Impact of head-of-bed elevation angle on the development of pressure ulcers and pneumonia in patients on mechanical ventilation: a systematic review and meta-analysis

Abstract

Background

Mechanical ventilation is crucial for patient management in intensive care units, but it comes with complications such as pressure ulcers and ventilator-associated pneumonia (VAP). The impact of head-of-bed elevation angles on these complications remains a critical area for investigation.

Methods

This systematic review and meta-analysis followed PRISMA guidelines and involved searches across PubMed, Embase, Web of Science, and Cochrane Library, conducted on September 19, 2023, with no date or language restrictions. We included randomized controlled trials that compared different head-of-bed elevation angles in adult ICU patients on mechanical ventilation. Data were extracted on study characteristics, quality assessed using the Cochrane risk of bias tool, and statistical analyses performed using chi-square tests for heterogeneity and fixed or random-effects models based on heterogeneity results.

Results

Six studies met inclusion criteria out of an initial 601 articles. These studies showed minimal heterogeneity (I² = 0.0% for pressure ulcers, p = 0.930; and for VAP, p = 0.797), supporting the use of fixed-effect models. Results indicated that a higher elevation angle (45°) significantly increased the risk of pressure ulcers (OR = 1.95, 95% CI: 1.12–3.37, p < 0.05) and decreased the incidence of VAP compared to a lower angle (30°) (OR = 0.51, 95% CI: 0.31–0.84, p < 0.05).

Conclusions

While higher head-of-bed elevation can reduce the risk of VAP in mechanically ventilated patients, it may increase the risk of pressure ulcers. Clinical strategies should carefully balance these outcomes to optimize patient care in ICU settings.

Registration

PROSPERO 2024 CRD42024570232.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-024-03270-9.

Introduction

Mechanical ventilation (MV) is a critical intervention in intensive care units (ICUs) worldwide, utilized to support patients with inadequate respiratory function. While lifesaving, the use of mechanical ventilation is associated with several complications, notably pressure ulcers (PUs) and pneumonia, which significantly affect patient outcomes and healthcare costs [1, 2]. Understanding and mitigating these risks is crucial in enhancing patient care and improving clinical outcomes. Pressure ulcers, also known as decubitus ulcers or bedsores, are areas of skin and underlying tissue damage resulting from prolonged pressure on the skin. They predominantly develop in patients who are immobile, such as those receiving mechanical ventilation. The presence of a pressure ulcer can lead to serious infections, prolonged hospital stays, increased healthcare expenses, and even mortality [3, 4]. The development of pressure ulcers in mechanically ventilated patients is influenced by multiple factors, including the duration of immobility, nutritional status, and the physical condition of the patient [5].

Pneumonia, particularly ventilator-associated pneumonia (VAP), is another significant complication for patients on mechanical ventilation. VAP arises from the aspiration of secretions, colonization of the lower respiratory tract, and impaired host defenses, contributing to higher morbidity and mortality rates among these patients [6, 7]. The position of the patient, particularly the elevation of the head of the bed, is a key factor in the prevention of VAP, as it helps reduce the risk of aspiration. The angle of head-of-bed elevation is a critical element in the management of patients on mechanical ventilation [8]. Current guidelines suggest elevating the head of the bed between 30 and 45 degrees to minimize the risk of both pressure ulcers and pneumonia. This recommendation is based on the premise that elevation can help in redistributing pressure and thus reducing the risk of ulcer formation, while also decreasing the likelihood of aspiration, a common precursor to pneumonia [9].

However, the optimal degree of head-of-bed elevation remains a subject of debate. While higher angles might reduce the risk of aspiration and subsequently pneumonia, they could potentially increase the shear and friction forces on the skin, thereby elevating the risk of developing pressure ulcers. Conversely, lower angles might decrease these forces but increase the risk of respiratory complications. Therefore, a delicate balance is required to optimize patient outcomes, highlighting the need for a systematic review and meta-analysis to consolidate existing data and provide clearer guidance on this issue.

This systematic review and meta-analysis aim to evaluate the impact of different head-of-bed elevation angles on the development of pressure ulcers and pneumonia in patients receiving mechanical ventilation. By integrating and analyzing data from multiple studies, this paper seeks to clarify how varying bed angles affect these critical outcomes, thereby guiding clinical practices to improve the care of mechanically ventilated patients. Through this comprehensive examination, we aim to establish evidence-based recommendations that can be readily implemented in clinical settings to minimize the risks associated with mechanical ventilation.

Methods

Search strategy for systematic review and meta-analysis

During the systematic review, the search strategy was designed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [10]. The literature search was conducted on September 19, 2023, utilizing four electronic databases: PubMed, Embase, Web of Science, and the Cochrane Library. No restrictions were placed on the publication date. The search incorporated a combination of key terms including “head-of-bed elevation,” “semirecumbent,” “backrest,” “head elevation,” “ICU,” “ventilation,” “ulcers,” and “ventilator.” These terms were carefully chosen to reflect the comprehensive scope required by the PICO (Patient, Intervention, Comparison, Outcome) framework, ensuring an exhaustive retrieval of pertinent studies for the meta-analysis. Additionally, no language limitations were imposed to broaden the inclusivity of the search. Manual screening of reference lists from relevant articles was also performed to identify any further potential studies.

Inclusion criteria

1. Study Design: Only randomized controlled trials (RCTs) investigating the effects of head-of-bed elevation angles on the incidence of pressure ulcers and pneumonia were included.

2. Participants: The study population comprised adult patients (aged 18 years and older) who were receiving mechanical ventilation in an intensive care unit (ICU).

3. Interventions: The analysis was restricted to studies that explicitly assessed the impact of varying head-of-bed elevation angles.

4. Comparators: Included studies were required to compare different elevation angles of the head of the bed.

5. Outcomes: The primary outcomes of interest focused on were the development of pressure ulcers and pneumonia.

Exclusion criteria

1. Non-empirical studies: opinion pieces, editorials, and reviews were systematically excluded

2. Studies Without Specific Angles: Any study that did not clearly specify the head-of-bed elevation angle, or varied the angle without adequate documentation, was excluded.

3. Incomplete Data: Studies were excluded if they contained incomplete outcome data or lacked key variables necessary for thorough analysis.

Data extraction process

During our systematic review and meta-analysis, literature screening and data extraction were conducted independently by two reviewers to ensure accuracy and minimize bias. These evaluators cross-checked their findings as a standard procedure. In cases where discrepancies arose, the reviewers engaged in discussions to resolve conflicts and, if necessary, consulted a third-party reviewer for an objective decision. The extracted data encompassed several key elements: the author(s) of each study, the year of publication, the number of cases examined, the country of the study, and the specific angles of head-of-bed elevation. In instances where relevant data were not available in the published report, we took additional steps to maintain data integrity and completeness. We contacted the original investigators via email to request any unpublished data pertaining to our study criteria.

Quality assessment of included studies

For our meta-analysis, the quality of each included study was evaluated using the Cochrane Collaboration’s risk of bias tool [11]. This assessment was performed independently by two reviewers to ensure objectivity and consistency. The reviewers scrutinized several critical domains to ascertain potential biases, including random sequence generation, allocation concealment, blinding of participants and personnel, completeness of outcome data, selective reporting, and other possible sources of bias. Each of these domains was assigned a risk level categorized as low, unclear, or high, based on the extent of bias observed. In situations where the reviewers disagreed on the risk assessment, discussions were held to reach a consensus. If an agreement could not be achieved through dialogue alone, a third-party reviewer was consulted to provide an additional perspective and help resolve the disagreement.

Statistical analyses

Our meta-analysis employed chi-square tests to assess study heterogeneity, quantified by the I² statistic. When I² was below 50% and the corresponding P-value was 0.10 or higher, suggesting minimal heterogeneity, we used a fixed-effect model to compute the combined effect size. Conversely, an I² of 50% or greater, or a P-value below 0.10, indicated significant heterogeneity, prompting the use of a random-effects model. Sensitivity analysis involved sequentially omitting individual studies to assess their impact on the overall effect size. Publication bias was evaluated through funnel plot symmetry and Egger’s linear regression test, with statistical significance set at a P-value of less than 0.05. Data analysis was conducted using Stata version 17.

Data items specification

Outcomes specification

We systematically listed and defined all outcomes pertinent to the scope of our review. For each included study, data were collected on the incidence of pressure ulcers and VAP as primary outcomes. We sought data across all relevant measures, time points, and analyses as reported in the studies. Where data on certain time points or measures were not reported, we used available data from similar contexts to maintain consistency across studies. This approach ensured comprehensive extraction and synthesis of data relevant to our primary outcomes.

Variables specification

In addition to primary outcomes, we defined and collected data on several variables critical for our analysis, including participant demographics (age, gender, medical condition), intervention characteristics (specific angles of head-of-bed elevation), and study settings (country, type of ICU). We also noted funding sources as disclosed in the original studies. Assumptions were made regarding missing or unclear information only after attempting to contact the original authors for clarification. In instances where no response was received, we used logical assumptions based on the most similar available data within the same context or reported by similar studies. This strategy was documented in our data extraction form to ensure transparency and replicability of our data handling processes.

Certainty assessment of evidence

To evaluate the certainty of the body of evidence for each outcome, we employed the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. This methodological framework assesses the quality of evidence across studies based on several domains including risk of bias, inconsistency, indirectness, imprecision, and publication bias.

Risk of bias

Evidence quality was downgraded if a significant number of studies showed high risks of bias that could impact the validity of the findings.

Inconsistency

We evaluated inconsistencies in the results across studies. If significant heterogeneity (I² > 50% and p-value < 0.10) was observed without a plausible explanation, the quality of evidence was downgraded.

Indirectness

Evidence was assessed for its direct applicability to the research question. Studies that did not directly address the PICO (Patient, Intervention, Comparison, Outcome) elements were considered indirect, leading to a downgrade in evidence quality.

Imprecision

The certainty of evidence was reduced if the confidence intervals of effect estimates were wide or if optimal information size (OIS) criteria were not met.

Publication bias

The presence of publication bias, assessed through funnel plot analysis and Egger’s regression test, also influenced the certainty grading. Symmetrical distribution and non-significant Egger’s test results supported the absence of significant publication bias, maintaining higher certainty levels.

By systematically applying these criteria, we determined the overall certainty of the evidence, categorizing it into four levels: high, moderate, low, or very low. This rigorous assessment helps ensure that our conclusions are based on robust and reliable data, providing clear guidance for clinical practice and further research.

Results

Search results and study selection

In the initial phase of our systematic review and meta-analysis, we conducted a comprehensive search across multiple electronic databases, identifying 601 potentially relevant articles. An algorithm was then utilized to remove duplicates, ensuring that each study was represented uniquely. Subsequent rigorous screening of titles and abstracts, based on predefined inclusion and exclusion criteria, further narrowed the selection. These criteria assessed various factors such as study methodology, demographic characteristics of participants, clinical outcomes, and research quality. After this preliminary evaluation, 25 articles were selected for detailed full-text review. During this stage, 19 articles were excluded for reasons including being review articles (n = 4), sequentially published works (n = 5), having insufficient data (n = 4), and lacking control groups in clinical trials (n = 6). Ultimately, 6 articles met al.l criteria and were included in the final meta-analysis [7, 12–16] (Fig. 1).

Fig. 1.

Study Selection Flowchart. This figure illustrates the selection process for studies included in the meta-analysis, starting from the initial identification through databases to the final inclusion

Study characteristics

The studies included in this meta-analysis collectively assessed the impact of head-of-bed elevation angles on outcomes for mechanically ventilated patients in intensive care settings. The meta-analysis compiled data from six studies, published between 2006 and 2022, covering diverse geographical locations including Iran, China, Germany, The Netherlands, and some studies with unspecified countries. The total sample size across all studies amounted to 502 patients, with each study comparing the effects of a 45° head-of-bed elevation against a 30° elevation. Intervention durations varied from as short as one day to up to seven days. The studies consistently involved adult ICU patients, with age details provided in four studies, showing average ages ranging from 60 to 70.6 years for treatment and control groups. The consistency in intervention across studies—varying only in duration but not in the angle of elevation—facilitates a focused analysis on the influence of elevation angle and duration on patient outcomes (Table 1).

Table 1.

Characteristics of included studies on the effects of Head-of-Bed Elevation

Author	Year	Country	Study Subjects	Age (years) (T/C)	Total Samples (T/C)	Intervention Mode	Funding
Güner et al. [7]	2022	Not Available	ICU mechanically ventilated patients	Not Available	40 (20/20)	T: Head-of-bed elevation 45° (5 days); C: 30° (5 days)	Not report
Ghezeljeh et al. [16]	2017	Iran	ICU mechanically ventilated patients	64.7/65.7	80 (40/40)	T: Head-of-bed elevation 45° (3 days); C: 30° (3 days)	√
Jiang et al. [15]	2016	China	Mechanically ventilated patients	68.0/70.6	46 (23/23)	T: Head-of-bed elevation 45° (7 days); C: 30° (7 days)	√
Schallom et al. [12]	2015	Not Available	ICU mechanically ventilated patients	Not Available	15 (8/7)	T: Head-of-bed elevation 45° (2 days); C: 30° (2 days)	√
Göcze et al. [13]	2013	Germany	Hemodynamically stable ICU MV patients	60.0/60.5	100 (50/50)	T: Head-of-bed elevation 45° (1 day); C: 30° (1 day)	Not report
van Nieuwenhoven et al. [14]	2006	The Netherlands	Mechanically ventilated patients	64.8/63.0	221 (112/109)	T: Head-of-bed elevation 45° (7 days); C: 30° (7 days)	Supported in part

T: Treatment

C: Control

ICU: Intensive Care Unit

Quality assessment results

The collective quality assessment of the included studies, based on the Cochrane Collaboration’s risk of bias tool, indicates a relatively high standard of methodological rigor. The majority of studies demonstrated a low risk of bias in the domains of random sequence generation, incomplete outcome data, and other potential sources of bias, suggesting strong internal validity. There were some concerns noted in allocation concealment and blinding of participants and personnel, with several studies showing an unclear or high risk of bias, potentially reflecting challenges in executing double-blind protocols within clinical settings. Blinding of outcome assessment was generally well-handled across studies, though some variability was evident, which could impact the subjective measures within the studies (Fig. 2).

Fig. 2.

Risk of Bias Assessment. Displayed using the Cochrane Collaboration’s tool, this figure categorizes the risk levels of included studies; red indicates a high risk of bias, and green indicates a low risk

Incidence of pressure ulcers relative to head-of-bed elevation

In the meta-analysis, five studies reported the incidence of pressure ulcers. A homogenous effect size distribution was found across these studies (I² = 0.0%, p = 0.930), justifying the use of a fixed-effect model for the synthesis of results. The combined data indicated a statistically significant increase in the risk of pressure ulcer development when employing a higher head-of-bed elevation angle of 45° compared to a lower angle of 30° (Odds Ratio [OR] = 1.95; 95% Confidence Interval [17]: 1.12–3.37; p < 0.05; Fig. 3). This suggests that while elevated positioning is generally recommended for ventilated patients to prevent complications such as ventilator-associated pneumonia, it may concurrently elevate the risk for pressure ulcers. These findings underscore the importance of a balanced and individualized approach to patient positioning, taking into account the trade-offs between different complications. Nursing staff and care teams should be vigilant in monitoring for the development of pressure ulcers, especially in patients positioned at higher bed elevations for extended periods.

Fig. 3.

Forest plots for pressure ulcer incidence. These plots compare the incidence of pressure ulcers between patients with head-of-bed elevated to 45° versus those elevated to 30°

Ventilator-associated pneumonia incidence and head-of-bed elevation angles

The meta-analytic review comprehensively assessed the incidence of VAP across five studies. The consistency in study results was confirmed by a lack of significant heterogeneity (I² = 0.0%, p = 0.797), which warranted the application of a fixed-effect model for result integration. The analysis revealed that a higher head-of-bed elevation angle of 45° significantly reduced the incidence of VAP when compared with a lower elevation angle of 30° (Odds Ratio [OR] = 0.51; 95% CI: 0.31–0.84; p < 0.05; Fig. 4). These findings have crucial implications for clinical practice, indicating that an elevated head-of-bed position is beneficial in mitigating the risk of VAP, a serious and frequent complication in mechanically ventilated patients. The protective effect of a 45° elevation underscores the need for critical care protocols to emphasize optimal positioning as a key preventive strategy against VAP. This data also supports the implementation of targeted interventions in the ICU setting to reduce the burden of pneumonia, thereby potentially improving patient outcomes, and reducing hospital length of stay and associated healthcare costs.

Fig. 4.

Forest plots for incidence of Ventilator-Associated Pneumonia (VAP). These plots show the effect of different head-of-bed elevations (45° vs. 30°) on the incidence of VAP in mechanically ventilated patients

Publication bias assessment in meta-analysis

Assessment of publication bias within this meta-analysis was conducted utilizing funnel plot analysis and Egger’s linear regression test. The funnel plots, designed with the studies included, demonstrated a symmetrical distribution, indicating no significant evidence of publication bias (Fig. 5). Complementary to the visual assessment, Egger’s linear regression test across various variables further substantiated the absence of publication bias, with all p-values exceeding the 0.05 threshold. These results collectively affirm the robustness of our meta-analysis findings.

Fig. 5.

Publication Bias Funnel Plot. This funnel plot assesses the symmetry of study results to identify potential publication bias across all included studies

GRADE assessment of certainty of evidence for key clinical outcomes in mechanical ventilation

Using the GRADE approach, we systematically evaluated the certainty of evidence for key outcomes in mechanical ventilation interventions involving varying head-of-bed elevations (Fig. 6). The evidence for the incidence of pressure ulcers at different elevation angles was assessed as ‘Low’ due to significant risks of bias and imprecision, with wide confidence intervals reflecting considerable uncertainty around the effect estimate. The Odds Ratio for developing pressure ulcers at a 45° elevation compared to 30° was 1.95 (95% CI: 1.12 to 3.37), indicating a higher associated risk. Although statistically significant, the broad confidence intervals necessitate a cautious interpretation.

Fig. 6.

GRADE assessment of certainty of evidence for key clinical outcomes in mechanical ventilation

For VAP, the quality of evidence was rated ‘Moderate’, moderated by variability in effect sizes and constrained precision despite minimal heterogeneity (low I² statistic). The protective effect of a 45° elevation is evident with an Odds Ratio of 0.51 (95% CI: 0.31 to 0.84), demonstrating statistical significance and consistent effect direction across studies.

Publication bias assessments showed no substantial evidence of bias, supported by symmetrical funnel plots and non-significant Egger’s test results (Fig. 5). This supports the robustness of our meta-analysis findings, enhancing the credibility of the evidence despite noted limitations.

Our findings are drawn with caution, acknowledging the inherent limitations in the evidence. Further research with more stringent randomization and improved blinding methods could provide clearer insights and potentially revise the confidence in the estimated effects of bed elevation strategies on clinical outcomes in mechanically ventilated patients. This careful and rigorous GRADE assessment ensures that our conclusions provide reliable guidance for clinical practice, pending future investigative confirmations.

Discussion

The interplay between head-of-bed elevation and patient outcomes in critical care is a nuanced area requiring careful consideration. Our meta-analysis delves into this multifaceted issue, offering insights into the optimization of care for mechanically ventilated patients. Head-of-bed elevation is a common clinical practice aimed at preventing complications such as VAP by mitigating the risk of aspiration. However, this practice is not without its trade-offs. Notably, the concurrent risk of pressure ulcer development poses a clinical dilemma [18, 19]. Pressure ulcers are a significant concern in the ICU, often leading to prolonged hospital stays, increased morbidity, and heightened healthcare costs. The physiological underpinnings suggest that steeper elevations may increase shear and friction forces on the skin, escalating the risk of tissue breakdown, especially in the context of the diminished mobility that accompanies mechanical ventilation [20, 21].

The dichotomous impact of head-of-bed elevation on the incidence of pressure ulcers and VAP presents a significant conundrum in intensive care management. The synthesis of results from five studies within our meta-analysis highlights the complexity of critical care interventions, particularly the subtleties of patient positioning. For pressure ulcers, the increased risk associated with a 45° head-of-bed elevation, as opposed to a 30° angle, may be attributed to multiple physiological and mechanical factors [22, 23]. The shearing forces, which are accentuated at steeper angles, coupled with the patient’s weight, can contribute to tissue ischemia and damage, particularly over bony prominences [24]. This effect might be exacerbated by the patient’s limited mobility while mechanically ventilated, as movement is often a natural counteraction to prolonged pressure. Therefore, while a higher angle may be prophylactic against pulmonary complications, it simultaneously predisposes patients to dermal and subdermal injuries.

This tension between recommended practices to reduce VAP and the unintended consequence of increased pressure ulcer risk necessitates a multifaceted approach to care. The ideal head-of-bed elevation needs to be a dynamic decision, factoring in the patient’s overall condition, skin integrity, and risk factors for both pressure ulcers and pneumonia. Interdisciplinary teams should collaborate to assess the need for advanced pressure-relief mattresses, regular repositioning schedules, and skin assessments, balancing these against the equally critical need to mitigate VAP risk [25, 26]. Moreover, the findings on VAP incidence reveal a protective benefit of a 45° elevation. The reduced risk can be mechanistically explained by the influence of gravity on respiratory secretions, reducing aspiration and subsequent colonization of pathogens in the lower airways. Our findings underscore the role of vigilant care protocols that include not just pharmacological interventions but also non-pharmacological measures such as optimal bed positioning.

Additionally, the absence of significant heterogeneity across studies suggests that these results are broadly applicable and not particular to specific subgroups or settings. Nonetheless, the underlying clinical judgment must remain central, taking into account individual patient’s needs, preferences, and overall goals of care. It is also crucial to consider the interplay of other factors, such as nutritional status, which can influence skin integrity and immunity, as well as the role of microclimate control in preventing both pressure ulcers and VAP [17, 27]. The use of adjunctive technologies to monitor skin temperature and moisture may further inform care strategies. Given the significant implications of these findings, future research should aim to explore the threshold at which bed elevation becomes a risk factor for pressure ulcers while remaining protective against VAP [28, 29]. This might involve innovative study designs that allow for adjustable bed positions according to patient response and the development of predictive models that could guide clinical decision-making.

Heterogeneity

The heterogeneity within our meta-analysis was systematically assessed using the I² statistic, which serves as a quantitative measure of the variability in effect estimates that is due to heterogeneity rather than chance. In our study, the I² values were remarkably low (I² = 0.0% for both pressure ulcer and ventilator-associated pneumonia outcomes), indicating no observed heterogeneity among the included studies. This uniformity is highlighted by consistent p-values (p = 0.930 and p = 0.797, respectively), further supporting the homogeneity of the effect sizes across studies. Such minimal heterogeneity is indicative of the robustness of our findings, suggesting that the intervention effects are stable across different study settings and populations. However, the absence of significant heterogeneity also prompts a cautious interpretation, as it could be reflective of the limited number of studies included and the potential for type II errors.

Several limitations within the studies included in our meta-analysis merit consideration. First, variability in the reporting of patient demographics and clinical settings may limit the generalizability of the findings. Additionally, the duration of head-of-bed elevation varied among studies, which could influence the incidence rates of both pressure ulcers and pneumonia. Furthermore, most studies did not account for potential confounding factors such as nutritional status, skin care protocols, and the precise duration of mechanical ventilation. These limitations underscore the necessity for cautious interpretation of the findings and highlight the need for future research to address these gaps.

Conclusions

A higher head-of-bed elevation is associated with a decreased risk of VAP in mechanically ventilated patients but also bears an elevated risk for pressure ulcer formation. It is imperative to judiciously weigh these outcomes to tailor patient care strategies that mitigate risks and enhance the overall benefit in critical care environments.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

Chan Lian contributed to the conception of the study; Chan Lian and Jiangnan Zhang contributed significantly to literature search, data extraction, quality assessment, data analyses and manuscript preparation; Chan Lian contributed improving the article for language and style and protocol preparation; Jiangnan Zhang helped perform the analysis with constructive discussions; Pengfei Wang and Wenwei Mao revised the manuscript and approved the final version.

Funding

The research was funded by 2022 Wenling City Social Development Science and Technology Project (2022S00121).

Data availability

The datasets used and/or analyzed during the present study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.