Integrated flexible patch for measuring ambulatory blood pressure and method thereof

Abstract

The invention provides an integrated flexible patch for measuring ambulatory blood pressure and a method thereof, and relates to the technical field of non-invasive blood pressure monitoring. The integrated flexible patch comprises a flexible substrate, a dry viscous electrode, a photoelectric probe and a control circuit; the dry viscous electrode and the photoelectric probe are connected to one side of the flexible substrate, and the control circuit is connected to the other side of the flexible substrate; the dry viscous electrode is adhered to a measurement position of a measurement object so as to obtain an ECG signal of the measurement object; the photoelectric probe is in contact with the skin of a measured object to obtain a PPG signal; the control circuit extracts the ECG signal and the PPG signal, carries out signal coupling, then transmits the ECG signal and the PPG signal to the PC terminal and calculates the blood pressure, the effect of noninvasive real-time blood pressure measurement can be achieved, it is ensured that a measured object wears the blood pressure comfortably, the two paths of signals are firstly stored and then fused, the natural synchronization effect is achieved, the fused path of signal facilitates follow-up processing of an upper computer, PTT calculation errors are reduced, and the accuracy of blood pressure measurement is improved. And the reliability and accuracy of blood pressure measurement are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of non-invasive blood pressure monitoring, and in particular to an integrated flexible patch for measuring dynamic blood pressure and a method thereof. Background Art

[0002] Blood pressure is one of the important physiological parameters that reflect the cardiovascular status of humans or animals. Blood pressure is volatile. Continuous non-invasive blood pressure measurement can detect arterial blood pressure beat by beat, which is helpful for the prevention, diagnosis, treatment and control of cardiovascular diseases. The current non-invasive blood pressure detection technology is generally divided into intermittent measurement and continuous measurement. Intermittent measurement methods include auscultation and oscillometric methods, which have the characteristics of high accuracy, but have high requirements on operators and can only obtain intermittent blood pressure values. Continuous measurement methods include arterial tension method, volume compensation method and pulse wave velocity method, etc. Although arterial tension method and volume compensation method are relatively mature, they are sensitive to the position of the sensor and long-term measurement leads to venous congestion and discomfort. The pulse wave velocity related method has become a research hotspot in recent years because of its advantages such as no interference and dynamic measurement.

[0003] The traditional blood pressure detection method based on pulse wave transmission time has certain problems, including: it can only measure a single blood pressure indicator, requires frequent calibration and has poor accuracy. The traditional method usually collects data at the wrist, fingers, limbs, etc. This will result in the measured pulse wave transmission time not only including the aortic pulse wave transmission time which is linearly related to blood pressure, but also including the cardiac ejection period, the conduction time of the radial artery or common carotid artery and the conduction time of the local capillary endings, resulting in errors between the detected blood pressure parameters and the actual blood pressure parameters. In addition, the traditional detection device is large in size, complicated to use, and the instrument is rigid and uncomfortable to wear, causing inconvenience to the user. Summary of the invention

[0004] The purpose of the present invention includes providing an integrated flexible patch for measuring dynamic blood pressure and a method thereof, which can make the measured object wear comfortably and achieve the effect of non-invasive continuous measurement of blood pressure. The ECG signal and the PPG signal are first stored and then fused to achieve the effect of natural synchronization. The fused signal is convenient for subsequent processing by the host computer on the PC side, reducing the error of pulse wave transmission time (PTT) calculation and improving the reliability and accuracy of blood pressure measurement.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides an integrated flexible patch for measuring dynamic blood pressure, the integrated flexible patch comprising a flexible substrate, a dry adhesive electrode, a photoelectric probe and a control circuit;

[0007] The dry adhesive electrode and the photoelectric probe are connected to one side of the flexible substrate, and the control circuit is connected to the other side of the flexible substrate, wherein the photoelectric probe is arranged in the middle of the flexible substrate, and the dry adhesive electrode is arranged on the edges of the flexible substrate, and the dry adhesive electrode and the photoelectric probe are connected to the control circuit through connecting wires penetrating the flexible substrate;

[0008] The dry adhesive electrode is used to adhere to the measuring position of the measured object to obtain the ECG signal of the measured object and transmit it to the control circuit; the photoelectric probe is used to contact the skin of the measured object to obtain the PPG signal and transmit it to the control circuit; the control circuit is used to extract the ECG signal and the PPG signal, and couple the signals, and then transmit them to the PC for calculating the blood pressure, thereby realizing non-invasive real-time measurement of dynamic blood pressure.

[0009] In an alternative embodiment, a dry adhesive electrode is disposed around the photoelectric probe.

[0010] In a second aspect, the present invention provides a method for measuring dynamic blood pressure. The method for measuring dynamic blood pressure adopts the integrated flexible patch of the aforementioned embodiment. The method for measuring dynamic blood pressure includes:

[0011] S1: collect ECG signals and PPG signals;

[0012] S2: store ECG signal and PPG signal;

[0013] S3: Filtering the ECG signal and the PPG signal;

[0014] S4: standardize ECG signal and PPG signal;

[0015] S5: superimpose the ECG signal and the PPG signal to obtain a PPG-ECG signal;

[0016] S6: extracting feature points of the PPG-ECG signal and calculating PTT;

[0017] S7: A regression model between PTT and blood pressure is established through machine learning, and the dynamic blood pressure calculation is then completed through this model.

[0018] In an optional embodiment, in S1 , the dry adhesive electrode and the photoelectric probe start collecting data simultaneously.

[0019] In an optional embodiment, in S2, the ECG signal and PPG signal collected within 2 seconds are stored.

[0020] In an optional implementation, in S2, the collected data is directly stored in the internal RAM of the control circuit.

[0021] In an optional embodiment, in S4, the values ​​of the two signals are scaled to the range of [0,1] using maximum-min normalization, which is achieved by the following formula: Normalized signal = (value-min) / (max-min), where value is the original signal value, and min and max are the minimum and maximum values ​​of the signal, respectively.

[0022] In an optional embodiment, in S5, the maximum value of the array data_E composed of ECG signal points is found, and the points less than (0.85*maximum value) are set to 0, and only the remaining points, i.e., the R wave of the ECG signal, are retained, and then the two signals are superimposed to obtain the PPG-ECG signal.

[0023] In an optional implementation, in S6, the PPG-ECG signal is first smoothed, and then feature points are found, wherein the feature points include the R peak of the ECG signal and the peak of the PPG signal.

[0024] In an optional implementation, in S6, the horizontal coordinate of the feature point is stored in the array time, and the first-order difference of the array time is calculated to obtain the interval time TIME of the feature point, TIME = first-order difference value / sampling frequency, if TIME>threshold time, the data is discarded, and the data obtained is the pulse wave transmission time. The pulse wave transmission time is averaged to obtain the pulse wave transmission time (PTT) within 2s, and a regression model between PTT and blood pressure is established through machine learning, and the dynamic blood pressure calculation is completed through the regression model.

[0025] The beneficial effects of the integrated flexible patch and method for measuring dynamic blood pressure provided by the embodiments of the present invention include:

[0026] 1. The one-piece flexible patch is small in size, light in weight, and soft in texture. It can be fixed to the measured object without additional adhesives or straps, making it comfortable for the measured object to wear;

[0027] 2. The method couples the two signals. If there is a problem of missed or wrong detection of feature points, only the abnormal points need to be removed without affecting the overall PTT calculation, thereby improving the robustness of the system;

[0028] 3. The method stores the two signals first and then fuses them to achieve the effect of natural synchronization, reduce the error of PTT calculation, and improve the reliability and accuracy of blood pressure measurement;

[0029] 4. The PPG-ECG signal is transmitted to the host computer on the PC via Bluetooth, which reduces the number of bytes of signal transmission, reduces the Bluetooth transmission power and the complexity of host computer signal processing, and reduces wireless transmission time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic diagram of the exploded structure of an integrated dynamic blood pressure measurement flexible patch provided in an embodiment of the present invention;

[0032] Figure 2 A flow chart of a method for dynamic blood pressure measurement provided by an embodiment of the present invention;

[0033] Figure 3 is the ECG signal after filtering;

[0034] Figure 4 is the PPG signal after filtering;

[0035] Figure 5 It is a schematic diagram of the normalized ECG signal and PPG signal;

[0036] Figure 6 The PPG-ECG signal is obtained by superimposing the ECG signal and the PPG signal;

[0037] Figure 7 Schematic diagram for extracting feature points of PPG-ECG signals;

[0038] Figure 8 and Fig. 9 This is the test result diagram of the regression model between blood pressure and PTT.

[0039] Icon: 1-flexible substrate; 2-dry adhesive electrode; 3-photoelectric probe; 4-control circuit. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0043] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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.

[0044] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0045] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0046] Please refer to Figure 1 This embodiment provides an integrated flexible patch for measuring dynamic blood pressure (hereinafter referred to as: integrated flexible patch), which includes a flexible substrate 1, a dry adhesive electrode 2, a photoelectric probe 3 and a control circuit 4.

[0047] Specifically, the dry adhesive electrode 2 and the photoelectric probe 3 are connected to one side of the flexible substrate 1, and the control circuit 4 is connected to the other side of the flexible substrate 1. The photoelectric probe 3 is arranged in the middle of the flexible substrate 1, and the dry adhesive electrode 2 can be annular or can be multiple spaced and arranged around the edges of the flexible substrate 1. The dry adhesive electrode 2 and the photoelectric probe 3 are connected to the control circuit 4 through a connecting wire that penetrates the flexible substrate 1.

[0048] The dry adhesive electrode 2 is used to adhere to the measurement position of the measurement object, so that the integrated flexible patch can be lightly and stably adhered to the measurement position. The measurement position of the measurement object here can be the pulse, chest, etc. of a person or animal. The dry adhesive electrode 2 is attached to the skin of the measurement object to ensure close contact with the skin during wearing, reduce motion artifacts during PPG signal measurement, and compared with commercial hydrogel electrodes, the impedance of the dry adhesive electrode 2 does not increase over time.

[0049] In this way, the integrated flexible patch is small in size, light in weight, and soft in texture. It can be fixed to the measured object without additional adhesives or straps, making the measured object comfortable to wear.

[0050] Among them, the dry adhesive electrode 2 can obtain the electrocardiogram signal (ECG signal) of the measured object by its conductivity, and transmit it to the control circuit 4. The photoelectric probe 3 is used to contact the skin of the measured object, and emit light of a preset wavelength to the skin, and then receive the light reflected by the skin to obtain the pulse wave signal (PPG signal), and transmit it to the control circuit 4. The control circuit 4 is used to extract the ECG signal and the PPG signal, and couple the signals, and then transmit them to the PC end for calculating the blood pressure, so as to realize the non-invasive real-time measurement of dynamic blood pressure.

[0051] Please refer to Figure 2 This embodiment also provides a method for measuring dynamic blood pressure (hereinafter referred to as: method), the method adopts the above-mentioned integrated flexible patch, and the method includes the following steps:

[0052] S1: Collect ECG signals and PPG signals.

[0053] Specifically, the ECG signal is collected by the dry adhesive electrode 2, and the PPG signal is collected by the photoelectric probe 3, and the two are set to start collecting at the same time.

[0054] S2: Store ECG signal and PPG signal.

[0055] Specifically, the ECG signal and PPG signal collected within 2 seconds are stored, that is, the stored PPG signal points and ECG signal points are respectively stored in the array data_P and the array data_E, so that it can be ensured that there is at least one heartbeat in the array data_E, and the baseline drift of the PPG signal within 2 seconds is not serious.

[0056] Moreover, the ECG signal and the PPG signal are collected at the same time, and the collected data are directly stored in the internal RAM of the control circuit 4, so as to avoid time errors between the two data paths caused by program processing, Bluetooth transmission and other processes.

[0057] S3: Filter the ECG signal and the PPG signal.

[0058] Specifically, the ECG signal and the PPG signal are respectively subjected to an average value filtering and smoothing process with a window length of 5. The processed ECG signal is as follows: Figure 3 As shown, the processed PPG signal is Figure 4 shown.

[0059] S4: Normalize the ECG signal and the PPG signal.

[0060] Specifically, the maximum and minimum normalization is used to scale the values ​​of the two signals to the range of [0,1], which can be achieved by the following formula: Normalized signal = (value-min) / (max-min), where value is the original signal value, and min and max are the minimum and maximum values ​​of the signal, respectively. Figure 5 shown.

[0061] S5: Superimpose the ECG signal and the PPG signal to obtain a PPG-ECG signal.

[0062] Specifically, in order to make the superimposed signal retain the phase information of the original signal and avoid the influence of the QS wave of the ECG signal and other information on the feature point extraction of the superimposed signal, the maximum value of the array data_E is found, and the points less than (0.85*maximum value) are set to 0, and only the remaining points, i.e., the R wave of the ECG signal, are retained. Then, the two signals are superimposed to obtain the PPG-ECG signal (such as Figure 6 The PPG-ECG signal is transmitted to the host computer on the PC via Bluetooth for further analysis.

[0063] The above S2 to S5 can be implemented by the control circuit 4 of the integrated flexible patch.

[0064] S6: Extract the characteristic points of the PPG-ECG signal and calculate the pulse wave transmission time (PTT).

[0065] Specifically, after the PPG-ECG signal is sent to the host computer on the PC, the PPG-ECG signal is subjected to wavelet denoising and smoothing, and then the characteristic points (R peak of the ECG signal and the main wave peak of the PPG signal) are found by the threshold local maximum method. Specifically, a window with a length of 5 is set to find the local maximum value within the window, and the characteristic points in the local maximum point are screened out by setting the peak significance and peak spacing thresholds, such as Figure 7 As shown, Figure 7 The feature points are marked with small circles. Specifically, the horizontal coordinates of the feature points are stored in the array time, and the first-order difference of the array time is calculated. TIME = first-order difference value / sampling frequency, and the interval time TIME of the feature points is obtained. If TIME> threshold time (0.3s), the data is eliminated and the obtained data is PTT. The average value of PTT is taken to obtain PTT within 2s.

[0066] Among them, if missed detection and false detection occur, the abnormal values ​​can be eliminated according to the threshold time to ensure that the PTT data are all real and valid PTT. Even if the feature points are missed or falsely detected, it will not affect the calculation of the overall average PTT.

[0067] S7: A regression model between PTT and blood pressure is established through machine learning, and the dynamic blood pressure (including systolic and diastolic blood pressure) is calculated through this model.

[0068] A regression model between PTT and blood pressure is established through machine learning, and the dynamic blood pressure calculation is completed through the regression model.

[0069] Specifically, 8 healthy test persons were selected for blood pressure experiments, aged between 22 and 27 years old, including 4 males and 4 females. The designed integrated flexible patch was used to measure the ECG-PPG signal of the test persons within 1 minute, the collected signal data was saved, and the average PTT was calculated. At the same time, an electronic sphygmomanometer was used to collect the upper arm blood pressure of the test persons as a reference blood pressure. The above process was repeated, and 20 sets of diastolic blood pressure (DBP)-PTT data and 20 sets of systolic blood pressure (SBP)-PTT data were collected for each test person. Based on the above data sets, multi-parameter fitting regression analysis was performed, and the input was three-dimensional data including PTT, PTT 2 , ln(PTT), and a 3rd-order multiple linear regression model was established. The DBP and SBP predicted by the model were compared with the actual values. The test results of the regression model between systolic and diastolic blood pressure and PTT (Regression Analysis of SBP) are shown in Figure 8 and Fig. 9 As shown, it can be seen that the predicted result of the regression model (Predicted) is close to the true value (Perfect prediction), and the correlation is higher than 0.8, that is, the prediction result of the regression model is more accurate.

[0070] The beneficial effects of the integrated flexible patch and method for measuring dynamic blood pressure provided in this embodiment include:

[0071] 1. The one-piece flexible patch is small in size, light in weight, and soft in texture. It can be fixed to the measured object without additional adhesives or straps, making it comfortable for the measured object to wear;

[0072] 2. The PPG signal is easily affected by ambient light and motion artifacts, resulting in unstable PPG signal acquisition. When the feature points of the PPG signal are missed, it will affect the correspondence with the feature points of the ECG signal, and further affect the PTT calculation of the entire signal. The traditional method uses various algorithms in the signal processing part to avoid the processing problem of the PPG signal, while the method provided in this embodiment couples the two signals. If the missed detection problem occurs, only the abnormal points need to be eliminated without affecting the overall PTT calculation, thereby improving the robustness of the system.

[0073] 3. The traditional two-way signal synchronous acquisition method is difficult to avoid the time difference caused by program execution, sensor communication time, etc.; the method provided in this embodiment stores the two-way signals first and then fuses them to achieve the effect of natural synchronization, reduce the error of PTT calculation, and improve the reliability and accuracy of blood pressure measurement.

[0074] 4. The pulse wave transmission time (PTT) is calculated by collecting the characteristic points (peaks, troughs, etc.) of the two signals, where the characteristic points of the two signals correspond one to one, and the regression model established by machine learning is used to complete the real-time detection of dynamic blood pressure.

[0075] 5. The PPG-ECG signal is transmitted to the host computer on the PC via Bluetooth, which reduces the number of bytes of signal transmission, reduces the Bluetooth transmission power and the complexity of host computer signal processing, and reduces wireless transmission time.

[0076] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An integrated flexible patch for measuring dynamic blood pressure, characterized in that: The integrated flexible patch comprises a flexible substrate (1), a dry adhesive electrode (2), a photoelectric probe (3) and a control circuit (4); The dry adhesive electrode (2) and the photoelectric probe (3) are connected to one side of the flexible substrate (1), and the control circuit (4) is connected to the other side of the flexible substrate (1), wherein the photoelectric probe (3) is arranged in the middle of the flexible substrate (1), and the dry adhesive electrode (2) is arranged on the edges of the flexible substrate (1), and the dry adhesive electrode (2) and the photoelectric probe (3) are both connected to the control circuit (4) through a connecting wire that penetrates the flexible substrate (1); The dry adhesive electrode (2) is used to adhere to the measurement position of the measurement object to obtain the ECG signal of the measurement object and transmit it to the control circuit (4); the photoelectric probe (3) is used to contact the skin of the measurement object to obtain the PPG signal and transmit it to the control circuit (4); the control circuit (4) is used to extract the ECG signal and the PPG signal, perform signal coupling, and then transmit them to the PC end for calculating the blood pressure, thereby realizing non-invasive real-time measurement of dynamic blood pressure.

2. The integrated flexible patch for measuring dynamic blood pressure according to claim 1, characterized in that: The dry adhesive electrode (2) is arranged around the photoelectric probe (3).

3. A method for measuring dynamic blood pressure, characterized in that: The method for measuring dynamic blood pressure adopts the integrated flexible patch according to claim 1, and the method for measuring dynamic blood pressure comprises: S1: collect ECG signals and PPG signals; S2: store ECG signal and PPG signal; S3: Filtering the ECG signal and the PPG signal; S4: standardize ECG signal and PPG signal; S5: superimpose the ECG signal and the PPG signal to obtain a PPG-ECG signal; S6: extracting feature points of the PPG-ECG signal and calculating PTT; S7: A regression model between PTT and blood pressure is established through machine learning, and the dynamic blood pressure calculation is then completed through this model.

4. The method for measuring dynamic blood pressure according to claim 3, characterized in that: In S1, the dry adhesive electrode (2) and the photoelectric probe (3) start collecting data simultaneously.

5. The method for measuring dynamic blood pressure according to claim 3, characterized in that: In S2, the ECG signal and PPG signal collected within 2 seconds are stored.

6. The method for measuring dynamic blood pressure according to claim 3, characterized in that: In S2, the collected data is directly stored in the internal RAM of the control circuit (4).

7. The method for measuring dynamic blood pressure according to claim 3, characterized in that: In S4, the maximum and minimum normalization is used to scale the values ​​of the two signals to the range of [0,1], which is achieved by the following formula: Normalized signal = (value-min) / (max-min), where value is the original signal value, and min and max are the minimum and maximum values ​​of the signal, respectively.

8. The method for measuring dynamic blood pressure according to claim 7, characterized in that: In S5, the maximum value of the array data_E composed of ECG signal points is found, and the points less than (0.85*maximum value) are set to 0, and only the remaining points, i.e., the R wave of the ECG signal, are retained, and then the two signals are superimposed to obtain the PPG-ECG signal.

9. The method for measuring dynamic blood pressure according to claim 8, characterized in that: In S6, the PPG-ECG signal is first smoothed, and then feature points are found by using a threshold local maximum method, wherein the feature points include the R peak of the ECG signal and the peak of the PPG signal.

10. The method for measuring dynamic blood pressure according to claim 9, characterized in that: In S6, the horizontal coordinates of the feature points are stored in the array time, and the first-order difference of the array time is calculated to obtain the interval time TIME of the feature points, TIME = first-order difference value / sampling frequency. If TIME>threshold time, the data is eliminated and the obtained data is the pulse wave conduction time. The average value of the pulse wave conduction time is taken to obtain the PTT within 2s.

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