Oxygenation improves during the first 8 h of extended-duration prone positioning in patients with respiratory failure: a retrospective study

BACKGROUND: A recent multicenter trial demonstrated decreased mortality when patients with acute respiratory distress syndrome were treated with prone positioning (PP). However, the optimal duration of this treatment has not been established. METHODS: From May 2010 to August 2013, 15 patients with respiratory failure underwent extended-duration prone positioning (more than 40 h) in the medical-surgical intensive care unit of a university hospital. The records of each patient were retrospectively investigated to evaluate the impact of prone positioning on the PaO(2)/FiO(2) ratio (PFR) during the first 40 h of therapy. RESULTS: The mean age of the patients was 72.2 ± 7.8 years, and the mean Acute Physiology and Chronic Health Evaluation II score was 19.0 ± 6.0. The hospital mortality rate was 47% (7/15), and the median duration of prone positioning was 47.5 h (46.5–67). The mean PFR before prone positioning was 193.8 ± 70.1, and it significantly improved to 274.7 ± 70.7 (p = 0.02) at 8 h after prone positioning initiation. Although PFR further improved to 294.1 ± 78.0 (p = 0.23) at 16 h, the change was not significant and PFR remained relatively constant at 289.0 ± 88.1, 294.6 ± 68.2, and 291.7 ± 72.7 at 24, 32, and 40 h, respectively. CONCLUSIONS: Extended-duration prone positioning resulted in a progressive improvement in oxygenation until 8 to 16 h after treatment initiation, after which there was no significant improvement. Further studies are warranted to clarify the optimal duration of prone positioning and the actual effectiveness of extended-duration PP for respiratory failure.