Background: The aim of this study was to explore the effects of different tidal volume (VT) ventilation on paraquat-induced acute lung injury or acute respiratory distress syndrome (ALI/ARDS) in piglets.
Material and Methods: We developed ALI/ARDS models in piglets by intraperitoneal injection of paraquat (PQ). The piglets were randomly divided into three groups: small VT group (VT=6 ml/kg, n=6), middle VT group (VT=10 ml/kg, n=6), and large VT group (VT=15 ml/kg, n=6), with the positive end-expiratory pressure (PEEP) set as 10 cmH2O. The hemodynamics were monitored by pulse-indicated continuous cardiac output (PiCCO) and the airway pressure changes and blood gas analysis indexes were recorded at different time points. The pathological changes were observed by lung puncture.
Results: The piglets showed ALI/ARDS in 4.5±0.8 hours after PQ intraperitoneal injection. PH, PaO2 and oxygenation indexes in the three groups all decreased after modeling success compared with baseline, and PaCO2 increased significantly. PH in the small VT group decreased most obviously after ventilation for 6 hours. PaO2 and oxygenation indexes in the small VT group showed the most obvious increase after ventilation for 2 hours and were much higher than the other two groups after ventilation for 6 hours. PaCO2 increased gradually after mechanical ventilation and the small VT group showed most obvious increase. The ELWI increased obviously after ventilation for 2 hours and then the small VT group clearly decreased. PIP and plateau pressure (Pplat) in the small VT group decreased gradually and in the middle and large VT group they increased after ventilation. The lung histopathology showed that the large VT group had the most severe damage and the small VT group had only minimal damage.
Conclusions: Small tidal volume ventilation combined with PEEP could alleviate the acute lung injury induced by paraquat and improve oxygenation.

Keywords: Acute Lung Injury - therapy, Animals, Blood Gas Analysis, Cardiac Output - physiology, Disease Models, Animal, Hemodynamics, Herbicides - toxicity, Injections, Intraperitoneal, Paraquat - toxicity, Positive-Pressure Respiration - methods, Respiratory Distress Syndrome, Adult - physiopathology, Swine, Tidal Volume - physiology, Time Factors