Prone positioning in acute respiratory distress syndrome: A critical review of clinical evidence and practical challenges

BACKGROUND: Early randomised controlled trials (RCTs) of prone positioning (PP) in acute respiratory distress syndrome (ARDS) failed to demonstrate a survival benefit despite consistent improvements in oxygenation. Subsequent meta-analyses suggested a survival advantage in patients with severe hypoxaemia, culminating in the landmark Proning Severe ARDS Patients (PROSEVA) trial, which reported a 28-day mortality rate of 16.0% in patients with a PaO₂/FiO₂ ratio <150 mmHg. However, the optimal criteria for repeating and discontinuing PP sessions remain uncertain. METHODS: A structured search of PubMed, Embase.com, and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted to identify RCTs evaluating PP in adults with ARDS with mortality as a prespecified principal outcome. Relevant clinical studies, meta-analyses, and review articles were also evaluated to provide context for the narrative review. RESULTS: Six RCTs were included in the main comparative analysis. Previous RCTs conducted before the PROSEVA trial used diverse protocols and treatment settings and did not demonstrate a survival benefit. Therefore, comparative assessments of these trials may provide valuable insights for optimising clinical practice. Based on a detailed comparison of the RCTs, the currently proposed benefits of early implementation of PP with prolonged duration may not fully explain the differences in outcomes observed across trials. Other potentially influential factors, including patient selection, timing, ventilatory management, centre experience, treatment delivery, and criteria for repeating and discontinuing PP sessions, warrant further evaluation in practical implementation studies. The development of automated equipment for PP may further improve procedural efficiency. This review critically examines both the positive and negative evidence regarding PP, highlighting methodological limitations and practical challenges to greater utilisation of PP. CONCLUSION: PP has established clinical value in severe ARDS, but important uncertainties remain regarding its optimal implementation. Concerted efforts are required to establish standardised protocols and to optimise implementation of PP in ARDS management.