Rationale of the study Acute Respiratory Distress Syndrome (ARDS) is an acute inflammatory state of the pulmonary parenchyma that causes hypoxemia, atelectasis, pulmonary congestion, and reduction in pulmonary compliance. Mechanical ventilation is actually life-saving, but it may traumatize the lungs (e.g. volutrauma, barotrauma, atelectrauma, and biotrauma). The use of low tidal volumes and high positive end-expiratory pressure (PEEP), aims at attenuating ventilator-associated lung injury. However, ARDS mortality still remains high. High frequency oscillation (HFO) is an alternative ventilatory technique that employs very low tidal volumes (1-4 ml/kg) administered at high frequencies (3-15 Hz). Prior observational studies have reported improvements in oxygenation, whereas recent two-center data on severe ARDS suggest a survival benefit from the intermittent, combined use of low-frequency HFO with a cuff leak, Recruitment maneuvers (RMs), and tracheal gas insufflation (TGI). The addition of TGI improves oxygenation and CO2 elimination; however, it is still unclear whether it affects survival. Two recently published multicenter studies showed either neutral (10) or negative results (11) with respect to survival when high frequency HFO without a cuff leak was used in the treatment of early ARDS. However, these negative results may be partly due to right ventricular overload/dysfunction/failure caused by the combination of high intrathoracic pressures and hypercapnia, with consequent hemodynamic instability and increased need of inotropic/vasopressor support. Accordingly, the investigators hypothesize that a different HFO strategy [employing a combination of a low frequency and a cuff leak - which augments CO2 elimination and is associated with relatively low mean tracheal pressures - could lead to different results.