Respiratory Distress Syndrome, AdultPositive-Pressure RespirationTidal VolumeRespiration, ArtificialProne PositionAcute Lung InjuryRespiratory MechanicsPulmonary Gas ExchangeBronchoalveolar Lavage FluidPulmonary AlveoliLungBarotraumaHigh-Frequency VentilationExtracorporeal Membrane OxygenationElafinLung InjuryPulmonary Edema