Fig. 1

Early microcirculatory response to acute variations in the FiO₂. a : Sidestream Dark Field imaging of the same site of sublingual microcirculation in one patient before (FiO₂ 0.5) and after 2 min of exposure to hyperoxia (2 min FiO₂ 1.0). Stars indicate regions of microvascular de-recruitment. b and c : Individual and mean (SD) changes in perfused vessel density (b) and proportion of perfused vessels (c) during acute variations in the FiO₂ in the hyperoxia group (n = 20). The same region of the sublingual mucosa was assessed continuously at each time point (start hyperoxia and end hyperoxia) for at least 2 min . *p < 0.05, ***p < 0.001, paired t-test