Fig. 1
Respiratory system compliance, PaO2:FiO2 ratio and ventilatory ratio along prone positioning. Lines and symbols show mean and standard deviation of each variable before prone positioning (PP), at day 1 and at day 2 in prone, before supine position (SP) and after back to SP; CRS: respiratory system compliance. *, x, + : p-value < 0.001 for comparisons of different time points with their respective pre-PP values in patients from group A, B, and C, respectively.°, ▪, ∞: p-value < 0.001 for comparisons between before SP and after SP in patients from group A B, and C, respectively. α: p-value < 0.01 for inter-group comparisons at different time points. β: p-value < 0.001 for inter-group comparisons at different time points