NEW YORK (Reuters Health) – Keeping hypoxic patients with acute respiratory distress syndrome (ARDS) in the prone position does not reduce mortality, although it might provide a slight benefit in the most severe cases.

This conclusion, reported November 11 in the Journal of the American Medical Association, is from a 25-center randomized trial in Italy and Spain.

“The hypothesis…was that mechanical ventilation could be less injurious if applied in the prone position…owing to the well-recognized greater homogeneity of stress and strain distribution across the lung parenchyma,” according to senior author Dr. Luciano Gattinoni from Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena di Milano, Italy, and the Prone-Supine II Study Group.

Between 2004 and 2008, 174 patients were randomized to supine positioning for a maximum of 20 hours per day, and 168 were kept in the prone position for a maximum of 18 hours per day, for up to 28 days or until ARDS resolved.

Patients with severe hypoxemia (PaO2:FIO2 ratio lower than 100 mmHg) and moderate hypoxemia (PaO2:FIO2 ratio between 100 and 200 mmHg) were evenly distributed between the two groups.

Tidal volumes were limited to a maximum of 8 mL/kg of ideal body weight and airway plateau pressures limited to 30 cm H20.

According to the investigators, the prone and supine groups had similar mortality rates at 28 days (31.0% and 32.8%, respectively) and at 6 months (47.0% and 52.3%, respectively).

Moreover, the prone group had a significantly higher complication rate (94.6% vs 76.4%; p < 0.001). Among patients with severe hypoxemia, however, there was a trend toward lower mortality with prone positioning both at 28 days (37.8% vs 46.1% in the supine group, relative risk 0.87) and at 6 months (52.7% vs 63.2%, RR 0.78). In patients with moderate hypoxemia, outcomes were similar no matter whether they were supine or prone. Near the end of their paper, Dr. Gattinoni and his associates ask, “Do the findings of this trial…represent the end of the prone positioning technique?” Certainly, they continue, prone positioning is not appropriate for “the unselected ARDS population.” However, the researchers conclude, the “potential role (of prone positioning) in patients with the most severe hypoxemia, for whom the possible benefit could outweigh the risk of complications, must be further investigated.” Reference:
JAMA 2009;302:1977-1984.