Method of expiration controlTechnical field
The present invention relates to a kind of method of expiration control, more specifically, relate to a kind of for controlling the method for expiration control containing the outlet valve of drive circuit in bi-directional.
Background technology
In the product design of Pneumatic electrical control type respirator, the control of outlet valve is to realize mechanical ventilation key, particularly with the Novel breathing apparatus of active expiration valve, using reducing expiratory resistance as one of the implementation goal controlled of exhaling.
Common respirator outlet valve has in the method for expiratory phase:
One: single pressure control, set changeless single outlet valve control signal entering after expiratory phase, make outlet valve be output as PEEP (end expiratory positive pressure) in whole expiratory phase.This scheme can produce corresponding expiratory resistance in whole expiration phase, makes patient produce the sensation of expiratory dyspnea.
Two: two-phase method, is divided into 2 stage controls entering the output pressure of air valve after expiratory phase.First open outlet valve in the first stage, second stage output PEEP (end expiratory positive pressure).Although this scheme can reduce expiratory resistance in the first stage, the division in each stage does not have mathematical model that reference is provided, and on hardware, there is no corresponding scheme support.
In addition, in the invention that is entitled as " proportional solenoid valve control method " that is 200810239313.7 at application number, disclose a kind of novel mechanism that can bi-directional drive control electromagnetic valve, this mechanism is controlled this electromagnetic valve by changing the pressure on electromagnetic valve both direction, reach and reduced costs, proposed high performance requirement.But in this scheme, do not relate to the control method of the optimization for reducing expiratory resistance, Based Intelligent Control patient respiratory
Summary of the invention
The object of the present invention is to provide a kind of control method of the optimization that reduces expiratory resistance, Based Intelligent Control patient respiratory.
To achieve these goals, the invention provides a kind of method of expiration control, for controlling the outlet valve containing drive circuit in bi-directional, said method comprising the steps of: step 1, before expiration starts, close outlet valve; Step 2, after expiration starts, is opened to maximum by outlet valve; Step 3, determines expiratory duration according to sampled signal; Step 4 closes to predetermined extent with specific curves relation by breather valve in expiratory duration; And step 5, return to step 1.
Wherein, described sampled signal is tidal volume Vt, the peak flow peak flow recording and the front airway pressure Pend that exhales, and described expiratory duration is determined according to following formula:
τ=R × C=Vt/peak flow formula 1
P (t)=Pend × exp (t/ τ) formula 2
Wherein, P (t) is the airway pressure in the expiration phase t moment, when artificially setting after end-tidal airway pressure PEEP according to expiration person's needs, make PEEP=P (t1)=Pend × exp (t1/ τ) can obtain from exhaling and start to the time t1 of the end of exhaling.
In addition, described specific curves relation is linearity, secondary or index curve relation.
In addition, the described step of closing described outlet valve is by realizing to outlet valve output maximum forward controlled pressure.
In addition, described maximum step that described outlet valve is opened to is by realizing to outlet valve output and the maximum reverse controlled pressure of maximum forward controlled pressure opposite direction.
The present invention has adopted a new method of expiration control, can make the expiratory resistance of respirator, anesthetic machine greatly reduce, reduce patient's acting of exhaling, and has increased patient and use the level of comfort of respirator.
Brief description of the drawings
Accompanying drawing described herein is used to provide a further understanding of the present invention, forms the application's a part, and schematic description and description of the present invention is used for explaining the present invention, does not form limitation of the invention.In the accompanying drawings:
Fig. 1 is the simplified electrical circuit diagram according to system model of the present invention;
Fig. 2 is according to the relation curve of expiratory gas flow of the present invention and time;
Fig. 3 is according to the relation curve of breath pressure of the present invention and time; And
Fig. 4 is according to the schematic circuit of the outlet valve containing drive circuit in bi-directional of the present invention.
Fig. 5 is the flow chart according to software control method of the present invention.
Detailed description of the invention
system modelling
As shown in Figure 1, the expiration phase system model of respirator is R, C first-order system.
As shown in Figure 2, in the relation curve of expiratory gas flow and time, the waveform of first half section time represents inspiratory phase flow waveform, and the waveform of time second half section represents expiratory phase flow waveform.
As shown in Figure 3, in the relation curve of breath pressure and time, the waveform of first half section time represents inspiratory phase pressure waveform, and the waveform of time second half section represents expiratory phase pressure waveform.
Calculate expiratory duration constant τ:
τ=R × C=Vt/peak flow formula 1
The unit of expiratory duration constant is second or millisecond.
Wherein, Vt is tidal volume, Unit/mL, the capacity summation of the breath of once exhaling; Peak flow represents peak flow, unit mL/s, the peak flow values of the breath of once exhaling.Vt and peak flow can be measured and be calculated in real time by the flow transducer of respirator.
Calculate the time t of the airway pressure that reaches end-tidal according to τ:
P (t)=Pend × exp (t/ τ) formula 2
Pend is the airway pressure of (when air-breathing end) before the expiration measuring, and P (t) is the airway pressure in the expiration phase t moment.In the time determining the setup pressure value (being P (t)=PEEP) of end-tidal, can obtain t.
hardware designs
The design of drive circuit of expiration proportioning valve adopts bidirectional current drive circuit (application number 200810239313.7 is entitled as " proportional solenoid valve control method ").As Fig. 4.
software control method
As shown in Figure 5,
Step 1 is exported maximum forward controlled pressure before expiration starts.(for preventing outlet valve gas leakage, often close the most sternly at expiratory phase outlet valve, need to export maximum pressure)
Step 2 is exported maximum reverse controlled pressure after expiration starts, and makes the resistance minimum of air flue.
Step 3, calculates τ according to formula 1, calculates t according to formula 2.
Step 4, before arriving the t moment, the slow controlled pressure that increases outlet valve, can pass through linear growth, or reach end-tidal airway pressure PEEP by modes such as exponential curve growths.
Step 5, returns to step 1.
The foregoing is only embodiments of the invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment of doing, be equal to replacement, improvement etc., within all should being included in claim scope of the present invention.