CN113288113B - Method for online measuring and calculating respiratory tract air resistance and compliance of noninvasive positive pressure respirator - Google Patents
Method for online measuring and calculating respiratory tract air resistance and compliance of noninvasive positive pressure respirator Download PDFInfo
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Abstract
The invention provides a method for online measuring and calculating respiratory tract air resistance and compliance of a noninvasive positive pressure respirator, wherein the respirator comprises an air flow source, an airway and an end-expiratory pulse pressure relief valve, the air flow source is communicated with a human respiratory system through the airway, and the end-expiratory pulse pressure relief valve is arranged on the airway; when the breathing machine is used for ventilation, the breathing machine controls the end-expiratory pulse pressure relief valve to open when detecting that the user is at the end of expiration, so that the airflow in the airway is quickly released, and the expiratory support pressure EPAP is controlled to jump down by delta P within delta t. At the moment, the lung deflates under the internal and external pressure difference, the pulmonary deflation flow Q (t) of the user at each moment in the time period is obtained through flow monitor data and air leakage flow calculation, and the respiratory tract air resistance R and the compliance C are obtained through calculation according to a formula. The method of the invention is helpful for medical staff to adjust the ventilation parameters of the breathing machine in time according to the ventilation condition of the patient, reduce the ventilation complication and improve the ventilation curative effect.
Description
Technical Field
The invention relates to the technical field of noninvasive positive pressure ventilation, in particular to a method for online measuring and calculating respiratory tract air resistance and compliance by a noninvasive positive pressure respirator.
Background
Noninvasive positive pressure ventilation is one of the important means for treating patients with various respiratory diseases at present. In the process of noninvasive positive pressure ventilation, the ventilation pressure and flow given by the breathing machine are adjusted in time by measuring respiratory tract air Resistance (R) and Compliance (C), so that ventilation complications can be effectively reduced, the ventilation curative effect of the breathing machine is improved, and the formulation of individual accurate ventilation strategies for different patients is realized.
When the early lung function plethysmograph is used, a patient to be detected needs to be placed in a closed box, and breathing is forcefully performed through an air suction port to measure, analyze and calculate breathing mechanics parameters; the method needs a special box body, is mainly suitable for patients in stable disease period and healthy physical examiners who visit hospitals, and has low confidence of obtained data and poor experience of detection process. The esophageal pressure test method was later used to measure the pressure generated when the gas flow passes through the airway by inserting a specific pressure acquisition device into the esophagus of the patient to be tested; however, this method is inevitable and is liable to cause adverse reactions such as esophageal inflammation. At present, a respirator is matched with a forced sinusoidal oscillation method (FOS) and a pulse oscillation method (IOS) for detection in hospitals, 5-10Hz oscillation air pressure and pulse air pressure are applied to a human respiratory system to obtain respiratory impedance of different frequencies, and required respiratory mechanics parameters are obtained after continuous recording, analysis and calculation are carried out on airway pressure and flow; in order to cooperate with the detection, the patient to be detected must be seated on a special chair, and the sitting posture is required to be correct, natural and the like.
The currently adopted dynamic measuring and calculating method of respiratory mechanics parameters is interfered by factors such as equipment structure and autonomous respiration force under the condition of noninvasive ventilation, so that the measuring and calculating precision needs to be further improved, and the reliability of a detection result is influenced due to errors of the measured and calculated results under different respiratory states.
Disclosure of Invention
The invention aims to provide a real-time online measuring and calculating method for the respiratory tract air resistance and compliance of a human body, which is used in cooperation with a breathing machine and is prevented from being interfered by factors such as oscillating air pressure, autonomous respiration force and the like, so as to solve the problems in the background art.
In order to achieve the purpose, the invention provides a method for online measuring and calculating respiratory tract air resistance and compliance of a noninvasive positive pressure respirator, which comprises an air flow source, an airway and an end-expiratory pulse relief valve, wherein the air flow source is communicated with a human respiratory system through the airway, the end-expiratory pulse relief valve is arranged on the airway, when a user is at the end of expiration, the respirator controls the end-expiratory pulse relief valve to be opened, the air flow in the airway is relieved, the expiratory support pressure EPAP is reduced by delta P within delta t, at the moment, the lung is released under the internal and external pressure difference delta P, and the released air flow Q (t) of the lung at the corresponding moment is recorded;
respiratory tract air resistance R and compliance C were calculated:
in some possible embodiments, the lung discharge flow Q (t) is obtained by subtracting the leakage flow from the flow of gas through the airway at the corresponding time.
In some possible embodiments, the ventilator further comprises a pressure monitor by which the real-time expiratory support pressure EPAP is obtained, and a flow monitor by which the real-time flow of gas through the airway is obtained.
In some possible embodiments, the ventilator further comprises a human-machine interface for displaying and/or uploading user airway resistance and compliance data.
In some possible embodiments, the end-tidal flow is detected when the flow monitor detects that the flow of air exhaled by the user is zero.
The technical scheme provided by the invention at least has the following beneficial effects:
1. the invention provides a novel method for measuring and calculating respiratory tract air resistance and compliance.A negative air pressure pulse with the width of delta t and the amplitude of delta P is generated aiming at expiratory support pressure at the end of expiration, so that short deflation of a lung occurs, and the respiratory tract air resistance R and the compliance C are calculated according to a formula by combining the detected pulmonary discharge flow Q (t); according to the method, the oscillation air pressure is not required to be generated, the detection can be realized by simply controlling the opening and closing actions of the end-expiratory pulse pressure relief valve, and the simplification of the structure of breathing machine equipment and the measurement and calculation process are facilitated.
2. The method can be combined with the original control system of the breathing machine, avoids the influence of spontaneous breathing factors, improves the accuracy of the measurement and calculation results, is beneficial to medical staff to adjust the ventilation parameters of the breathing machine in time according to the ventilation condition of a patient, reduces the ventilation complications and improves the ventilation curative effect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of ventilation performed by a ventilator in accordance with example 1 of the present invention, wherein A is the airflow discharged during a brief deflation period of the lungs, and B is the leakage airflow;
FIG. 2 is a schematic diagram of the variation of ventilation pressure and spontaneous breathing effort in embodiment 1 of the present invention, wherein IPAP is inspiratory support pressure, EPAP is expiratory support pressure, P mus For spontaneous respiratory effort, T I Is the inspiration time, T is the breathing cycle;
FIG. 3 is a circuit discharge model constructed to simulate the deflation of the lungs through the airway in example 1 of the present invention, with airway resistance R as resistance, compliance C as capacitance, negative pressure pulse Δ P as voltage, and lung discharge flow Q (t) as current through the circuit;
FIG. 4 is a graph of the respiratory gas flow in the lungs as a function of time in example 1 of the present invention;
wherein: the system comprises a fan 1, a controller 2, an end-expiratory pulse pressure relief valve 3, a pressure monitor 4, a flow monitor 5, a fan drive 6 and a valve drive 7.
Detailed Description
In order to facilitate understanding of the present invention, the technical solutions in the present invention will be described more fully and in detail with reference to the drawings and the preferred embodiments, but the scope of the present invention is not limited to the following specific embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of the present invention.
It will be understood that when an element is referred to as being "coupled" or "connected" to another element, it can be directly coupled, connected or communicated with the other element or indirectly coupled, connected or communicated with the other element via other intervening elements.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Example 1
Referring to fig. 1, a method for online measuring and calculating airway resistance and compliance is used in cooperation with a noninvasive positive pressure ventilator, the ventilator includes an airflow source, an airway, a controller 2, an end-expiratory pulse relief valve 3, a pressure monitor 4 and a flow monitor 5, the airflow source is communicated with a respiratory system of a human body through the airway, the end-expiratory pulse relief valve 3 is arranged on the airway, sensing probes of the pressure monitor 4 and the flow monitor 5 are arranged inside the airway, and the controller 2 is respectively electrically connected with the pressure monitor 4, the flow monitor 5, a valve driver 7 of the end-expiratory pulse relief valve 3 and a driving of the airflow source.
In this embodiment, the ventilator further comprises a human-machine interface for displaying and/or uploading user respiratory tract air resistance and compliance data; the airflow source is specifically a fan 1, and the airflow source is driven by a correspondingly arranged fan drive 6.
When the breathing machine is used, the breathing machine outputs the inspiration supporting pressure IPAP after monitoring the inspiration action of the user, and the breathing machine switches to output the expiration supporting pressure EPAP after monitoring the expiration action of the user.
During ventilator ventilation, in order to dynamically detect airway resistance R and compliance C, ventilation measures as shown in fig. 2 are taken at the end of inspiration. Specifically, when the flow monitor 5 detects that the end-expiratory airflow of the user is 0, the intra-pulmonary pressure at this time and the external ventilation pressure reach a balance, that is, the intra-pulmonary pressure is equal to the expiratory support pressure EPAP, and at this time, t =0; the controller 2 controls the end-expiratory pulse pressure relief valve 3 to open the flow for venting, and controls the expiratory support pressure EPAP of the respirator to rapidly decrease by delta P within a next period of time delta t, so that a differential pressure equal to delta P is formed between the air pressure of the lung and the external ventilation pressure, the lung of the user can deflate for a short time under the action of the differential pressure delta P, the deflation condition is shown as an encircled enlargement part in fig. 4, the air flow passing through the ventilation channel in real time and obtained by the flow monitor 5 subtracts the air leakage flow to obtain the lung deflation flow Q (t) in the deflation process, and relevant data are uploaded to the respirator controller 2 for calculation and analysis.
Referring to fig. 3, the process of deflation of the lungs through the airway is modeled as a circuit discharge process. Equation (1) represents the discharge current Q of the capacitor C through the resistor R as a function of time t under voltage:
namely, the lung discharge flow Q (t) varies in size in the time domain under the action of the pressure difference Δ P.
Formula (2) can be derived from formula (1), and respiratory tract air resistance R is calculated when t = 0:
meanwhile, R calculated at time t =0 is substituted into equation (1) where 0 < t < Δ t, and equation (3) is further derived, and respiratory compliance C is calculated:
since the minus sign in the formula (2) and the formula (3) represents that the taken voltage is opposite to the current reference direction, in order not to be affected by the sign, the formulas (4) and (5) can be obtained by sorting:
the above method was simulated and the data obtained are shown in table 1 below.
TABLE 1 respiratory mechanics parameter measurements
Compared with the prior art, the method disclosed by the invention can be used for measuring and calculating the respiratory tract air resistance and compliance in real time, the oscillation air pressure is not required to be generated, the opening and closing of the end-expiratory pulse pressure relief valve are simply controlled, and the operation is simpler and easier. Because the influence of spontaneous respiration factors is avoided, the deviation of the measurement result can be reduced to be within 10 percent (as shown in a simulation result shown in table 1), and the deviation of the result is usually more than 20 percent because the interference caused by spontaneous respiration cannot be avoided in many conventional measurement methods.
The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and various modifications and changes may be made by those skilled in the art. Any improvement or equivalent replacement directly or indirectly applied to other related technical fields within the spirit and principle of the invention and the contents of the specification and the drawings of the invention shall be included in the protection scope of the invention.
Claims (2)
1. A method for online measuring and calculating respiratory tract air resistance and compliance of a noninvasive positive pressure respirator is characterized in that the respirator comprises an air flow source, an airway, an end-expiratory pulse relief valve, a pressure monitor and a flow monitor, wherein the air flow source is communicated with a respiratory system of a human body through the airway, the end-expiratory pulse relief valve is arranged on the airway, the pressure monitor obtains a real-time expiratory support pressure (EPAP), and the flow monitor obtains a real-time gas flow passing through the airway;
when the user is at the end of expiration, the respirator controls the end-expiration pulse pressure release valve to open, releases airflow inside the airway, enables the expiration support pressure EPAP to jump down by delta P within delta t, at the moment, the lung deflates under the difference of internal pressure and external pressure, and records the discharged airflow Q (t) of the lung at the corresponding moment; subtracting the air leakage flow from the air flow passing through the air passage at the corresponding moment to obtain the lung air leakage flow Q (t); when the flow monitor detects that the airflow exhaled by the user is zero, the end-expiratory condition is determined;
respiratory tract air resistance R and compliance C were calculated:
2. the method for on-line airway pressure and compliance estimation by noninvasive positive pressure ventilator of claim 1, wherein the ventilator further comprises a human-computer interface for displaying and/or uploading user airway pressure and compliance data.
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| CN106267493A (en) * | 2016-08-26 | 2017-01-04 | 苏州凯迪泰医学科技有限公司 | Medical breathing machine and continuously measuring and calculating airway resistance and the method for compliance |
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| WO2006012205A2 (en) * | 2004-06-24 | 2006-02-02 | Convergent Engineering, Inc. | METHOD AND APPARATUS FOR NON-INVASIVE PREDICTION OF INTRINSIC POSITIVE END-EXPIRATORY PRESSURE (PEEPi) IN PATIENTS RECEIVING VENTILATOR SUPPORT |
| DE102016012824A1 (en) * | 2016-10-25 | 2018-04-26 | Drägerwerk AG & Co. KGaA | Method and apparatus for adaptively controlling positive end-expiratory pressure (PEEP) |
| CN110237375B (en) * | 2019-04-18 | 2022-07-08 | 北京雅果科技有限公司 | Breathing machine and negative pressure sputum excretion machine |
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| CN107205695A (en) * | 2013-11-06 | 2017-09-26 | 呼吸技术医疗有限公司 | Method and apparatus for measuring airway resistance and lung compliance |
| CN106267493A (en) * | 2016-08-26 | 2017-01-04 | 苏州凯迪泰医学科技有限公司 | Medical breathing machine and continuously measuring and calculating airway resistance and the method for compliance |
| CN111298255A (en) * | 2020-02-22 | 2020-06-19 | 湖南城市学院 | Method for automatically triggering breathing machine to switch and output breathing gas pressure based on ventilation volume |
| CN111544719A (en) * | 2020-05-11 | 2020-08-18 | 武云珍 | Estimation method of dynamic positive end-expiratory pressure in mechanical ventilation |
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