Effect of the prone position on recruitability in acute respiratory distress syndrome due to COVID-19 pneumonia

OBJECTIVE: This study aimed to assess the effect of prone position on oxygenation and lung recruitability in patients with acute respiratory distress syndrome due to COVID-19 receiving invasive mechanical ventilation. METHODS: This prospective study was conducted in the intensive care unit between December 10, 2021, and February 10, 2022. We included 25 patients admitted to our intensive care unit with acute respiratory distress syndrome due to COVID-19 who had undergone prone position. We measured the respiratory system compliance, recruitment to inflation ratio, and PaO(2)/FiO(2) ratio during the baseline supine, prone, and resupine positions. The recruitment to inflation ratio was used to assess the potential for lung recruitability. RESULTS: In the prone position, PaO(2)/FiO(2) increased from 82.7 to 164.4 mmHg (p<0.001) with an increase in respiratory system compliance (p=0.003). PaO(2)/FiO(2) decreased to 117 mmHg (p=0.015) in the resupine with no change in respiratory system compliance (p=0.097). The recruitment to inflation ratio did not change in the prone and resupine positions (p=0.198 and p=0.621, respectively). In all patients, the median value of respiratory system compliance during supine was 26 mL/cmH(2)O. In patients with respiratory system compliance<26 mL/cmH(2)O (n=12), respiratory system compliance increased and recruitment to inflation decreased from supine to prone positions (p=0.008 and p=0.040, respectively), whereas they did not change in those with respiratory system compliance ≥26 mL/cmH(2)O(8) (n=13) (p=0.279 and p=0.550, respectively) (ClinicalTrials registration number: NCT05150847). CONCLUSION: In the prone position, in addition to the oxygenation benefit in all patients, we detected lung recruitment based on the change in the recruitment to inflation ratio with an increase in respiratory system compliance only in acute respiratory distress syndrome due to COVID-19 patients who have <26 mL/cmH(2)O baseline supine respiratory compliance.