 The prognosis of ARDS still remains grave 3-7. The primary objective of the present study, is to definitively determine the effect of HFO-TGI on the survival of patients with severe ARDS. Consequently, we will increase the size of the studied population see also NCT00416260, in order to achieve sufficient statistical power. The secondary objective is to test the hypothesis that lung recruitment is the major underlying mechanism for the HFO-TGI-associated improvement in oxygenation 1,2 and respiratory compliance 2. 