Sequential blood gas analysis of mice exposed to mechanical ventilation with high tidal volume (30 mL/kg). (a) The impact of mechanical ventilation with 2% nitrogen in air on the lungs in a time-dependent manner was investigated. Animals showed deteriorated gas exchange before ventilation (0 hour) because of respiratory insufficiency caused by general anesthesia. Although mechanical ventilation improved gas exchange for the first hour, partial pressures of arterial oxygen (PaO2) were decreased with time and partial pressure of arterial carbon dioxide (PaCO2) increased with time. N = 3 to 6 for each time point. (b) Blood gas analysis for arterial blood after the end of 2 hours of mechanical ventilation with high tidal volume. There was improved pulmonary function in mice exposed to ventilator-induced lung injury (VILI) for 2 hours under 2% hydrogen compared with nitrogen controls. N = 8 for each group. *P < 0.05 versus VILI 30 minutes/N2 and VILI 30 minutes/H2; #P < 0.05 versus VILI 2 hours/N2.