PaO / FiO ratio responsiveness to prone positioning in intubated patients with severe COVID-19: a retrospective observational study.

Aim: Prone positioning of coronavirus disease 2019 (COVID-19) patients could improve oxygenation. However, clinical data on prone positioning of intubated COVID-19 patients are limited. We investigated trends of PaO / FiO ratio values in patients during prone positioning to identify a predictive factor for early detection of patients requiring advanced therapeutic intervention such as extracorporeal membrane oxygenation (ECMO).

Methods: This retrospective, observational cohort study was undertaken between April 2020 and May 2021 in a tertiary referral hospital for COVID-19 in Osaka, Japan. We included intubated adult COVID-19 patients treated with prone positioning within the first 72 h of admission to the intensive care unit and followed them until hospital discharge or death. Primary outcomes were in-hospital mortality and escalation of care to ECMO. We used unsupervised k-means clustering modeling to categorize COVID-19 patients by PaO / FiO ratio responsiveness to prone positioning.

Results: The final study cohort comprised 54 of 155 consecutive severe COVID-19 patients. Three clusters were generated according to trends in PaO / FiO ratios during prone positioning (cluster A,  = 16; cluster B,  = 24; cluster C,  = 14). Baseline characteristics of all clusters were almost similar. Cluster A (no increase in PaO / FiO ratio during prone positioning) had a significantly higher proportion of patients placed on ECMO or who died (6/16, 37.5%). Numbers of patients with ECMO and with in-hospital death were significantly different between the three groups ( = 0.017).

Conclusion: In Japanese patients intubated due to COVID-19, clinicians should consider earlier escalation of treatment, such as facility transfer or ECMO, if the PaO / FiO ratio does not increase during initial prone positioning.