Respiration/Ventilation and TracheostomyImpact of patient position on the incidence of ventilator-associated pneumonia: A meta-analysis of randomized controlled trials
Introduction
Ventilator-associated pneumonia (VAP) is the most common infection among mechanically ventilated patients and has been associated with increased mortality, morbidity, length of intensive care unit (ICU) stay and duration of mechanical ventilation. The pathogenesis of VAP starts with bacterial colonization of the oral cavity followed by aspiration of oropharyngeal fluids along the endotracheal tube [1], [2]. Bacterial colonization of the stomach and gastroesophageal aspiration may also contribute to the pathogenesis of VAP [3]. Gastroesophageal aspiration is promoted by the presence of the nasogastric tube and supine body position [4]. Experimental studies with radioactive-labeled enteral feeding suggested that endotracheal aspiration of gastric contents occurred more frequently among patients positioned supinely (lying on the back) rather than semirecumbently (patient's head and back elevated at 45°) [5]. On the basis of these findings, the Centers for Disease Control and Prevention suggested treatment of mechanically ventilated patients in a semirecumbent 45° position as a VAP-preventive measure [6].
Despite the recommendation of several professional associations, the above intervention has not been widely used as standard clinical policy [7], and mechanically ventilated patients treated in the ICU are most frequently positioned in a small back rest elevation of 10° to 30° [8]. This may be at least partly attributed to the insufficient awareness of the benefit of this position, the disagreement about who is responsible for patients' bed positioning, and certain difficulties in enabling and reinforcing such strategies [7]. Prone positioning (lying with the front or face downward) has been supported by several researchers for the management of patients with acute lung injury (ALI) or adults respiratory distress syndrome (ARDS) [9], [10], [11]. Certain randomized control trials (RCTs), studying the effect of prone and semirecumbent position on various outcomes, have supported that nonsupine position (semirecumbent 45° or prone position) of the patient may lead to reduction of VAP incidence and/or shorter duration of mechanical ventilation and ICU stay. However, current evidence is rather controversial, and available RCTs have small sample sizes and reduced statistical power. The mechanism of how prone position may decrease the incidence of VAP is still unclear. On the other hand, the role of pronation in the improvement of oxygenation among patients with ALI or ARDS has been well documented [9], [10], [11]. Furthermore, pronation has a drainage effect of respiratory secretions, which has not been systematically investigated [12]. We sought to perform a meta-analysis of RCTs to determine the effect of prone and semirecumbent 45° positional strategies on the incidence of VAP and various other clinical outcomes among mechanically ventilated patients.
Section snippets
Data sources
This meta-analysis was conducted according to the guidelines issued by the “quality of reporting of meta-analyses” conference [13]. To identify relevant RCTs, we systematically searched PubMed (until December 2007) and Cochrane Central Register of Controlled Trials by using the following keywords: “prone” or “semirecumbent” using as a limit “type of article: Randomized Controlled Trial.” Furthermore, we reviewed the references of the included RCTs. Abstracts of conference proceedings were not
Selected randomized controlled trials
In Fig. 1, we present a flow diagram describing the selection process followed to identify the pool of RCTs included in the meta-analysis. PubMed search yielded 579 potentially relevant articles; search using the Cochrane Central Register of Controlled Trials did not reveal any additional relevant RCTs. Seven RCTs [12], [15], [16], [17], [18], [19], [20] of the 579 initially located articles fulfilled the inclusion criteria for this meta-analysis. It should be noted that 2 studies by Beuret et
Discussion
The most important finding of this meta-analysis is that patients positioned semirecumbently 45° have significantly lower incidence of clinically diagnosed VAP compared to patients positioned supinely. On the other hand, despite the noted moderate trend toward lower incidence of clinically diagnosed VAP among patients positioned pronely compared to patients positioned supinely, the results are not statistically significant. Furthermore, it should be noted that no significant difference was
References (29)
- et al.
Nursing the ARDS patient in the prone position: the experience of qualified ICU nurses
Intensive Crit Care Nurs
(2001) - et al.
Clinical guidelines for the use of the prone position in acute respiratory distress syndrome
Intensive Crit Care Nurs
(2001) - et al.
Improving the quality of reports of meta-analyses of randomized controlled trials: the QUOROM statement
Lancet
(1999) - et al.
Evidence-based assessment of diagnostic tests for ventilator-associated pneumonia. Executive summary
Chest
(2000) - et al.
Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial
Lancet
(1999) - et al.
Association of respiratory tract colonization with adherence of gram-negative bacilli to epithelial cells
J Infect Dis
(1979) - et al.
Nosocomial respiratory infections with gram-negative bacilli. The significance of colonization of the respiratory tract
Ann Intern Med
(1972) - et al.
Role of colonization of the upper intestinal tract in the pathogenesis of ventilator-associated pneumonia
Clin Infect Dis
(1997) - et al.
Gastroesophageal reflux in intubated patients receiving enteral nutrition: effect of supine and semirecumbent positions
J Parenter Enteral Nutr
(1992) - et al.
Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: the effect of body position
Ann Intern Med
(1992)