Lung inflammation caused by large tidal volume mechanical ventilation. A. Histological analysis showed a preserved lung parenchymal structure in the group ventilated with an 8-ml/kg tidal volume for 60 min. In contrast, an increased thickness of the alveolar wall and inflammatory cell invasion were observed in the group ventilated with 40-ml/kg tidal volume. Bars = 100 μm in the upper panels, and = 50 μm in the lower panels. B. Mechanical ventilation with a large tidal volume increased the lung W/D weight ratio significantly. This was not observed in the group mechanically ventilated with a small tidal volume. n = 8 mice in each group; *p < 0.05 vs. control and 8 ml/kg. C. The expression of MIP-2 and IL-6 gene was markedly increased in the lungs mechanically ventilated with a large tidal volume. n = 8 mice in each group; *p < 0.05 vs. control and 8 ml/kg. D. The ATP concentration in BAL fluid was significantly higher in mice ventilated with a large tidal volume than in non-ventilated control mice. n = 4–8 mice in each group; *P < 0.05 vs. control.