Fig. 8

Porcine mechanical ventilation model with the oropharyngeal P. aeruginosa challenge. a Timeline of the porcine mechanical ventilation model. b Animal position during 48 h of mechanical ventilation. The pigs were placed in the prone position, and the surgical bed was oriented at − 30° to achieve an orientation of the respiratory system corresponding to the semi-recumbent position in humans. c Mucus adhesion to the ETTs after 48 h of mechanical ventilation. The PVC-ETT was clearly blocked by purulent secretions, while the CS-AgNPs@PAAm-Gelatin-ETT was clean and unobstructed. d VAP histological score of pigs intubated with PVC-ETTs and CS-AgNPs@PAAm-Gelatin-ETTs: 0, no injury; 1, purulent mucous plugging; 2, bronchiolitis; 3, pneumonia; 4, confluent pneumonia; and 5, abscessed pneumonia (***p < 0.001). e All pulmonary sections were stained with hematoxylin and eosin (H&E). Right upper lobe (RUL), right middle lobe (RML), right lower lobe (RLL), left upper lobe (LUL), and left lower lobe (LLL). H&E staining of lungs from a pig intubated with PVC-ETT. The arrows (RUL, RML, LLL) represented that extensive polymorphonuclear infiltration was found within the alveolar spaces. A purulent mucus plug was found and arrowed within the bronchiole lumen with surrounding inflammatory infiltration (RLL). Abnormal accumulations of red blood cells were observed and arrowed in the alveoli (LUL). H&E staining of lungs from a pig intubated with CS-AgNPs@PAAm-Gelatin-ETT. All five lung lobes possessed intact alveolar walls with no inflammatory infiltration (RUL). No mucous blockage was observed in the bronchioles (RML, RLL) or the terminal bronchioles (LUL, LLL) (100 × scale bar = 100 μm, 400 × scale bar = 50 μm)