A method and system for detecting respiratory power based on a respiratory impedance model

Abstract

The application provides a respiratory power detection method and system based on a respiratory impedance model, and belongs to the technical field of medical instruments, and comprises the following steps: generating oscillating airflow with a frequency of 5-35 Hz through a gas oscillation source; collecting the respiratory flow signal of a subject by using a flow sensor, and collecting the airway opening pressure signal of the subject during respiration by using a pressure sensor; performing amplitude-frequency analysis on the collected flow signal and pressure signal, and calculating the respiratory impedance in the range of 5-35 Hz; combining the respiratory impedance model, estimating the model parameters, including airway resistance, airway inertia, tissue impedance and lung tissue respiratory impedance; constructing a respiratory power calculation formula based on the estimated model parameters; measuring the flow rate of normal respiration of the subject, and obtaining the respiratory power through the respiratory power calculation formula. The respiratory power calculation formula is constructed through the respiratory impedance model, and at this time, the respiratory power can be obtained only by measuring the flow rate of normal respiration of the subject.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of medical devices, and particularly relates to a respiratory power detection method and system based on a respiratory impedance model. BACKGROUND

[0002] Diaphragm function assessment is an important tool in the fields of respiratory medicine, rehabilitation medicine and critical care medicine throughout the whole process of disease prevention, diagnosis and rehabilitation. As the most important respiratory muscle, diaphragm dysfunction can directly lead to respiratory failure, and is closely related to serious clinical problems such as increased mortality risk and prolonged mechanical ventilation time. In particular, in the critical care field, early weaning can increase the risk of mortality, and delayed weaning can lead to diaphragm muscle function decline.

[0003] The commonly used non-invasive diaphragm function assessment methods, such as maximum inspiratory pressure, are easily affected by subjective factors of the subjects, and have poor repeatability and accuracy, and have certain limitations. Bedside ultrasound has certain advantages in diaphragm function and structure analysis due to its non-invasive, convenient and good tolerance characteristics, but the test results are easily affected by the experience of the operator, so it is still limited in clinical application, and lacks a unified assessment standard. The clinical gold standard method is to assess diaphragm function by an invasive method through an esophageal and gastric balloon catheter, which is not conducive to the application and promotion of clinical practice.

[0004] Diaphragm mainly exhibits two functions in the process of respiration: generating force and contraction. The ideal indicator for evaluating diaphragm function is the work or power done by diaphragm to overcome resistance during respiration. However, the force of diaphragm needs to be accurately detected by an invasive method, and the change in diaphragm length and contraction speed is also difficult to detect. Therefore, it is necessary to develop a new respiratory power detection method and system to provide a new way for clinical non-invasive diaphragm function assessment. SUMMARY

[0005] The present application provides a respiratory power detection method based on a respiratory impedance model, which realizes non-invasive quantitative and accurate evaluation of diaphragm function, and provides a new way for clinical non-invasive diaphragm function assessment.

[0006] The present application adopts the following technical solutions:

[0007] A respiratory power detection method based on a respiratory impedance model, comprising the following steps:

[0008] Generating an oscillating airflow of 5-35 Hz by a gas oscillation source;

[0009] Collecting the respiratory flow signal of the subject by using a flow sensor Collecting the airway opening pressure signal of the subject during respiration by using a pressure sensor

[0010] ​The collected flow signal and pressure signal are subjected to amplitude-frequency analysis, and the respiratory impedance in the range of 5-35 Hz is calculated ;

[0011] (1)

[0012] wherein, is an imaginary unit, is a time variable, is a cross-power spectral density function of the pressure and flow signals, is an auto-power spectral density function of the flow signal, 5, 10, 15, 20, 25, 35 are taken;

[0013] In combination with the respiratory impedance model, the model parameters, including airway resistance, airway inertia tissue impedance and lung tissue respiratory impedance, are estimated;

[0014] Based on the estimated model parameters, a respiratory power calculation formula is constructed;

[0015] The flow rate of the subject during normal breathing is measured, and the respiratory power is obtained through the respiratory power calculation formula.

[0016] A respiratory power detection system for the above method, the system comprises: a flow sensor, a pressure sensor, a gas oscillation source, a gas pipeline, a flow deviation device, a screen, a microprocessor, one end of the gas pipeline is connected with the gas oscillation source, the flow sensor and the pressure sensor are located at the other end of the gas pipeline, the flow deviation device is located at the end close to the gas oscillation source, the screen is fixed at the end of the flow deviation device, the screen is separated from the flow deviation device by opening the buckle, the flow sensor is used for detecting the gas flow in the gas pipeline, the pressure sensor is used for detecting the pressure in the gas pipeline, the flow deviation device is used for exchanging with the external gas during the test when the subject breathes, the screen is used for preventing the oscillating gas flow generated by the gas oscillation source from leaking out during the measurement of the respiratory impedance of the subject, and the processor is used for calculating the respiratory impedance of the subject by analyzing the signals of the flow sensor and the pressure sensor during the measurement of the respiratory impedance, and driving the gas oscillation source to generate an expected oscillating gas flow signal through a driving module; during the measurement of the respiratory power, the respiratory power of the subject is calculated through the respiratory flow signal and the respiratory impedance model.

[0017] The present application has the following beneficial effects:

[0018] The present application generates an oscillating gas flow of 5-35 Hz by driving a loudspeaker, collects the respiratory flow of the subject through a flow sensor , collects the airway opening pressure of the subject during breathing through a pressure sensor . The flow signal and the pressure signal Amplitude-frequency analysis can yield the respiratory impedance Z in the 5-35Hz range. Combined with a respiratory impedance model, the model parameters are estimated using system identification methods. , , , , , Finally, a formula for calculating respiratory power is constructed using a respiratory impedance model. At this point, respiratory power can be obtained simply by measuring the flow rate of the subject's normal breathing. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system described in this invention;

[0020] Figure 2 This is the equivalent circuit model of the respiratory impedance model used in this invention to estimate respiratory power. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0022] like Figure 1 As shown, this invention proposes a respiratory power detection system based on a respiratory impedance model. The system includes: a flow sensor, a pressure sensor, a gas oscillation source, a gas pipeline, a deflection device, a screen, a microprocessor, a power module, a display module, and a drive module. One end of the gas pipeline is connected to the gas oscillation source, and the flow sensor and pressure sensor are located at the other end of the gas pipeline. The deflection device is located near the gas oscillation source, and the screen is fixed to the end of the deflection device by a snap fastener. Opening the snap fastener releases the screen from the deflection device. The flow sensor detects the gas flow rate within the gas pipeline. The pressure sensor detects the pressure within the gas pipeline. The deflection device facilitates gas exchange between the subject and the external environment during the test. The screen prevents the leakage of the oscillating airflow generated by the gas oscillation source during the measurement of the subject's respiratory impedance. The processor calculates the subject's respiratory impedance by analyzing the signals from the flow sensor and pressure sensor during respiratory impedance measurement, and drives the gas oscillation source to generate the expected oscillating airflow signal via the drive module. During respiratory power measurement, the processor calculates the subject's respiratory power using the respiratory flow signal and the respiratory impedance model.

[0023] The present invention also provides a respiratory power detection method based on a respiratory impedance model using the above system, the specific steps of which are as follows:

[0024] Measuring different oscillation frequencies Conditional respiratory resistance :like Figure 1 As shown, the system generates an oscillating airflow of 5-35Hz by driving a gas oscillation source, and at the same time, the subject's respiratory flow is collected by a flow sensor. The airway opening pressure was collected by a pressure sensor during the subject's breathing. By analyzing the flow signal and pressure signals Amplitude-frequency analysis can obtain respiratory impedance in the range of 5-35Hz. Under normal circumstances You can choose 5, 10, 15, 20, 25, or 35.

[0025] (1)

[0026] in, The imaginary unit, For time variables, Let be the cross-power spectral density function of the pressure and flow signals. Let be the auto-power spectral density function of the flow signal.

[0027] (2)

[0028] (3)

[0029] Estimated parameters of the impedance breathing model include: such as Figure 2 The impedance breathing model shown consists of two parallel compartments representing different alveolar regions. The impedance sources of each compartment include airway resistance (…). , ), airway inertial tissue resistance ( , The resulting airway resistance and lung tissue respiratory resistance It is connected in series. and These represent the airway impedance of each compartment:

[0030] (4)

[0031] (5)

[0032] Assuming the respiratory impedance of the lung tissue in both compartments is equal, and replaced by a constant-phase model characterized by parameters G and H, the lung tissue respiratory impedance... The mathematical expression is:

[0033] (6)

[0034] The calculation method for α is as follows:

[0035] (7)

[0036] in, , These are parameters to be determined; therefore, a respiratory impedance model is constructed, and the expression for respiratory impedance is as follows:

[0037] (8)

[0038] Determine the error criterion E, and use the least squares (LS) method to... Figure 2 The impedance breathing model shown is used for model parameter estimation. The final model parameters can be obtained. , , , , , . Figure 2 The expression for the total lung impedance in the model is as follows:

[0039] (9)

[0040] in, In frequency impedance under Hz conditions Measured values ​​of the real part. for Figure 2 Model at frequency impedance under Hz conditions The estimated value of the real part; where In frequency impedance under Hz conditions Measured value of the imaginary part for Figure 2 Model at frequency impedance under Hz conditions An estimate of the imaginary part.

[0041] Estimating respiratory power using an impedance breathing model: The respiratory impedance equivalent circuit model constructed using the impedance breathing model is used to collect the flow rate Q in the expiratory oral cavity, which is equivalent to the current I in the circuit. The total impedance Z of the respiratory system is obtained by estimating the model parameters (equivalent to the resistance R, capacitance C, and inductance L in the circuit). By analogy with the method for calculating the power P of the circuit system (formula (10)), and combined with formula (1), the cross power spectral density function of the pressure signal and the flow signal can be obtained. Through further investigation The integral is taken, i.e. the respiratory work done by the diaphragm to overcome the elastic resistance and the elastic resistance of the lungs during the lung ventilation process of the respiratory system :

[0042] (10)

[0043] (11)

[0044] (12)

[0045] The screen device in the opening Figure 1 , the gas oscillation source is closed, the flow Q(t) of the normal breathing of the subject is measured, and the respiratory work of the subject can be obtained by using formula (12).

Claims

1. A method for detecting respiratory power based on a model of respiratory impedance, characterized in that, The method comprises the following steps: Oscillatory airflow generated by a gas oscillation source; Collecting respiratory flow signal of subject using flow sensor Collecting airway opening pressure signal of subject while breathing using pressure sensor ; The amplitude-frequency analysis is performed on the collected flow signal and pressure signal to calculate the respiratory impedance ; (1) wherein is the imaginary unit, is the time variable, is the cross power spectral density function of the pressure and flow signals, is the auto power spectral density function of the flow signal, is the frequency; Combining a respiratory impedance model, estimating model parameters, including airway resistance, airway inertance, tissue impedance, and lung tissue respiratory impedance; Based on the estimated model parameters, constructing a respiratory power calculation formula; Measuring the flow of the subject's normal breathing, and obtaining the respiratory power through the respiratory power calculation formula; The respiratory impedance model comprises two compartments representing different alveolar regions, each compartment being composed of an airway resistance, an airway inertance tissue impedance and a lung tissue respiratory impedance in series; the impedance sources of each compartment include an airway resistance , , an airway inertance tissue impedance , , and a lung tissue respiratory impedance in series, and represent the airway impedance of each compartment, respectively. (4) (5) the lung tissue respiratory impedance of the two compartments is equal, The mathematical expression is: (6) Wherein the calculation method of α is as follows: (7) , is a pending parameter; thereby constructing a respiratory impedance model, in which the expression of respiratory impedance is: (8)； The respiratory impedance equivalent circuit model is constructed to collect the respiratory flow rate of the expiratory oral cavity The current I in the equivalent circuit; the resistance R, the capacitance C, and the inductance value L in the equivalent circuit, respectively, through the respiratory impedance model parameters, to obtain the respiratory impedance Z of the respiratory system, and combine formula (1) to obtain the mutual power spectrum density function of the pressure signal and the flow signal , by further integrating , that is, the respiratory power : (11) (12) Turning off the gas oscillation source, measuring the normal breathing flow rate of the subject The respiratory power of the subject is obtained using equation (12).

2. The respiratory power detection method based on a respiratory impedance model according to claim 1, characterized in that, frequency of the oscillating air flow values of 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz and 35 Hz.

3. The respiratory power detection method based on a respiratory impedance model according to claim 2, characterized in that, Determine error criterion E, select least square method to carry out model parameter estimation to respiratory impedance model, finally obtain model parameter , , , , , : (9) wherein is the respiratory impedance at frequency Hz is the measured value of the real part, wherein is the respiratory impedance at frequency Hz is the estimated value of the real part; wherein is the respiratory impedance at frequency Hz is the measured value of the imaginary part, is the impedance at frequency Hz is the estimated value of the imaginary part.

4. A respiration power detection system for use in the method of any one of claims 1 to 3, characterized in that The system comprises a flow sensor, a pressure sensor, a gas oscillation source, a gas path pipeline, a flow deviation device, a screen, and a microprocessor. One end of the gas path pipeline is connected to the gas oscillation source. The flow sensor and the pressure sensor are located at the other end of the gas path pipeline. The flow deviation device is located near the end of the gas oscillation source. The screen is fixed at the end of the flow deviation device. Opening the buckle, the screen is separated from the flow deviation device. The flow sensor is used to detect the gas flow in the gas path pipeline. The pressure sensor is used to detect the pressure in the gas path pipeline. The flow deviation device is used for gas exchange with the outside air during the subject's breathing during the test. The screen is used to prevent the oscillatory airflow generated by the gas oscillation source from leaking out during the measurement of the subject's respiratory impedance. The processor is used to calculate the subject's respiratory impedance by analyzing the signals of the flow sensor and the pressure sensor during the measurement of the respiratory impedance, and to drive the gas oscillation source to generate the expected oscillatory airflow signal through the driving module. During the measurement of the respiratory power, the subject's respiratory power is calculated through the respiratory flow signal and the respiratory impedance model.

5. The respiratory power detection system based on a model of respiratory impedance according to claim 4, characterized in that, It also includes a power module and a display module for power supply and display.

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