Respiratory Failure pneumonia HEAD OF BED ELEVATION IN THE ICU

SUMMARY
Nosocomial pneumonia is commonplace in the intensive care unit (ICU) and is associated with pulmonary aspiration of contaminated gastric secretions. Semi-recumbent patient positioning (head of bed elevation)
significantly decreases the incidence of both pulmonary aspiration as well as subsequent development of bacterial pneumonia and may be associated with reduced ICU mortality. 2

Approved 12/07/05
This guideline will focus on one such strategy: semirecumbent positioning or “head of bed” elevation. Maintenance of the head at greater than 30-45 degrees has been suggested as a clinically useful method for reducing a patient’s risk of VAP and ICU mortality. A full discussion of the strategies for VAP prevention is beyond the scope of this guideline and the reader is referred to reference 2 for such details. Head of bed elevation also reduces intracranial pre
ssure (ICP) and optimizes cerebral perfusion pressure
(CPP) in patients with closed head injury (4)

LITERATURE REVIEW
Torres et al. performed a prospective, randomized, two-period crossover trial in 19 mechanically ventilated medical ICU patients in which gastric secretions were radiolabelled with Technetium-99m sulphur colloid (5). Patients were randomly placed in either the supine or semirecumbent (45-degree angle) position and the presence of radioactivity in
bronchial secretions was subsequently assessed. All patients had nasogastric tubes in place. Forty-eight hours later, the
study was repeated in each patient using the alternate position. All patients demonstrated an increase in radioactivity count illustrating that pulmonary aspiration of gastric secretions occurs, regardless of patient position. The radioactivity recovered in the endobronchial samples of semirecumbent patients, however, was significantly lower than
that of supine patients (p=0.036) confirming that head of bed elevation is significantly protective. The authors concluded that supine positioning promotes the development of VAP and that semirecumbent positioning of mechanically ventilated patients is a simple and effective means to minimizing aspiration of gastric contents (Class II)

Kollef carried out a prospective descriptive cohort study of 277 mechanically ventilated patients of whom 43 developed VAP while 234 did not (6). Univariate and multivariate analyses were subsequently performed to identify risk factors that were independently associated with VAP and mortality. Age, organ failure, prior antibiotic administration, and supine h
ead positioning (30-degree angle) during the first 24 hours of mechanical ventilation were all independently associated with VAP in multivariate analysis. Supine position and organ failure were independently associated with patient mortality in multivariate analysis. VAP occurred in 34% of supine patients and 11% of semirecumbent patients (p<0.001). ICU mortality was 30% in supine patients and 8.9% in semirecumbent patients (p<0.001) (Class II).

Drakulovic, Torres, et al. subsequently performed a prospective, randomized trial of supine vs. semirecumbent (45-degree angle) positioning in the prevention of nosocomial pneumonia among 86 mechanically ventilated medical ICU patients (7). The study was terminated early during a planned interim analysis due to the finding of a statistically significant difference in pneumonia between patient groups. Microbiologically confirmed pneumonia occurred in 5% of semirecumbent patients and 23% in supine patients (p=0.018; 95% CI 4-33%). The risk
reduction associated with semirecumbent positioning was 78%. In a multivariate analysis of risk factors associated with development of pneumonia, enteral nutrition (odds ratio 11. and supine body position (odds ratio 6.1) were identified as significant independent risk factors. The study showed a trend towards a reduction in mortality (18% in semirecumbent patients and 28% in supine patients (p=0.289)), but the trial was not powered to detect such a difference if present (Class I). Durward et al. performed a prospective evaluation of the impact of supine vs. various semirecumbent positions (15, 30, and 60 degrees) on ICP, CPP, and CVP in patients with a Glasgow Coma Score of ≤ 8
and traumatic closed head injury or near-drowning (4). ICP was highest in all patients in the supine position and decreased significantly at 15 and 30 degrees of elevation while maintaining CPP and cardiac index. Elevation to 60 degrees caused a fall in CPP and cardiac index, an increase in CVP, and a variable response in ICP (Class II).
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