Background:Although the use of extra-corporeal membrane oxygenation (ECMO) has been rapidly increasing,the benefit of ECMO in patients with acute respiratory distress syndrome (ARDS) remains unclear.Our objective was to investigate the effect of venovenous ECMO (VV-ECMO) on adult patients with severe ARDS.Methods:We conducted a multi-center,retrospective,cohort study in the intensive care units (ICUs) of six teaching hospitals between January 2013 and December 2018.Patients with severe ARDS who received W-ECMO support were included.The detailed demographic data and physiologic data were used to match ARDS patients without ECMO.The primary endpoint was the 28-day mortality.Results:Ninety-nine patients with severe ARDS supported by VV-ECMO and 72 patients without ECMO were included in this study.The acute physiology and chronic health evaluation Ⅱ score was 23.1 ± 6.3 in the ECMO group and 24.8 ± 8.5 in the control group (P =0.1195).The sequential organ failure assessment score was 12.8 ± 3.4 in the ECMO group and 13.7 ± 3.5 in the control group (P =0.0848).The 28-day mortality of patients with ECMO support was 39.4％,and that of the control group was 55.6％.The survival analysis curve showed that the 28-day mortality in the ECMO group was significantly lower than that in the control group (P =0.0097).Multivariate Cox regression analysis showed that the independent predictors of the 28-day mortality were the requirement of vasopressors before ECMO (hazard ratio [HR]:1.006;95％ confidence interval [CI]:1.001-1.013;P =0.030) and duration of mechanical ventilation before ECMO (HR:3.299;95％ CI:1.264-8.609;P =0.034).Conclusions:This study showed that ECMO improved the survival of patients with severe ARDS.The duration of mechanical ventilation and the requirement of vasopressors before ECMO might be associated with an increased risk of death.