• Thomas C Rollinson, Luke A McDonald, Joleen Rose, Glenn Eastwood, Rahul Costa-Pinto, Lucy Modra, Akinori Maeda, Zoe Bacolas, James Anstey, Samantha Bates, Scott Bradley, Jodi Dumbrell, Craig French, Angaj Ghosh, Kimberley Haines, Tim Haydon, Carol Hodgson, Jennifer Holmes, Nina Leggett, Forbes McGain, Cara Moore, Kathleen Nelson, Jeffrey Presneill, Hannah Rotherham, Simone Said, Meredith Young, Peinan Zhao, Andrew Udy, Anis Chaba, Rinaldo Bellomo, and NetoAry SerpaASDepartment of Intensive Care, Austin Health, Melbourne, Victoria, Australia.Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Victoria, Australia..
• Department of Intensive Care, Austin Health, Melbourne, Victoria, Australia.
• Acta Anaesthesiol Scand. 2024 Mar 1; 68 (3): 361371361-371.

BackgroundProne 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 PaO2 :FiO2 ratio during prone and secondly, the time to peak oxygenation.MethodsMulti-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 PaO2 :FiO2 ratio effect and time to peak PaO2 :FIO2 ratio effect was measured.ResultsWe 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 PaO2 :FIO2 ratio was 137 (±49) for all prone episodes. During the first episode. the mean PaO2 :FIO2 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.ConclusionsIn ventilated adults with COVID-19 acute hypoxemic respiratory failure, peak PaO2 :FIO2 ratio effect occurred during the first prone positioning episode and after 9 h. Subsequent episodes also improved oxygenation but with diminished effect on PaO2 :FIO2 ratio. This information can help guide the number and duration of prone positioning episodes.© 2023 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.

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