Previous studies showed that the addition of cyclic short recruitment maneuvers (Sigh) to assisted mechanical ventilation: improves oxygenation without increasing ventilation pressures and FiO2; decreases the tidal volumes by decreasing the patient's inspiratory drive; increases the EELV by regional alveolar recruitment; decreases regional heterogeneity of lung parenchyma; decreases patients' inspiratory efforts limiting transpulmonary pressure; improves regional compliances. Thus, physiologic studies generated the hypothesis that addition of Sigh to pressure support ventilation (PSV, the most common assisted mechanical ventilation mode) might decrease ventilation pressures and FiO2, and limit regional lung strain and stress through various synergic mechanisms potentially yielding decreased risk of VILI, faster weaning and improved clinical outcomes.