Effect of prone positioning during mechanical ventilation on mortality among patients with acute respiratory distress syndrome: a systematic review and meta-analysis

Abstract

Background: Mechanical ventilation in the prone position is used to improve oxygenation and to mitigate the harmful effects of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). We sought to determine the effect of prone positioning on mortality among patients with ARDS receiving protective lung ventilation.

Methods: We searched electronic databases and conference proceedings to identify relevant randomized controlled trials (RCTs) published through August 2013. We included RCTs that compared prone and supine positioning during mechanical ventilation in patients with ARDS. We assessed risk of bias and obtained data on all-cause mortality (determined at hospital discharge or, if unavailable, after longest follow-up period). We used random-effects models for the pooled analyses.

Results: We identified 11 RCTs (n=2341) that met our inclusion criteria. In the 6 trials (n=1016) that used a protective ventilation strategy with reduced tidal volumes, prone positioning significantly reduced mortality (risk ratio 0.74, 95% confidence interval 0.59-0.95; I2=29%) compared with supine positioning. The mortality benefit remained in several sensitivity analyses. The overall quality of evidence was high. The risk of bias was low in all of the trials except one, which was small. Statistical heterogeneity was low (I2<50%) for most of the clinical and physiologic outcomes.

Interpretation: Our analysis of high-quality evidence showed that use of the prone position during mechanical ventilation improved survival among patients with ARDS who received protective lung ventilation.

© 2014 Canadian Medical Association or its licensors.

Figures

Figure 1:

Selection of randomized controlled trials (RCTs) for the meta-analysis. ARDS = acute respiratory distress syndrome.

Figure 2:

Effect of prone positioning during mechanical ventilation on all-cause mortality among patients with acute respiratory distress syndrome in trials that used protective lung ventilation (tidal volume p = 0.05). CI = confidence interval, RR = risk ratio.

Figure 3:

Effect of prone positioning during mechanical ventilation on all-cause mortality according to prespecified patient-level and trial-level subgroups. Risk ratios less than 1.0 indicate a decreased risk of death with prone positioning. *Severe hypoxemia = ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (Pao2/Fio2) < 100 mm Hg; moderate = Pao2/Fio2 ratio 100–199 mm Hg; mild = Pao2/Fio2 ratio 200–299 mm Hg. CI = 95% confidence interval, RR = risk ratio. Baseline Pao2/Fio2 ratios were unavailable for 10 patients in 3 trials.,,