Hemodynamic detection system and method based on few electrodes and signal correlation

Abstract

The present application relates to a kind of based on few electrode and signal correlation hemodynamics detection system and method, belong to biomedical signal detection and processing technical field.The system includes microcontroller module, thoracic impedance excitation module, thoracic impedance signal detection module, electrocardiogram signal detection module, display module, storage module, wired device, wireless device and four electrodes.The system only uses four electrodes to realize the synchronous measurement of thoracic impedance signal, thoracic impedance change signal, thoracic impedance change differential signal, electrocardiogram signal and breathing signal, optimizes the wiring complex problem in current thoracic impedance and electrocardiogram detection, and extracts hemodynamics related characteristic parameters in combination with the physiological timing relationship between signals, with accurate, simple, efficient, low cost advantage.The present application is helpful to develop portable noninvasive hemodynamics detection equipment and heart function detection equipment, and corresponding wearable device, improves the clinical applicability of equipment.

Description

Technical Field

[0001] This invention belongs to the field of biomedical signal detection and processing technology, and relates to a hemodynamic detection system and method based on fewer electrodes and signal correlation. Background Technology

[0002] In recent years, with the surge in the number of cardiovascular disease patients, cardiac function analysis methods and equipment based on chest impedance signals and electrocardiogram (ECG) signals have become increasingly valuable for the diagnosis and treatment of cardiovascular diseases. Clinically, chest impedance signals and ECG signals are commonly used for non-invasive hemodynamic monitoring and cardiac function analysis.

[0003] Conventional methods require at least seven electrodes to simultaneously detect chest impedance and electrocardiogram (ECG) signals, with four electrodes dedicated to chest impedance and three to ECG. This approach results in complex wiring between the subject and the device, a large number of electrodes required, and poor subject comfort, ease of measurement, and device portability. Portable or wearable devices that simultaneously detect chest impedance and ECG signals using fewer electrodes are still rare.

[0004] Currently, most non-invasive hemodynamic and cardiac function testing devices on the market require a large number of electrodes and leads to connect to the human body and are relatively large in size. This limits the application scope of the devices, and their high price hinders their promotion in community and home healthcare.

[0005] In the field of biomedical signal processing, when locating the features of a certain physiological signal, the corresponding feature point extraction strategy is usually formulated based solely on the time-frequency domain characteristics of the physiological signal. This approach is easily affected by factors such as signal fluctuations or individual differences, which can lead to positioning errors and results in low robustness.

[0006] Therefore, there is an urgent need for a portable and accurate hemodynamic monitoring device. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a hemodynamic detection system and method based on fewer electrodes and signal correlation, so as to solve the problems of complex measurement wiring, high detection cost, poor equipment portability, and large parameter calculation errors caused by inaccurate positioning of signal feature points in existing hemodynamic detection equipment and cardiac function analysis and diagnostic equipment.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] 1. A hemodynamic detection system based on few electrodes and signal correlation, comprising a microcontroller module, a chest impedance excitation module, a chest impedance signal detection module, an electrocardiogram signal detection module, a display module, a storage module, a wired device, a wireless device, and four electrodes (E1 to E4).

[0010] The microcontroller module is connected to the chest impedance excitation module, chest impedance signal detection module, electrocardiogram signal detection module, display module, storage module, wired device, and wireless device;

[0011] The four electrodes are in contact with human skin. Electrode E1 is connected only to the chest impedance excitation module and is an excitation electrode. Electrodes (E2 and E3) are measurement electrodes and are connected only to the chest impedance signal detection module and the electrocardiogram (ECG) signal detection module. Electrode E4 is a grounding electrode and is connected to the chest impedance excitation module, the chest impedance signal detection module, the ECG signal detection module, and the microcontroller module. It serves as both an excitation electrode forming a current loop with the human body and a measurement electrode providing a voltage reference point for the chest impedance signal detection module and the ECG signal detection module. The measurement electrodes (E2 and E3) are placed at the base of the neck and the xiphoid process of the chest, respectively. The excitation electrode E1, which is connected only to the chest impedance excitation module, is placed 3 cm above the measurement electrode at the base of the neck, and the grounding electrode E4 is placed 3 cm below the measurement electrode at the xiphoid process.

[0012] The chest impedance excitation module is used to provide excitation signals.

[0013] The chest impedance signal detection module is used to condition multi-channel chest impedance correlation signals and outputs a mixed signal Z0&RESP containing the basic chest impedance signal Z0 and the respiratory signal RESP, a chest impedance change signal ΔZ, and a chest impedance change differential signal dZ / dt.

[0014] The ECG signal detection module is used to regulate the ECG signal and output a single-lead ECG signal.

[0015] The microcontroller module uses a digital filter to separate the mixed signals Z0 and RESP to obtain the basic thoracic impedance signal Z0 and the respiratory signal RESP. It also uses a digital filter to denoise the acquired multi-channel thoracic impedance correlation signal and ECG signal. The microcontroller module also provides a sinusoidal current signal to the thoracic impedance excitation module.

[0016] The microcontroller module transmits multi-channel chest impedance-related signals and electrocardiogram signals to the display module, storage module, wired devices, and wireless devices for display, storage, and processing. It also reads data stored in the storage module and receives instructions from the wired and wireless devices.

[0017] Preferably, the chest impedance signal detection module includes a voltage follower, an instrumentation amplifier, a demodulation circuit, a high-pass filter circuit, a low-pass filter circuit, a chest impedance signal amplification and filtering module, a differentiating circuit, and a voltage boosting circuit; the electrocardiogram signal detection module includes a voltage follower, an instrumentation amplifier, a low-pass filter circuit, an electrocardiogram signal amplification and filtering module, and a voltage boosting circuit.

[0018] The voltage signals collected by the measuring electrodes (E2, E3) are first input to a voltage follower, and then the differential voltage between electrodes E2 and E3 is amplified by an instrumentation amplifier. The output signal of the instrumentation amplifier is the amplified chest impedance amplitude modulation signal. The chest impedance amplitude modulation signal is then input to the high-pass filter circuit in the chest impedance signal detection module and the low-pass filter circuit in the ECG signal detection module through two separate inputs.

[0019] In the chest impedance signal detection module, a high-pass filter circuit with a cutoff frequency of 1kHz is used to remove the electrocardiogram signal contained in the chest impedance amplitude modulation signal. Then, a demodulation circuit is used to demodulate the original chest impedance signal from the chest impedance amplitude modulation signal, which includes the basic chest impedance signal Z0, the respiratory signal RESP, and the chest impedance change signal ΔZ. Next, the original chest impedance signal is split into two paths for processing. One path passes through a low-pass filter circuit with a cutoff frequency of 2Hz to obtain a mixed signal Z0&RESP containing the basic chest impedance signal and the respiratory signal. The other path passes through a high-pass filter circuit with a cutoff frequency of 1Hz to remove the DC component from the original chest impedance signal. After passing through the chest impedance signal amplification and filtering module, one path passes through a voltage boosting circuit to obtain the chest impedance change signal ΔZ, and the other path passes through a differentiating circuit, a low-pass filter circuit, and a voltage boosting circuit to obtain the chest impedance change differential signal dZ / dt.

[0020] In the ECG signal detection module, a low-pass filter circuit with a cutoff frequency of 100Hz is used to remove the high-frequency amplitude modulation signal; then the ECG signal is obtained through the ECG signal amplification and filtering module and the voltage boosting circuit.

[0021] Preferably, the thoracic impedance signal amplification and filtering module includes an amplification circuit, a low-pass filter circuit, and a 50Hz notch filter circuit; the electrocardiogram signal amplification and filtering module includes a 50Hz notch filter circuit, a high-pass filter circuit, and an amplification circuit.

[0022] Preferably, the chest impedance excitation module includes a bandpass filter circuit and a voltage-controlled current source.

[0023] Preferably, the microcontroller module includes a digital-to-analog converter (DAC) for generating a chest impedance excitation signal and an analog-to-digital converter (ADC) for converting multi-channel chest impedance-related signals and electrocardiogram (ECG) signals into digital signals.

[0024] The analog-to-digital converter (ADC) synchronously samples four channels of signals (Z0 & RESP, ΔZ, dZ / dt, ECG).

[0025] 2. A hemodynamic detection method based on fewer electrodes and signal correlation, specifically: denoising the corresponding signals according to the time-frequency characteristics of multi-channel chest impedance correlation signals and electrocardiogram signals, suppressing respiratory interference by utilizing the correlation between multi-channel chest impedance correlation signals and electrocardiogram signals, and extracting the characteristic parameters of the corresponding signals by combining the temporal correlation between multi-channel chest impedance correlation signals and electrocardiogram signals.

[0026] Furthermore, a digital low-pass filter is used to remove high-frequency noise from the multi-channel chest impedance-related signal and the electrocardiogram (ECG) signal; using the respiratory signal RESP, an adaptive filtering algorithm is employed to suppress baseline drift caused by respiration in the chest impedance change signal ΔZ, the differential chest impedance change signal dZ / dt, and the ECG signal.

[0027] Furthermore, from a physiological perspective, the electrophysiological and temporal characteristics of the heart are analyzed to correspond to time features. By using time-domain sliding windowing, zero-crossing detection, VMD decomposition, and main frequency reconstruction, the characteristic parameters of the electrocardiogram signal, such as P, QRS, and T wave peak points, are extracted.

[0028] Furthermore, by combining the differential signal of chest impedance change with the electrocardiogram signal, the characteristic points A, B, C, X, Y, O, and E of the differential signal of chest impedance change are detected from the signal timing relationship reflected by the electromechanical characteristics of the human heart's functional structure, thereby analyzing and obtaining human hemodynamic parameters.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) This invention can make full use of the electrical signals detected from the human body to extract multi-channel chest impedance correlation signals, including chest impedance baseline signals, chest impedance change signals, chest impedance change differential signals, and respiratory signals, as well as single-lead electrocardiogram signals, for a total of 5 channels. Combining the physiological significance and temporal relationship of these signals, a method for locating different signal feature points is formulated to ensure the accuracy of hemodynamic parameter calculation and realize the detection and analysis function of hemodynamics and cardiac function based on chest impedance method.

[0031] The detection system of this invention optimizes the complex wiring problem of synchronous detection of multi-channel chest impedance-related signals and electrocardiogram signals. It achieves simultaneous detection of chest impedance signals and electrocardiogram signals using only four electrodes, and is simple and efficient.

[0032] (2) The measuring electrodes and some measuring devices of the present invention are shared in the detection of multi-channel chest impedance correlation signals and electrocardiogram signals. The system is highly efficient, saves volume and cost, and is conducive to the development of portable hemodynamic detection equipment and wearable devices.

[0033] (3) The signal feature point localization method involved in the system of the present invention extracts feature parameters from multiple perspectives based on the analysis of the time and frequency characteristics of the signal, combined with the physiological significance and the temporal relationship of related physiological signals, and has high accuracy.

[0034] (4) The present invention has greater applicability and potential for development in community and home healthcare.

[0035] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0037] Figure 1 This is a simplified structural diagram of the hemodynamic detection system based on fewer electrodes and signal correlation of the present invention;

[0038] Figure 2 This is a diagram showing the internal structure of the detection front end of the hemodynamic detection system based on few electrodes and signal correlation of the present invention;

[0039] Figure 3 This is a time-domain waveform diagram of the detection signal of the system of the present invention;

[0040] Figure 4 This is a feature point localization map of the hemodynamic detection method based on few electrodes and signal correlation of the present invention;

[0041] Figure 5 This is a schematic diagram illustrating the feasibility verification of a hemodynamic detection system based on few electrodes and signal correlation in an embodiment of the present invention;

[0042] Figure 6 This is a comparison of the time-domain waveforms of the detection signals obtained using the detection system of this invention and a detection system based on conventional multi-electrode synchronous measurement of chest impedance and electrocardiogram. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0044] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0045] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, 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, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0046] Please see Figures 1-6 This invention provides a hemodynamic detection system based on fewer electrodes and signal correlation, such as... Figure 1 As shown, the system includes a chest impedance excitation module, a chest impedance signal detection module, an electrocardiogram signal detection module, a display module, a storage module, wired devices, wireless devices, and a microcontroller module connected to them, as well as four electrodes.

[0047] Please see Figure 2 The front end of the detection system consists of a chest impedance excitation module, a chest impedance signal detection module, an electrocardiogram signal detection module, a microcontroller module, and four electrodes (E1, E2, E3, E4).

[0048] Four electrodes are placed on the surface of human skin using silver / silver chloride electrode pads. E1 is the excitation electrode, E2 and E3 are the measurement electrodes, and E4 is the grounding electrode. It serves as both an excitation electrode to form a current loop with the human body and a measurement electrode to provide a voltage reference point for the detection of chest impedance and electrocardiogram signals.

[0049] The microcontroller module includes a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC), and also has the necessary computing and communication functions.

[0050] The DAC is used to provide a sinusoidal voltage excitation signal, with an output frequency of 20kHz to 100kHz and a peak-to-peak value of 1V to 3V.

[0051] The ADC is used to acquire multi-channel chest impedance-related signals, including mixed signals containing basic chest impedance and respiratory signals (Z0 & RESP), chest impedance change signals (ΔZ), and differential chest impedance change signals (dZ / dt), as well as single-lead electrocardiogram (ECG) signals, for a total of 4 channels.

[0052] The bandpass filter circuit in the chest impedance excitation module is used to remove the DC bias in the DAC output signal and smooth the waveform. The passband gain is 2, and the output of the bandpass filter circuit is used as the input of the voltage-controlled current source.

[0053] The voltage-controlled current source uses a Howland current source. When a sinusoidal voltage signal with a frequency of 20kHz to 100kHz and a peak-to-peak value of 2V to 6V is input, a sinusoidal current signal with a frequency of 20kHz to 100kHz and a peak-to-peak value of 2mA to 6mA is output between electrodes E1 and E4.

[0054] When a sinusoidal current signal passes through the human body, it is modulated into a voltage signal by the change in the body's chest impedance.

[0055] The multi-channel chest impedance-correlated signal detection and ECG signal detection use three electrodes: E2, E3, and E4.

[0056] In the chest impedance signal detection module and the ECG signal detection module, the voltages of electrodes E2 and E3 are first obtained by utilizing the high input impedance of the voltage follower. Then, the differential voltages of electrodes E2 and E3 are amplified by utilizing the high input impedance, high common-mode rejection ratio, and low noise characteristics of the instrumentation amplifier. The amplification factor is 10 to 20. The output signal of the instrumentation amplifier is the amplified chest impedance amplitude-modulated signal.

[0057] The chest impedance amplitude-modulated signal contains not only chest impedance information but also electrocardiogram (ECG) signals. The chest impedance amplitude-modulated signal is input to the high-pass filter circuit in the chest impedance signal detection module and the low-pass filter circuit in the ECG signal detection module through two separate inputs.

[0058] Since the frequency range of ECG signals is mainly concentrated in the range of 0.5 to 45 Hz, and the chest impedance information is contained in the amplitude modulation signal with a frequency of not less than 20 kHz, a high-pass filter circuit with a cutoff frequency of 1 kHz is used in the chest impedance signal detection module to remove the ECG signal contained in the chest impedance amplitude modulation signal; a low-pass filter circuit with a cutoff frequency of 100 Hz is used in the ECG signal detection module to remove the high-frequency amplitude modulation signal, and at the same time suppress high-frequency noise, so as to obtain the ECG signal after amplification by the instrumentation amplifier.

[0059] The demodulation circuit in the chest impedance signal detection module uses an envelope half-wave detector circuit to demodulate the original chest impedance signal from the chest impedance amplitude modulation signal. This signal includes the basic chest impedance signal, respiratory signal, and chest impedance change signal.

[0060] The original thoracic impedance signal was split into two paths for processing, resulting in a mixed signal containing the baseline thoracic impedance signal and the respiratory signal, as well as a thoracic impedance change signal. Specifically:

[0061] Since the basic thoracic impedance signal is approximately the DC component of the original thoracic impedance signal, and the respiratory signal is mainly the low-frequency component of the original thoracic impedance signal with a frequency of 0.05 to 2 Hz, the original thoracic impedance signal is passed through a low-pass filter circuit with a cutoff frequency of 2 Hz to obtain a mixed signal containing the basic thoracic impedance signal and the respiratory signal.

[0062] Since the frequency range of the chest impedance change signal is approximately 1–20 Hz, the DC component in the original chest impedance signal is first removed by a high-pass filter circuit with a cutoff frequency of 1 Hz, which can also effectively suppress lower-frequency respiratory interference.

[0063] The chest impedance signal amplification and filtering module consists of an amplification circuit, a low-pass filter circuit, and a 50Hz notch filter circuit.

[0064] Since the demodulated chest impedance change signal is still very weak and not convenient to be directly acquired by ADC, an amplifier circuit is used to further amplify the chest impedance change signal. The amplification factor of the amplifier circuit is 100 to 200.

[0065] During signal conditioning, the signal with changing chest impedance is easily affected by high-frequency noise and 50Hz power frequency interference. Therefore, a low-pass filter circuit and a 50Hz notch filter circuit are used to denoise the signal in order to improve the signal-to-noise ratio.

[0066] The output of the chest impedance signal amplification and filtering module is a chest impedance change signal containing negative voltage. However, the ADC in the microprocessor module can only acquire positive voltage signals. Therefore, the ADC cannot be used directly for acquisition. A voltage boosting circuit is needed to boost the signal to above the positive voltage to meet the input range of the ADC.

[0067] The voltage boosting circuit is implemented by an adder circuit, which adds a DC signal to the original signal to make the output signal within the positive voltage range.

[0068] The chest impedance change signal is used to obtain the chest impedance change differential signal through a differentiating circuit.

[0069] Since the differentiating circuit amplifies high-frequency noise, a low-pass filter circuit with a cutoff frequency of 20Hz is used at the output to suppress high-frequency noise. Finally, the impedance change differential signal is input to the ADC through a voltage boosting circuit.

[0070] The ECG signal amplified by the instrumentation amplifier needs further amplification and noise reduction to improve the signal-to-noise ratio. This is done using an ECG signal amplification and filtering module.

[0071] The ECG signal amplification and filtering module consists of a 50Hz notch filter circuit, a high-pass filter circuit, and an amplification circuit.

[0072] The 50Hz notch filter circuit is used to suppress power frequency noise, and the high-pass filter circuit is used to remove the DC component from the ECG signal after it has been amplified by the instrumentation amplifier, so as to ensure that the signal after amplification by the amplifier circuit will not be saturated and distorted, while effectively suppressing baseline drift.

[0073] The amplification circuit in the ECG signal amplification and filtering module is used to further amplify the ECG signal to improve the quality of the signal acquired by the ADC. Otherwise, the quality of the acquired signal will be poor due to the limitations of the ADC accuracy. The amplification factor of the amplification circuit is 50 to 100.

[0074] The ECG signal output from the ECG signal amplification and filtering module is boosted to a positive voltage range by the voltage boosting circuit before being input to the ADC.

[0075] The high-pass and low-pass filter circuits in the chest impedance signal detection module and the ECG signal detection module both use second-order Butterworth filters; the 50Hz notch filter circuits in the chest impedance signal amplification and filtering module and the ECG signal amplification and filtering module both use double-T notch filters; and the bandpass filter circuit in the chest impedance excitation module uses a second-order voltage-controlled voltage source bandpass filter.

[0076] The digital filter used to separate the thoracic baseline impedance signal and the respiratory signal from the mixed signal containing the thoracic baseline impedance signal and the respiratory signal is an IIR low-pass filter, also known as a DC tracking filter. Its difference equation is y(n)=y(n-1)+[x(n)-y(n-1)] / 2 k .

[0077] Experiments at a sampling frequency of 200Hz showed that when k is taken as the recommended value of 9, the basic thoracic impedance signal can be obtained from the mixed signal; when k is taken as the recommended value of 7, the respiratory signal can be obtained from the mixed signal.

[0078] Using an IIR low-pass filter and a moving average filter can effectively remove high-frequency noise from multi-channel chest impedance-related signals and electrocardiogram signals. The difference equation of the IIR low-pass filter is y(n)=y(n-1)+[x(n)-x(n-4)] / 4. This filter has a 50Hz notch effect when the sampling frequency is 200Hz.

[0079] Using the acquired respiratory signals, an adaptive filtering algorithm can suppress baseline drift caused by respiration in the chest impedance change signal, the differential chest impedance change signal, and the electrocardiogram signal.

[0080] Please see Figure 1 The signals acquired by the ADC of the microcontroller module can be transmitted to wired or wireless devices via the communication interface, stored in the storage module connected to the microcontroller module, or directly displayed on the display module connected to the microcontroller module.

[0081] The microcontroller can read data stored in the storage module and can also receive instructions from wired or wireless devices.

[0082] Please see Figure 3 The multi-channel chest impedance correlation signal and electrocardiogram signal waveforms obtained using the detection system of this invention are clear.

[0083] Electrocardiogram (ECG) signals reflect the electrophysiological activity of the heart. In a normal heart, electrical excitation begins at the sinoatrial node, with the P wave representing atrial excitation. This excitation is conducted through the internodal tracts to the atrioventricular node, forming the PR segment. The excitation then travels downwards through the His bundle and the left and right bundle branches to the left and right ventricles, forming the QRS wave. Depolarization is complete, but repolarization has not yet begun, forming the ST segment, which corresponds to ventricular systole. The T wave then indicates the closure of the aortic valves, followed by the opening of the atrioventricular valves, symbolizing ventricular diastole. This process corresponds to one cardiac cycle.

[0084] The thoracic impedance signal reflects the impedance changes caused by factors such as changes in vascular volume and blood flow velocity. When the heart contracts, blood is ejected into the aorta, causing the aortic lumen to expand, increasing the cross-sectional area, increasing blood volume, and decreasing thoracic impedance. When the heart relaxes, blood returns to the heart, decreasing blood volume and increasing thoracic impedance.

[0085] In the differential signal of chest impedance changes, wave A is an atrial systolic wave, which occurs during atrial systole. Point B symbolizes the opening point of the aorta, which is the starting point of ventricular ejection. Wave C is a ventricular systolic wave, which is related to the ejection of blood from the aorta and pulmonary arteries during ventricular systole. Point X represents the closure of the aortic valve and the end of left ventricular ejection. Immediately afterwards, the pulmonary valve closes to form point Y. Wave O indicates the opening of the left atrioventricular valve. Point E is the filling point of the ventricle. The above process corresponds to one cardiac cycle of the electrocardiogram signal.

[0086] By employing time-domain sliding windowing, zero-crossing detection, VMD decomposition, and main frequency reconstruction, characteristic parameters of electrocardiogram signals, such as P, QRS, and T wave peak points, are extracted.

[0087] By combining the differential signal of chest impedance change with the electrocardiogram signal, the characteristic points A, B, C, X, Y, O, and E of the differential signal of chest impedance change are detected from the signal timing relationship reflected by the electromechanical characteristics of the human heart's functional structure.

[0088] Please see Figure 4 The detection method of this invention can accurately locate signal feature points.

[0089] Please see Figure 5 The study used a few-electrode detection method and a conventional multi-electrode detection method to simultaneously measure chest impedance signals and electrocardiogram signals. The signals detected by the two methods were compared experimentally to verify the feasibility of a hemodynamic detection system based on few electrodes and signal correlation.

[0090] In the experiment, the excitation current source was connected to electrodes E1 and E4 to inject a sinusoidal current excitation signal with a frequency of 40kHz and a peak-to-peak value of 2mA into the human thoracic cavity. The few-electrode detection module was connected to electrodes E2, E3, and E4, outputting a chest impedance change signal (ΔZ), a chest impedance change differential signal (dZ / dt), and a single-lead electrocardiogram (ECG) signal, for a total of 3 channels. The multi-electrode detection module was connected to electrodes E2, E3, E4, E5, E6, and E7. Electrodes E2, E3, and E4 were used to detect chest impedance signals, while electrodes E5, E6, E7, and E4 were used to detect ECG signals. The multi-electrode detection module output a chest impedance change signal (ΔZ), a chest impedance change differential signal (dZ / dt), and a standard three-lead ECG signal (ECG_Ⅰ, ECG_Ⅱ, ECG_Ⅲ), for a total of 5 channels. The output signals from both the few-electrode and multi-electrode detection modules were transmitted to the host computer for synchronous display.

[0091] Please see Figure 6 The multi-channel chest impedance correlation signal detected using the few-electrode method of this invention is not significantly different from that detected using the conventional multi-electrode method; the time domain feature points of the ECG signal detected using the few-electrode method are consistent with those of the standard three-lead ECG signal detected using the multi-electrode method.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A hemodynamic detection system based on few electrodes and signal correlation, characterized in that, The system includes a microcontroller module, a chest impedance excitation module, a chest impedance signal detection module, an electrocardiogram signal detection module, and four electrodes E1 to E4; The microcontroller module is connected to the chest impedance excitation module, the chest impedance signal detection module, and the electrocardiogram signal detection module. The four electrodes are in contact with human skin. Electrode E1 is connected only to the chest impedance excitation module and is an excitation electrode. Electrodes E2 and E3 are measurement electrodes and are connected only to the chest impedance signal detection module and the electrocardiogram signal detection module. Electrode E4 is a grounding electrode and is connected to the chest impedance excitation module, the chest impedance signal detection module, the electrocardiogram signal detection module, and the microcontroller module. It serves as both an excitation electrode forming a current loop with the human body and a measurement electrode providing a voltage reference point for the chest impedance signal detection module and the electrocardiogram signal detection module. Measurement electrodes E2 and E3 are placed at the base of the neck and the xiphoid process of the chest, respectively. Excitation electrode E1, which is only connected to the chest impedance excitation module, is placed 3 cm above the measurement electrode at the base of the neck, and grounding electrode E4 is placed 3 cm below the measurement electrode at the xiphoid process. The chest impedance excitation module is used to provide excitation signals; The chest impedance signal detection module is used to condition multi-channel chest impedance correlation signals and outputs a mixed signal Z0&RESP containing the basic chest impedance signal Z0 and the respiratory signal RESP, a chest impedance change signal ΔZ, and a chest impedance change differential signal dZ / dt. The ECG signal detection module is used to modulate the ECG signal and output a single-lead ECG signal. The microcontroller module uses a digital filter to separate the mixed signals Z0 and RESP to obtain the basic thoracic impedance signal Z0 and the respiratory signal RESP. It also uses a digital filter to denoise the acquired multi-channel thoracic impedance correlation signal and ECG signal. The microcontroller module also provides a sinusoidal current signal to the thoracic impedance excitation module.

2. The hemodynamic detection system according to claim 1, characterized in that, The chest impedance signal detection module includes a voltage follower, an instrumentation amplifier, a demodulation circuit, a high-pass filter circuit, a low-pass filter circuit, a chest impedance signal amplification and filtering module, a differentiating circuit, and a voltage boosting circuit; the electrocardiogram signal detection module includes a voltage follower, an instrumentation amplifier, a low-pass filter circuit, an electrocardiogram signal amplification and filtering module, and a voltage boosting circuit. The voltage signals collected by measuring electrodes E2 and E3 are first input to a voltage follower, and then the differential voltage between electrodes E2 and E3 is amplified by an instrumentation amplifier. The output signal of the instrumentation amplifier is the amplified chest impedance amplitude modulation signal. The chest impedance amplitude modulation signal is then input to the high-pass filter circuit in the chest impedance signal detection module and the low-pass filter circuit in the ECG signal detection module through two separate paths. In the chest impedance signal detection module, a high-pass filter circuit with a cutoff frequency of 1kHz is used to remove the electrocardiogram signal contained in the chest impedance amplitude modulation signal. Then, a demodulation circuit is used to demodulate the original chest impedance signal from the chest impedance amplitude modulation signal, which includes the basic chest impedance signal Z0, the respiratory signal RESP, and the chest impedance change signal ΔZ. Next, the original chest impedance signal is split into two paths for processing. One path passes through a low-pass filter circuit with a cutoff frequency of 2Hz to obtain a mixed signal Z0&RESP containing the basic chest impedance signal and the respiratory signal. The other path passes through a high-pass filter circuit with a cutoff frequency of 1Hz to remove the DC component from the original chest impedance signal. After passing through the chest impedance signal amplification and filtering module, one path passes through a voltage boosting circuit to obtain the chest impedance change signal ΔZ, and the other path passes through a differentiating circuit, a low-pass filter circuit, and a voltage boosting circuit to obtain the chest impedance change differential signal dZ / dt. In the ECG signal detection module, a low-pass filter circuit with a cutoff frequency of 100Hz is used to remove the high-frequency amplitude modulation signal; then the ECG signal is obtained through the ECG signal amplification and filtering module and the voltage boosting circuit.

3. The hemodynamic detection system according to claim 2, characterized in that, The thoracic impedance signal amplification and filtering module includes an amplification circuit, a low-pass filter circuit, and a 50Hz notch filter circuit; the electrocardiogram signal amplification and filtering module includes a 50Hz notch filter circuit, a high-pass filter circuit, and an amplification circuit.

4. The hemodynamic detection system according to claim 1, characterized in that, The chest impedance excitation module includes a bandpass filter circuit and a voltage-controlled current source.

5. The hemodynamic detection system according to claim 1, characterized in that, The microcontroller module includes a digital-to-analog converter (DAC) for generating chest impedance excitation signals and an analog-to-digital converter (ADC) for converting multi-channel chest impedance-related signals and electrocardiogram (ECG) signals into digital signals. The analog-to-digital converter (ADC) synchronously samples four channel signals: Z0&RESP, ΔZ, dZ / dt, and ECG.

6. The hemodynamic detection system according to any one of claims 1 to 5, characterized in that, The system also includes a display module, a storage module, wired devices, and wireless devices; the microcontroller module transmits multi-channel chest impedance-related signals and electrocardiogram signals to the display module, storage module, wired devices, and wireless devices for display, storage, and processing, and reads data stored in the storage module and receives instructions from the wired devices and wireless devices.

7. The hemodynamic detection system according to any one of claims 1 to 5, characterized in that, The detection method of this system is as follows: the corresponding signals are denoised based on the time-frequency characteristics of the multi-channel chest impedance correlation signal and the electrocardiogram signal, respiratory interference is suppressed by the correlation between the multi-channel chest impedance correlation signal and the electrocardiogram signal, and the characteristic parameters of the corresponding signals are extracted by combining the time-series correlation between the multi-channel chest impedance correlation signal and the electrocardiogram signal.

8. The hemodynamic detection system according to claim 7, characterized in that, A digital low-pass filter was used to remove high-frequency noise from the multi-channel chest impedance-related signal and the electrocardiogram (ECG) signal. An adaptive filtering algorithm was used to suppress baseline drift caused by respiration in the chest impedance change signal ΔZ, the differential chest impedance change signal dZ / dt, and the ECG signal using the respiratory signal RESP.

9. The hemodynamic detection system according to claim 7, characterized in that, From a physiological perspective, we analyze the electrophysiological and temporal characteristics of the heart and their corresponding time features. By using time-domain sliding windowing, zero-crossing detection, VMD decomposition, and main frequency reconstruction, we extract the characteristic parameters of the electrocardiogram signal, such as P, QRS, and T wave peak points.

10. The hemodynamic detection system according to claim 7, characterized in that, By combining the differential signal of chest impedance change with the electrocardiogram signal, the characteristic points A, B, C, X, Y, O, and E of the differential signal of chest impedance change are detected from the signal timing relationship reflected by the electromechanical characteristics of the human heart's functional structure, and then the human hemodynamic parameters are analyzed and obtained.

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