This prospective, randomised controlled trial assessed the effect of early application of prone positioning in patients with severe acute respiratory distress syndrome (ARDS). Primary outcome was mortality at day 28. Inclusion criteria included endotracheal intubation and mechanical ventilation for ARDS for less than 36 h and severe ARDS (defined as PaO₂; FIO₂ ratio of <150 mm Hg, with an FIO₂ of ≥0.6; a positive end-expiratory pressure (PEEP) of ≥5 cm of water, and a …