Magnitude and time to peak oxygenation effect of prone positioning in ventilated adults with COVID‐19 related acute hypoxemic respiratory failure

Background Prone positioning may improve oxygenation in acute hypoxemic respiratory failure and was widely adopted in COVID‐19 patients. However, the magnitude and timing of its peak oxygenation effect remain uncertain with the optimum dosage unknown. Therefore, we aimed to investigate the magnitude of the peak effect of prone positioning on the PaO 2 :FiO 2 ratio during prone and secondly, the time to peak oxygenation. Methods Multi‐centre, observational study of invasively ventilated adults with acute hypoxemic respiratory failure secondary to COVID‐19 treated with prone positioning. Baseline characteristics, prone positioning and patient outcome data were collected. All arterial blood gas (ABG) data during supine, prone and after return to supine position were analysed. The magnitude of peak PaO 2 :FiO 2 ratio effect and time to peak PaO 2 :FIO 2 ratio effect was measured. Results We studied 220 patients (mean age 54 years) and 548 prone episodes. Prone positioning was applied for a mean (±SD) 3 (±2) times and 16 (±3) hours per episode. Pre‐proning PaO 2 :FIO 2 ratio was 137 (±49) for all prone episodes. During the first episode. the mean PaO 2 :FIO 2 ratio increased from 125 to a peak of 196 ( p < .001). Peak effect was achieved during the first episode, after 9 (±5) hours in prone position and maintained until return to supine position. Conclusions In ventilated adults with COVID‐19 acute hypoxemic respiratory failure, peak PaO 2 :FIO 2 ratio effect occurred during the first prone positioning episode and after 9 h. Subsequent episodes also improved oxygenation but with diminished effect on PaO 2 :FIO 2 ratio. This information can help guide the number and duration of prone positioning episodes.