A non-invasive monitoring method of lung function status based on dielectric constant measurement

Abstract

The present invention relates to a non-invasive monitoring method of lung function status based on dielectric constant measurement, and belongs to the field of bioelectrical engineering. The method comprises the following steps: S1: placing two electrodes including a resin pad dielectric contact layer between the fifth and sixth ribs of the chest and back of a subject, and measuring the dielectric constant signal of the chest of the subject; S2: performing analog-to-digital conversion on the analog signal of the measurement node constant to obtain a digital signal of the dielectric constant of the chest; S3: performing signal filtering and signal correction on the digital signal of the dielectric constant; S4: extracting the signal reference characteristic value through the unified dielectric constant signal of the chest tissue. It can measure the change of lung gas volume and the change of lung function at the same time, and the hardware structure is simple, and there is no need to consider the influence of contact impedance on the measurement stability, thereby improving the accuracy of the measurement.

Description

Technical Field

[0001] The invention belongs to the field of bioelectrical engineering and relates to a non-invasive monitoring method of lung function status based on dielectric constant measurement. Background Art

[0002] The detection and monitoring of lung function status plays an important role in the respiratory management of patients. Non-invasive and complete bedside assessment of respiratory status is of great significance for patients to assess the severity of the disease and the relief of the disease, as well as the response to drug intervention. It is also particularly useful for guiding mechanical respiratory support. Measuring lung mechanics and lung volumes can provide other valuable information about global lung function.

[0003] At present, the traditional non-invasive monitoring of lung function status mainly uses the differential pressure flow sensor measurement method connected to the respiratory cannula and the resistance volume plethysmography method that does not affect the respiratory airflow. The differential pressure flow sensor measurement method measures the flow and volume of the gas exhaled or inhaled by the patient through the differential pressure flow sensor, and analyzes the lung ventilation indicators of human respiratory physiology according to the time-volume curve and the flow-volume curve, such as slow vital capacity, spontaneous ventilation and forced vital capacity. According to the laws of physics, the differential pressure measurement pulmonary function tester assumes that the fluid flow rate at a certain moment is Q, and the volume of the fluid flowing in a certain time t is V, then V = ∫Qdt or Q = dV / dt; and the inspiration / expiration capacity V can be calculated from the fluid flow rate Q flowing through the cross-sectional area A and the inspiration / expiration time t. Although commercially available pulmonary function monitoring devices that use this technology are very popular, interpreting the data collected using this device requires a thorough understanding of the physiological, clinical, and technical aspects of the measurement. In addition, this bedside pulmonary function monitoring device only provides a rapid assessment of respiratory mechanics and cannot measure some pulmonary functional changes. It also requires the placement of an airflow sensor in the subject's ventilator airway, which may hinder the subject's normal breathing and cause inaccurate assessment results.

[0004] Resistance volume volumography is a method of injecting 1-5mA current from the surface of the human chest cavity through a pair of electrodes using a four-electrode method, and another pair of measuring electrodes measuring the voltage change, calculating the change in the resistance value of exhalation and inspiration, and analyzing the change in lung gas volume and lung function according to the characteristics of the resistance change curve. For the change in respiratory tidal volume of 100-2500mL, the calculated value is very close to the volume recorded on the spirometer. This technology will eliminate carbon dioxide absorbents, nose clips, and conventional airway obstacles, and has sufficient frequency response under normal test conditions. Although resistance volume volumography does not affect the respiratory airway, resistance volume volumography requires sticking measuring electrodes on the body surface, and there is contact impedance between the electrodes and the skin, which has a greater impact on the measured value. During tidal breathing, the movement of the chest cavity will cause unstable electrode contact, resulting in inconsistency in the resistance measurement results, making it difficult to obtain good impedance measurement results. In order to reduce the contact impedance, the four-electrode method used has reduced the impact of the contact impedance on the measurement to a certain extent, but there is still contact impedance and the introduction of more electrodes increases the complexity of the measurement. Moreover, the air inhaled by the lungs is almost an insulator, and the chest impedance value is relatively large. Measuring the resistance value has high requirements on hardware design, such as the constant current source, which leads to high cost of the monitoring device.

[0005] At present, there are mainly the following methods for non-invasive monitoring of lung function. ① The differential pressure flow sensor measurement method, its principle is to measure the pressure changes in the respiratory tidal process through the air pressure sensor. Currently, this technology is widely used in commercial products. Its advantages mainly lie in its simple principle and wide range of applications. However, the presence of the air pressure sensor may hinder airway breathing, and it can only perform a rapid assessment of respiratory mechanics; ② Respiratory induction volume tracing method, its principle is to detect the change in inductance of the resonant circuit caused by the change in the cross-sectional area of ​​the coil wrapped around the surface of the chest and abdominal cavity caused by the lateral movement of the chest and abdominal cavity, thereby causing the change in the amplitude of the resonant oscillation to change with the respiratory volume. It can obtain more accurate chest and abdominal respiratory movement conditions than impedance respiratory volume tracing, has strong anti-interference ability, and is suitable for dynamic monitoring of lung function status, but can only obtain changes in respiratory volume, and cannot distinguish when there are organic lesions in the chest cavity, and is not suitable for some Inaccurate measurements may occur in subjects with mild chest deformities; ③ Electromagnetic induction plethysmography uses the basic principle of electromagnetic induction to measure chest and abdominal respiratory movements. An insulating coil bent into a certain collision is used as a signal pickup. The coil is wrapped around the cross-section of the object being measured, and the change in chest cross-sectional area is measured using an external magnetic field. There is a contradiction between high signal-to-noise ratio and low system power consumption. At the same time, chest and abdominal signals also have coupling interference; ④ The basic principle of resistance plethysmography uses the quadrupole method to measure chest resistance. The lung function status is evaluated through resistance measurement curve analysis, which can obtain both lung gas volume information and lung tissue function change information. However, there are problems such as high difficulty in designing the constant current source required for resistance measurement and a large impact of contact resistance on monitoring accuracy, which makes it difficult to meet actual clinical needs.

[0006] Among the existing lung function status monitoring methods, the differential pressure flow sensor measurement method that uses non-electrical parameters as the measurement medium calibrates the lung gas volume measurement information, but it is insufficient for lung function monitoring. Respiratory induction plethysmography and electromagnetic induction plethysmography can only measure gas volume and are very sensitive to the sensor placement. Resistance plethysmography has the problem that contact resistance affects measurement stability, and air is almost an insulator, making resistance measurement inconvenient. Therefore, there is an urgent need for a status monitoring method that can measure changes in lung gas volume and monitor functional changes in chest tissue at the same time, solve the problem of complex hardware circuit design and the need to consider contact impedance, and improve the sensitivity and clinical practicality of lung function status monitoring. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a non-invasive monitoring method of lung function status based on dielectric constant measurement. To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A non-invasive monitoring method for lung function status based on dielectric constant measurement, the method comprising the following steps:

[0009] S1: placing two electrodes including a resin pad dielectric contact layer between the fifth and sixth ribs on the front chest and back of the subject, and measuring the dielectric constant signal of the subject's chest;

[0010] S2: converting the analog signal of the measurement node constant into a digital signal of the chest dielectric constant;

[0011] S3: Perform signal filtering and signal correction on the dielectric constant digital signal;

[0012] S4: Extract signal reference eigenvalues ​​through the unified dielectric constant signal of chest tissue.

[0013] Optionally, S1 specifically includes: placing electrodes on a resin pad, the dielectric constant of the resin pad is known, placing two electrodes on the chest and back of the subject respectively, and measuring the capacitance value between the electrode plates through an AC bridge;

[0014] The capacitance value is measured using the two-electrode method. The electrode plates are not in direct contact with the chest, but are connected through a resin pad. The thickness of the resin pad is known, and the dielectric constant is known. The capacitance value between the plates is measured using an AC bridge.

[0015] The dielectric constant characterizes the ability of a material to allow an electric field to pass through it;

[0016] The unit volume electric polarization vector P is defined as the number of dipoles per unit volume, where v is the unit volume, N is the number of electric dipoles per unit volume, and p i is the polarization vector of a single dipole:

[0017]

[0018] The electric flux D0 in space is expressed as, ε0 is the dielectric constant in vacuum, and E0 is the electric field strength in space:

[0019] D0=ε0E0 (2)

[0020] ε0 is the dielectric constant in vacuum, and the electric energy in the medium is expressed as:

[0021] D=ε0E0+P (3)

[0022] When the electric field is not strong, there is a simple linear relationship between the electric polarization vector and the electric field:

[0023] P=χε0E0 (4)

[0024] χ is the electric susceptibility, and the final electric flux D is expressed as:

[0025] D=ε0(1+χ)E0 (5)

[0026] Right now:

[0027] D=εE0 (6)

[0028] ε=ε0ε r (7)

[0029] ε r =1+χ (8)

[0030] ε r is the relative dielectric constant. When there is only air between two parallel plates, the capacitance is expressed as:

[0031] C1=C0+C f +C d (9)

[0032] C0 represents the capacitance generated by vacuum, C f It represents the capacitance generated by the edge effect, C d It represents the distributed capacitance. When the medium to be measured is not in contact with the plate:

[0033] C2=C m +C f +C d (10)

[0034] C m It indicates the new capacitance generated after the dielectric medium is added;

[0035] The capacitance in a vacuum is:

[0036]

[0037] S represents the plate area, D represents the distance between the two plates, and after adding the resin pad dielectric medium, ε r1 is the dielectric constant of the resin pad, and the capacitance expression is:

[0038]

[0039] in:

[0040] C m =C2-C1+C0 (13)

[0041] The dielectric constant of the human chest cavity to be measured is:

[0042]

[0043] The error in measurement comes from the measurement of chest thickness. Assuming the actual chest thickness is t, and the thickness with error is t', the error of the measured dielectric constant is:

[0044]

[0045] Optionally, S2 specifically includes: converting the dielectric constant information collected by S1 from an analog signal to a digital signal, converting the time-continuous and amplitude-continuous analog signal to a time-discrete and amplitude-discrete digital signal, through a sampling, holding, quantization and encoding process.

[0046] Optionally, S3 is specifically:

[0047] The signal after S2 conversion sets the maximum and minimum values ​​of the signal, removes abnormal values, and uses a specific filtering algorithm to filter the signal to obtain a stable and clear waveform; when the signal has a slight overall drift due to disturbance, the signal is corrected by multiplying it by a certain set coefficient.

[0048] Optionally, the S4 is specifically:

[0049] Through simulation, the size and distribution of the dielectric constant of the chest cavity when the chest cavity is in different states of respiratory tide are determined. According to the dielectric constant value at this time, it is determined that the respiratory state is not the reference value at the moment, and the dielectric constant waveform characteristics of the respiratory process are extracted. The respiratory state is determined according to the waveform characteristics; the dielectric constant measurement characteristic curve when different lesions exist in the chest cavity is simulated, and the reference characteristic value of the dielectric constant when different lesions of the lungs are determined;

[0050] The reference values ​​of dielectric constants of different lung tissues are as follows:

[0051] At a frequency of 1000 Hz, the dielectric constant of the heart is 352850, the dielectric constant of the spine is 2702, the dielectric constant of the deflated lung is 252050, and the dielectric constant of the inflated lung is 141510;

[0052] At a frequency of 1585 Hz, the dielectric constant of the heart is 280860, the dielectric constant of the spine is 2013, the dielectric constant of the deflated lung is 183070, and the dielectric constant of the inflated lung is 97700;

[0053] At a frequency of 2512 Hz, the dielectric constant of the heart is 213770, the dielectric constant of the spine is 1430, the dielectric constant of the deflated lung is 124820, and the dielectric constant of the inflated lung is 64862;

[0054] At a frequency of 3981 Hz, the dielectric constant of the heart is 153690, the dielectric constant of the spine is 999, the dielectric constant of the deflated lung is 81752, and the dielectric constant of the inflated lung is 41850;

[0055] At a frequency of 6310 Hz, the dielectric constant of the heart is 105290, the dielectric constant of the spine is 708, the dielectric constant of the deflated lung is 52691, and the dielectric constant of the inflated lung is 26731;

[0056] At a frequency of 10,000 Hz, the dielectric constant of the heart is 70,054, the dielectric constant of the spine is 522, the dielectric constant of the deflated lung is 34,044, and the dielectric constant of the inflated lung is 17,174;

[0057] At a frequency of 15849 Hz, the dielectric constant of the heart is 46157, the dielectric constant of the spine is 404, the dielectric constant of the deflated lung is 22305, and the dielectric constant of the inflated lung is 11212;

[0058] At a frequency of 25119 Hz, the dielectric constant of the heart is 30566, the dielectric constant of the spine is 329, the dielectric constant of the deflated lung is 14912, and the dielectric constant of the inflated lung is 7478;

[0059] At a frequency of 39811 Hz, the dielectric constant of the heart is 20534, the dielectric constant of the spine is 281, the dielectric constant of the deflated lung is 10202, and the dielectric constant of the inflated lung is 5110;

[0060] At a frequency of 63096 Hz, the dielectric constant of the heart is 14064, the dielectric constant of the spine is 250, the dielectric constant of the deflated lung is 7154, and the dielectric constant of the inflated lung is 3583;

[0061] At a frequency of 100,000 Hz, the dielectric constant of the heart is 9846, the dielectric constant of the spine is 228, the dielectric constant of the deflated lung is 5145, and the dielectric constant of the inflated lung is 2581;

[0062] At a frequency of 158490 Hz, the dielectric constant of the heart is 7049, the dielectric constant of the spine is 211, the dielectric constant of the deflated lung is 3794, and the dielectric constant of the inflated lung is 1914;

[0063] At a frequency of 251190 Hz, the dielectric constant of the heart is 5148, the dielectric constant of the spine is 197, the dielectric constant of the deflated lung is 2855, and the dielectric constant of the inflated lung is 1462;

[0064] At a frequency of 398110 Hz, the dielectric constant of the heart is 3800, the dielectric constant of the spine is 182, the dielectric constant of the deflated lungs is 2167, and the dielectric constant of the inflated lungs is 1147;

[0065] At a frequency of 630960 Hz, the dielectric constant of the heart is 2780, the dielectric constant of the spine is 166, the dielectric constant of the deflated lung is 1623, and the dielectric constant of the inflated lung is 917;

[0066] At a frequency of 1000000 Hz, the dielectric constant of the heart is 1967, the dielectric constant of the spine is 145, the dielectric constant of the deflated lungs is 1171, and the dielectric constant of the inflated lungs is 733.

[0067] Optionally, S4 also includes S5: monitoring and analyzing the lung function status of the subject according to the node constant signal and the reference characteristic value; comparing the dielectric constant values ​​of the human respiratory tide at different stages and the dielectric constant values ​​when the lung function is affected by different diseases by measuring the unified dielectric constant value of the human chest cavity, and establishing a corresponding relationship with the human lung respiratory function status according to the dielectric constant reference value determined by S4; when applied, first measure the dielectric constant value of the human body in different respiratory states, and compare it with the dielectric constant reference value determined by S4, and if it is within the range of the dielectric constant reference value of a certain stage of the respiratory state, it is determined that the lung respiratory state of the subject is in this stage; if the characteristics of the respiratory measurement dielectric constant curve are consistent with the characteristics of the stored dielectric constant measurement curve of a subject with a certain lung abnormality, it is determined that the subject is suspected of having such a lung abnormality, thereby determining the subject's lung respiratory function status through the dielectric constant measurement information.

[0068] The beneficial effect of the present invention is that: the present method is to analyze the shortcomings of the existing lung function state detection method, and on the theoretical basis of studying the dielectric properties of the various parts of the human chest tissue and the whole under different excitation amplitude frequencies, and the dielectric properties of the tissue after functional changes, the non-contact electrode method is used to measure the human chest capacitance, and the chest capacitance digital signal is obtained by analog-to-digital conversion of the measured capacitance signal, and the capacitance signal is converted into a chest unified dielectric constant signal after signal processing, combined with the research basis of the dielectric properties of the chest tissue structure, theoretical analysis is performed to obtain the human chest function state information, and a lung function monitoring method based on the chest dielectric constant information is proposed to reflect the respiratory function state. The method can measure the change of lung gas volume and the change of lung function at the same time. At the same time, the hardware structure is simple, and there is no need to consider the influence of contact impedance on the measurement stability, which improves the accuracy of measurement, ensures the effectiveness and practicality of lung function state monitoring, and greatly promotes the clinical promotion and application of lung function monitoring equipment based on electrical parameter media.

[0069] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0071] Figure 1 It is a flow chart of the present invention;

[0072] Figure 2 Schematic diagram for non-contact measurement of chest dielectric constant;

[0073] Figure 3 A diagram of the lung inhalation state inferred from known measured dielectric constant values ​​for the application of the present invention simulation;

[0074] Figure 4 A diagram of the lung exhalation state inferred from known measured dielectric constant values ​​for the application of the present invention simulation;

[0075] Figure 5 Measure the dielectric constant value for the simulation. DETAILED DESCRIPTION

[0076] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0077] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0078] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0079] like Figure 1 As shown, the present invention proposes a non-invasive monitoring method for lung function status based on dielectric constant measurement.

[0080] (1) Non-contact measurement of chest dielectric constant signal

[0081] like Figure 2 As shown, the electrodes are placed on a resin pad whose dielectric constant is known and close to that of air. Two electrodes are respectively placed on the chest and back of the subject, and the capacitance between the electrode plates is measured using an AC bridge.

[0082] The invention is characterized in that: the capacitance value is measured by a two-electrode method, the electrode plates are not in direct contact with the chest, but are connected through a resin pad, the thickness of the resin pad is known, the dielectric constant is known, and the capacitance value between the plates is measured through an AC bridge.

[0083] The dielectric constant characterizes the ability of a material to allow an electric field to pass through it. The dielectric constant of biological tissue is a core parameter in the study of bioelectromagnetics. The dielectric constant of biological tissue is related to the polarization characteristics under the action of an external electric field.

[0084] The unit volume electric polarization vector P is defined as the number of dipoles per unit volume, where v is the unit volume, N is the number of electric dipoles per unit volume, and p i is the polarization vector of a single dipole:

[0085]

[0086] The electric flux D0 in space is expressed as, ε0 is the dielectric constant in vacuum, and E0 is the electric field strength in space:

[0087] D0=ε0E0 (2)

[0088] ε0 is the dielectric constant in vacuum, and the electric energy in the medium is expressed as:

[0089] D=ε0E0+P (3)

[0090] When the electric field is not strong, there is a simple linear relationship between the electric polarization vector and the electric field:

[0091] P=χε0E0 (4)

[0092] χ is the electric susceptibility, and the final electric flux D is expressed as:

[0093] D=ε0(1+χ)E0 (5)

[0094] Right now:

[0095] D=εE0 (6)

[0096] ε=ε0ε r (7)

[0097] ε r =1+χ (8)

[0098] ε r is the relative dielectric constant. When there is only air between two parallel plates, the capacitance is expressed as:

[0099] C1=C0+C f +C d (9)

[0100] C0 represents the capacitance generated by vacuum, C f It represents the capacitance generated by the edge effect, C d It represents the distributed capacitance. When the medium to be measured is not in contact with the plate:

[0101] C2=Cm +C f +C d (10)

[0102] C m It indicates the new capacitance generated after the dielectric medium is added;

[0103] The capacitance in a vacuum is:

[0104]

[0105] S represents the plate area, D represents the distance between the two plates, and after adding the resin pad dielectric medium, ε r1 is the dielectric constant of the resin pad, and the capacitance expression is:

[0106]

[0107] in:

[0108] C m =C2-C1+C0 (13)

[0109] The dielectric constant of the human chest cavity to be measured is:

[0110]

[0111] The error in measurement comes from the measurement of chest thickness. Assuming the actual chest thickness is t, and the thickness with error is t', the error of the measured dielectric constant is:

[0112]

[0113] (2) Analog-to-digital conversion of dielectric constant measurement signal

[0114] The collected dielectric constant information is converted from an analog signal to a digital signal, and the time-continuous and amplitude-continuous analog signal is converted into a time-discrete and amplitude-discrete digital signal. After sampling, holding, quantization and encoding, the anti-interference ability of the collected dielectric constant signal is improved to ensure the stability of the signal transmission process.

[0115] (3) Dielectric constant signal filtering and correction

[0116] The converted signal has noise signals due to the interference of the clinical environment. At the same time, the slight movement of the subject's body causes a slight deviation of the signal. Through theoretical analysis and experimental research on the signal, the maximum and minimum values ​​of the signal are set, individual abnormal values ​​are removed, and the signal is filtered using a specific filtering algorithm to obtain a stable and clear waveform. When the signal has a slight overall drift due to disturbance, the signal is multiplied by a certain set coefficient to correct the signal and return it to the normal range.

[0117] (4) Extraction of reference eigenvalues ​​of chest unified dielectric constant signal

[0118] Through simulation, the size and distribution of the chest dielectric constant when the chest is in different states of respiratory tide are determined. According to the dielectric constant value at this time, it is determined that the respiratory state is not the reference value at the moment, and the dielectric constant waveform characteristics of the respiratory process are extracted, and the respiratory state is determined according to the waveform characteristics. The dielectric constant measurement characteristic curve when different lesions exist in the simulated chest cavity is used to determine the reference characteristic value of the dielectric constant when different lesions occur in the lungs. Through further clinical trials, the dielectric constant measurement curves of different patients at different breathing moments are collected, and the simulation model is calibrated to make the reference characteristic value closer to reality. Table 1 shows the dielectric constant values ​​of human chest tissue at different frequencies, which can be used as a certain standard reference. The lung function status is determined and evaluated by measuring the dielectric constant value.

[0119] Table 1 shows the reference values ​​of dielectric constants of different lung tissues determined experimentally

[0120]

[0121]

[0122] (5) Monitoring lung function status based on dielectric constant signals

[0123] By measuring the unified dielectric constant value of the human chest cavity, comparing the dielectric constant values ​​at different stages of human respiratory tide and the dielectric constant values ​​when the lung function is affected by different diseases, the respiratory function status of the subjects' lungs is determined based on the determined dielectric constant reference value.

[0124] Figure 3 and Figure 4 This is a simplified simulation diagram of the lung breathing state inferred from the known measured dielectric constant value simulated by the present invention. The light color of the lung represents the expanded lung area, and the dark color represents the deflated lung area. Figure 3 This is the inhalation stage. The three pictures from left to right represent the progress of the human body's inhalation process. The light-colored expanded lung area gradually expands, and the dark-colored deflated lung area gradually shrinks. The ventilation order of the right lung is somewhat earlier than that of the left lung. Figure 4 This is the exhalation stage. The three pictures from left to right represent that as the exhalation process progresses, the dark-colored deflated area of ​​the lung gradually expands, and the light-colored expanded area of ​​the lung gradually shrinks. The ventilation order of the right lung is still ahead of the left lung.

[0125] Figure 5 To see the dielectric constant value measured in the simulation.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A non-invasive monitoring method for lung function status based on dielectric constant measurement, characterized in that: The method comprises the following steps: S1: placing two electrodes including a resin pad dielectric contact layer between the fifth and sixth ribs on the front chest and back of the subject, and measuring the dielectric constant signal of the subject's chest; S2: converting the analog signal of the measurement node constant into a digital signal of the chest dielectric constant; S3: Perform signal filtering and signal correction on the dielectric constant digital signal; S4: extracting signal reference characteristic values ​​through the unified dielectric constant signal of chest tissue; S1 specifically includes: placing electrodes on a resin pad, the dielectric constant of which is known, placing two electrodes on the chest and back of the subject respectively, and measuring the capacitance between the electrode plates by an AC bridge; The capacitance value is measured using the two-electrode method. The electrode plates are not in direct contact with the chest, but are connected through a resin pad. The thickness of the resin pad is known, and the dielectric constant is known. The capacitance value between the plates is measured using an AC bridge. The dielectric constant characterizes the ability of a material to allow an electric field to pass through it; The unit volume electric polarization vector P is defined as the number of dipoles per unit volume, where v is the unit volume, N is the number of electric dipoles per unit volume, and p i is the polarization vector of a single dipole: The electric flux D0 in space is expressed as, ε0 is the dielectric constant in vacuum, and E0 is the electric field strength in space: D0=ε0E0(1.2) ε0 is the dielectric constant in vacuum, and the electric energy in the medium is expressed as: D=ε0E0+P(1.3) When the electric field is not strong, there is a simple linear relationship between the electric polarization vector and the electric field: P = χε0E0(1.4) χ is the electric susceptibility, and the final electric flux D is expressed as: D=ε0(1+χ)E0(1.5) Right now: D=εE0(1.6) e=e0e r (1.7) e r =1+x(1.8) ε r is the relative dielectric constant. When there is only air between two parallel plates, the capacitance is expressed as: C1=C0+C f +C d (1.9) C0 represents the capacitance generated by vacuum, C f It represents the capacitance generated by the edge effect, C d It represents the distributed capacitance. When the medium to be measured is not in contact with the plate: C2=C m +C f +C d (1.10) C m It indicates the new capacitance generated after the dielectric medium is added; The capacitance in a vacuum is: S represents the plate area, D represents the distance between the two plates, and after adding the resin pad dielectric medium, ε r1 is the dielectric constant of the resin pad, and the capacitance expression is: in: C m =C2-C1+C0(1.13) The dielectric constant of the human chest cavity to be measured is: The error in measurement comes from the measurement of chest thickness. Assuming the actual chest thickness is t, and the thickness with error is t', the error of the measured dielectric constant is:

2. A non-invasive monitoring method for lung function status based on dielectric constant measurement according to claim 1, characterized in that: The S2 is specifically: converting the dielectric constant information collected by S1 from an analog signal to a digital signal, converting the time-continuous and amplitude-continuous analog signal into a time-discrete and amplitude-discrete digital signal, through a sampling, holding, quantization and encoding process.

3. The non-invasive monitoring method of lung function status based on dielectric constant measurement according to claim 1, characterized in that: The S4 is specifically: Through simulation, the size and distribution of the dielectric constant of the chest cavity when the chest cavity is in different states of respiratory tide are determined. According to the dielectric constant value at this time, it is determined that the respiratory state is not the reference value at the moment, and the dielectric constant waveform characteristics of the respiratory process are extracted. The respiratory state is determined according to the waveform characteristics; the dielectric constant measurement characteristic curve when different lesions exist in the chest cavity is simulated, and the reference characteristic value of the dielectric constant when different lesions of the lungs are determined; The reference values ​​of dielectric constants of different lung tissues are as follows: At a frequency of 1000 Hz, the dielectric constant of the heart is 352850, the dielectric constant of the spine is 2702, the dielectric constant of the deflated lung is 252050, and the dielectric constant of the inflated lung is 141510; At a frequency of 1585 Hz, the dielectric constant of the heart is 280860, the dielectric constant of the spine is 2013, the dielectric constant of the deflated lung is 183070, and the dielectric constant of the inflated lung is 97700; At a frequency of 2512 Hz, the dielectric constant of the heart is 213770, the dielectric constant of the spine is 1430, the dielectric constant of the deflated lung is 124820, and the dielectric constant of the inflated lung is 64862; At a frequency of 3981 Hz, the dielectric constant of the heart is 153690, the dielectric constant of the spine is 999, the dielectric constant of the deflated lung is 81752, and the dielectric constant of the inflated lung is 41850; At a frequency of 6310 Hz, the dielectric constant of the heart is 105290, the dielectric constant of the spine is 708, the dielectric constant of the deflated lung is 52691, and the dielectric constant of the inflated lung is 26731; At a frequency of 10,000 Hz, the dielectric constant of the heart is 70,054, the dielectric constant of the spine is 522, the dielectric constant of the deflated lung is 34,044, and the dielectric constant of the inflated lung is 17,174; At a frequency of 15849 Hz, the dielectric constant of the heart is 46157, the dielectric constant of the spine is 404, the dielectric constant of the deflated lung is 22305, and the dielectric constant of the inflated lung is 11212; At a frequency of 25119 Hz, the dielectric constant of the heart is 30566, the dielectric constant of the spine is 329, the dielectric constant of the deflated lung is 14912, and the dielectric constant of the inflated lung is 7478; At a frequency of 39811 Hz, the dielectric constant of the heart is 20534, the dielectric constant of the spine is 281, the dielectric constant of the deflated lung is 10202, and the dielectric constant of the inflated lung is 5110; At a frequency of 63096 Hz, the dielectric constant of the heart is 14064, the dielectric constant of the spine is 250, the dielectric constant of the deflated lung is 7154, and the dielectric constant of the inflated lung is 3583; At a frequency of 100,000 Hz, the dielectric constant of the heart is 9846, the dielectric constant of the spine is 228, the dielectric constant of the deflated lung is 5145, and the dielectric constant of the inflated lung is 2581; At a frequency of 158490 Hz, the dielectric constant of the heart is 7049, the dielectric constant of the spine is 211, the dielectric constant of the deflated lung is 3794, and the dielectric constant of the inflated lung is 1914; At a frequency of 251190 Hz, the dielectric constant of the heart is 5148, the dielectric constant of the spine is 197, the dielectric constant of the deflated lung is 2855, and the dielectric constant of the inflated lung is 1462; At a frequency of 398110 Hz, the dielectric constant of the heart is 3800, the dielectric constant of the spine is 182, the dielectric constant of the deflated lungs is 2167, and the dielectric constant of the inflated lungs is 1147; At a frequency of 630960 Hz, the dielectric constant of the heart is 2780, the dielectric constant of the spine is 166, the dielectric constant of the deflated lung is 1623, and the dielectric constant of the inflated lung is 917; At a frequency of 1000000 Hz, the dielectric constant of the heart is 1967, the dielectric constant of the spine is 145, the dielectric constant of the deflated lungs is 1171, and the dielectric constant of the inflated lungs is 733.

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