Fig. 4

Lung findings. Pink lines and dots represent animals from the pneumonia-with-VILI group, and the green ones represent those animals from the pneumonia-without-VILI group. A Macroscopic findings: on the left, non-dependent images of an animal from the pneumonia-with-VILI group and on the right, from the pneumonia-without-VILI group. B Significantly higher EVLW in the pneumonia-with-VILI group at the end of the study (p = 0.02). C Lung weight-to-body weight ratio was significantly higher in animals with pneumonia and VILI (p = 0.009). D The wet lung weight-to-dry lung weight ratio was significantly higher in the pneumonia-with-VILI group (p = 0.029). E Percentage of lobes affected with histological features in both study groups. F Histological score evaluated in both groups (0–3). G I: Lung tissue microscopic findings in pneumonia-without-VILI animals presenting inflammatory neutrophilic infiltrate ( +). G II and III: Lung tissue microscopic findings in pneumonia-with-VILI animals showed moderate neutrophil infiltration of the alveolar space and septae, severe edema and hemorrhage, as well as neutrophil infiltration ( +), severe thickening of interlobular septae (#) and evident presence of hyaline membranes (black arrows) surrounding alveoli. Abbreviations: ARDS: acute respiratory distress syndrome; ATII: alveolar epithelial type II cells; VILI: ventilator-induced lung injury. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001