Li Wang, Xiao Li, Zongxia Yang, Xueli Tang, Qiang Yuan, Lijing Deng, Xin Sun

Ventilator-associated pneumonia (VAP) is associated with increased mortality, prolonged length of hospital stay and increased healthcare costs in critically ill patients. Guidelines recommend a semi-recumbent position (30º to 45º) for preventing VAP among patients requiring mechanical ventilation. However, due to methodological limitations in existing systematic reviews, uncertainty remains regarding the benefits and harms of the semi-recumbent position for preventing VAP. To assess the effectiveness and safety of semi-recumbent positioning versus supine positioning to prevent ventilator-associated pneumonia (VAP) in adults requiring mechanical ventilation. We searched CENTRAL (2015, Issue 10), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1946 to October 2015), EMBASE (2010 to October 2015), CINAHL (1981 to October 2015) and the Chinese Biomedical Literature Database (CBM) (1978 to October 2015). We included randomised controlled trials (RCTs) comparing semi-recumbent versus supine positioning (0º to 10º), or RCTs comparing alternative degrees of positioning in mechanically ventilated patients. Our outcomes included clinically suspected VAP, microbiologically confirmed VAP, intensive care unit (ICU) mortality, hospital mortality, length of ICU stay, length of hospital stay, duration of ventilation, antibiotic use and any adverse events. Two review authors independently and in duplicate screened titles, abstracts and full texts, assessed risk of bias and extracted data using standardised forms. We calculated the mean difference (MD) and 95% confidence interval (95% CI) for continuous data and the risk ratio (RR) and 95% CI for binary data. We performed meta-analysis using the random-effects model. We used the grading of recommendations, assessment, development and evaluation (GRADE) approach to grade the quality of evidence. We included 10 trials involving 878 participants, among which 28 participants in two trials did not provide complete data due to loss to follow-up. We judged all trials to be at high risk of bias. Semi-recumbent position (30º to 60º) versus supine position (0° to 10°) A semi-recumbent position (30º to 60º) significantly reduced the risk of clinically suspected VAP compared to a 0º to 10º supine position (eight trials, 759 participants, 14.3% versus 40.2%, RR 0.36; 95% CI 0.25 to 0.50; risk difference (RD) 25.7%; 95% CI 20.1% to 30.1%; GRADE: moderate quality evidence).There was no significant difference between the two positions in the following outcomes: microbiologically confirmed VAP (three trials, 419 participants, 12.6% versus 31.6%, RR 0.44; 95% CI 0.11 to 1.77; GRADE: very low quality evidence), ICU mortality (two trials, 307 participants, 29.8% versus 34.3%, RR 0.87; 95% CI 0.59 to 1.27; GRADE: low quality evidence), hospital mortality (three trials, 346 participants, 23.8% versus 27.6%, RR 0.84; 95% CI 0.59 to 1.20; GRADE: low quality evidence), length of ICU stay (three trials, 346 participants, MD -1.64 days; 95% CI -4.41 to 1.14 days; GRADE moderate quality evidence), length of hospital stay (two trials, 260 participants, MD -9.47 days; 95% CI -34.21 to 15.27 days; GRADE: very low quality evidence), duration of ventilation (four trials, 458 participants, MD -3.35 days; 95% CI -7.80 to 1.09 days), antibiotic use (three trials, 284 participants, 84.8% versus 84.2%, RR 1.00; 95% CI 0.97 to 1.03) and pressure ulcers (one trial, 221 participants, 28% versus 30%, RR 0.91; 95% CI 0.60 to 1.38; GRADE: low quality evidence). No other adverse events were reported. Semi-recumbent position (45°) versus 25° to 30° We found no statistically significant differences in the following prespecified outcomes: clinically suspected VAP (two trials, 91 participants, RR 0.74; 95% CI 0.35 to 1.56; GRADE: very low quality evidence), microbiologically confirmed VAP (one trial, 30 participants, RR 0.61; 95% CI 0.20 to 1.84: GRADE: very low quality evidence), ICU mortality (one trial, 30 participants, RR 0.57; 95% CI 0.15 to 2.13; GRADE: very low quality evidence), hospital mortality (two trials, 91 participants, RR 1.00; 95% CI 0.38 to 2.65; GRADE: very low quality evidence), length of ICU stay (one trial, 30 participants, MD 1.6 days; 95% CI -0.88 to 4.08 days; GRADE: very low quality evidence) and antibiotic use (two trials, 91 participants, RR 1.11; 95% CI 0.84 to 1.47). No adverse events were reported. A semi-recumbent position (≧ 30º) may reduce clinically suspected VAP compared to a 0° to 10° supine position. However, the evidence is seriously limited with a high risk of bias. No adequate evidence is available to draw any definitive conclusion on other outcomes and the comparison of alternative semi-recumbent positions. Adverse events, particularly venous thromboembolism, were under-reported.