The Truth Behind the Lie: Prone Positioning in Severe Acute Respiratory Distress Syndrome

Published - Written by John Staples

Physicians have long realized that a little change in position can go a long way. Is Mr. X’s peripheral arterial disease causing him ischemic rest pain? Keep those legs dependant. Is Mrs. Y getting orthopnea from uncontrolled heat failure? Sit her up and she might get some relief. Is the sight of blood making your medical student a little lightheaded? Perhaps he’d better lie down.

In patients with the acute respiratory distress syndrome (ARDS), the positional solution is more complicated. Mechanically ventilating ARDS patients in the prone position improves ventilation-perfusion matching but risks accidental extubation and complicates daily medical care. Clinicians could flip a coin to decide what to do with their patients (“Heads up … face up?”), but both doctors and patients would greatly prefer an evidence-based solution.

Heeding this call for evidence, Dr. Claude Guérin (Hôpital de la Croix-Rousse, Lyon, France) and colleagues report the results of the PROSEVA trial in this week’s NEJM. This multicenter study randomized 466 mechanically-ventilated patients with severe ARDS to undergo prone-positioning or to be left supine. Patients in the prone group were turned by an experienced team (see video at and were prone for 73% of eligible patient-hours, a higher intensity of prone positioning than applied in previous trials.

At the completion of the trial, the 28-day all-cause mortality observed in the prone group was about half that observed in the supine group (16% vs 33%; HR 0.39, 95%CI 0.25-0.63). The prone group also required less aggressive ventilator settings and had fewer cardiac arrests. Other adverse effects were not significantly different between the two groups.

In an accompanying editorial, Dr Guy W Soo Hoo (Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA) notes that a treatment effect of this size is “virtually unprecedented in modern medicine.” He notes that the results of PROSEVA are compelling but reminds readers that the trial enrolled a highly select group of patients with severe ARDS, took place in centers with substantial experience in prone-positioning, and ensured that patients were prone for a substantial proportion of time.

Proper body position can optimize ventilation (just ask any yogi, soprano, or expectant mother) and can provide hydrostatic benefits (as your presyncopal medical student can attest). Thanks to the PROSEVA trial, intensivists can be more confident that these principles result in substantial practical benefits when prone-positioning patients with severe ARDS.

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