Research On Key Technologies Of Ventilation Mode Based On Active Servo Lung

The ventilator is an important tool in treating patients with acute/chronic respiratory failure or insufficiency. The ventilation modes are the ventilation rlues and determine the efficacy of clinical treatment and therefore possess significant research value. In order to improve the man-machine harmony and avoid the risks that exist in live tests, this paper made a profound research based on an active servo lung. And the key technologies included building the model of the ventilation system, establishing the testing platform, estimation of the model's parameters and control methods of ventilation based on man-machine harmony. The content and final conclusions are as follows:(1) A non-linear time-varying system model is built with compliance, resistance and pressure produced by the respiratory muscles. Its suitability was verified by analyzing the clinical ventilation data from different patients and comparing it with available typical mechanical modes. And the pneumatics models of the blocks of the ventilator gas way were built. By combining the models mentioned above, the lumped parameter model was built, providing basic theories for ventilation mode research.(2) Based on active servo lung, the testing platform for ventilation mode research is established to avoid risks that exist in live tests. This platform aims at eliminating problems caused by the current platform for its poor simulation and debug capacity, low controlling accuracy and inability to conduct the assist ventilation mode.(3) A pre-ventilation measurement method for the circuit compliance is proposed to analyze of the circuit diffluence quantitatively. A least square physiological method based on the proportional assist ventilation(PAV) is presented to estimate the resistence and the compliance of the respiratory system. Compared with M.Younes'method, this method improves the resistance estimation availability from 48.9% to 73.7% and eliminates the single shot measurement error and improves the estimation accuracy.(4) In order to improve the man-machine harmony during ventilation, and concerning the ventilation level, the ventilation safety and the man-machine synchrony, the corresponding improvement methods are put forward. They are as follows:①A volume proportional compensation method and an pressure compensation method under invasive ventilation are presented to eliminate the impacts caused by the circuit on tidal volume and by the endotracheal tube on the airway pressure, respectively. As proved by the theoretical analysis and the test results, the tidal volume is improved from EC /( EC + Er s )×Vset to the set value Vs et and the airway pressure is improved from Pr ef ?λRT V to the set value Pr ef.( Er s, EC , Rr s, RT andλare the elasticity coefficient of the respiratory system and the circuit, the resistance of the respiratory system and the endotracheal tube, the auto penalty coefficient, respectively.) ②The PI parameter fuzzy self-modified control method has been used. The test results have proved that this method, compared with taditional PI, efficiently reduces pressure overshoot and oscillation, and improves the ventilation safety.③A first order adaptive ventilation control method has been presented. The theoretical analysis and the test results have proved that, by using this method, the pressure overshoot and oscillation are eliminated, that the pressure rise time is accurately controlled, and that under the guarantee for the tidal volume, the smallest airway pressure can be calculated and reduce the hurt of high airway pressure and improve the ventilation safety.④The basis flow has been adopted to gain the flow and pressure double close-up ventilation control method. The theoretical analysis and the simulation results indicate that this method traces the movement of the patient's respiratory muscles timely and efficiently, improves the man-machine harmony, lowers the effective output resistance of the ventilator, reduces the work that the ventilator does to the patiet and is good for the recovery of the patient's spontaneous respiration ability.⑤The on-line automatic regulation of the pressure support(PS) level has been realized according to the expertise, the fuzzy logic and reasoning method. Compard the simulation results with actual adjustment results, this method has reached the optimal choice of the PS level, that ensured the safety level of the physiological parameters, and decreased the occurrence probability of the ventilation safety problems and the man-machine asynchrony problems caused by improper PS level.(5) The volume control and pressure control ventilation mode have been successfully realized and applied to the anesthesia machine AS3000, and their validity has been testified by clinical data. The pressure support ventilation mode has been realized on the ventilator Shangrila590, the control ability of the pressure rise time and the stability of the airway pressure is close to or even better than those of the foreign ventilator brands. Three dual control ventilation modes, the volume assured pressure support, the pressure regulted volume control and the adaptive support ventilation mode, have been realized on the Shangrila590, as indicated by the test results, the output flow, the airway pressure and the volume curve of the three modes meet the standard, and we can carry out further animal and human experimentation. By using the PI parameter fuzzy self-modified control method, the PAV mode has been realized on the Shangrila590, and the stability conditions of th PAV system has been obtained, which is a firm step in the quest of the PAV mode research.The above-mentioned investigations have definite referential values and practical meanings for further research on ventilation modes and for improving the ventilator functions and the marketability of the product.