To screen and evaluate the therapeutic effect of various combined treatments on acute lung injury (ALI) of rats induced by smoke inhalation in military airtight cabins.

A total of 78 male SD rats were randomly divided into control group (Group A), injury group (Group B), single treatment groups (Groups C-F) and combined treatment groups (Groups G-M), with 6 rats per group. Groups C-F were treated with oxygen inhalation, heparin sodium nebulization, dexamethasone (Dex) or N-acetylcysteine (NAC) pre-injection, respectively, while Groups G-M were treated with a combination of two or more therapeutic measures above. Blood gas [arterial partial pressure of oxygen (PaO₂), arterial partial pressure of carbon dioxide (PaCO₂) and pH], carbon oxygen hemoglobin (COHb) and its clearance rate (CCR), lung pathological changes, lung wet-to-dry weight ratio (W/D), pulmonary permeability index (PPI), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) activity and the content of malonaldehyde (MDA) and nitric oxide (NO) were measured at 24 h post-exposure to evaluate the effects of the various therapeutic measures.

Compared with Group B, the PaO₂ was increased significantly in Groups G, H and J [(89.1±11.5) mmHg vs (106.0±9.2) mmHg, (108.1±10.9) mmHg and (108.1±4.3) mmHg, P<0.01 or 0.05]. CCR in Groups G-M was significantly higher than that in Group B (P<0.01 or 0.05). Lung pathological score in Groups G~M as decreased significantly compared with Group B (P<0.01). PPI in Group E and M was decreased significantly compared with Group B (2.42±0.38, 1.96±0.91 vs 7.02±1.05, P<0.01). W/D in Groups H, J, L and M was decreased significantly compared with Group B (4.63±0.08, 4.58±0.06, 4.47±0.14, 4.49±0.13 vs 4.88±0.21, P<0.01 or 0.05). GSH-Px activity was significantly increased in Groups G, I, K, L and M compared with Group B [(108.1±3.5)U/mgprot, (125.0±6.3) U/mgprot, (151.2±29.6)U/mgprot, (125.1±25.6)U/mgprot, (139.4±30.0)U/mgprot vs (95.8±12.1)U/mgprot, P<0.01 or 0.05)]. SOD activity significantly was increased in Groups G, J, K, L and M and the content of MDA significantly decreased in Groups G, H, I, J and L compared with Group B (P<0.01 or 0.05). The content of NO was decreased significantly in Groups G~M compared with Group B (P<0.01 or 0.05). The indices related with ALI which could be ameliorated with treatments were the most in Group M among Groups G-M and the semi quantitative score was highest in Group M.

The combined treatment of NAC and Dex pre-injection, high concentration of heparin sodium nebulization and oxygen inhalation is the most effective and comprehensive therapy for ALI induced by smoke inhalation in rats among different combinations.