Comparison of venovenous extracorporeal membrane oxygenation, prone position and supine mechanical ventilation for severely hypoxemic acute respiratory distress syndrome: a network meta-analysis

Purpose: Severe acute respiratory distress syndrome (ARDS) with PaO2/FiO(2) < 80 mmHg is a life-threatening condition. The optimal management strategy is unclear. The aim of this meta-analysis was to compare the effects of low tidal volumes (V-t), moderate V-t, prone ventilation, and venovenous extracorporeal membrane oxygenation (VV-ECMO) on mortality in severe ARDS. Methods: We performed a frequentist network meta-analysis of randomised controlled trials (RCTs) with participants who had severe ARDS and met eligibility criteria for VV-ECMO or had PaO2/FiO(2) < 80 mmHg. We applied the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) methodology to discern the relative effect of interventions on mortality and the certainty of the evidence. Results: Ten RCTs including 812 participants with severe ARDS were eligible. VV-ECMO reduces mortality compared to low V-t (risk ratio [RR] 0.77, 95% confidence interval [CI] 0.59-0.99, moderate certainty) and compared to moderate V-t (RR 0.75, 95% CI 0.57-0.98, low certainty). Prone ventilation reduces mortality compared to moderate V-t (RR 0.78, 95% CI 0.66-0.93, high certainty) and compared to low V-t (RR 0.81, 95% CI 0.63-1.02, moderate certainty). We found no difference in the network comparison of VV-ECMO compared to prone ventilation (RR 0.95, 95% CI 0.72-1.26), but inferences were based solely on indirect comparisons with very low certainty due to very wide confidence intervals. Conclusions: In adults with ARDS and severe hypoxia, both VV-ECMO (low to moderate certainty evidence) and prone ventilation (moderate to high certainty evidence) improve mortality relative to low and moderate V-t strategies. The impact of VV-ECMO versus prone ventilation remains uncertain.