Construction and evaluation of a graded rat model for smoke inhalation lung injury

Objective: To address the critical impact of smoke inhalation lung injury on burn patient prognosis and the lack of animal models simulating varying injury severity, we established a graded rat model to facilitate research into its pathological mechanisms and treatments. Methods: Eighteen male Wistar rats were divided into a control group and groups exposed to smoke for 5, 10, 15, 30 minutes ( n =3 per group). A custom smoke chamber and specific materials (50 g pine wood chips + 10 mL kerosene) were used. Post-exposure assessments included lung function, lung coefficient (wet weight), histopathology (H&E staining), and leukocyte count and IL-6 levels in alveolar lavage fluid. Results: Lung function declined significantly in all exposure groups versus controls, with progressive worsening over time. The lung coefficient increased significantly in the 15- and 30-minute groups. Histology revealed intact structure at 5 and 10 minutes, alveolar rupture and neutrophil infiltration at 15 minutes, and hyaline membranes at 30 minutes. Leukocyte count and IL-6 levels rose markedly after 15 and 30 minutes of exposure. Statistical comparisons confirmed progressive injury severity with longer exposure. Conclusions: Graded rat models of mild, moderate, and severe inhalation lung injury were successfully established following 5, 15, and 30 minutes of smoke exposure, respectively. Injury and inflammation intensified significantly with exposure duration, providing a valuable foundation for further research.