Fig. 1.  Protocol schema. Pressure support level was progressively decreased to constant positive airway pressure (CPAP) and then reset to the level at which the minimum oxygen consumption had been observed (Resting phase). CPAP was then applied for 1 h or interrupted if the patient developed signs of respiratory distress (see text). Finally, a phase of assist/control (A/C) ventilation was performed to measure oxygen consumption under this condition and respiratory mechanics.