CN117617937A - Hemodynamic detection system and method based on fewer electrodes and signal correlation - Google Patents
Hemodynamic detection system and method based on fewer electrodes and signal correlation Download PDFInfo
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Abstract
The invention relates to a hemodynamic detection system and method based on fewer electrodes and signal correlation, and belongs to the technical field of biomedical signal detection and processing. The system comprises a microcontroller module, a chest impedance excitation module, a chest impedance signal detection module, an electrocardiosignal detection module, a display module, a storage module, wired equipment, wireless equipment and four electrodes. The system only uses four electrodes to realize synchronous measurement of thoracic cavity basic impedance signals, thoracic impedance change differential signals, electrocardiosignals and respiratory signals, optimizes the problem of complex wiring in current thoracic impedance and electrocardiograph detection, combines the physiological time sequence relationship among signals to extract relevant characteristic parameters of hemodynamics, and has the advantages of accuracy, simplicity, high efficiency and low cost. The invention is beneficial to research and development of portable noninvasive hemodynamic detection equipment, cardiac function detection equipment and corresponding wearable equipment, and improves the clinical applicability of the equipment.
Description
Technical Field
The invention belongs to the technical field of biomedical signal detection and processing, and relates to a hemodynamic detection system and method based on fewer electrodes and signal correlation.
Background
In recent years, along with the rapid increase of the number of cardiovascular patients, the heart function analysis method and equipment based on the chest impedance signals and the electrocardiosignals have important value for diagnosing and treating cardiovascular diseases. Clinically, chest impedance signals and electrocardiographic signals are commonly used for noninvasive hemodynamic detection and cardiac functional analysis and diagnosis.
Conventional methods require the use of at least 7 electrodes to simultaneously detect the thoracic impedance signal and the electrocardiographic signal, with 4 electrodes dedicated to acquiring the thoracic impedance signal and 3 electrodes dedicated to acquiring the electrocardiographic signal, which results in a complex wiring between the subject and the detection device, a large number of electrode pads, and poor comfort, ease of measurement, and portability of the device for the subject. It is also rare to use a portable or wearable device that uses fewer electrodes to detect both thoracic impedance signals and electrocardiographic signals.
At present, the common noninvasive hemodynamic detection equipment and cardiac function detection equipment on the market often need more electrodes and lead wires to be connected with a human body, and the equipment is large in size, so that the application range of the equipment is limited, the equipment is high in price, and popularization of community and family medical treatment is not facilitated.
In the field of biomedical signal processing, when a certain physiological signal characteristic is positioned, a corresponding characteristic point extraction strategy is usually formulated only from the time-frequency domain characteristics of the physiological signal, and the method is easily influenced by factors such as signal fluctuation or individual difference to cause positioning errors, so that the robustness is not high.
Thus, there is a need for a portable and accurate hemodynamic detection apparatus.
Disclosure of Invention
In view of the above, the invention aims to provide a hemodynamic detection system and a hemodynamic detection method based on fewer electrodes and signal correlation, which solve the problems of complex measurement wiring, high detection cost, poor equipment portability and large parameter calculation error caused by inaccurate positioning of signal characteristic points in the existing hemodynamic detection equipment and cardiac function analysis and diagnosis equipment.
In order to achieve the above purpose, the present invention provides the following technical solutions:
1. a hemodynamic detection system based on fewer electrodes and signal correlation comprises a microcontroller module, a chest impedance excitation module, a chest impedance signal detection module, an electrocardiosignal detection module, a display module, a storage module, wired equipment, wireless equipment and four electrodes (E1-E4).
The microcontroller module is connected with the chest impedance excitation module, the chest impedance signal detection module, the electrocardiosignal detection module, the display module, the storage module, the wired equipment and the wireless equipment;
the four electrodes are in contact with the skin of the human body, wherein the electrode E1 is only connected with the chest impedance excitation module and belongs to an excitation electrode; the electrodes (E2, E3) belong to measuring electrodes and are only connected with the chest impedance signal detection module and the electrocardiosignal detection module; the electrode E4 is a grounding electrode and is connected with the chest impedance excitation module, the chest impedance signal detection module, the electrocardiosignal detection module and the microcontroller module, and is used as an excitation electrode and a human body to form a current loop, and is also used as a measurement electrode to provide a voltage reference point for the chest impedance signal detection module and the electrocardiosignal detection module; the measuring electrodes (E2, E3) are respectively arranged at the cervical root and the xiphoid process of the chest of the human body, the exciting electrode E1 which is only connected with the chest impedance exciting module is arranged at the position 3cm above the measuring electrode at the cervical root, and the grounding electrode E4 is arranged at the position 3cm below the measuring electrode at the xiphoid process.
The chest impedance excitation module is used for providing an excitation signal.
The chest impedance signal detection module is used for conditioning multichannel chest impedance related signals and outputting signals Z containing chest fundamental impedance 0 And a mixed signal Z of a respiratory signal RESP 0 &RESP, thoracic impedance change signal Δz, and thoracic impedance change differential signal dZ/dt;
the electrocardiosignal detection module is used for conditioning electrocardiosignals and outputting single-lead electrocardiosignals ECG.
The microcontroller module uses a digital filter to mix the signal Z 0 &RESP separation is carried out to obtain a thoracic cavity basic impedance signal Z 0 And respiratory signal RESP, and denoise the multi-channel chest impedance related signal and electrocardiosignal obtained by using a digital filter; the microcontroller module also provides a sine wave current signal to the thoracic impedance excitation module.
The microcontroller module transmits the multichannel chest impedance related signals and the electrocardiosignals to the display module, the storage module, the wired equipment and the wireless equipment for displaying, storing and processing, reads the data stored in the storage module and receives instructions from the wired equipment and the wireless equipment.
Preferably, the chest impedance signal detection module comprises a voltage follower, an instrument amplifier, a demodulation circuit, a high-pass filter circuit, a low-pass filter circuit, a chest impedance signal amplification and filter module, a differential circuit and a voltage lifting circuit; the electrocardiosignal detection module comprises a voltage follower, an instrument amplifier, a low-pass filter circuit, an electrocardiosignal amplifying and filtering module and a voltage lifting circuit;
the voltage signals collected by the measuring electrodes (E2, E3) are firstly input into a voltage follower, then the differential voltage between the electrode E2 and the electrode E3 is amplified by an instrument amplifier, and the output signal of the instrument amplifier is an amplified chest impedance amplitude modulation signal; and respectively inputting the chest impedance amplitude modulation signals into a high-pass filter circuit in the chest impedance signal detection module and a low-pass filter circuit in the electrocardiosignal detection module through two paths.
In the chest impedance signal detection module, a high-pass filter circuit with a cutoff frequency of 1kHz is used for removing electrocardiosignals contained in chest impedance amplitude modulation signals; then the demodulation circuit is utilized to demodulate the original chest impedance signal from the chest impedance amplitude modulation signal, including the chest fundamental impedance signal Z 0 A respiratory signal RESP and a thoracic impedance change signal Δz; secondly, dividing the original chest impedance signal into two paths of processing, and obtaining a mixed signal Z containing the chest base impedance signal and the respiratory signal by a low-pass filter circuit with the cut-off frequency of 2Hz 0 &RESP, the other path removes the direct current component in the original chest impedance signal through a high-pass filter circuit with the cut-off frequency of 1 Hz; and after passing through the thoracic impedance signal amplifying and filtering module, one path of the thoracic impedance change signal delta Z is obtained through the voltage lifting circuit, and the other path of the thoracic impedance change signal dZ/dt is obtained through the differential circuit, the low-pass filtering circuit and the voltage lifting circuit.
A low-pass filter circuit with cut-off frequency of 100Hz is used in an electrocardiosignal detection module to remove the high-frequency amplitude modulation signal; and then obtaining an electrocardiosignal ECG through an electrocardiosignal amplifying and filtering module and a voltage lifting circuit.
Preferably, the thoracic impedance signal amplifying and filtering module comprises an amplifying circuit, a low-pass filtering circuit and a 50Hz trap circuit; the electrocardiosignal amplifying and filtering module comprises a 50Hz trap circuit, a high-pass filtering circuit and an amplifying circuit.
Preferably, the chest impedance excitation module comprises a band-pass filter circuit and a voltage-controlled current source.
Preferably, the microcontroller module comprises a digital-to-analog converter DAC for generating a thoracic impedance excitation signal and an analog-to-digital converter ADC for converting the multichannel thoracic impedance-associated signal and the electrocardiographic signal into digital signals;
the analog-to-digital converter ADC outputs a signal (Z 0 &RESP, Δ Z, dZ/dt, ECG) are sampled synchronously.
2. A hemodynamic detection method based on fewer electrodes and signal correlation specifically comprises the following steps: denoising corresponding signals according to the time-frequency characteristics of the multichannel chest impedance associated signals and the electrocardiosignals, inhibiting respiratory interference by utilizing the association of the multichannel chest impedance associated signals and the electrocardiosignals, and extracting characteristic parameters of the corresponding signals by combining the time sequence association of the multichannel chest impedance associated signals and the electrocardiosignals.
Further, a digital low-pass filter is used for removing high-frequency noise in the multichannel chest impedance related signal and the electrocardiosignal; an adaptive filtering algorithm is used to suppress the chest impedance change signal deltaz, the chest impedance change differential signal dZ/dt and the respiratory-induced baseline wander in the electrocardiographic signal ECG using the respiratory signal RESP.
Further, the electrophysiological and time phase characteristics of the heart are analyzed according to the physiological angle, and the electrocardiosignal characteristic parameters P, QRS and T peak value points are extracted through a time domain sliding window and zero crossing detection method, a VMD decomposition method and a main frequency reconstruction method.
Further, the characteristic point A, B, C, X, Y, O, E of the differential signal of the chest impedance change is detected from the signal timing relationship represented by the electro-mechanical characteristics of the heart function structure of the human body by combining the differential signal of the chest impedance change with the electrocardiograph signal, and then the hemodynamic parameters of the human body are analyzed and obtained.
The invention has the beneficial effects that:
(1) The invention can fully utilize the electric signals detected from the human body, extract multichannel chest impedance associated signals including chest impedance base signals, chest impedance change differential signals and respiratory signals and single-lead electrocardiosignals from the signals, and 5 channels of signals in total, and combines the physiological significance and time sequence relation of the signals to formulate a method for positioning characteristic points of different signals, thereby ensuring the accuracy of calculation of hemodynamic parameters and realizing the detection and analysis functions of hemodynamics and heart functions based on the chest impedance method.
The detection system optimizes the problem of complex wiring in synchronous detection of multichannel chest impedance associated signals and electrocardiosignals, realizes simultaneous detection of chest impedance signals and electrocardiosignals by only four electrodes, and has the characteristics of simplicity and high efficiency.
(2) The measuring electrode and part of measuring devices of the system are shared in the detection of the multichannel chest impedance associated signal and the electrocardiosignal, the system has high efficiency, saves the volume and the cost, and is beneficial to the research and development of portable hemodynamic detection equipment and wearable equipment.
(3) The signal feature point positioning method related by the system of the invention combines physiological significance and the time sequence relation of related physiological signals on the basis of analyzing the time-frequency features of the signals, extracts feature parameters from various angles, and has higher accuracy.
(4) The invention has stronger applicability and potential development prospect in community and family medical treatment.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
Drawings
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
FIG. 1 is a simplified block diagram of a hemodynamic detection system based on fewer electrodes and signal correlation of the present invention;
FIG. 2 is an internal block diagram of the detection front end of the hemodynamic detection system based on fewer electrodes and signal correlation of the present invention;
FIG. 3 is a time domain waveform diagram of a detection signal of the system of the present invention;
FIG. 4 is a plot of the localization of feature points of the hemodynamic detection method of the present invention based on fewer electrodes and signal correlation;
FIG. 5 is a schematic diagram of feasibility verification for a hemodynamic detection system based on fewer electrodes and signal correlation, in an embodiment of the invention;
fig. 6 is a time domain waveform comparison of a detection signal obtained using the detection system of the present invention and using a conventional multi-electrode based synchronous measurement of thoracic impedance and electrocardiography.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1 to 6, the present invention provides a hemodynamic detection system based on fewer electrodes and signal correlation, as shown in fig. 1, the system includes a chest impedance excitation module, a chest impedance signal detection module, an electrocardiograph signal detection module, a display module, a storage module, a wired device, a wireless device, and a microcontroller module connected to both electrodes.
Referring to fig. 2, the front end of the detection system is composed of a chest impedance excitation module, a chest impedance signal detection module, an electrocardiosignal detection module, a microcontroller module and four electrodes (E1, E2, E3, E4).
The four electrodes are placed on the skin surface of a human body by using silver/silver chloride electrode plates, E1 belongs to an excitation electrode, E2 and E3 belong to measurement electrodes, E4 is a grounding electrode, and the four electrodes are used as the excitation electrode and the human body to form a current loop and also used as the measurement electrode to provide voltage reference points for chest impedance signal and electrocardiosignal detection.
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.
The DAC is used for providing sine wave voltage excitation signals, and the output frequency is 20 kHz-100 kHz, and the peak-to-peak value is 1V-3V.
The ADC is used for acquiring a mixed signal (Z) containing a thoracic cavity base impedance signal and a respiratory signal 0 &RESP), a multi-channel chest impedance-related signal including a chest impedance-varying signal (Δz), a chest impedance-varying differential signal (dZ/dt), and a single-lead electrocardiographic signal (ECG), a total of 4-channel signals.
The band-pass filter circuit in the chest impedance excitation module is used for removing direct current bias in the DAC output signal and smoothing the waveform, the passband gain is 2, and the output of the band-pass filter circuit is used as the input of the voltage-controlled current source.
The voltage-controlled current source adopts a Howlan current source, and under the input of the sine wave voltage signal frequency of 20 kHz-100 kHz and peak-to-peak value of 2V-6V, sine wave current signals with the frequency of 20 kHz-100 kHz and peak-to-peak value of 2 mA-6 mA are output between the E1 electrode and the E4 electrode.
The sine wave current signal is modulated into a voltage signal by the chest impedance change signal of the human body through the human body.
The multichannel chest impedance-related signal detection and the electrocardiosignal detection use three electrodes E2, E3 and E4.
In the chest impedance signal detection module and the electrocardiosignal detection module, firstly, the voltage of the E2 electrode and the E3 electrode is obtained by utilizing the characteristic of high input impedance of a voltage follower, then the differential voltage of the E2 electrode and the E3 electrode is amplified by utilizing the characteristics of high input impedance, high common mode rejection ratio and low noise of an instrument amplifier, the amplification factor is 10-20, and the output signal of the instrument amplifier is an amplified chest impedance amplitude modulation signal.
The chest impedance amplitude modulation signal not only comprises chest impedance information but also comprises an electrocardiosignal, and the chest impedance amplitude modulation signal is respectively input into a high-pass filter circuit in the chest impedance signal detection module and a low-pass filter circuit in the electrocardiosignal detection module through two paths.
Because the frequency range of the electrocardiosignal is mainly concentrated at 0.5-45 Hz, and the chest impedance information is contained in an amplitude-modulated signal with the frequency not less than 20kHz, a high-pass filter circuit with the cut-off frequency of 1kHz is used in the chest impedance signal detection module to remove the electrocardiosignal contained in the chest impedance amplitude-modulated signal; a low-pass filter circuit with cut-off frequency of 100Hz is used in the electrocardiosignal detection module to remove high-frequency amplitude modulation signals, and high-frequency noise can be restrained at the same time, so that the electrocardiosignal amplified by the instrument amplifier is obtained.
The demodulation circuit in the chest impedance signal detection module adopts an envelope half-wave detection circuit and is used for demodulating an original chest impedance signal from the chest impedance amplitude modulation signal, wherein the signal comprises a chest fundamental impedance signal, a respiratory signal and a chest impedance change signal.
The original chest impedance signal is divided into two paths to be processed, and a mixed signal containing a chest base impedance signal and a respiratory signal and a chest impedance change signal are obtained respectively. The method comprises the following steps:
because the thoracic cavity basic impedance signal is approximately the direct current component in the original thoracic impedance signal, the respiration signal is mainly the low-frequency component with the frequency of 0.05-2 Hz in the original thoracic impedance signal, and therefore the mixed signal containing the thoracic cavity basic impedance signal and the respiration signal is obtained by the low-pass filter circuit with the cut-off frequency of 2 Hz.
Because the frequency range of the chest impedance change signal is about 1-20 Hz, the direct current component in the original chest impedance signal is removed by the high-pass filter circuit with the cut-off frequency of 1Hz, and the respiratory disturbance with lower frequency can be effectively restrained.
The chest impedance signal amplifying and filtering module consists of an amplifying circuit, a low-pass filtering circuit and a 50Hz trap circuit.
Because the demodulated chest impedance change signal is weak and is inconvenient to collect by using the ADC directly, the chest impedance change signal is further amplified by using an amplifying circuit, and the amplification factor of the amplifying circuit is 100-200.
In the signal conditioning process, the chest impedance change signal is easily interfered by high-frequency noise and 50Hz power frequency, so that a low-pass filter circuit and a 50Hz trap circuit are used for denoising the signal to improve the signal-to-noise ratio.
The chest impedance signal amplifying and filtering module outputs a chest impedance change signal containing negative voltage, and the ADC in the microprocessor module can only collect the positive voltage signal, so that the ADC can not be directly used for collection, and the signal needs to be lifted to be above the positive voltage through the voltage lifting circuit so as to meet the input range of the ADC.
The voltage boosting circuit is realized by an adder circuit, and an output signal is positioned in a positive voltage range by adding a direct current signal to a primary signal.
The chest impedance change differential signal is obtained by the differential circuit.
Since the differentiating circuit amplifies high frequency noise, a low pass filter circuit with a cut-off frequency of 20Hz is used at the output to suppress the high frequency noise, and finally, the impedance varying differentiating signal is inputted to the ADC through the voltage boosting circuit.
The electrocardiosignals amplified by the instrument amplifier need to be further amplified and denoised to improve the signal to noise ratio, and are processed by using an electrocardiosignal amplifying and filtering module.
The electrocardiosignal amplifying and filtering module consists of a 50Hz trap circuit, a high-pass filtering circuit and an amplifying circuit.
The 50Hz trap circuit is used for suppressing power frequency noise, and the high-pass filter circuit is used for removing direct current components in the electrocardiosignals amplified by the instrument amplifier so as to ensure that the signals amplified by the amplifying circuit are not saturated and distorted, and meanwhile, the baseline drift is effectively suppressed.
The amplifying circuit in the electrocardiosignal amplifying and filtering module is used for further amplifying the electrocardiosignal so as to improve the quality of the signal acquired by the ADC, otherwise, the quality of the acquired signal is poor due to the limitation of the accuracy of the ADC, and the amplification factor of the amplifying circuit is 50-100.
And the electrocardiosignals output by the electrocardiosignal amplifying and filtering module are lifted to a positive voltage range by a voltage lifting circuit and input to the ADC.
The high-pass filter circuit and the low-pass filter circuit in the chest impedance signal detection module and the electrocardiosignal detection module both adopt second-order Butterworth filters; the 50Hz trap circuits in the chest impedance signal amplifying and filtering module and the electrocardiosignal amplifying and filtering module are double T-shaped trap circuits; the band-pass filter circuit in the chest impedance excitation module uses a second-order voltage-controlled voltage source band-pass filter.
The digital filter used for separating the chest base impedance signal and the respiratory signal from the mixed signal containing the chest base impedance signal and the respiratory signal is an IIR low-pass filter, also called a DC tracking filter, and the difference equation is y (n) =y (n-1) + [ x (n) -y (n-1)]/2 k 。
Tests under the sampling frequency of 200Hz prove that when k takes the recommended value of 9, the chest cavity basic impedance signal can be obtained from the mixed signal; when k takes the recommended value 7, a respiration signal can be obtained from the mixed signal.
The high-frequency noise in the multichannel chest impedance related signal and the electrocardiosignal can be effectively removed by using an IIR low-pass filter and a moving average filter, wherein the differential equation of the IIR low-pass filter is y (n) =y (n-1) + [ x (n) -x (n-4) ]/4, and the filter has a 50Hz notch effect when the sampling frequency is 200 Hz.
By using the acquired respiratory signal, the self-adaptive filtering algorithm can restrain baseline drift caused by respiration in the thoracic impedance change signal, the thoracic impedance change differential signal and the electrocardiosignal.
Referring to fig. 1, signals collected by the microcontroller module ADC may be sent to a wired device or a wireless device through a communication interface in a wired or wireless manner, or may be stored in a memory module connected to the microcontroller module, or may be directly displayed on a display module connected to the microcontroller module.
The microcontroller may read the data stored in the memory module and may also receive instructions from the wired or wireless device.
Referring to fig. 3, waveforms of the multichannel chest impedance related signal and the electrocardiosignal obtained by the detection system of the invention are clear.
The electrocardiosignal reflects the electrophysiological activity of the heart, the electrical activation of the normal heart starts from the sinus node, the P wave represents the activation of the atrium, the P wave is conducted to the atrioventricular node through the internode to form a PR section, the activation is downwards conducted to the left ventricle and the right ventricle through the his bundle, the left bundle branch and the right bundle branch to form a QRS wave, the depolarization is completed, the repolarization does not start to form an ST section, the ST section corresponds to the ventricular systole, the T wave then represents the closure of an arterial valve, the atrioventricular valve is opened, the ventricular diastole is symbolized, and the process corresponds to a cardiac cycle.
The chest impedance signal reflects impedance changes caused by factors such as blood vessel volume and blood flow speed changes, and when the heart contracts, blood is injected into the main artery to expand the aortic cavity, the sectional area is increased, the blood volume is increased, and the chest impedance is reduced; when the heart is relaxed, blood returns to the heart, blood volume decreases and chest impedance increases.
In the differential signal of the chest impedance change, the A wave is an atrial contraction wave, the A wave is in an atrial systole, the B point represents an aortic opening point and is a ventricular ejection starting point, the C wave is an ventricular contraction wave, the C wave is related to main and pulmonary artery ejection during ventricular contraction, the X point represents aortic valve closure, the left ventricular ejection is finished, the Y point is formed by closing the pulmonary valve, the O wave represents left ventricular valve opening, the E point is a ventricular filling point, and the process corresponds to one cardiac cycle of an electrocardiosignal.
And extracting the characteristic parameters P, QRS and T peak value points of the electrocardiosignal by using a time domain sliding window and zero crossing detection method, VMD decomposition method and main frequency reconstruction method.
The differential signal characteristic point A, B, C, X, Y, O, E of the thoracic impedance change is detected from the signal timing relationship represented by the electro-mechanical characteristics of the human heart function structure by combining the thoracic impedance change differential signal with the electrocardiographic signal.
Referring to fig. 4, the signal feature point can be accurately located by using the detection method of the present invention.
Referring to fig. 5, the thoracic impedance signal and the electrocardiographic signal are measured simultaneously by using a few-electrode detection method and a conventional multi-electrode detection method, and the signals detected by the two methods are compared through experiments to verify the feasibility of the hemodynamic detection system based on the correlation of the few electrodes and the signals.
In the experiment, an excitation current source is connected with electrodes E1 and E4, and a sine wave current excitation signal with the frequency of 40kHz and the peak-to-peak value of 2mA is injected into the chest of a human body; the fewer electrode detection module is connected with the electrodes E2, E3 and E4 and outputs a chest impedance change signal (delta Z), a chest impedance change differential signal (dZ/dt) and a single-lead Electrocardiosignal (ECG) which are 3-channel signals in total; the multi-electrode detection module is connected with electrodes E2, E3, E4, E5, E6 and E7, wherein the electrodes E2, E3 and E4 are used for detecting chest impedance signals, the electrodes E5, E6, E7 and E4 are used for detecting electrocardiosignals, and the multi-electrode detection module outputs a chest impedance change signal (delta Z), a chest impedance change differential signal (dZ/dt) and standard three-lead electrocardiosignals (ECG_I, ECG_II and ECG_III) which are 5-channel signals; and the output signals of the fewer electrode detection module and the multiple electrode detection module are transmitted to an upper computer for synchronous display.
Referring to fig. 6, there is no significant difference between the multi-channel chest impedance correlation signal detected using the present invention with the few electrodes and the conventional multi-electrode approach; the time domain feature points of the standard three-lead electrocardiosignal detected by the multi-electrode method and the electrocardiosignal detected by the low-electrode method are consistent.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (10)
1. The hemodynamic detection system based on the correlation of fewer electrodes and signals is characterized by comprising a microcontroller module, a chest impedance excitation module, a chest impedance signal detection module, an electrocardiosignal detection module and four electrodes (E1-E4);
the microcontroller module is connected with the chest impedance excitation module, the chest impedance signal detection module and the electrocardiosignal detection module;
the four electrodes are in contact with the skin of the human body, wherein the electrode E1 is only connected with the chest impedance excitation module and belongs to an excitation electrode; the electrodes (E2, E3) belong to measuring electrodes and are only connected with the chest impedance signal detection module and the electrocardiosignal detection module; the electrode E4 is a grounding electrode and is connected with the chest impedance excitation module, the chest impedance signal detection module, the electrocardiosignal detection module and the microcontroller module, and is used as an excitation electrode and a human body to form a current loop, and is also used as a measurement electrode to provide a voltage reference point for the chest impedance signal detection module and the electrocardiosignal detection module; the measuring electrodes (E2, E3) are respectively arranged at the cervical root and the xiphoid process of the chest of the human body, the exciting electrode E1 which is only connected with the chest impedance exciting module is arranged at the position 3cm above the measuring electrode at the cervical root, and the grounding electrode E4 is arranged at the position 3cm below the measuring electrode at the xiphoid process;
the chest impedance excitation module is used for providing an excitation signal;
the chest impedance signal detection module is used for conditioning multichannel chest impedance related signals and outputting signals Z containing chest fundamental impedance 0 And a mixed signal Z of a respiratory signal RESP 0 &RESP, thoracic impedance change signal Δz, and thoracic impedance change differential signal dZ/dt;
the electrocardiosignal detection module is used for conditioning electrocardiosignals and outputting single-lead electrocardiosignals ECG;
the microcontroller module uses a digital filter to mix the signal Z 0 &RESP separation is carried out to obtain a thoracic cavity basic impedance signal Z 0 And respiratory signal RESP, and denoise the multi-channel chest impedance related signal and electrocardiosignal obtained by using a digital filter; the microcontroller module also provides a sine wave current signal to the thoracic impedance excitation module.
2. The hemodynamic detection system of claim 1, wherein the chest impedance signal detection module comprises 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 filter module, a differentiation circuit, and a voltage boost circuit; the electrocardiosignal detection module comprises a voltage follower, an instrument amplifier, a low-pass filter circuit, an electrocardiosignal amplifying and filtering module and a voltage lifting circuit;
the voltage signals collected by the measuring electrodes (E2, E3) are firstly input into a voltage follower, then the differential voltage between the electrode E2 and the electrode E3 is amplified by an instrument amplifier, and the output signal of the instrument amplifier is an amplified chest impedance amplitude modulation signal; respectively inputting the chest impedance amplitude modulation signals into a high-pass filter circuit in the chest impedance signal detection module and a low-pass filter circuit in the electrocardiosignal detection module through two paths;
in the chest impedance signal detection module, a high-pass filter circuit with a cutoff frequency of 1kHz is used for removing electrocardiosignals contained in chest impedance amplitude modulation signals; then the demodulation circuit is utilized to demodulate the original chest impedance signal from the chest impedance amplitude modulation signal, including the chest fundamental impedance signal Z 0 A respiratory signal RESP and a thoracic impedance change signal Δz; secondly, dividing the original chest impedance signal into two paths of processing, and obtaining a mixed signal Z containing the chest base impedance signal and the respiratory signal by a low-pass filter circuit with the cut-off frequency of 2Hz 0 &RESP, the other path removes the direct current component in the original chest impedance signal through a high-pass filter circuit with the cut-off frequency of 1 Hz; after passing through the thoracic impedance signal amplifying and filtering module, one path of the thoracic impedance change signal delta Z is obtained through the voltage lifting circuit, and the other path of the thoracic impedance change signal delta Z/dt is obtained through the differential circuit, the low-pass filtering circuit and the voltage lifting circuit;
a low-pass filter circuit with cut-off frequency of 100Hz is used in an electrocardiosignal detection module to remove the high-frequency amplitude modulation signal; and then obtaining an electrocardiosignal ECG through an electrocardiosignal amplifying and filtering module and a voltage lifting circuit.
3. The hemodynamic detection system of claim 2, wherein the chest impedance signal amplification and filtering module includes an amplification circuit, a low pass filtering circuit, and a 50Hz trap circuit; the electrocardiosignal amplifying and filtering module comprises a 50Hz trap circuit, a high-pass filtering circuit and an amplifying circuit.
4. The hemodynamic detection system of claim 1, wherein the chest impedance excitation module comprises a bandpass filter circuit and a voltage-controlled current source.
5. The hemodynamic detection system of claim 1, wherein 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 the multichannel chest impedance correlation signal and the cardiac signal into digital signals;
the analog-to-digital converter ADC outputs a signal (Z 0 &RESP, Δ Z, dZ/dt, ECG) are sampled synchronously.
6. The hemodynamic detection system of any one of claims 1 to 5, further comprising a display module, a storage module, a wired device, and a wireless device; the microcontroller module transmits the multichannel chest impedance related signals and the electrocardiosignals to the display module, the storage module, the wired equipment and the wireless equipment for displaying, storing and processing, reads the data stored in the storage module and receives instructions from the wired equipment and the wireless equipment.
7. The hemodynamic detection system of any one of claims 1 to 5, wherein the system comprises: denoising corresponding signals according to the time-frequency characteristics of the multichannel chest impedance associated signals and the electrocardiosignals, inhibiting respiratory interference by utilizing the association of the multichannel chest impedance associated signals and the electrocardiosignals, and extracting characteristic parameters of the corresponding signals by combining the time sequence association of the multichannel chest impedance associated signals and the electrocardiosignals.
8. The hemodynamic detection system of claim 7, wherein a digital low pass filter is used to remove high frequency noise from the multichannel chest impedance correlation signal and the cardiac signal; an adaptive filtering algorithm is used to suppress the chest impedance change signal deltaz, the chest impedance change differential signal dZ/dt and the respiratory-induced baseline wander in the electrocardiographic signal ECG using the respiratory signal RESP.
9. The hemodynamic detection system of claim 7, wherein the cardiac electrophysiology and phase characteristics are analyzed for their temporal characteristics at physiological angles, and the cardiac signal characteristic parameters P, QRS, T peak points are extracted by time domain sliding window and zero crossing detection and VMD decomposition and dominant frequency reconstruction methods.
10. The hemodynamic detection system of claim 7, wherein the differential signal of thoracic impedance change is combined with an electrocardiographic signal to detect the characteristic point A, B, C, X, Y, O, E of the differential signal of thoracic impedance change from a signal timing relationship exhibited by an electro-mechanical property of a functional structure of a human heart for analysis to obtain a hemodynamic parameter of the human.
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