BARCELONA--A Spanish study published recently in the Lancet provides additional evidence that placing critically ill, ventilated patients in a semirecumbent position minimizes the likelihood of nosocomial pneumonia.[1] Antoni Torres, MD, Director of Institut Clínic de Pneumologia i Cirurgia Toràcica, Barcelona, Spain, and one of the authors of the study, noted that "use of the semirecumbent position is followed by a twofold reduction in the incidence of nosocomial pneumonia."

The pharmacoeconomic impact of these results should be substantial, Dr. Torres suggested. "It is clear that reducing the incidence of nosocomial pneumonia leads to decreases in antibiotic costs and length of stay in the ICU and hospital."

The study recorded the frequency of both clinically suspected and microbiologically confirmed nosocomial pneumonia in 86 intubated, mechanically ventilated patients. Patients were randomized into supine and semirecumbent body position groups. Pneumonia was clinically suspected in three (8%) of the 39 semirecumbent patients and in 16 (34%) of the 47 supine patients. Laboratory analysis confirmed pneumonia in two (5%) and 11 (23%) patients, respectively.

In an accompanying editorial,[2] Nigel R. Webster, MB ChB, PhD, who is a professor of anesthesia and intensive care at the University of Aberdeen, United Kingdom, noted that the US Centers for Disease Control and Prevention also advocates the semirecumbent position as a means of lowering the risk of nosocomial pneumonia in critically ill patients.[3] The problem presented by nosocomial pneumonia is far from trivial: A European study by Vincent and colleagues[4] of approximately 10,000 patients showed that almost one third (30.4%) had developed a nosocomial infection in either the intensive care unit (ICU) or hospital. More than half of the infections were in the respiratory tract.

In most adult medical and surgical ICUs, the incidence of nosocomial pneumonia may be as high as 17.6 cases per 1,000 ventilator days; in burn units, the incidence may be even higher: up to 35 cases per 1,000 days. Because nosocomial pneumonia increases mortality and the cost of care, any steps that can lower its incidence might well improve patient outcome. But how can a change in position alter the risk of pneumonia?

Drakulovic and colleagues, the authors of the Spanish study, believe that the source of infection is microaspiration of colonized gastric contents; they noted that gastroesophageal reflux is common in mechanically ventilated patients. The infection is spread by retrograde oropharyngeal colonization and aspiration to lower airways. To test this hypothesis, the authors performed a multivariate analysis and found that both a supine body position and administration of enteral nutrition were independent risk factors for both clinically suspected and microbiologically confirmed nosocomial pneumonia.

The presence of both risk factors had an additive effect on the incidence of nosocomial pneumonia. For example, the highest frequency of clinically suspected pneumonia (50%) occurred in patients treated in the supine position who were being fed enterally. The incidence of pneumonia among those treated in the supine position who did not receive enteral nutrition was 10%, and it was 9% among those who were fed enterally but treated in the semirecumbent position. Only 6% of those who did not receive enteral nutrition and were treated in a semirecumbent position developed pneumonia. Similar results were obtained when the authors analyzed the incidence of microbiologically confirmed pneumonia.

The only other independent predictor of confirmed nosocomial pneumonia was the need for mechanical ventilation for seven or more days. Neither age, sex, APACHE II score, nor Glasgow Coma Scale score could independently predict the development of pneumonia.

Although mortality was lower in the semirecumbent group than in the supine group, this difference did not reach significance, possibly because of the small sample size. The authors had intended to enroll more patients, but the study was terminated early after an interim analysis detected the markedly lower incidence of nosocomial pneumonia in the semirecumbent patients.

--Marjorie Winters

References
1. Drakulovic MB, Torres A, Bauer TT, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. Lancet. 1999;354:1851-1858.
2. Webster NR. Importance of position in which patients are nursed in intensive-care units [commentary]. Lancet. 1999;354:1835-1836.
3. Centers for Disease Control and Prevention. Guidelines for prevention of nosocomial pneumonia. MMWR Morb Mortal Wkly Rep. 1997;46:1-79.
4. Vincent JL, Bihari DJ, Suter PM, et al. The prevalence of nosocomial infection in intensive care units in Europe: results of the European Prevalence of Infection in Intensive Care (EPIC) study. EPIC International Advisory Committee. JAMA. 1995;274:639-644.

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