Effects Of Inverse Ratio Ventilation On Cardio-pulmonary Function In Oleic Acid-Induced Lung Injury

[Objectives]This experiment was to study the effects of inverse ratio ventilation (IRV) on the treatment of acute lung injury and its value in clinical application.[Subjects and methods]1. A model of oleic Acid-induced lung Injury was set up: the testing dog, motionless after an anesthesia, was connected with a ventilator to control its breathing, When the predictor read a stable physical index, the dog was injected with, Oleic Acid (0.15-0.20ml/kg) through the central vein, given within 3 minutes, One ventilation, every 30 minutes: PaO2/FiO2≤300 Until ALI model was founded successful.2. The machine (Siemens, 300) tests the airway presurre including peak-pressure, the plateau pressure, the mean airway pressure as well as the dynamic thorace pneumonic compliance3. Cardiac output was measured with a hemodynamic. Monitor (Spacelab. U.S.A) and an assessment apparatus (Spacelab; U.S.A) Was used to measure these physical indexes, including Pulmonary arterial pressure Pvlmonary wedge pressure and mean arterial pressure etc;4. The partial pressure of oxygen was measured with blood gas analyzer (BAYER 248).[Results]1. Compared with that of IPPV group, the mean airway pressures in creased significantly (p<0.05) while the peak airway pressure and the plateau pressures were decreased apparently (p<0.05) and had a little change on the thoracopheanomic compliance; Positive-end expiratory pressure (PEEP) was applied and the different levels of PEEP produced significantly changes (P<0.05) in the airway pressure with the increasing of PEEP: the airwaypressure increasing apparently; When the ratio of IRV was 3:1, the mean airway pressures increase significantly, compared with other ratio of IRV. 2. Compared with the means of IPPV; There were little change in cardiac output, pulmonary arterial pressure pulmonary Wedge pressure as well as the mean arterial pressure in means of pressure, but these physical index were apparent change if the levels of PEEP Were different (P<0.05), compared with IPPV Ventilation mode PaO2 was increased apparently through IRV (p<0.05) and PEEP of different levels had a significant effect on PaO2 (P<0.05). [Conclusions]IRV contributes a lot to the increase of the mean airway pressure and PaO2, and the decrease of the peak airway pressure, Its effect on cardiac circulation system remained the same as the conventional ventilation. It helps reduce the incidence of the concerned pulmonary injury and, improve the oxygenation to meet the body's demand for oxygen. The difference of PEEP level increases both the peak airway pressure and the mean airway pressure, The higher the level, the more effective its inhabitior of the cardiac circalation Although, the PaO2 function was greatly improved, the V/Q radio showed little improvement. Meanwhile the rise of the peak pressure induced high incidence of harotrauma, and harred the recovery of pulmonary tissue of ALI patient, thus the selection of the best PEEP level was the priority in the course of treatment.