Exclusion criteria: Lung disease or pulmonary parenchyma damage, respiratory inspired fraction of oxygen (FiO2) >60% and/or positive end-expiratory pressure (PEEP) > 10 centimetres of water (cmH2O) and/or hemodynamic instability (mean arterial pressure (MAP) < 65 millimetres of mercury (mmHg) although use of vasopressors] , hemofiltered patients through a central jugular catheter, patients on strict dorsal decubitus by medical prescription, and high respiratory infectious risk.