IL6 and acute respiratory distress syndrome: However, prolonging mechanical ventilation to more than 6 h in the current experimental models would also have some limitations: (1) only changes in IL-6 protein levels were observed, since protein synthesis of PCIII and caspase-3 requires more than 6 h, and (2) keeping small animals with ALI alive for 6 h requires administration of larger volumes of fluids, sometimes vasoactive drugs (for example, noradrenaline) to keep MAP higher than 70 mmHg, and bicarbonate to counteract intense metabolic acidosis.