Semi-recumbent position for the prevention of ventilator-associated pneumonia in adults requiring mechanical ventilation

RATIONALE: Ventilator-associated pneumonia (VAP) is associated with increased mortality, hospital stay, and healthcare costs in critically ill patients. Although guidelines recommend a semi-recumbent position for VAP prevention, the evidence remains uncertain due to limitations in prior reviews. This update revises the 2016 review. OBJECTIVES: To assess the effectiveness and safety of semi-recumbent versus supine or another positioning, and different degrees or types of semi-recumbent positioning in mechanically ventilated intensive care unit (ICU) patients. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, AMED, three Chinese databases, and two trial registries up to 3 October 2025, and screened reference lists. ELIGIBILITY CRITERIA: We included randomised controlled trials (RCTs) comparing semi-recumbent versus supine or another positioning, or different degrees or types of semi-recumbent positioning in mechanically ventilated adult ICU patients. OUTCOMES: Outcomes include clinically suspected or microbiologically confirmed VAP, ICU or hospital mortality, length of ICU or hospital stay, duration of ventilation, and pressure ulcers. RISK OF BIAS: We assessed the risk of bias using Cochrane's RoB 1 tool. SYNTHESIS METHODS: Paired review authors independently screened studies, assessed risk of bias, and extracted data. We performed random-effects meta-analyses using mean difference (MD) for continuous and risk ratio (RR) for binary outcomes with 95% confidence intervals (CI). We evaluated evidence certainty using GRADE. INCLUDED STUDIES: This update includes 38 new RCTs, making a total of 48 included studies (7955 participants). SYNTHESIS OF RESULTS: 1. Semi-recumbent position versus supine position: 17 studies, 2640 participants A semi-recumbent position, versus a supine position, reduces clinically suspected VAP (RR 0.42, 95% CI 0.33 to 0.52; 14 studies, 2411 participants; high-certainty evidence), but may result in little to no difference in microbiologically confirmed VAP (RR 0.57, 95% CI 0.25 to 1.27; 5 studies, 555 participants; low-certainty evidence), and probably results in little to no difference in ICU or hospital mortality (RR 0.80, 95% CI 0.59 to 1.08; 3 studies, 430 participants; RR 0.86, 95% CI 0.67 to 1.12; 5 studies, 570 participants; both moderate-certainty evidence). Due to very low-certainty evidence, we do not know the effects on ICU or hospital length of stay (MD -3.25 days, 95% CI -7.14 to 0.63; 5 studies, 466 participants; MD -8.17 days, 95% CI -40.10 to 23.76; 3 studies, 320 participants). It may reduce the duration of ventilation (MD -3.26 days, 95% CI -6.02 to -0.51; 7 studies, 688 participants; low-certainty evidence). We do not know the effect on pressure ulcers (RR 0.69, 95% CI 0.30 to 1.56; 4 studies, 840 participants; very low-certainty evidence). 2. Semi-recumbent position 30° to 45° versus < 30°: 11 studies, 1153 participants A semi-recumbent position at 30° to 45°, versus < 30°, reduces clinically suspected VAP (RR 0.48, 95% CI 0.39 to 0.59; 8 studies, 810 participants; high-certainty evidence). It may result in little to no difference in microbiologically confirmed VAP (RR 0.53, 95% CI 0.28 to 1.02; 5 studies, 451 participants), ICU or hospital mortality (RR 0.69, 95% CI 0.20 to 2.29; 3 studies, 271 participants; RR 0.66, 0.37 to 1.17; 2 studies, 145 participants), or duration of ventilation (MD -0.62 days, 95% CI -4.17 to 2.93; 1 study, 87 participants) (all low-certainty evidence). There is no evidence for ICU or hospital stay. It probably increases pressure ulcers (RR 2.79, 95% CI 1.28 to 6.11; 6 studies, 712 participants; moderate-certainty evidence). 3. Semi-recumbent position 40° to 45° versus 30°: 14 studies, 1374 participants A semi-recumbent position at 40° to 45°, versus 30°, probably results in little to no difference in clinically suspected VAP (RR 0.91, 95% CI 0.62 to 1.33; 10 studies, 1026 participants; moderate-certainty evidence), but may reduce microbiologically confirmed VAP (RR 0.53, 95% CI 0.28 to 0.99; 4 studies, 218 participants; low-certainty evidence). There were no deaths in ICU (1 study, 46 participants; low-certainty evidence). Due to very low-certainty evidence, we do not know the effects on hospital mortality (RR 1.21, 95% CI 0.27 to 5.50; 2 studies, 221 participants), length of ICU stay (MD -1.28 days, 95% CI -6.69 to 4.12; 2 studies, 221 participants), or duration of ventilation (MD -1.09 days, 95% CI -4.60 to 2.43; 2 studies, 206 participants). There is no evidence for hospital stay. It probably increases pressure ulcers (RR 2.42, 95% CI 1.16 to 5.06; 10 studies, 943 participants; moderate-certainty evidence). 4. Semi-recumbent position versus semi-recumbent lateral or lateral rotation position: 7 studies, 708 participants A semi-recumbent position, versus semi-recumbent lateral or lateral rotation, probably increases clinically suspected and microbiologically confirmed VAP (RR 1.99, 95% CI 1.48 to 2.70; 6 studies, 608 participants; RR 5.14, 95% CI 2.53 to 10.44; 1 study, 100 participants; both moderate-certainty evidence), but may result in little to no difference in hospital mortality (RR 2.50, 95% CI 0.53 to 11.89; 1 study, 60 participants; low-certainty evidence). There is no evidence on ICU mortality. It probably prolongs the length of ICU or hospital stay and the duration of ventilation (days: MD 5.69, 95% CI 5.44 to 5.94; 2 studies, 120 participants; MD 6.25, 95% CI 4.09 to 8.41; 2 studies, 240 participants; MD 5.99, 95% CI 1.60 to 10.38; 4 studies, 400 participants; all moderate-certainty evidence). There is no evidence for pressure ulcers. Evidence was limited on the semi-recumbent position at 60° versus 45°, or versus other positions (e.g. semi-recumbent rotation, lateral Trendelenburg, or prone position). AUTHORS' CONCLUSIONS: Compared with supine positioning, semi-recumbent positioning reduces VAP, and may shorten the duration of ventilation. Higher head-of-bed angles (≥ 30° or 40° to 45°) probably reduce VAP, but increase pressure ulcers, with other comparisons remaining uncertain. Compared with fixed-angled semi-recumbent positioning, semi-recumbent lateral or lateral rotation positioning probably reduces VAP and shortens the duration of ventilation, and length of ICU and hospital stay. Evidence on adverse events and comparisons with alternative positions remains inconclusive. LIMITATIONS: evidence certainty was limited by risk of bias, imprecision due to small sample sizes, and inconsistency across studies. Inadequate reporting of actual head-of-bed angle for semi-recumbent positioning and variation in VAP definitions may influence our findings. FUNDING: No funding. REGISTRATION: Protocol (2012) DOI: 10.1002/14651858.CD009946 Original review (2016) DOI: 10.1002/14651858.CD009946.pub2.