The aim of this study was to evaluate the effect of positive end-expiratory pressure (PEEP) on EELV, compliance of the respiratory system (Crs), and stress/strain in children with acute respiratory distress syndrome (ARDS), and compare it with children "at risk of ARDS" and those with no lung injury using the modified nitrogen washout/washin technique (see electronic supplementary material). *PEEP 10 vs. 4 mmHg, p < 0.05; **PEEP 10 vs. 6 mmHg, p < 0.05; # ARDS vs. at risk of ARDS, p < 0.05; ARDS acute respiratory distress syndrome, PEEP positive end-expiratory pressure. [Extracted from the article]