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Time course change for P/F ratio of later proning versus early proning. Supine is immediately before PP. Post represents 7 h after completing PP. There was statistical significance (asterisks) in initiating prone positioning when the P/F ratio decreased to ≤150 (defined as later proning), and there was no statistical significance in initiating prone positioning when the P/F ratio was >150 (defined as early proning).
