Abstract
BACKGROUND: The role of the ratio between the arterial partial pressure of oxygen and the inspired fraction of oxygen (PaO(2)/FiO(2) ratio) during the change in position is not fully established. METHODS: This retrospective, single-center cohort study included 98 patients with severe COVID-19 pneumonia. OBJECTIVE: This study aimed to evaluate the predictive value of the PaO(2)/FiO(2) ratio for survival in patients with severe COVID-19 pneumonia between changing from supine to prone positions and vice versa. The PaO(2)/FiO(2) ratio was measured preproning (T0), 30 min to 1 hour (T1), and 48 h after prone positioning (T2), and 30 min to 1 h after re-supination (T3). RESULTS: The PaO(2)/FiO(2) ratio at T2 and T3 was higher in the survivors than in the non-survivors (T2= 251.5 vs. 208.5, p= 0.032; T3= 182 vs. 108.5, p<0.001). The PaO(2)/FiO(2) ratio at T3 was an independent protective factor (Hazard Ratio (HR)= 0.993; 95% Confidence Interval (CI)= 0.989-0.998; p= 0.006) for survival. A threshold of ≤129 for the PaO(2)/FiO(2) ratio at T3 predicted non-survival with a sensitivity and specificity of 67.86 and 80.95, respectively (Area Under the Curve (AUC)= 0.782; 95% CI 0.687-0.859). CONCLUSION: The PaO(2)/FiO(2) ratio is a significant protective factor of survival in severe COVID-19 pneumonia within 30 min-1 hour after returning to the supine position (re-supination).