PSV group settings. Initially, clinicians will set PSV to meet the following targets: tidal volume (Vt) of 6-8 mL/Kg of predicted body weight (PBW), with respiratory rate (RR) 20-35 bpm. In presence of Vt >8 ml/kg PBW and/or RR <20 bpm, PSV zero (CPAP) will be selected. FiO2 will be left as selected before the pre-randomization Sigh test, while PEEP will be left as clinically set.