A method and apparatus for determining respiratory mechanics parameters of a respiratory system
By constructing a mathematical model of the respiratory system, collecting airway pressure and flow in real time, and solving for unknowns using the minimization objective function and interior point method, the problem of inaccurate estimation of respiratory parameters in existing technologies is solved, and accurate estimation of the inspiratory and expiratory phases is achieved, which is applicable to conditions such as chronic obstructive pulmonary disease.
Patent Information
- Application Number
- CN202411136805.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-19
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2044-08-19
AI Technical Summary
Existing technologies cannot take into account the changes in mechanical parameters of the respiratory system during the inspiratory and expiratory phases in real time and non-invasively when estimating conditions such as chronic obstructive pulmonary disease and acute respiratory distress syndrome, resulting in inaccurate estimation of respiratory parameters.
A mathematical model of the respiratory system was constructed, and airway pressure and flow were collected in real time. The unknowns were solved by minimizing the objective function and the interior point method. Constraints were set to estimate the resistance and elasticity during the inspiratory and expiratory phases, and the active breathing of the patient was taken into account.
It improves the accuracy of respiratory parameter estimation, enabling accurate estimation of resistance and elasticity at different respiratory stages, and is applicable to situations involving active breathing.
Smart Images
Figure CN119026357B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of respirators, in particular to a method and device for determining respiratory mechanics parameters of a respiratory system. BACKGROUND
[0002] As an effective means for artificially replacing the self-ventilation function, the respirator has been widely used in respiratory failure caused by various reasons, anesthesia and respiratory management during major surgery, respiratory support treatment and emergency resuscitation, and occupies a very important position in the field of modern medicine. When the respirator is intelligently controlled, the resistance and elastic mechanics parameters of the patient's respiratory system need to be estimated in real time, so as to adjust the support pressure, flow and other parameters of the respirator, and provide more suitable respiratory support.
[0003] For the estimation of the respiratory mechanics parameters of the patient, the main problems existing in the prior art include one or several of the following cases: invasive, interfering with normal ventilation, not real-time, not applicable to the case where the patient has active respiration. The existing inspiratory occlusion method is only applicable to the case where there is no active respiration and cannot be performed in real time. It can only be performed in the volume control mode, and the patient needs to be relaxed. It will interfere with the mechanical ventilation of the patient; the linear regression algorithm based on the least square method and various improvements can be estimated in real time but only applicable to the case where there is no active respiration; the esophageal pressure method for measuring esophageal pressure instead of equivalent pressure of respiratory muscle or diaphragmatic electromyography is applicable to the case where there is active respiration and can also be monitored in real time but is invasive; there are studies using constraint optimization algorithm to explore real-time and non-invasive estimation of respiratory mechanics parameters and patient active respiration for patients with active respiration. However, in the case of chronic obstructive pulmonary disease, acute respiratory distress syndrome and other conditions, since the method does not consider the lesion, the mechanics parameters of the patient's respiratory system change obviously in different stages of inspiration and expiration. The respiratory parameters obtained by the parameter estimation algorithm using the constraint optimization algorithm still need to be improved. SUMMARY
[0004] The purpose of the present application is to provide a method and device for determining respiratory mechanics parameters of a respiratory system, which improves the accuracy of respiratory parameter estimation.
[0005] To achieve the above-mentioned purpose, the present application provides the following solutions:
[0006] In a first aspect, the present application provides a method for determining respiratory mechanics parameters of a respiratory system, comprising:
[0007] real-time acquisition of airway pressure and airway flow of the respiratory system;
[0008] constructing a respiratory system mathematical model including an inhalation phase and an exhalation phase according to the real-time collected airway pressure and airway flow; unknown quantities in the respiratory system mathematical model include respiratory mechanics parameters and an equivalent pressure of patient active respiration; the respiratory mechanics parameters include resistance in the inhalation phase, resistance in the exhalation phase, elasticity in the inhalation phase, and elasticity in the exhalation phase;
[0009] constructing an objective function of the respiratory system mathematical model; a value of the objective function is a sum of squares of differences between the real-time collected airway pressure and airway pressure calculated by the unknown quantities in a set time period;
[0010] solving the unknown quantities in the objective function based on a set constraint condition, aiming to minimize the value of the objective function; the set constraint condition includes a set size relationship of the unknown quantities in the inhalation phase and the exhalation phase, and a value range constraint of each respiratory mechanics parameter.
[0011] Optionally, the respiratory system mathematical model is represented as:
[0012]
[0013]
[0014] wherein, t SOE represents a time point when the inhalation phase of the ventilator ends and the exhalation phase starts, t N represents a time point when the respiratory cycle ends, R in represents the resistance in the inhalation phase, R ex represents the resistance in the exhalation phase, E in represents the elasticity in the inhalation phase, E ex represents the elasticity in the exhalation phase, P ao (t) is the airway pressure at time t, is the airway flow at time t, V(t) is the airway volume at time t, P mus (t) is the equivalent pressure of patient active respiration at time t, P0 is a constant.
[0015] Optionally, the objective function is represented as:
[0016]
[0017] wherein, J represents the value of the objective function, SOE represents a time point when the inhalation phase ends, and N represents a time point when the exhalation phase ends.
[0018] Optionally, the set size relationship of the unknown quantities in the inhalation phase and the exhalation phase includes: the resistance in the exhalation phase is greater than the resistance in the inhalation phase, and the elasticity in the exhalation phase is equal to the elasticity in the inhalation phase.
[0019] Optionally, based on set constraints, the unknowns in the objective function are solved to minimize the value of the objective function, specifically including:
[0020] Based on the set constraints, the objective function is solved using the interior point method to obtain multiple estimation results that meet the set constraints; the estimation result with the smallest objective function value among the multiple estimation results that meet the set constraints is taken as the solution of the objective function.
[0021] Optionally, real-time acquisition of airway pressure and airway flow in the respiratory system, specifically including:
[0022] When a patient is mechanically ventilated using a ventilator in pressure support or pressure control ventilation mode, a pressure sensor is used at the patient end to collect the airway pressure of the respiratory system, and a flow sensor is used to collect the airway flow of the respiratory system.
[0023] Secondly, this application provides a device for determining respiratory mechanics parameters of a respiratory system, comprising:
[0024] The pressure and flow acquisition module is used to acquire airway pressure and airway flow in the respiratory system in real time.
[0025] A respiratory system mathematical model construction module is used to construct a respiratory system mathematical model including an inspiratory phase and an expiratory phase based on the real-time collected airway pressure and airway flow. The unknowns in the respiratory system mathematical model include respiratory mechanical parameters and the equivalent pressure of the patient's active breathing. The respiratory mechanical parameters include resistance during the inspiratory phase, resistance during the expiratory phase, elasticity during the inspiratory phase, and elasticity during the expiratory phase.
[0026] The objective function construction module is used to construct the objective function of the respiratory system mathematical model; the value of the objective function is the sum of squares of the differences between the airway pressure collected in real time and the airway pressure calculated through the unknown quantity within a set time period.
[0027] The unknown quantity solving module is used to solve for the unknown quantities in the objective function based on set constraints, with the goal of minimizing the value of the objective function; the set constraints include the setting of the relationship between the magnitudes of the unknown quantities in the inhalation and exhalation phases, as well as the constraints on the range of values of each respiratory mechanics parameter.
[0028] Optionally, the pressure and flow acquisition module includes a pressure sensor and a flow sensor, both of which are connected to the tubing between the ventilator and the patient.
[0029] According to the specific embodiments provided in this application, the following technical effects are disclosed:
[0030] The application provides a method and device for determining respiratory mechanics parameters of a respiratory system, wherein the respiratory mechanics parameters in a mathematical model of the respiratory system include resistance in an inhalation stage, resistance in an exhalation stage, elasticity in the inhalation stage and elasticity in the exhalation stage, and the size relationship of unknown quantities in the inhalation and exhalation stages is set by setting a constraint condition, so that the respiratory system with obviously different resistance and elasticity in the inhalation and exhalation stages can be estimated; and the estimation result is judged, the estimation result meeting the size relationship of unknown quantities in the inhalation and exhalation stages is first selected, and then the result with the minimum target function is taken as the estimation of the unknown quantity from the estimation results, so that the accuracy of the respiratory parameter estimation is improved. BRIEF DESCRIPTION OF DRAWINGS
[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.
[0032] Figure 1 A flowchart of a method for determining respiratory mechanics parameters of a respiratory system according to an embodiment of the present application is shown in the figure.
[0033] Figure 2 A functional module diagram of a device for determining respiratory mechanics parameters of a respiratory system according to an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION
[0034] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0035] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.
[0036] The application provides a method for determining respiratory mechanics parameters of a respiratory system, as shown in the figure, the method for determining respiratory mechanics parameters of the respiratory system comprises: Figure 1 The method for determining respiratory mechanics parameters of the respiratory system comprises:
[0037] Step 101: Real-time acquisition of airway pressure and airway flow of the respiratory system.
[0038] Step 102: constructing a respiratory system mathematical model including an inhalation phase and an exhalation phase according to the real-time collected airway pressure and airway flow; unknown quantities in the respiratory system mathematical model include respiratory mechanics parameters and an equivalent pressure of patient active breathing; the respiratory mechanics parameters include resistance in the inhalation phase, resistance in the exhalation phase, elasticity in the inhalation phase, and elasticity in the exhalation phase.
[0039] Step 103: constructing an objective function of the respiratory system mathematical model; a value of the objective function is a sum of squares of differences between the real-time collected airway pressure and airway pressure calculated by the unknown quantities in a set time period.
[0040] Step 104: solving the unknown quantities in the objective function based on a set constraint condition to minimize the value of the objective function; the set constraint condition includes a set of size relationship of the unknown quantities in the inhalation phase and the exhalation phase, and a range constraint of each respiratory mechanics parameter.
[0041] The set constraint condition sets the size relationship of the resistances in the inhalation phase and the exhalation phase, and the size relationship of the elasticities in the inhalation phase and the exhalation phase, and the range constraint of each respiratory mechanics parameter. After solving, the estimated results are first judged, and the results meeting the set size relationship of the resistances in the inhalation phase and the exhalation phase are selected, and then the result with the minimum objective function is selected as the estimation of the unknown quantities from the results.
[0042] The application estimates the respiratory mechanics parameters in different phases of breathing and the active breathing of the patient by using the airway pressure, flow, and volume curves collected at the patient end.
[0043] The step 101 specifically includes: when a ventilator is used to mechanically ventilate a patient in a pressure support or pressure control ventilation mode, collecting the airway pressure of the respiratory system at the patient end by using a pressure sensor, and collecting the airway flow of the respiratory system by using a flow sensor.
[0044] The respiratory system refers to the respiratory system of the patient.
[0045] The application sets the pressure sensor and the flow sensor near the patient end on the pipeline connected between the ventilator and the patient.
[0046] The respiratory system is divided into the inhalation phase and the exhalation phase, and the respiratory system mathematical model is expressed as:
[0047]
[0048]
[0049] Wherein, t SOE represents the time when the inhalation phase of the ventilator ends and the exhalation phase starts, tN denotes the end time of the respiratory cycle, R in denotes the resistance of the inhalation phase, R ex denotes the resistance of the exhalation phase, E in denotes the elastance of the inhalation phase, E ex denotes the elastance of the exhalation phase, P ao (t) is the airway pressure at time t, P (t) is the airway flow at time t, V(t) is the airway volume at time t, P mus (t) is the equivalent pressure of the patient's active breathing at time t, P0 is a constant, P0 is used for zeroing. The respiratory cycle includes an inhalation phase and an exhalation phase.
[0050] The application sets the mechanical parameters of the respiratory system, that is, the resistance and elastance parameters, in the inhalation phase and the exhalation phase, estimates the resistance of the inhalation phase, the resistance of the exhalation phase, the elastance of the inhalation phase, and the elastance of the exhalation phase, and can estimate the respiratory system whose resistance and elastance are obviously different in the inhalation and exhalation phases.
[0051] The application estimates the resistance of the inhalation phase R in , the resistance of the exhalation phase R ex , the elastance of the inhalation phase E in , and the elastance of the exhalation phase E ex by using an optimization constraint method.
[0052] The objective function of the constraint method is set as:
[0053]
[0054] wherein J represents the value of the objective function, SOE represents the time point at which the inhalation phase ends, and N represents the time point at which the exhalation phase ends.
[0055] The constraint condition includes the value range constraint of each respiratory mechanics parameter in the unknown quantity.
[0056] The application sets the coefficients in the size relationship matrix of the resistance of the inhalation phase, the resistance of the exhalation phase, the elastance of the inhalation phase, and the elastance of the exhalation phase in the optimization constraint method, so that the resistance of the exhalation phase can be controlled to be greater than the resistance of the inhalation phase, and the size relationship of the elastance of the inhalation and exhalation phases can be controlled.
[0057] The standard form of the optimization constraint method is as follows:
[0058]
[0059] The constraint condition is set as follows:
[0060] Ax≤b
[0061] A eq x=b eq
[0062] l≤x≤u
[0063] Wherein, H is the quadratic term coefficient matrix, f is the linear term coefficient matrix, g is the constant term, T represents the transpose, x is the column vector composed of the time-varying values of the resistance in the inspiration phase, the resistance in the expiration phase, the elasticity in the inspiration phase, the elasticity in the expiration phase and the equivalent pressure of the patient's active breathing, A is the matrix of the size relationship of the respiratory mechanics parameters in the inspiration and expiration phases and the time-varying trend of the patient's active breathing, b is the product of the time-varying trend matrix of the unknown and the unknown, A eq is the matrix indicating that the unknown is a constant value in the time-varying trend of the unknown, b eq is the product of the matrix indicating that the unknown is constant and the unknown, l is the minimum value of the unknown, and u is the maximum value of the unknown.
[0064] Wherein, A and b are used to set the relationship between the resistance in the inspiration phase and the resistance in the expiration phase, and the relationship between the elasticity in the inspiration phase and the elasticity in the expiration phase. At the same time, the change trend of the patient's active breathing is constrained.
[0065] Wherein, l and u are the constraint conditions of the maximum and minimum value range of the unknown characteristics: for the resistance and elasticity, the maximum and minimum range of the physiological characteristics is used as the maximum and minimum value of the estimated value; for the patient's action, the maximum and minimum range in physiology is used as the maximum and minimum value of the estimated value of the patient's action.
[0066] For the A matrix, for the chronic obstructive pulmonary disease, the resistance in the expiration phase is greater than the resistance in the inspiration phase.
[0067] Wherein, step 104 specifically comprises: based on the set constraint condition, using the interior point method to solve the unknown in the objective function with the goal of minimizing the value of the objective function.
[0068] Wherein, the set constraint condition sets the size relationship of the resistance in the inspiration and expiration phases, and the size relationship of the elasticity in the inspiration and expiration phases, and at the same time, the value range of each respiratory mechanics parameter is constrained.
[0069] The step 104 of the present application obtains a series of estimated results, representing different time points at which the minimum value of the patient's active breathing appears, judges these estimated results, selects the results that meet the set size relationship of the inspiration and expiration phase resistances, selects a group of results with the minimum objective function value of the optimization constraint method from these results as the estimated results.
[0070] The obtained series of estimation results are judged, and for the slow obstructive pulmonary disease, a first step is to select results meeting the setting of the resistance in the expiration phase being greater than the resistance in the inspiration phase; a second step is to select, from the results in the first step, a set of results with the minimum objective function value of the optimization constraint method as the estimation result.
[0071] The ventilator is adjusted according to the respiratory mechanics parameters solved by the step 104.
[0072] Based on the same inventive concept, the embodiment of the present application also provides a respiratory mechanics parameter determination device of a respiratory system for implementing the respiratory mechanics parameter determination method of the respiratory system.
[0073] In an exemplary embodiment, as shown in Figure 2 A respiratory mechanics parameter determination device of a respiratory system is provided, which includes:
[0074] A pressure flow acquisition module 201 is configured to acquire, in real time, airway pressure and airway flow of the respiratory system.
[0075] A respiratory system mathematical model construction module 202 is configured to construct a respiratory system mathematical model including an inspiration phase and an expiration phase according to the acquired airway pressure and airway flow in real time; unknown quantities in the respiratory system mathematical model include respiratory mechanics parameters and an equivalent pressure of patient active respiration; the respiratory mechanics parameters include resistance in the inspiration phase, resistance in the expiration phase, elasticity in the inspiration phase, and elasticity in the expiration phase.
[0076] A target function construction module 203 is configured to construct a target function of the respiratory system mathematical model; a value of the target function is a sum of squares of differences between the acquired airway pressure in real time and airway pressure calculated by the unknown quantities in a set time period.
[0077] An unknown quantity solving module 204 is configured to solve the unknown quantities in the target function based on a set constraint condition, with the aim of minimizing the value of the target function; the set constraint condition includes a set size relationship of the unknown quantities in the inspiration phase and the expiration phase, and a value range constraint of each respiratory mechanics parameter.
[0078] The constraint conditions are set for the size relationship of the resistance of the inhalation and exhalation stages and the size relationship of the elasticity of the inhalation and exhalation stages, and the value range of each respiratory mechanics parameter is constrained.
[0079] The pressure flow acquisition module comprises a pressure sensor and a flow sensor, and the pressure sensor and the flow sensor are arranged on a pipeline connected between the breathing machine and the patient.
[0080] The technical features of the above embodiments can be combined in any manner, and to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.
[0081] The principles and implementation modes of the present application are described by using specific examples herein, and the above embodiment descriptions are only used to help understand the method and core idea of the present application; meanwhile, for the general technical personnel in the art, the specific implementation modes and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present application should not be understood as a limitation.
Claims
1. A method for determining respiratory mechanics parameters of a respiratory system, characterized in that, The method for determining the respiratory mechanics parameters of the respiratory system includes: Real-time acquisition of airway pressure and airway flow in the respiratory system; Based on the real-time collected airway pressure and airway flow, a respiratory system mathematical model including the inspiratory and expiratory phases is constructed; the unknowns in the respiratory system mathematical model include respiratory mechanical parameters and the equivalent pressure of the patient's active breathing; the respiratory mechanical parameters include resistance during the inspiratory phase, resistance during the expiratory phase, elasticity during the inspiratory phase, and elasticity during the expiratory phase. The objective function for constructing the mathematical model of the respiratory system is: the value of the objective function is the sum of squares of the differences between the airway pressure collected in real time and the airway pressure calculated through the unknown quantity within a set time period. Based on defined constraints, the unknowns in the objective function are solved to minimize its value. Specifically, this includes: Based on the set constraints, the objective function is solved using the interior point method, yielding multiple estimation results that satisfy the set constraints. The estimation result with the smallest objective function value among these results is taken as the solution to the objective function. The set constraints include setting the magnitude relationship of unknowns during the inhalation and exhalation phases, as well as constraints on the value range of each respiratory mechanics parameter. Specifically, the set constraints include setting the magnitude relationship of resistance and elasticity during the inhalation and exhalation phases. The set constraints set the magnitude relationship of resistance and elasticity during the inhalation and exhalation phases, and simultaneously constrain the value range of each respiratory mechanics parameter. After solving, the estimation results are first judged, and the results that satisfy the set magnitude relationship of resistance during the inhalation and exhalation phases are selected. Then, the result with the smallest objective function value among these results is taken as the estimate of the unknowns. The standard form of the optimization constraint method is as follows: The constraints are expressed as follows: ; in, The value of the objective function. It is the coefficient matrix of the quadratic terms. f The coefficient matrix of the first-order terms. For constant terms, T Indicates transpose. This is a matrix showing the magnitude relationship of respiratory mechanics parameters during the inspiratory and expiratory phases and the temporal variation trend of the patient's active breathing. b The product of the trend matrix of unknown quantities and the unknown quantity, x is a column vector composed of the time-partial values of the resistance during the inspiratory phase, the resistance during the expiratory phase, the elasticity during the inspiratory phase, the elasticity during the expiratory phase, and the equivalent pressure of the patient's active breathing. By setting constraints on A and b, the relationship between the resistance during the inspiratory phase and the resistance during the expiratory phase, and the relationship between the elasticity during the inspiratory phase and the elasticity during the expiratory phase are set. At the same time, the trend of the patient's active breathing is constrained, so as to achieve the estimation of respiratory systems with significantly different resistance and elasticity during the inspiratory and expiratory phases. This is a matrix representing the constant value of unknown quantities in the trend change of unknown quantities. To represent the product of a matrix with constant unknowns and the unknowns, The minimum value of the unknown quantity. The maximum value of the unknown quantity; and Constraints on the maximum and minimum range of unknown features: For resistance and elasticity, the maximum and minimum range of the physiological features are used as the maximum and minimum values of the estimated values; for patient effects, the maximum and minimum range of the physiological features are used as the maximum and minimum values of the estimated patient effects. The mathematical model of the respiratory system is expressed as follows: in, This indicates the moment when the inspiratory phase of the ventilator ends and the expiratory phase begins. t N Indicates the end time of the respiratory cycle. This indicates the resistance during the inhalation phase. This indicates the resistance during the exhalation phase. This indicates the elasticity during the inhalation phase. Indicates the flexibility during the exhalation phase. Let be the airway pressure at time t. Let be the airway flow rate at time t. Let be the airway volume at time t. Let t be the equivalent pressure of the patient's active breathing. It is a constant.
2. The method for determining respiratory mechanics parameters of the respiratory system according to claim 1, characterized in that, The objective function is expressed as: Where J represents the value of the objective function, SOE represents the time point at which the inhalation phase ends, and N represents the time point at which the exhalation phase ends.
3. The method for determining respiratory mechanics parameters of the respiratory system according to claim 2, characterized in that, The relationship between the unknown quantities in the inhalation and exhalation phases is set as follows: the resistance in the exhalation phase is greater than the resistance in the inhalation phase, and the elasticity in the exhalation phase is equal to the elasticity in the inhalation phase.
4. The method for determining respiratory mechanics parameters of the respiratory system according to claim 1, characterized in that, Real-time acquisition of airway pressure and airway flow in the respiratory system, specifically including: When a patient is mechanically ventilated using a ventilator in pressure support or pressure control ventilation mode, a pressure sensor is used at the patient end to collect the airway pressure of the respiratory system, and a flow sensor is used to collect the airway flow of the respiratory system.
5. A device for determining respiratory mechanics parameters of a respiratory system, characterized in that, The respiratory mechanics parameter determination device for the respiratory system employs the respiratory mechanics parameter determination method for the respiratory system according to any one of claims 1-4, and the respiratory mechanics parameter determination device for the respiratory system comprises: The pressure and flow acquisition module is used to acquire airway pressure and airway flow in the respiratory system in real time. A respiratory system mathematical model construction module is used to construct a respiratory system mathematical model including an inspiratory phase and an expiratory phase based on the real-time collected airway pressure and airway flow. The unknowns in the respiratory system mathematical model include respiratory mechanical parameters and the equivalent pressure of the patient's active breathing. The respiratory mechanical parameters include resistance during the inspiratory phase, resistance during the expiratory phase, elasticity during the inspiratory phase, and elasticity during the expiratory phase. The objective function construction module is used to construct the objective function of the respiratory system mathematical model; the value of the objective function is the sum of squares of the differences between the airway pressure collected in real time and the airway pressure calculated through the unknown quantity within a set time period. The unknown quantity solution module is used to solve for the unknown quantities in the objective function based on set constraints, with the goal of minimizing the value of the objective function; the set constraints include setting the relationship between the magnitudes of the unknown quantities in the inhalation and exhalation phases, as well as the range constraints of the values of each respiratory mechanics parameter; the set constraints specifically include setting the relationship between the magnitudes of the resistance in the inhalation and exhalation phases, and the relationship between the magnitudes of the elasticity in the inhalation and exhalation phases. The constraints are expressed as follows: ; in, This is a matrix showing the magnitude relationship of respiratory mechanics parameters during the inspiratory and expiratory phases and the temporal variation trend of the patient's active breathing. b The product of the trend matrix of unknown quantities and the unknown quantity, x is a column vector composed of the time-partial values of the resistance during the inspiratory phase, the resistance during the expiratory phase, the elasticity during the inspiratory phase, the elasticity during the expiratory phase, and the equivalent pressure of the patient's active breathing. By setting constraints on A and b, the relationship between the resistance during the inspiratory phase and the resistance during the expiratory phase, and the relationship between the elasticity during the inspiratory phase and the elasticity during the expiratory phase are set. At the same time, the trend of the patient's active breathing is constrained, so as to achieve the estimation of respiratory systems with significantly different resistance and elasticity during the inspiratory and expiratory phases. The mathematical model of the respiratory system is expressed as follows: in, This indicates the moment when the inspiratory phase of the ventilator ends and the expiratory phase begins. t N Indicates the end time of the respiratory cycle. This indicates the resistance during the inhalation phase. This indicates the resistance during the exhalation phase. This indicates the elasticity during the inhalation phase. Indicates the flexibility during the exhalation phase. Let be the airway pressure at time t. Let be the airway flow rate at time t. Let be the airway volume at time t. Let t be the equivalent pressure of the patient's active breathing. It is a constant.
6. The respiratory mechanics parameter determination device for a respiratory system according to claim 5, characterized in that, The pressure and flow acquisition module includes a pressure sensor and a flow sensor, both of which are installed on the tubing connecting the ventilator and the patient.