The trial will test the hypothesis that a VT of 4 ml/kg PBW combined with low flow CO2 removal improves outcome in patients with severe ARDS (PFs ≤ 200 and PEEP ≥ 10) compared to ventilation with a VT of 6 ml/kg PBW. The study will accrue a maximum of 230 patients over approximately 12-18 months.