Source: L. Gattinoni and the Prone-Supine Study Group. N Engl J Med 2001;345:568-73

Reviewer:  M. Cereda, MD

Background
It has been known for years that prone positioning of patients with acute respiratory failure improves their PaO2, sometimes dramatically. However, the effect of this manoeuvre on clinical outcomes has never been investigated.

Study design
Multicenter randomised trial. 304 patients with acute respiratory failure (94% of whom had ARDS) were recruited in 30 ICUs and were randomised to receive either:
· Prone positioning for at least 6 hours/day for 10 days.
· Supine positioning only.
 All patients received standard ventilatory treatment according to accepted guidelines.

Endpoints
· Mortality at 10 days, at discharge from the ICU, and at 6 months.
· Oxygenation values
· Incidence of pressure sores and of other complications related to positioning (i.e. accidental extubation and dislodgement of lines, etc.).

Results
In spite of the fact that patients randomised to prone position responded with an improvement in oxygenation, they did not have better survival rates than patients in the supine group. Only the patients with more severe disease had a significant improvement in survival, but only at 10 days. Prone position was not associated with increased complications.

Comments
Prone positioning does not seem to have a role in the routine treatment of ARDS. However, this technique should probably not be abandoned since it might still benefit the sicker patients and its use is safe. The limited amount of time spent by the patients in the prone position and the fact that relatively large tidal volumes (10 ml/kg) were used might have negatively affected the results of this study.