Shu Ling Hu, Hong Li He, Chun Pan, Ai Ran Liu, Song Qiao Liu, Ling Liu, Ying Zi Huang, Feng Mei Guo, Yi Yang, Hai Bo Qiu Critical Care 2014, 18:R109 (28 May 2014)

Introduction: Prone positioning (PP) has been reported to improve the survival of patients with severe acute respiratory distress syndrome (ARDS). However, it is uncertain whether the beneficial effects of PP are associated with positive end-expiratory pressure (PEEP) levels and long durations of PP. In this meta-analysis, we aimed to evaluate whether the effects of PP on mortality could be affected by PEEP and the duration of PP and to identify which patients might benefit the most from PP.

Methods: Randomized controlled trials (RCTs) that compared prone and supine ventilation were retrieved by searching the following electronic databases: PubMed/MEDLINE, the Cochrane Library, the Web of Science, and Elsevier Science (inception to May 2013). Two investigators independently selected RCTs and assessed their quality. The data extracted from the RCTs were combined in a cumulative meta-analysis and were analyzed using the methods recommended by the Cochrane Collaboration.

Results: A total of nine RCTs with 2,242 patients were included. All of the studies received scores of three points using the methods recommended by Jadad. One trial did not conceal allocation. This meta-analysis revealed that, compared with supine positioning (SP), PP decreased the 28- to 30-day mortality of ARDS patients with a partial pressure of arterial oxygen/fraction of inspired oxygen (P/F) <=100 mm Hg (risk ratio (RR) = 0.71; 95% confidence interval (CI): 0.57 to 0.89; P = 0.003; n = 508). PP was shown to reduce both 60-day (RR = 0.82; 95% CI: 0.68 to 0.99; P = 0.04; n = 518) and 90-day (RR = 0.57; 95% CI: 0.43 to 0.75; P <0.0001; n = 516) mortality in ARDS patients ventilated with PEEP >=10 cm H2O. Moreover, PP reduced 28- to 30-day mortality when the duration of PP was greater than 12 h/d (RR = 0.73; 95% CI: 0.54 to 0.99; P = 0.04; n = 1,067).

Conclusions: PP reduced mortality among severe ARDS patients and patients receiving relatively high PEEP levels. Moreover, long-term PP improved the survival of ARDS patients.

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