A non-invasive diaphragm function assessment device and method

Abstract

The present invention provides a non-invasive diaphragm function assessment device and method, which belongs to the field of medical devices. The device includes: a magnetic stimulation module, a flow sensor, a pressure sensor, a gas oscillation source, an airway pipeline, a microprocessor, a power module, a display module and a drive module. The present invention also provides a non-invasive diaphragm function assessment method, which uses an oscillating airflow to collect the subject's respiratory flow using a flow sensor, and collects the airway opening pressure signal when the subject breathes through a pressure sensor. By analyzing the flow signal and the pressure signal amplitude and frequency, the respiratory impedance can be obtained, and then combined with the respiratory impedance model, the model parameters are estimated using a system identification method, and finally the intrathoracic pressure is estimated by combining the airway opening pressure signal with the respiratory model. Finally, the respiratory impedance model is constructed to estimate the change in intrathoracic pressure under magnetic stimulation conditions, thereby achieving non-invasive diaphragm function assessment.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and in particular relates to a non-invasive diaphragm function assessment device and method. Background Art

[0002] As the most important respiratory muscle of the human body, diaphragm dysfunction can directly lead to respiratory failure and is closely related to serious clinical problems such as increased risk of death and prolonged mechanical ventilation. In the intensive care unit (ICU), more than 60% of mechanically ventilated patients have diaphragm dysfunction, which makes the assessment of diaphragm function an important part of evaluating patients' autonomous breathing ability and whether they can be taken off the ventilator.

[0003] Traditional diaphragm function assessment methods, such as maximum inspiratory pressure and maximum nasal inspiratory pressure, are simple and widely used, but they rely on the subjective cooperation of patients, and the measurement results have poor repeatability and certain limitations. Although detection methods such as twitch transdiaphragmatic pressure (TwPdi) and twitch esophageal pressure (TwPes) are more accurate, they require the placement of esophageal and gastric balloon tubes during the test, which causes discomfort to patients and limits their clinical application. In recent years, non-invasive diaphragm function detection technology has gradually received attention. Among them, twitch oral pressure (TwPao) and bedside ultrasound have become promising tools for real-time monitoring of diaphragm function due to their non-invasive, convenient and well-tolerated characteristics. However, twitch oral pressure detection technology is only suitable for intubated patients, and ultrasonic diaphragm detection technology is easily affected by the operator's experience. Although it solves the problem that traditional technology is easily affected by subjective factors of the subjects, it is still limited in clinical application. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a non-invasive diaphragm function assessment device and method, which, based on the respiratory impedance model technology, realizes non-invasive quantitative and accurate assessment of diaphragm function, and solves the problem that traditional non-invasive diaphragm assessment technology is easily affected by subjective factors of the subjects.

[0005] The present invention provides a non-invasive diaphragm function assessment device, which includes: a magnetic stimulation module, a flow sensor, a pressure sensor, a gas oscillation source, an airway pipeline, a microprocessor, a first bias flow device, and a second bias flow device; wherein,

[0006] The magnetic stimulation module is used to output a magnetic induction stimulation signal;

[0007] Gas pipelines are used for gas circulation;

[0008] The flow sensor is used to detect the gas flow in the gas pipeline;

[0009] The pressure sensor is used to detect the oral cavity pressure of the subject;

[0010] The magnetic stimulation module is used to stimulate the bilateral phrenic nerves to induce diaphragmatic contraction;

[0011] The first flow deviation device is used for the gas pipeline to discharge gas to the outside, and is in a low resistance state when the gas is discharged and in a high resistance state when the gas is taken in;

[0012] The second bias flow device is used for external gas to enter the gas pipeline, which is in a low resistance state when the gas enters and in a high resistance state when the gas exits;

[0013] The microprocessor is used to analyze the signals of the flow sensor and the pressure sensor, and drive the gas oscillation source to generate the expected oscillation gas flow signal.

[0014] The present invention also provides a non-invasive diaphragm function assessment method, the method comprising the following steps:

[0015] Step 1. Measure respiratory impedance at different frequencies f , including: generating an oscillating airflow through a gas oscillation source, and at the same time, collecting the subject's respiratory flow signal through a flow sensor , the pressure sensor collects the pressure signal of the airway opening when the subject breathes , by analyzing the subject's respiratory flow signal and pressure signal The amplitude-frequency of the pulse was analyzed to obtain the respiratory impedance Z(f) at different frequencies f, where f was 5, 10, 15, 20, 25, and 35.

[0016] ;

[0017] Among them, i is the imaginary unit, t is the time variable;

[0018] Step 2. Establish a respiratory model and estimate respiratory model parameters, including: determining the error criterion E and using the least squares method to estimate respiratory model parameters; the respiratory model parameters obtained include airway viscosity resistance , airway inertia resistance , lung tissue viscosity resistance , lung inertia resistance , lung compliance , alveolar air compliance ;

[0019] ;

[0020] in, is the measured value of the real part of the impedance at frequency f, is the real part estimate of the impedance of the respiratory model; where is the measured value of the imaginary part of impedance at frequency f, is the estimated value of the imaginary part of the impedance of the respiratory model;

[0021] Step 3. Estimate intrathoracic pressure using the breathing model , including: during normal breathing, = 0, intrathoracic pressure is derived using the respiratory model The calculation formula is:

[0022] ;

[0023] Step 4. Stimulate the phrenic nerve with the magnetic stimulation module and estimate the intrathoracic pressure with the respiratory model. The diaphragm function was assessed by changes in

[0024] The present invention has the following beneficial effects:

[0025] The present invention provides a non-invasive diaphragm function assessment device and method, which generates an oscillating airflow of 5-35 Hz by driving a speaker and collects the respiratory flow of the subject through a flow sensor. The pressure sensor is used to collect the airway opening pressure of the subject during breathing. By comparing the flow signal and pressure signal Amplitude-frequency analysis can obtain the respiratory impedance Z at 5-35Hz. Combined with the respiratory impedance model, the system identification method is used to estimate the model parameters: airway viscosity resistance , airway inertia resistance , lung tissue viscosity resistance , lung inertia resistance , lung compliance , alveolar air compliance , the intrathoracic pressure can be estimated by combining the airway opening pressure with the respiratory model . Finally, a respiratory impedance model is constructed to estimate the changes in intrathoracic pressure under magnetic stimulation conditions, thereby achieving non-invasive diaphragm function assessment. The present invention solves the problem that traditional non-invasive diaphragm function assessment methods are easily affected by subjective factors of subjects or operators, and provides an effective technical means for clinically assessing the diaphragm function status of subjects and whether offline conditions are met in time to avoid diaphragm function decline due to offline delays. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the non-invasive diaphragm function assessment device of the present invention;

[0027] Figure 2 Schematic diagram of the breathing model used for estimating intrathoracic pressure in the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0029] The present invention provides a non-invasive diaphragm function assessment device, such as Figure 1 As shown, the non-invasive diaphragm function assessment device includes: a magnetic stimulation module, a flow sensor, a pressure sensor, a gas oscillation source, an air pipeline, a first bias flow device, a second bias flow device, and a microprocessor. The magnetic stimulation module is used to output magnetic induction stimulation signals; the air pipeline is used for gas circulation; the flow sensor is used to detect the gas flow in the air pipeline; the pressure sensor is used to detect the oral pressure of the subject's breathing; the first bias flow device is used for the air pipeline to discharge gas to the outside, and is in a low resistance state when the air is discharged and in a high resistance state when the air is in; the second bias flow device is used for external gas to enter the air pipeline, and is in a low resistance state when the air is in, and is in a high resistance state when the air is discharged; the magnetic stimulation module is used to stimulate the bilateral phrenic nerves to induce diaphragm contraction; the processor is used to analyze the signals of the flow sensor and the pressure sensor, and drive the gas oscillation source to generate the expected oscillation airflow signal. To ensure gas safety, a filter is set at the air pipeline.

[0030] Preferably, the magnetic stimulation module includes a stimulation host, a stimulation coil and a cooling system, and the maximum magnetic induction intensity output is at least 2 Tesla.

[0031] Preferably, the pressure sensor has a range of at least -500Pa to 500Pa, with a linearity of ≤2%; the flow sensor has a range of at least -1.5L / s to 1.5L / s, with a linearity of ≤2%.

[0032] Preferably, the gas oscillation source is composed of a driving module and a speaker, and the driving module generates oscillating gas with different frequencies of 5-35 Hz by driving the speaker.

[0033] Preferably, the non-invasive diaphragm function assessment device also includes a power module and a display module.

[0034] The present invention also provides a non-invasive diaphragm function assessment method, which uses the above-mentioned non-invasive diaphragm function assessment device, and the specific steps are as follows:

[0035] Step 1. Measure the respiratory impedance Z(f) at different frequencies f: Figure 1 As shown, a gas oscillator generates an oscillating airflow of 5-35 Hz. At the same time, a flow sensor collects the subject's respiratory flow signal. , the pressure sensor is used to collect the airway opening pressure signal when the subject breathes By comparing the flow signal and pressure signal By analyzing the amplitude and frequency, the respiratory impedance Z(f) at 5-35Hz can be obtained. Usually, f can be 5, 10, 15, 20, 25, or 35.

[0036] ;

[0037] Among them, i is the imaginary unit, t is the time variable;

[0038] Step 2. Establish a breathing model and estimate breathing model parameters: Figure 2 The respiratory model shown in Figure 1 shows the force generated by the respiratory muscles. Airway resistance must be overcome and lung tissue impedance , generating respiratory flow signal , airway impedance Including airway viscosity resistance , airway inertia resistance ; Lung tissue impedance Including lung tissue viscosity resistance , lung inertia resistance , lung compliance ; is the intrathoracic pressure, is the ambient atmospheric pressure. Then the error criterion E is determined, and the least squares method (LS) is used to estimate the respiratory model parameters. Finally, the respiratory model parameters can be obtained, including airway viscosity resistance , airway inertia resistance , lung tissue viscous resistance , lung inertia resistance , lung compliance ; also includes the air compliance in the alveoli ;

[0039] ;

[0040] in, is the measured value of the real part of the impedance at frequency f, is the real part estimate of the impedance of the respiratory model; where is the measured value of the imaginary part of impedance at frequency f, is the estimated value of the imaginary part of the impedance of the respiratory model;

[0041] Step 3. Estimate intrathoracic pressure using the breathing model : During normal breathing, the effective frequency of airflow is below 1 Hz, and the inertial component of the gas in the airway is very small. =0, then use Figure 2 The respiratory model shown can derive the intrathoracic pressure The calculation formula for .

[0042] ;

[0043] Step 4. Stimulate the phrenic nerve through the magnetic stimulation module and estimate the intrathoracic pressure through the model. The change value Assess diaphragm function. When it is less than 7.2 cmH2O, the patient is considered to have diaphragm dysfunction or fail to meet the conditions for weaning from the ventilator.

Claims

1. A non-invasive diaphragm function assessment method, characterized in that: The method comprises the following steps: Step 1. Measure respiratory impedance at different frequencies f , including: generating an oscillating airflow through a gas oscillation source, and at the same time, collecting the subject's respiratory flow signal through a flow sensor , the pressure sensor collects the pressure signal of the airway opening when the subject breathes , by analyzing the subject's respiratory flow signal and pressure signal The amplitude-frequency of the pulse was analyzed to obtain the respiratory impedance Z(f) at different frequencies f, where f was 5, 10, 15, 20, 25, and 35. ； Among them, i is the imaginary unit, t is the time variable; Step 2. Establish a respiratory model and estimate respiratory model parameters, including: determining the error criterion E and using the least squares method to estimate respiratory model parameters; the respiratory model parameters obtained include airway viscosity resistance , airway inertia resistance , lung tissue viscosity resistance , Lung inertia resistance , lung compliance , alveolar air compliance ; ； in, is the measured value of the real part of the impedance at frequency f, is the real part estimate of the impedance of the respiratory model; where is the measured value of the imaginary part of impedance at frequency f, is the estimated value of the imaginary part of the impedance of the respiratory model; Step 3. Estimate intrathoracic pressure using the breathing model , including: normal breathing, = 0, intrathoracic pressure is derived using the respiratory model The calculation formula is: ； Step 4. Stimulate the phrenic nerve with the magnetic stimulation module and estimate the intrathoracic pressure with the respiratory model. The changes in the value of diaphragm function were evaluated.

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