A method for detecting a ventilator pipeline

Abstract

The present invention discloses a method for detecting a ventilator pipeline, including establishing a model according to various parameters and corresponding equivalent relationships; connecting the ventilator pipeline well; supplying air to the pipeline at a constant flow rate Q V to the pipeline until the airway pressure in the pipeline rises to 10 cmH2O, and recording the moment t1; if the airway pressure cannot rise to 10 cmH2O within 10 s, the detection is ended; otherwise, continue the detection; supply air at a constant flow rate until the airway pressure in the pipeline rises to 40 cmH2O. By performing linear system analysis and modeling on the pipeline, and using the flow rate measured by the flow sensor and the pressure value measured by the pressure sensor to estimate the parameters in the model, the compliance, resistance, and leakage amount parameters of the pipeline can be conveniently and accurately obtained, which not only facilitates the operation, but also greatly improves the test efficiency and the accuracy of the measurement results.

Description

Technical Field

[0001] The present invention relates to a method for detecting a ventilator pipeline. Background Art

[0002] A ventilator is an important life support device used in departments such as the hospital ICU, etc., for treating patients with respiratory function disorders. The ventilator delivers gas to the patient according to the modes and parameters set by the user. The ventilator is connected to the patient through a pipeline, so the state of the pipeline will directly affect the ventilation effect.

[0003] The several most critical parameters related to ventilation of the pipeline are: compliance, resistance, and leakage volume. These parameters will affect the ventilation control and parameter calculation of the ventilator. For example: If the flow sensor is located upstream of the inhalation branch of the pipeline, then the influence of pipeline compliance needs to be considered when calculating the tidal volume; when performing operations related to airway pressure control or judgment, pipeline resistance is a factor that needs to be considered; and when calculating all parameters related to flow, the pipeline leakage volume is an important influencing factor.

[0004] Therefore, the acquisition of these key pipeline parameters has become a prerequisite for ensuring high-quality and normal ventilation of the ventilator. Although the standard pipeline has marked parameters such as compliance and resistance when leaving the factory, these parameters may change after long-term use. In addition, during the normal use of the ventilator, in addition to the breathing pipeline, components such as a humidifier may also need to be connected, and these components will also affect the parameters of the pipeline. This requires the ventilator to be able to dynamically detect the pipeline to determine the values of its key parameters.

[0005] The traditional method for detecting the pipeline is to manually measure the pipeline parameters. For example, the compliance and leakage volume can be obtained by filling a certain volume of gas into a closed pipeline and observing the change in pressure inside the pipeline; while the resistance can be obtained by inputting a constant flow of gas into an open pipeline and observing the pressure difference between the inhalation end and the exhalation end of the pipeline. The disadvantages of these methods for pipeline leakage volume are inconvenient operation and poor measurement accuracy.

[0006] With the development of technology, some methods for automatically detecting pipeline parameters have also emerged one after another. However, most of these methods only process and automate the above-mentioned manual measurement methods through software by using an MCU, and there are still problems of low test efficiency and poor measurement accuracy. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for detecting a ventilator pipeline to solve the problems of inconvenient operation and poor measurement accuracy of the traditional pipeline detection method mentioned in the above background art.

[0008] To achieve the above object, the present invention provides the following technical solutions: A method for detecting a ventilator pipeline, comprising the following steps:

[0009] Step 1: Establish a linear respiratory mechanics model of the pipeline according to the corresponding equivalent relationship between the resistance and compliance in the known respiratory gas path and the resistance and capacitance in the circuit;

[0010] Step 2: Connect the ventilator pipeline well, and connect the Y-piece port of the respiratory pipeline to the plug for sealing;

[0011] Step 3: Close the expiratory valve, and send air into the ventilator pipeline at a constant flow rate Q V Open the inspiratory valve to send air into the ventilator pipeline until the airway pressure in the pipeline rises to P1, record the moment t1 at this time, and preset that under normal circumstances, air is sent at a constant flow rate Q V until the airway pressure rises to P1, and the time is T1, and compare t1 and T1;

[0012] If t1 > T1, it is considered that the leakage amount is too large and the pipeline test fails, and the detection ends;

[0013] On the contrary, if t1 ≤ T1, continue the detection;

[0014] Step 4: Continue to send air at a constant flow rate Q V until the airway pressure in the pipeline rises to P2. During this process, set a time interval T, and record the airway pressure P, the air supply flow rate Q V during the rising process every time the time interval T is increased, and the moment t2 when the airway pressure reaches P2;

[0015] Step 5: Use the air supply flow rate Q measured by the flow sensor V and the airway pressure P measured by the pressure sensor to estimate the parameters in the linear respiratory mechanics model of the pipeline, so as to obtain the pipeline compliance C T the pipeline leakage air resistance R L and the pipeline resistance R T parameters, where: the following formula is obtained through the linear respiratory mechanics model of the pipeline:

[0016]

[0017]

[0018] where t is the comparison moment, and u is the time variable in the integral formula;

[0019] P(t) is the airway pressure at moment t, Q V is the air supply flow rate, Q L is the pipeline leakage flow rate, C T is the pipeline compliance, RL is the air resistance due to pipeline leakage, R T is the pipeline resistance; Q T Q(t) is the pipeline storage flow rate at time t L Q(t) is the pipeline leakage flow rate at time t V Q(u) is the air supply flow rate at u L du is the integral symbol, representing the integrand variable. Q(u) is the pipeline leakage flow rate at u

[0020] Preferably, in step three, Q V is 5 L / min, P1 is 10 cmH 2 O, and T1 is 10 s

[0021] Preferably, in step four, P2 is 40 cmH 2 O, and T is 10 ms

[0022] Preferably, step five includes the following steps:

[0023] Step 5.1: After discretization, the following formula is obtained using the Least Square Fitting method:

[0024]

[0025] Where:

[0026]

[0027] k3 = R T (10);

[0028]

[0029] In formulas (4)-(13), K1, K2, K3, and K4 respectively represent intermediate variable one, intermediate variable two, intermediate variable three, and intermediate variable four. n is a natural number, representing the nth sampling value. S1 and S2 respectively represent intermediate variable five and intermediate variable six. Δt represents the sampling time. P(n) represents the airway pressure at the nth sampling point. Q V Q(n) represents the air supply flow rate at the nth sampling point

[0030] Step 5.2: It can be obtained by Cramer's rule:

[0031]

[0032]

[0033] Therefore, the pipeline parameters are:

[0034] RT = k3(25);

[0035] In formulas (14)-(25), D, D1, D2, D3, and D4 respectively represent intermediate variable seven, intermediate variable eight, intermediate variable nine, intermediate variable ten, and intermediate variable eleven.

[0036] Compared with the prior art, the advantages and benefits of the present invention are as follows:

[0037] Through linear system analysis and modeling of the pipeline, the present invention estimates the parameters in the model using the flow rate measured by the flow sensor and the pressure value measured by the pressure sensor. In this way, the compliance, resistance, and leakage parameters of the pipeline can be conveniently and accurately obtained, which not only facilitates operation but also greatly improves the test efficiency and the accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the linear model diagram of the respiratory mechanics of the pipeline of the present invention;

[0039] Figure 2 is the flow chart of pipeline detection of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Please refer to Figure 1-2 , the present invention provides a technical solution: a method for detecting a ventilator pipeline, including the following steps:

[0042] Step 1: Establish a linear model of respiratory mechanics of the pipeline according to the corresponding equivalent relationship between the resistance and compliance in the known respiratory gas path and the resistance and capacitance in the circuit;

[0043] Step 2: Connect the ventilator pipeline well, and connect the Y-piece port of the respiratory pipeline to the plug for sealing;

[0044] Step 3: Close the expiratory valve, and send gas to the ventilator pipeline at a constant flow rate Q V Open the inspiratory valve to send gas to the ventilator pipeline until the airway pressure in the pipeline rises to P1, record the time t1 at this time, and preset that under normal circumstances, the time for sending gas at a constant flow rate Q V to rise to P1 is T1, and compare t1 and T1;

[0045] If t1 > T1, it is considered that the leakage is excessive and the pipeline test fails, and the detection ends;

[0046] On the contrary, if t1 ≤ T1, continue the detection;

[0047] Further, in step three, Q V is 5 L / min, P1 is 10 cmH 2 O, and T1 is 10 s.

[0048] Step four: Continue to supply air at a constant flow rate Q V until the airway pressure in the pipeline rises to P2. During this process, at a regular time interval T, record the airway pressure P, the air supply flow rate Q V during the rising process for each increase in the time interval T, and the moment t2 when the airway pressure reaches P2;

[0049] Further, in step four, P2 is 40 cmH 2 O, and T is 10 ms.

[0050] Step five: Use the air supply flow rate Q measured by the flow sensor V and the airway pressure P measured by the pressure sensor to estimate the parameters in the respiratory mechanics linear model of the pipeline to obtain the pipeline compliance C T 、the pipeline leakage air resistance R L and the pipeline resistance R T parameters, where: the following formula is obtained through the respiratory mechanics linear model of the pipeline:

[0051]

[0052] where t is the comparison moment, and u is the time variable in the integral formula;

[0053] P(t) is the airway pressure at moment t, Q V is the air supply flow rate, Q L is the pipeline leakage flow rate, C T is the pipeline compliance, R L is the pipeline leakage air resistance, R T is the pipeline resistance; Q T (t) is the pipeline storage flow rate at moment t, Q L (t) is the pipeline leakage flow rate at moment t, Q V (u) is the air supply flow rate at u, Q L (u) is the pipeline leakage flow rate at u, and du is the integral symbol, indicating the integrand variable.

[0054] In the present invention, by performing linear system analysis and modeling on the pipeline, and using the flow rate measured by the flow sensor and the pressure value measured by the pressure sensor to estimate the parameters in the model, the compliance, resistance, and leakage amount parameters of the pipeline can be conveniently and accurately obtained. This not only facilitates the operation but also greatly improves the test efficiency and the accuracy of the measurement results.

[0055] Further, Step 5 includes the following steps:

[0056] Step 5.1: After discretization, the following formula is obtained by using the Least Square Fitting method:

[0057]

[0058] Where:

[0059]

[0060] k3 = R T (10);

[0061]

[0062] In formulas (4)-(13), K1, K2, K3, and K4 respectively represent intermediate variable one, intermediate variable two, intermediate variable three, and intermediate variable four. n is a natural number representing the nth sampling value. S1 and S2 respectively represent intermediate variable five and intermediate variable six. Δt represents the sampling time. P(n) represents the airway pressure at the nth sampling point, and Q V (n) represents the gas supply flow rate at the nth sampling point.

[0063] Step 5.2: It can be obtained by Cramer's rule that:

[0064]

[0065]

[0066] Therefore, the pipeline parameters are:

[0067]

[0068] R T = k3 (25);

[0069] In formulas (14)-(25), D, D1, D2, D3, and D4 respectively represent intermediate variable seven, intermediate variable eight, intermediate variable nine, intermediate variable ten, and intermediate variable eleven.

[0070] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A ventilator pipeline detection method, characterized in that: The following steps are involved: Step 1: Establish a respiratory mechanics linear model of the pipeline based on the known equivalent relationship between the resistance and compliance in the respiratory airway and the resistance and capacitance in the circuit; Step 2: Connect the ventilator tube and connect the Y-piece port of the breathing tube to the plug for sealing; Step 3: Close the exhalation valve and keep the flow rate Q constant. V Open the inhalation valve to supply air to the ventilator pipeline until the airway pressure in the pipeline rises to P1, and record the time t1 at this time. Under normal circumstances, the constant flow rate Q is preset. V The time from air supply until the airway pressure rises to P1 is T1, and t1 is compared with T1; If t1>T1, it is considered that the leakage is too large, the pipeline test fails, and the test ends; On the contrary, if t1≤T1, continue to detect; Step 4: Continue with constant flow rate Q V Supply air until the airway pressure in the pipeline rises to P2. During this process, set a time interval T and record the airway pressure P and air flow Q during the rising process at each time interval T. V , and the time t2 when the airway pressure reaches P2; Step 5: Use the flow sensor to measure the air flow Q V The airway pressure P measured by the pressure sensor is used to estimate the parameters in the respiratory mechanics linear model of the circuit to obtain the circuit compliance C T , Pipeline leakage air resistance R L And the pipeline resistance R T Parameters, where: The following formula is obtained through the respiratory mechanics linear model of the pipeline: Among them, t is the comparison time, and u is the time variable in the integral formula; P(t) is the airway pressure at time t, Q V is the air flow rate, Q L is the pipeline leakage flow, C T is the pipeline compliance, R L is the pipeline leakage resistance, R T is the pipeline resistance; Q T (t) is the pipeline storage flow at time t, Q L (t) is the pipeline leakage flow at time t, Q V (u) is the air flow rate at time u, Q L (u) is the pipeline leakage flow at time u, du is the integral symbol, representing the integrand.

2. A ventilator pipeline detection method according to claim 1, characterized in that: Step 3 Q V is 5L / min, P1 is 10cmH2O, and T1 is 10s.

3. A ventilator pipeline detection method according to claim 1, characterized in that: In step 4, P2 is 40 cmH2O and T is 10 ms.

4. A ventilator circuit detection method according to claim 1, characterized in that: Step five includes the following steps: Step 5.1, after discretization, use the Least Square Fitting method to get the following formula: in: k3=R T (10); In formulas (4)-(13), K1, K2, K3, and K4 represent intermediate variables 1, 2, 3, and 4, respectively; n is a natural number, representing the nth sampling value; S1 and S2 represent intermediate variables 5 and 6, respectively; Δt represents the sampling time; P(n) represents the airway pressure at the nth sampling point; Q V (n) represents the air flow rate at the nth sampling point, Step 5.2, can be obtained by Cramer's law: Therefore, the pipeline parameters are: R T =k3 (25); In formulas (14)-(25), D, D1, D2, D3, and D4 represent intermediate variable seven, intermediate variable eight, intermediate variable nine, intermediate variable ten, and intermediate variable eleven, respectively.

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