This document discusses the use of extracorporeal membrane oxygenation (ECMO) for severe acute respiratory distress syndrome (ARDS). It summarizes several studies on the topic: an early randomized controlled trial from 1974-1994 found no significant difference in survival between ECMO and conventional ventilation; newer data from clinical trials and reviews suggest there may be a survival benefit to ECMO, but the evidence is unclear whether this is due to ECMO itself or the care received at specialized ECMO centers. The document specifically reviews the CESAR trial, a UK randomized controlled trial from 2009 that found reduced mortality and increased functional independence with referral for consideration of ECMO compared to conventional management alone. It also summarizes a cohort study of H1