Elsevier

The Lancet

Volume 354, Issue 9193, 27 November 1999, Pages 1851-1858
The Lancet

Articles
Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial

https://doi.org/10.1016/S0140-6736(98)12251-1Get rights and content

Summary

Background

Risk factors for nosocomial pneumonia, such as gastro-oesophageal reflux and subsequent aspiration, can be reduced by semirecumbent body position in intensive-care patients. The objective of this study was to assess whether the incidence of nosocomial pneumonia can also be reduced by this measure.

Methods

This trial was stopped after the planned interim analysis. 86 intubated and mechanically ventilated patients of one medical and one respiratory intensive-care unit at a tertiary-care university hospital were randomly assigned to semirecumbent (n=39) or supine (n=47) body position. The frequency of clinically suspected and microbiologically confirmed nosocomial pneumonia (clinical plus quantitative bacteriological criteria) was assessed in both groups. Body position was analysed together with known risk factors for nosocomial pneumonia.

Findings

The frequency of clinically suspected nosocomial pneumonia was lower in the semirecumbent group than in the supine group (three of 39 [8%] vs 16 of 47 [34%]; 95% CI for difference 10·0–42.0, p=0·003). This was also true for microbiologically confirmed pneumonia (semirecumbent 2/39 [5%] vs supine 11/47 [23%]; 4.2–31.8, p=0·018). Supine body position (odds ratio 6.8 [1.7–26.7], p=0·006) and enteral nutrition (5.7 [1.5–22.8], p=0·013) were independent risk factors for nosocomial pneumonia and the frequency was highest for patients receiving enteral nutrition in the supine body position (14/28, 50%). Mechanical ventilation for 7 days or more (10·9 [3.0–40·4], p=0·001) and a Glasgow coma scale score of less than 9 were additional risk factors.

Interpretation

The semirecumbent body position reduces frequency and risk of nosocomial pneumonia, especially in patients who receive enteral nutrition. The risk of nosocomial pneumonia is increased by long-duration mechanical ventilation and decreased consciousness.

Introduction

Pneumonia is the most frequent nosocomial infection among intensive-care-unit (ICU) patients.1 The frequency of nosocomial pneumonia in the ICU has been reported as between 9% and 70%, depending on the definition and the population studied.2, 3 Additionally, the incidence of nosocomial pneumonia varies among types of ICUs and ranges from 4.7 cases per 1000 ventilator days for paediatric ICUs to 35 cases per 1000 ventilator days in burn ICUs.4, 5 The incidence of nosocomial pneumonia in medical and surgical ICUs has been reported to range from 12.8 to 17.6 per 1000 ventilator days.6 The recognised pathogenetic sequence of nosocomial pneumonia is abnormal oropharyngeal colonisation and subsequent aspiration. The colonisation of the oropharynx may be augmented by regurgitation of colonised gastric content. Colonisation of the stomach is favoured by the use of systemic or local antacid drugs and enteral nutrition, which alkalise gastric secretions and hence facilitate bacterial growth.7 Although controversial, gastric reflux and subsequent aspiration to lower airways could play a part in the pathogenesis of nosocomial pneumonia.8

Two studies with radioactively labelled gastric contents showed that reflux can be reduced and subsequent aspiration avoided by positioning mechanically ventilated patients in a semirecumbent position.8, 9 In addition, an elevated head position (angle >30°) was also protective against nosocomial infection in an epidemiological study.10 Although pneumonia was the most common nosocomial infection in that study, data on nosocomial pneumonia alone were not available. Kollef described in a cohort study a three-fold risk of nosocomial pneumonia, in patients with a supine head position during the first 24 h of mechanical ventilation.11 Although the semirecumbent position has been strongly recommended by the US Centers for Disease Control and Prevention (CDC), the benefit for prevention of nosocomial pneumonia has never been proven in a randomised clinical trial.4 We therefore investigated the frequency of nosocomial pneumonia in intubated and mechanically ventilated patients, randomly assigned to either supine or semirecumbent body positions.

Section snippets

Patients

Patients were recruited from June 1, 1997, until May 31, 1998, in the Hospital Clinic, a 1000-bed tertiary-care university hospital in two ICUs, a six-bed respiratory ICU, and eight-bed medical ICU.

All patients were routinely subjected to standard measures for general critical care and prevention of nosocomial pneumonia in mechanically ventilated patients, namely: sterile endotracheal suctioning; no change of mechanical ventilation tubing systems; stress ulcer prophylaxis with sucralfate (1 g

Patients

90 patients were randomly assigned with semirecumbent or supine body position (figure 1). Four patients were excluded from the analysis: one died during resuscitation 2 h after initiation of the protocol and three because of protocol violation (reintubated patients all in semirecumbent position).

A total of 86 patients (65 male and 21 female, mean age 65 years [SD15]) completed the clinical trial. Among the 86 patients the reasons for termination of the protocol were: change in position for more

Discussion

The pathogenesis of nosocomial pneumonia includes microaspiration to lower airways of abnormally colonised oropharyngeal or gastric contents, or both.4 However, the role of the gastric reservoir for the pathogenesis of bacterial nosocomial pneumonia is controversial. Some studies found no clear sequence of colonisation from the stomach to the pharynx or the airways,17, 18, 19 whereas other studies provided clear evidence of the contributing role of the gastric reservoir to the pathogenesis of

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