Prone Positioning in Patients With Moderate and Severe Acute Respiratory Distress Syndrome: A Randomized Controlled Trial

CONTEXT: Post hoc analysis of a previous trial has suggested that prone positioning may improve survival in patients with severe hypoxemia and with acute respiratory distress syndrome (ARDS). OBJECTIVE: To assess possible outcome benefits of prone positioning in patients with moderate and severe hypoxemia who are affected by ARDS. Design, Setting, and PATIENTS: The Prone-Supine II Study, a multicenter, unblinded, randomized controlled trial conducted in 23 centers in Italy and 2 in Spain. Patients were 342 adults with ARDS receiving mechanical ventilation, enrolled from February 2004 through June 2008 and prospectively stratified into subgroups with moderate (n = 192) and severe (n = 150) hypoxemia. INTERVENTIONS: Patients were randomized to undergo supine (n = 174) or prone (20 hours per day; n = 168) positioning during ventilation. MAIN OUTCOME MEASURES: The primary outcome was 28-day all-cause mortality. Secondary outcomes were 6-month mortality and mortality at intensive care unit discharge, organ dysfunctions, and the complication rate related to prone positioning. RESULTS: Prone and supine patients from the entire study population had similar 28-day (31.0% vs 32.8%; relative risk [RR], 0.97; 95% confidence interval [CI], 0.84-1.13; P = .72) and 6-month (47.0% vs 52.3%; RR, 0.90; 95% CI, 0.73-1.11; P = .33) mortality rates, despite significantly higher complication rates in the prone group. Outcomes were also similar for patients with moderate hypoxemia in the prone and supine groups at 28 days (25.5% vs 22.5%; RR, 1.04; 95% CI, 0.89-1.22; P = .62) and at 6 months (42.6% vs 43.9%; RR, 0.98; 95% CI, 0.76-1.25; P = .85). The 28-day mortality of patients with severe hypoxemia was 37.8% in the prone and 46.1% in the supine group (RR, 0.87; 95% CI, 0.66-1.14; P = .31), while their 6-month mortality was 52.7% and 63.2%, respectively (RR, 0.78; 95% CI, 0.53-1.14; P = .19). CONCLUSION: Data from this study indicate that prone positioning does not provide significant survival benefit in patients with ARDS or in subgroups of patients with moderate and severe hypoxemia. Trial Registration clinicaltrials.gov Identifier: NCT00159939