Histological lesions due to mechanical ventilation. Representative histological sections show less perivascular hemorrhage in metformin-pretreated (HiP-Met) compared to untreated (HiP-C) animals after exposure to one hour of injurious ventilation. Perivascular hemorrhage was not observed in the lungs of animals exposed to protective ventilation (LoP-C). Results are presented as medians (range); n = 4 animals per group. *P < 0.05 for HiP-C group vs. all other groups. LoP-C: low pressure-no metformin; LoP-Met: low pressure-metformin; HiP-C: high pressure-no metformin; HiP-Met: high pressure-metformin.