Method and system for continuously monitoring blood pressure through combination of ECG and SCG

Abstract

The invention belongs to the technical field of blood pressure monitoring, and particularly discloses an ECG and SCG combined continuous blood pressure monitoring method and system.The method comprises the following steps that an ECG signal and an SCG signal of the chest of a person to be detected are collected through an ECG electrode and an SCG sensor; carrying out signal averaging on the ECG signal and the SCG signal by adopting an averaging method; after average ECG signal and SCG signal segments are obtained, automatically identifying ECG and SCG signal feature points; according to the feature points of the ECG and SCG signals, feature parameters of the ECG and SCG signals are extracted; and constructing a blood pressure estimation model based on the ECG and SCG signal characteristic parameters, and outputting a blood pressure estimation result. By adopting the technical scheme, based on the synchronous ECG and SCG time domain characteristic parameters, the degree of dependence on the amplitude type parameters with large individual difference is reduced, the universality is higher, and the measurement precision is higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of blood pressure monitoring, and relates to a method and system for continuous blood pressure monitoring by combining ECG and SCG. Background Art

[0003] Hypertension is an important risk factor for cardiovascular disease. Studies have shown that if systolic blood pressure is reduced by 10 mmHg, the risk of cardiovascular disease can be reduced by 20%, the risk of coronary heart disease can be reduced by 17%, the risk of stroke and heart failure can be reduced by 27% and 28% respectively. Therefore, effective blood pressure control is crucial for the prevention and treatment of cardiovascular disease.

[0004] An important measure to strengthen the control of hypertension is to monitor blood pressure, and then carry out drug treatment and lifestyle intervention according to the monitored high blood pressure values. Blood pressure fluctuations can scientifically and effectively reflect individual physical changes, blood flow rate, body metabolism, and the health status of tissue and organ functions in the body. However, due to the volatility of human blood pressure, a single measurement cannot meet the requirements of blood pressure monitoring, and factors such as emotional fluctuations and physical activity can also affect blood pressure. Therefore, accurate continuous dynamic blood pressure and its short-term fluctuation pattern monitoring are of great significance in health management and clinical diagnosis.

[0005] Traditional blood pressure measurement techniques, such as oscillometric method, Korotkoff sound method, volume compensation method, etc., have been developed for decades and are often used in clinical practice to measure blood pressure. However, traditional methods cannot measure blood pressure continuously. Therefore, current research mainly uses other blood pressure-related signals to indirectly monitor blood pressure continuously and dynamically, such as photoplethysmography (PPG) and ballistocardiogram (BCG).

[0006] Whether based on PPG or BCG signals, vascular or heart beat signals measured from the body surface have the potential to be used for continuous monitoring of blood pressure, but currently they still face the problems of large individual differences and low measurement accuracy. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for continuous blood pressure monitoring by combining ECG and SCG, which reduces the reliance on parameters with large individual differences such as amplitude, is more universal, and has higher measurement accuracy.

[0008] In order to achieve the above object, the basic scheme of the present invention is: a method for continuous blood pressure monitoring by combining ECG and SCG, comprising the following steps:

[0009] Using ECG electrodes and SCG sensors, ECG signals and SCG signals from the chest of the subject are collected;

[0010] The ECG signal and the SCG signal were averaged using the averaging method;

[0011] After obtaining the averaged ECG signal and SCG signal segments, the threshold method is used to automatically identify the characteristic points of the ECG and SCG signals;

[0012] According to the characteristic points of ECG and SCG signals, characteristic parameters of ECG and SCG signals are extracted;

[0013] Based on the characteristic parameters of ECG and SCG signals, a blood pressure estimation model is constructed to output the blood pressure estimation results. The working principle and beneficial effects of this basic solution are: this technical solution monitors ECG and SCG signals synchronously on the chest, and the chest measurement is more stable and less subject to interference. Blood pressure is estimated using the time parameters obtained from the ECG and SCG characteristic points, reducing the dependence on the signal amplitude parameters, thereby avoiding the problem of low blood pressure estimation accuracy caused by differences in signal strength caused by different individuals, and the measurement accuracy is higher.

[0014] Furthermore, the method of averaging the ECG signal and the SCG signal using the averaging method is as follows:

[0015] Each calculation uses 20s of ECG and SCG data, and the threshold method is used to automatically extract the R wave of the ECG signal, and the average heart rate HR_mean is calculated based on the RR interval;

[0016] Get the R wave position corresponding to the heart rate in the range of [HR_mean-5,HR_mean+5];

[0017] The starting point is 30-50 points before the R wave. The starting point is determined by the coverage length of the SCG signal. Each data point is moved forward by a fixed number of points. The ECG signal and SCG signal are intercepted to obtain the signal segment data set.

[0018] The amplitudes of the ECG signal segments and the SCG signal segments are averaged to obtain average ECG and SCG signals for extracting feature points.

[0019] The averaged ECG and SCG signals were obtained by using the averaging method for subsequent use.

[0020] Further, according to the time position of the characteristic points of the ECG and SCG signals, the steps of extracting the characteristic parameters of the ECG and SCG signals are as follows:

[0021] According to the time position of the characteristic points of ECG and SCG signals, the cardiac cycle parameters are calculated:

[0022] PEP=tAO-tQ,

[0023] LVET=tAC-tAO,

[0024] Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure; tQ, tAO, and tAC represent the time points of the Q wave, AO point, and AC point in a cardiac cycle, respectively;

[0025] The myocardial contraction index CCt is:

[0026] CCt=PEP / LVET.

[0027] The time interval between the Q wave of the ECG and the AO peak of the SCG is considered to be a substitute for PEP, which is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility. LVET is commonly used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure, dynamic monitoring of cardiac function changes and judgment of left ventricular systolic dysfunction. Myocardial contractility index is an important parameter for evaluating myocardial contractility. The present invention mainly uses LVEF and Tei index as examples to estimate myocardial contractility index.

[0028] Furthermore, based on the characteristic parameters of ECG and SCG signals, a blood pressure estimation model is constructed. The specific steps are as follows:

[0029] Since PEP and LVET have different sizes at different heart rates, PEP and LVET are corrected for heart rate:

[0030] PEP'=PEP / HR

[0031] LVET'=LVET / HR

[0032] Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure, dynamic monitoring of cardiac function changes and judgment of left ventricular systolic dysfunction; PEP' and LVET' are signal characteristic parameters after heart rate correction; HR is heart rate;

[0033] Through nonlinear fitting, the blood pressure estimation model is obtained:

[0034] Systolic blood pressure: SBP = A 1 ×e CCt +B 1 ×e PEP '-C 1 ×e LVET '+D 1

[0035] Diastolic blood pressure: DBP = A 2 ×e CCt +B 2×e PEP '-C 2 ×e LVET '+D 2

[0036] Among them, A1, B1, C1, D1 and A2, B2, C2, D2 are fitting coefficients; the nonlinear fitting method is used to obtain the calculation formula of systolic and diastolic pressure, e CCt , e PEP′ , e LVET′ It is a form of nonlinear fitting.

[0037] The blood pressure estimation model has a simple structure, has the ability to measure blood pressure continuously, uses fewer parameters, has a simple formula, and is easier to integrate into wearable devices.

[0038] The present invention also provides a system for continuous blood pressure monitoring by combining ECG and SCG, comprising a data acquisition module and a processing module, wherein the data acquisition module is used to acquire ECG signals and SCG signals from the chest of a subject to be tested, and an output end of the data acquisition module is connected to the processing module;

[0039] The processing module executes the method of the present invention to perform blood pressure monitoring.

[0040] This system uses data acquisition modules and processing modules to estimate blood pressure based on synchronized ECG and SCG characteristic parameters, and has the ability to measure blood pressure continuously.

[0041] Further, the data acquisition module includes at least two ECG electrodes, an SCG sensor, and a flexible substrate;

[0042] The ECG electrodes are installed on both sides of the flexible substrate, and the SCG sensor is located at the center of the flexible substrate;

[0043] The flexible substrate is attached to the chest of the person to be tested, and a hemispherical protrusion is arranged on the side of the flexible substrate that contacts the person to be tested, and the hemispherical protrusion is located directly below the SCG sensor.

[0044] The selected signals are SCG and ECG signals measured on the chest surface, which are more convenient for wearable monitoring. The addition of a hemispherical protrusion under the SCG sensor improves the signal acquisition quality, thus laying the foundation for the application of continuous dynamic blood pressure monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of a data acquisition module of a system for continuous blood pressure monitoring by combining ECG and SCG according to the present invention;

[0046] Figure 2 It is a periodogram of ECG and SCG synchronous acquisition in the method of the present invention for continuous blood pressure monitoring by combining ECG and SCG;

[0047] Figure 3 The ECG and SCG data segment images obtained by using the averaging method in the method for continuous blood pressure monitoring by combining ECG and SCG of the present invention;

[0048] Figure 4 It is an ECG and SCG signal feature point extraction image of the method for combining ECG and SCG to continuously monitor blood pressure of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0050] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0051] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0052] Traditional blood pressure monitoring uses an inflatable cuff, which cannot achieve continuous blood pressure monitoring, and the inflation and deflation cause discomfort, especially at night, which has a greater impact on the user, thus affecting the accuracy of blood pressure measurement. The solution of using ECG and PPG to measure blood pressure together and the solution of PPG measurement alone require more complex hardware solutions. The PPG signal is easily affected by motion artifacts, skin color, etc., and there are large individual differences. There are certain differences in the PPG waveforms of different individuals. For example, the PPG waveforms of some people do not have dicrotic waves. The characteristic parameters proposed by some studies are not applicable to all forms of PPG signals. Therefore, there is no accurate conclusion on the parameter selection of the blood pressure measurement method based on PPG characteristic parameters.

[0053] The BCG method of measuring blood pressure is usually not suitable for wearable methods. Although there are studies on wrist BCG, the wrist has a larger range of motion and the signal quality is more easily affected by movement.

[0054] The present invention discloses a method for continuous blood pressure monitoring by combining ECG and SCG, comprising the following steps:

[0055] Using ECG electrodes (ADS1291, AD8232 and other integrated chips can also be used) and SCG (Seismocardiography, a type of BCG signal that measures the heart and large blood vessel pulsation signals on the chest surface, theoretically carrying more blood pressure related information) sensors, the ECG (electrocardiography) signal and SCG signal of the chest of the person being tested are collected, such as Figure 2 As shown;

[0056] The ECG signal and the SCG signal were averaged using the averaging method;

[0057] After obtaining the averaged ECG signal and SCG signal segments, the threshold method (using the existing method) is used to automatically identify the ECG and SCG signal feature points, such as Figure 4 As shown;

[0058] According to the characteristic points of ECG and SCG signals, characteristic parameters of ECG and SCG signals are extracted;

[0059] Based on the characteristic parameters of ECG and SCG signals, a blood pressure estimation model is constructed to output the blood pressure estimation results.

[0060] In a preferred embodiment of the present invention, the characteristic points of ECG and SCG signals are important reference points for determining each interval in the cardiac cycle, such as the PR interval, QRS complex, QT interval, etc. in electrical activity, and the pre-ejection period and isovolumetric contraction period in mechanical activity. Therefore, the identification of ECG and SCG characteristic points is particularly important.

[0061] Taking into account the differences in the waveform of the SCG signal, the average method is used to average the ECG signal and the SCG signal as follows:

[0062] Each calculation uses a 20-s ECG and SCG data segment, uses the threshold method to automatically extract the R wave of the ECG signal, and calculates the average heart rate HR_mean based on the RR interval;

[0063] Get the R wave position corresponding to the heart rate in the range of [HR_mean-5,HR_mean+5];

[0064] The starting point is 30-50 points before the R wave. The starting point is determined by the coverage length of the SCG signal. Each data point is moved forward by a fixed number of points. The ECG signal and SCG signal are intercepted to obtain the signal segment data set.

[0065] The amplitude of the ECG signal segment and the SCG signal segment are averaged to obtain the average ECG and SCG signals for extracting feature points, such as Figure 3 shown.

[0066] In a preferred embodiment of the present invention, the cardiac cycle (CC) parameter is the duration between specific cardiac events and is closely related to cardiac physiology and function.

[0067] The time interval between the Q wave of the ECG and the AO peak of the SCG is considered to be a surrogate value for PEP, which is a measure of the isovolumetric contraction period of the heart and an indicator of cardiac contractility. LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure, dynamic monitoring of cardiac function changes and judgment of left ventricular systolic dysfunction.

[0068] According to the time position of the characteristic points of ECG and SCG signals, the steps of extracting the characteristic parameters of ECG and SCG signals are as follows:

[0069] According to the time position of the characteristic points of ECG and SCG signals, the cardiac cycle parameters are calculated:

[0070] PEP=tAO-tQ,

[0071] LVET=tAC-tAO,

[0072] Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure; tQ, tAO, and tAC represent the time points of the Q wave, AO point, and AC point in a cardiac cycle, respectively;

[0073] Myocardial contractility index is an important parameter for evaluating myocardial contractility. The present invention mainly uses LVEF and Tei index as examples to estimate myocardial contractility index. The ratio of PEP to LVET is called contractility coefficient (CCt), which is an important indicator for measuring left ventricular dysfunction. Decreased left ventricular function leads to increased PEP / LVET. Myocardial contractility index CCt is:

[0074] CCt=PEP / LVET.

[0075] In a preferred embodiment of the present invention, a blood pressure estimation model is constructed based on the characteristic parameters of ECG and SCG signals, and the specific steps are as follows:

[0076] Since PEP and LVET have different sizes at different heart rates, PEP and LVET are corrected for heart rate:

[0077] PEP'=PEP / HR

[0078] LVET'=LVET / HR

[0079] Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure, dynamic monitoring of cardiac function changes and judgment of left ventricular systolic dysfunction; PEP' and LVET' are signal characteristic parameters after heart rate correction; HR is heart rate;

[0080] Through nonlinear fitting, the blood pressure estimation model is obtained:

[0081] Systolic blood pressure: SBP = A 1 ×e CCt +B 1 ×e PEP '-C 1 ×e LVET '+D 1

[0082] Diastolic blood pressure: DBP = A 2 ×e CCt +B 2 ×e PEP '-C 2 ×e LVET '+D 2

[0083] Among them, A1, B1, C1, D1 and A2, B2, C2, D2 are fitting coefficients; the nonlinear fitting method is used to obtain the calculation formula of systolic and diastolic pressure, e CCt , e PEP′ , e LVET′ It is a form of nonlinear fitting.

[0084] The present invention also provides a system for continuously monitoring blood pressure by combining ECG and SCG, including a data acquisition module and a processing module. The data acquisition module is used to collect ECG signals and SCG signals from the chest of a subject, and the output end of the data acquisition module is electrically connected to the processing module (such as STM32F405RGT6, etc.).

[0085] The processing module executes the method of the present invention to monitor blood pressure. The system uses a data acquisition module and a processing module to estimate blood pressure based on synchronous ECG and SCG characteristic parameters, and has the ability to measure blood pressure continuously.

[0086] In a preferred embodiment of the present invention, Figure 1 As shown, the data acquisition module includes at least two ECG electrodes and an ECG acquisition chip (such as KS1081, etc.), an SCG sensor (such as ADXL327, etc.), and a flexible substrate. The ECG electrodes are installed (such as inlaying, bonding, welding, etc.) on both sides of the flexible substrate, and the SCG sensor can be an acceleration sensor chip, and the SCG sensor is located (such as inlaying, bonding, welding, etc.) at the center of the flexible substrate.

[0087] The flexible substrate (such as a flexible circuit board, or a triangular layout or a chest strap) is attached to the chest of the person to be tested. The side of the flexible substrate that contacts the person to be tested is provided with a hemispherical protrusion, which is located directly below the SCG sensor. When in use, the hemispherical protrusion contacts the skin, and when the data acquisition module is attached to the chest, the hemispherical protrusion presses against the measurement point to better detect the SCG signal.

[0088] Compared with measuring PPG or BCG signals on the wrist or extremities, the solution of synchronously monitoring ECG and SCG on the chest has better stability and less interference. The flexible circuit board makes the sensor fit the chest wall better, and the wearing method does not cause the discomfort caused by the inflatable blood pressure monitor.

[0089] The selected signals are SCG and ECG signals measured on the chest surface, which are more convenient for wearable monitoring. The addition of a hemispherical protrusion under the SCG sensor improves the signal acquisition quality, thus laying the foundation for the application of continuous dynamic blood pressure monitoring.

[0090] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0091] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for continuous blood pressure monitoring using ECG and SCG, characterized in that: The steps include: Using ECG electrodes and SCG sensors, ECG signals and SCG signals from the chest of the subject are collected; The ECG signal and the SCG signal were averaged using the averaging method; After obtaining the averaged ECG signal and SCG signal segments, the threshold method is used to automatically identify the characteristic points of the ECG and SCG signals; According to the characteristic points of ECG and SCG signals, characteristic parameters of ECG and SCG signals are extracted; Based on the characteristic parameters of ECG and SCG signals, a blood pressure estimation model is constructed to output the blood pressure estimation results.

2. The method for continuous blood pressure monitoring by combining ECG and SCG as claimed in claim 1, characterized in that: The method of averaging the ECG signal and the SCG signal using the averaging method is as follows: Each calculation uses 20s of ECG and SCG data, and the threshold method is used to automatically extract the R wave of the ECG signal, and the average heart rate HR_mean is calculated based on the RR interval; Get the R wave position corresponding to the heart rate in the range of [HR_mean-5,HR_mean+5]; The starting point is 30-50 points before the R wave. The starting point is determined by the coverage length of the SCG signal. Each data point is moved forward by a fixed number of points. The ECG signal and SCG signal are intercepted to obtain the signal segment data set. The amplitudes of the ECG signal segments and the SCG signal segments are averaged to obtain average ECG and SCG signals for extracting feature points.

3. The method for continuous blood pressure monitoring by combining ECG and SCG as claimed in claim 1, characterized in that: According to the time position of the characteristic points of ECG and SCG signals, the steps of extracting the characteristic parameters of ECG and SCG signals are as follows: According to the time position of the characteristic points of ECG and SCG signals, the cardiac cycle parameters are calculated: PEP=tAO-tQ, LVET=tAC-tAO, Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure; tQ, tAO, and tAC represent the time points of the Q wave, AO point, and AC point in a cardiac cycle, respectively; The myocardial contraction index CCt is: CCt=PEP / LVET.

4. The method for continuous blood pressure monitoring by combining ECG and SCG as claimed in claim 1, characterized in that: Based on the characteristic parameters of ECG and SCG signals, a blood pressure estimation model is constructed. The specific steps are as follows: Since PEP and LVET have different sizes at different heart rates, PEP and LVET are corrected for heart rate: PEP'=PEP / HR LVET'=LVET / HR Among them, PEP is a measure of the isovolumetric contraction cycle of the heart and an indicator of cardiac contractility; LVET is often used to estimate the cardiac contraction time interval and can be used as an indicator for dynamic monitoring of cardiac function and prediction of heart failure, dynamic monitoring of cardiac function changes and judgment of left ventricular systolic dysfunction; PEP' and LVET' are signal characteristic parameters after heart rate correction; HR is heart rate; Through nonlinear fitting, the blood pressure estimation model is obtained: Systolic blood pressure: SBP = A1 × e CCt +B1×e PEP '-C1×e LVET '+D1 Diastolic blood pressure: DBP = A2 × e CCt +B2×e PEP '-C2×e LVET '+D2 Among them, A1, B1, C1, D1 and A2, B2, C2, D2 are fitting coefficients; the nonlinear fitting method is used to obtain the calculation formula of systolic and diastolic pressure, e CCt , e PEP′ , e LVET′ It is a form of nonlinear fitting.

5. A system for continuous blood pressure monitoring by combining ECG and SCG, characterized in that: It includes a data acquisition module and a processing module, wherein the data acquisition module is used to collect ECG signals and SCG signals from the chest of the subject to be tested, and the output end of the data acquisition module is connected to the processing module; The processing module executes the method according to any one of claims 1-4 to perform blood pressure monitoring.

6. The system for continuous blood pressure monitoring by combining ECG and SCG as claimed in claim 5, characterized in that: The data acquisition module includes at least two ECG electrodes, an SCG sensor, and a flexible substrate; The ECG electrodes are installed on both sides of the flexible substrate, and the SCG sensor is located at the center of the flexible substrate; The flexible substrate is attached to the chest of the person to be tested, and a hemispherical protrusion is arranged on the side of the flexible substrate in contact with the person to be tested, and the hemispherical protrusion is located directly below the SCG sensor.

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