Patients with acute respiratory distress syndrome (ARDS) who were placed in the prone position had improved gas exchange and reduced intensity of inspiratory effort compared with the supine position, according to study results published in the American Journal of Respiratory and Critical Care Medicine.

In this feasibility study, researchers determined the intensity of spontaneous breathing via esophageal balloon in adult patients with moderate to severe ARDS ( Identifier: NCT03768154). Breathing intensities were compared at baseline (supine) and after being moved to the prone position. Patients were sequentially assigned to each of the following conditions: spontaneous breathing (supine); muscle paralysis (supine); muscle paralysis (prone); and spontaneous breathing (prone). Before switching from supine to prone position, patients were paralyzed with rocuronium.

Among the 12 patients with moderate to severe ARDS, PaO2/fraction of inspired oxygen (FIO2) was 160 mm Hg in the supine position. After being moved to the prone position, oxygenation levels increased to 239 mm Hg. Furthermore, both spontaneous inspiratory effort and dynamic lung stress were also lower in the prone position. Other respiratory parameters including positive end expiratory pressure (PEEP), plateau pressure, tidal volume, respiratory system compliance, and respiratory rate remained unchanged when comparing supine position and prone positions. In addition, prone positioning was associated with a reduction in serum interleukin-6 levels.

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The researchers noted that the study was limited by the small number of patients, and should be considered exploratory and descriptive. However, despite limitations, the results suggest that prone positioning is a promising technique “to render spontaneous effort less injurious.”

“In comparison to supine position, prone position during spontaneous breathing improves gas exchange, reduces the intensity of spontaneous inspiratory effort and dynamic lung stress, and attenuates systemic inflammation,” the study authors concluded.


Yoshida T, Tanaka A, Roldan R, et al. Prone position reduces spontaneous inspiratory effort in patients with acute respiratory distress syndrome: a bi-center study. Am J Respir Crit Care Med. Published online February 10, 2021. doi:10.1164/rccm.202012-4509LE