Purpose

Severe acute respiratory distress syndrome (ARDS) with PaO₂/FiO₂ < 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/FiO₂ < 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.