Introduction: Prone positioning improves oxygenation and reduces mortality in patients with acute respiratory distress syndrome (ARDS). However, the underlying physiological mechanisms, particularly during repeated sessions, remain unclear. Thus, we aimed to explore these mechanisms by using oxygenation, lung compliance (Cst), and lung ultrasound (LUS) assessments in intubated patients with COVID-19 ARDS. Methods: In this prospective observational study, which was approved by institutional ethics committees (No. 2012203) and registered on ClinicalTrials.gov (NCT04692779), intubated adults with COVID-19 ARDS who underwent prone positioning were enrolled. Oxygenation (PaO2/FIO2 ratio), global and regional LUS scores, and Cst were evaluated at baseline, 1, 4, and 15 hours after initiating prone positioning, and 1-2 hours after supination across the first three prone sessions. Treatment success was defined as survival to hospital discharge without the need for extracorporeal membrane oxygenation. Results: Sixty patients were included, 17 patients (28%) achieved treatment success. Of the 60 patients, 14 received a single prone session, 12 received two sessions, and 34 received three or more. No significant differences were observed between the treatment success and failure groups during the first prone session. In the second session, post-supine dorsal LUS scores were lower in the treatment success group compared to the failure group 7.0 (5.5–8.0) vs. 9.0 (7.0–9.5), p=0.005. Ventral LUS scores returned to baseline post-supine in the success group but remained elevated in the failure group. Cst was higher in the success group at 4 hours post-prone, 15 hours post-prone, and 1–2 hours post-supine (all p< 0.05). By the third prone session, post-supine PaO2/FIO2 ratio was higher in the success group compared to the failure group 181.3±69.8 vs. 125.2±54.7 mmHg, p=0.017. Conclusions: In patients with COVID-19 ARDS, treatment success was associated with sustained dorsal recruitment, improved lung compliance, and ventral re-recruitment after supination, especially during the second prone session. Integrating oxygenation, lung compliance, and LUS scores provides a comprehensive assessment of response to prone positioning and may guide clinical decision-making.
Weiss et al. (Sun,) studied this question.