Rescue oxygenation Rescue oxygenation methodology may include high frequency oscillation (HFO) with/without tracheal gas insufflation (TGI), prone positioning, inhaled nitric oxide, and extracorporeal membrane oxygenation. The duration of the rescue oxygenation session will be at least 10 hours with allowance for an unlimited extension if PaO2<60 mmHg. Rescue initiation criterion: PaO2<60 mmHg for more than 30 min at FiO2=1.0, in the absence of any reversible cardio-respiratory pathology and/or ventilator malfunction.