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