sensors commonly used in the prior art may be used, which will not be described in detail here.

The arterial blood pressure calculation unit 1313 is configured to receive the detection values output by the cuff sphygmomanometer 1311 and the cuff pressure sensor 1312, and calculate equivalent arterial blood pressure corresponding to different cuff pressures.

Due to the existence of the cuff and the cuff pressure, the blood vessels at the cuff position will be squeezed, causing a drop in blood pressure, which is recorded as ΔP. The blood pressure drop ΔP is proportional to the cuff pressure, and its specific formula is:

$\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; k</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}$

Pc, Ps, and Pd are the cuff pressure, systolic blood pressure, and diastolic blood pressure measured at the current time respectively. The above blood pressure values can be obtained after the cuff sphygmomanometer completes a detection process. The cuff pressure can be obtained through sensor measurement, and the systolic and diastolic blood pressures are taken from the current blood pressure measurement values. In this way, the blood pressure drop can be obtained only by obtaining the value of the constant K.

Through the above-mentioned blood pressure drop ΔP, and then according to the mean arterial pressure obtained from the measurement, the equivalent blood pressure can be obtained by the following formula:

${\mathrm{<span\; class="notranslate">\; BP</span>}}_{\mathrm{<span\; class="notranslate">\; eq</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="A20071000291700181.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="A20071000291700181.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, BP _eq is the equivalent blood pressure; P ₀ is the average arterial pressure obtained in the current measurement, L ₁ and L ₂ are the cuff width and the length from the end of the cuff to the finger respectively; P _c , P _s , and P _d are the cuff pressure, systolic blood pressure and diastolic blood pressure measured at that time, respectively.

The unit outputs the calculated equivalent arterial blood pressure as an arterial blood pressure value.

It can be known from the above that the equivalent blood pressure BP _eq can be calculated only by obtaining the constant K. The constant k needs to be calculated according to the detected value under special circumstances, and the specific calculation method is as follows.

Because when the external pressure and the internal pressure are equal, the amplitude of the photoplethysmographic signal will reach a maximum value. Therefore, using the amplitude variation of the photoplethysmographic signal at the finger, the constant k can be calculated by the following equation:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; fc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, P ₀ is the average arterial pressure obtained in the current measurement, and P _fc is the pressure in the finger measured in the current measurement; the pressure P _fc in the finger remains unchanged when the cuff pressure changes, which can be measured by a pressure sensor, or by using The resulting pressure change estimate is obtained; P _c [t _m ] represents the corresponding cuff pressure value when the amplitude of the photoplethysmographic signal reaches a maximum value during the cuff pressure change process. The above formula is actually derived from formula (1), and the constant K is obtained by bringing this formula into the measured value under special circumstances. Therefore, calculating the constant K requires measuring the pressure at the finger.

The finger pressure sensor 1314 is used to detect the pressure on the finger.

The constant k calculation unit 1315 is configured to receive the pressure at the finger detected by the finger pressure sensor 1314, the blood pressure detection value output by the cuff sphygmomanometer 1311, and the cuff pressure output by the cuff pressure sensor 1312 Detect the value, and calculate the constant k according to the formula (3):

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; fc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Wherein, P ₀ is the average arterial pressure obtained by the cuff sphygmomanometer 1311 in the current measurement, P _fc is the pressure at the finger measured by the finger pressure sensor 1314 in the current measurement; P _c [t _m ] is During the cuff pressure change process, the cuff pressure value measured by the cuff pressure sensor 1314 when the amplitude of the photoplethysmography signal reaches a maximum value; P _s and P _d are the systolic pressure measured by the cuff sphygmomanometer 1311 respectively and diastolic blood pressure.

The pulse wave transit time measurement unit 132 includes an ECG signal detection unit 1321 , a photoplethysmography signal detection unit 1322 , a preprocessing unit 1323 , an apex detection unit 1324 , and a pulse wave transit time calculation unit 1325 .

The electrocardiographic signal detection unit 1321 is configured to detect the electrocardiographic signal of the subject. The electrocardiographic signal is a bioelectrical signal describing the potential change generated by the heart during the excitation process. In the prior art, there are many methods for detecting ECG signals, which are often used in detection, and will not be repeated here.

The photoplethysmography signal detection unit 1322 is configured to detect the photoplethysmography signal of the subject. The photoplethysmographic signal is an optical signal representing the change of arterial blood volume. Photoplethysmographic signals can be detected at extremities, such as fingers, by light-emitting diodes and photoelectric sensors. The measuring elements and measuring methods specifically used by the unit are common knowledge known to those skilled in the art, and will not be described in detail here.

The preprocessing unit 1323 is configured to receive the electrocardiographic signal output by the electrocardiographic signal detection unit 1321 and the photoplethysmographic signal output by the photoplethysmographic signal detection unit 1322, and filter and amplify the above signals, so that Filter out the clutter of the detection signal for subsequent processing. The filtered and amplified signal is used as the output signal of the unit.

The vertex detection unit 1324 is configured to receive the filtered and amplified signal output by the preprocessing unit 1323, detect and obtain the vertex of the R-wave of the ECG signal and the vertex, bottom point or middle point of the photoplethysmography signal, and These points serve as reference points for calculating the pulse wave transit time. These reference points can also be detected by the first or second derivative of the signal.

The pulse wave transit time calculation unit 1325 is configured to receive the apex, bottom point or intermediate point of the R-wave apex of the electrocardiographic signal output by the apex detection unit 1324 and the apex, bottom point or middle point of the photoplethysmography signal, and use the above-mentioned special signal point as a reference point , and according to the time difference between the reference point on the ECG signal and the reference point on the photoplethysmography signal in the same cycle, the pulse wave transit time is calculated and output.

The detection unit 13 can finally obtain a series of corresponding arterial blood pressure and pulse wave transit time of the subject under different applied pressures through the above-mentioned various detection devices and calculations, and output the above results as detection values.

The fitting unit 14, under the control of the control signal provided by the control unit 11, receives the detected values of arterial blood pressure and pulse wave transit time corresponding to each other under different pressures output by the detection unit 13, and calculates the corresponding The arterial blood pressure and the pulse wave transit time form a sampling point, and the obtained set of sampling points are fitted, and the obtained fitting curve is output as a calibration curve of the relationship between the pulse wave transit time and the arterial blood pressure.

FIG. 3 shows the distribution of the sampling points on the coordinate axis with the pulse wave transit time as the ordinate and the equivalent blood pressure as the abscissa. A series of data points on the coordinate axis correspond to the above sampling points, that is, these data points identify a set of pulse wave transit times output by the detection unit and the corresponding equivalent blood pressure BP _eq .

The fitting of the sampling points by the fitting unit 14 specifically adopts a first-order curve to fit. The calibration curve can already be used to calibrate the blood pressure monitor. For ease of use, the expression of the fitting curve can also be continuously calculated. This process is realized by the calculation unit 15 .

The calculation unit 15 receives the primary curve obtained by the fitting unit, calculates and outputs the coefficient a and the constant b in the equation PTT=a·BP _eq +b=a·BP+b representing the primary curve, and uses pulse The sphygmomanometer for measuring arterial blood pressure by the wave transit time method uses this constant to obtain the above-mentioned linear curve equation to realize the calibration of blood pressure measurement. Since the coefficients a and b are obtained by using multiple sampling points, relatively accurate arterial blood pressure BP can be obtained by using the coefficients a and b.

It should be noted that, in fact, the combination of various units and subunits contained in the device may vary, some units may be implemented through circuits or software, and sensors may adopt various forms suitable for this occasion in the prior art sensor. As for the specific implementation of each of the above units, those skilled in the art can obtain it without creative work according to the technical ideas and specific embodiments provided by the present invention and according to the prior art.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (7)

1. A pulse wave transit time method measures an initial calibration device for arterial blood pressure, characterized in that it comprises: The control unit is used to provide control signals to coordinate the operation of each functional unit; a pressure unit for applying external pressure to the artery; The detection unit is used to detect the arterial blood pressure and pulse wave transit time of the subject under different applied pressures; The fitting unit receives the detected values of arterial blood pressure and pulse wave transit time under different pressures output by the detection unit, and forms a sampling point with the corresponding arterial blood pressure and pulse wave transit time, and samples the obtained set of Points are fitted, and the obtained fitting curve is output as a calibration curve of the relationship between pulse wave transit time and arterial blood pressure. 2. The device according to claim 1, wherein the detection unit comprises the following subunits: The arterial blood pressure detection unit is used to detect the arterial blood pressure corresponding to different pressures during the pressurization process of the pressure unit; The pulse wave transit time measurement unit is used to measure the pulse wave transit time; under the control of the control unit, the unit obtains the pulse wave transmission under a certain pressure while the arterial blood pressure detection unit detects the arterial blood pressure under the pressure time. 3. The device according to claim 2, wherein the arterial blood pressure output by the arterial blood pressure detection unit is specifically the equivalent arterial blood pressure corresponding to different cuff pressures, the unit comprising: A cuff-type sphygmomanometer is used to detect mean arterial pressure, systolic pressure and diastolic pressure; and, the cuff of the sphygmomanometer simultaneously serves as the pressure unit; Cuff pressure sensor for detecting cuff pressure; The arterial blood pressure calculation unit is used to receive the detection value output by the cuff sphygmomanometer and the cuff pressure sensor, and calculate the equivalent arterial blood pressure corresponding to different cuff pressures using the following equation: ${\mathrm{<span\; class="notranslate">\; BP</span>}}_{\mathrm{<span\; class="notranslate">\; eq</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}$ Wherein, BP _eq is the equivalent arterial blood pressure; P ₀ , P _s and P _d are the arterial mean pressure, systolic pressure and diastolic pressure measured by the cuff sphygmomanometer respectively, and L ₁ and L ₂ are the cuff width and the length from the end of the cuff to the finger; P _c is the cuff pressure value detected by the cuff pressure sensor, and k is a constant. 4. The device according to claim 3, wherein the arterial blood pressure detection unit further comprises: Finger pressure sensor, which is used to detect the pressure on the finger; The constant k calculation unit is used to receive the pressure at the finger detected by the finger pressure sensor, the blood pressure detection value output by the cuff type sphygmomanometer, and the cuff pressure detection value output by the cuff pressure sensor, and according to the following The formula calculates the constant k: $\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; fc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}$ Wherein, P ₀ is the average arterial pressure obtained by the current measurement of the cuff-type sphygmomanometer, P _fc is the pressure at the finger of the current measurement measured by the finger pressure sensor; P _c [t _m ] is During the process of cuff pressure change, the cuff pressure value measured by the cuff pressure sensor when the amplitude of the photoplethysmography signal reaches the maximum value; P _s and P _d are the systolic and diastolic blood pressure measured by the cuff sphygmomanometer, respectively. 5. The device according to any one of claims 2-4, wherein the pulse wave transit time measuring unit comprises: An electrocardiographic signal detection unit for detecting the electrocardiographic signal of the subject; The photoplethysmography signal detection unit is used to detect the photoplethysmography signal of the subject; A preprocessing unit, configured to receive the electrocardiographic signal output by the electrocardiographic signal detection unit and the photoplethysmographic signal output by the photoplethysmographic signal detection unit, and filter and amplify the above signals; A vertex detection unit, configured to receive the filtered and amplified signal output by the preprocessing unit, and detect and obtain the vertex of the R-wave of the ECG signal and the vertex, bottom point or middle point of the photoplethysmography signal; The pulse wave transit time calculation unit is used to receive the apex, bottom point or intermediate point of the R-wave apex of the electrocardiographic signal output by the apex detection unit and the apex, bottom point or middle point of the photoplethysmography signal, and use the above-mentioned special signal point as a reference point, and The time difference between the reference point on the electrical signal and the reference point on the photoplethysmographic signal in the same period is used to calculate the pulse wave transit time. 6. The device according to claims 2-4, characterized in that the fitting of the sampling points by the fitting unit specifically adopts a linear curve for fitting. 7. The device according to claim 6, further comprising a computing unit, which calculates the equation PTT=a·BP _eq +b=a representing the primary curve according to the primary curve obtained by the fitting unit The coefficient a and constant b in BP+b are output together, and the sphygmomanometer that uses the pulse wave transit time method to measure arterial blood pressure can use the above coefficients and constants to obtain the above-mentioned linear curve equation to realize the calibration of blood pressure measurement.

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