Key messages
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For adults on breathing machines (ventilators) in an intensive care unit (ICU), raising the head of the bed to about a 30° to 45° angle instead of lying flat probably reduces lung infections and may shorten the time patients need a ventilator, without changes in death rates during the ICU or overall hospital stay.
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Raising the head of the bed higher (40º to 45º versus 30º; or 30º to 45° versus less than 30º) probably lowers the risk of lung infection but increases the risk of bedsores. Adding side-to-side turning (rotation) to a raised head position probably gives extra benefits, including fewer lung infections and a shorter time on a ventilator, in the ICU and in hospital.
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More large, well-designed trials are needed to determine the optimal bed angle and to assess the effects on survival and potential harms.
What is ventilator-associated pneumonia?
Ventilator-associated pneumonia is a lung infection that develops in patients who have been using a ventilator (a machine that helps with breathing) for more than 48 hours. It is associated with an increased risk of death, longer stay in the ICU and in hospital overall, and greater healthcare costs.
What is 'head-end elevation' or a semi-recumbent position?
Head-end elevation means raising the upper body rather than lying flat. The head of the bed is usually raised between 30° and 45°, although angles from 15° to 60° may be used. This is often called a 'semi‑recumbent' or 'semi‑upright' position.
There are also different types of semi-recumbent positions with additional components; for example:
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semi-recumbent lateral or lateral rotation position where patients are in a semi-recumbent position and also rotated from side to side, either manually or continuously using a motorised turning bed; and
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semi-recumbent rotation position where the head-of-bed angle is rotated through several different degrees (for example, 20º, then 30º, and then 45º).
What did we want to find out?
For ICU patients on ventilators, is raising the head of the bed (semi-recumbent position) better than a flat bed and other bed positions for reducing:
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lung infections;
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death during the ICU stay or overall hospital stay;
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the length of stay in the ICU or hospital;
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the duration of assisted breathing through a ventilator; and
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bedsores?
What did we do?
We searched for studies that compared semi-recumbent positioning with any other positioning, or different degrees or types of semi-recumbent positioning, in ICU adult patients requiring a ventilator. We compared and summarised the results and assessed how confident we are in the findings, based on factors such as the study design and methods.
What did we find?
We found 48 studies involving 7955 patients in ICUs using ventilators. Thirty-seven trials were conducted in China, two in Iran, and one each in Austria, France, India, Spain, Türkiye, the United Kingdom, and the Netherlands. Two studies were conducted across several high-income countries. Participants were typically around 55 years old, and about one-third were women. Study size ranged from 25 to 855 participants.
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Comparing head-end elevation with flat position (17 studies with 2640 participants), raising the head of the bed reduces the risk of lung infections, and may also reduce the duration of assisted breathing through a ventilator, without changes in death rates during ICU stay or overall hospital stay. However, its impact on the length of ICU and hospital stay and bedsores remains uncertain.
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Comparing different levels of head-end elevation (30º to 45° versus less than 30º; 11 studies with 1153 participants, or 40º to 45º versus 30º; 14 studies with 1374 participants), raising the head of the bed higher probably reduces the risk of lung infections, but increases the risk of bedsores. However, these positions may not make a difference in reducing the risk of death during the ICU stay or overall hospital stay. The effects on time spent in ICUs or hospitals, or how long the patient needs assisted breathing with a ventilator machine, remain uncertain.
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Compared to regular head-end elevation (7 studies with 708 participants), adding side-to-side turning probably further reduces the risk of lung infections, and shortens the duration of assisted breathing through a ventilator, as well as the length of stay in both ICU and hospital.
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The effects of raising the head of the bed to a very high angle (60° versus 45°), or using other body positions, are unclear (for example, different rotational positions, positions where patients are lying face down on their stomach, or positions where the patient's feet are lifted to be higher than their head).
What are the limitations of the evidence?
Our confidence in the results is limited. Many studies did not report whether patients remained in their assigned positions, and some did not clearly define lung infections, making the findings less reliable and harder to apply in practice.
How up to date is this evidence?
This updates our previous version of the review, published in 2016. The evidence is current to 3 October 2025.
Read the full abstract
Background
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.
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 strategy
We searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, AMED, three Chinese databases, and two trial registries up to 3 October 2025, and screened reference lists.
Selection criteria
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.
Data collection and analysis
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.
Main results
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.
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
