Effects of mechanical ventilation on cell apoptosis in lung tissue of rat with acute lung injury

Objective To investigate the effects of different tidal volumes and positive end expiratory pressures on cell apoptosis in lung tissue of rats with acute lung injury.Methods Forty healthy male Sprague-Dawley rats were randomly(random number)divided into five groups,namely low tidal volume group(LV,VT 8 mL/kg),high tidal volume group(HV,VT 30 mL/kg),low tidal volume group with PEEP 2cmH2O(LV2P,VT 8 mL/kg,PEEP 2 cmH2O),low tidal volume group and PEEP 5cmH2O (LV5P,VT 8 mL/kg,PEEP 5 cmH2O)and low tidal volume group and PEEP 8 cmH2O(LV8P,VT 8 mL/kg,PEEP 8 cmH2O).After intravenous administration of oleic acid(OA,0.1 mL/kg),the rat model of acute lung injury was made.Mechanical ventilation was employed in rats of the experiment groups.Rats were sacrificed and their whole lungs were taken after mechanical ventilation for 2 hours.The transferase d-UTP end labeling assay(TUNEL)was used to define the extent and distribution of apoptotic cells in bronchus and lung tissues.The level of caspase-3 protein was determined by immunohistochemistry.Results The apoptotic cells on both alveolar septum and bronchial epithelium obviously increased with high level of caaspase-3 protein in HV group.The number of apoptotic cells obviously decreased with decrease in caspase-3 protein after PEEP ventilation.These changes were more significant in LV5P than those in other groups(P ＜ 0.01).Conclusions The mechanical ventilation with low tidal volume and PEEP produces protective effects on lung from injury.The cell apoptosis plays an important role in the course of VILI. Key words: Acute lung injury;  Ventilation;  Apoptosis;  Caspase-3 protein