Timeline representation of the main procedures used in rats subjected to various ventilation modes. The animals of the control group (C group) were killed immediately after the initial period of spontaneous ventilation. Squares indicate induction of paralysis. BALF = broncho–alveolar lavage fluid; EL and RL = lung dynamic elastance and resistance; NPTOMV or NPWBMV, PPMV, and SV = groups of animals that underwent 4 h of thorax-only or whole-body negative pressure ventilation, positive pressure mechanical ventilation, and spontaneous ventilation, respectively; P-V = respiratory system pressure–volume curves; W/D = lung wet-to-dry ratio.