Fig. 1

Box and whiskers plots of the change in the ratio of oxygen partial pressure (PaO₂) to fraction of inspired oxygen (FiO₂) in arterial blood in prone position and supine position, before and after administering inhaled nitric oxide (iNO) and almitrine in patients with severe acute respiratory distress syndrome secondary to coronavirus disease 2019. *, ^#, and ^& denote a p value < 0.05 for paired Wilcoxon (with Benjamini–Hochberg correction) following Friedman test, as compared to supine (before prone), supine (after prone), and supine with iNO, respectively