Study on rats with acute respiratory distress syndrome induced by intratracheal instillation of lipopolysaccharide in different ways

Objective To explore the rat model with acute respiratory distress syndrome (ARDS) induced by instillation of lipopolysaccharide (LPS) in endoscopic assisted endotracheal intubation and tracheal exposure. Methods Totally 32 Sprague Dawley rats were randomly divided into 4 groups: the EC group (instillation of isosmotic NaCl solution in endoscopic assisted endotracheal intubation), EL group (instillation of LPS in endoscopic assisted endotracheal intubation), IC group (instillation of isosmotic NaCl solution in tracheal exposure), and IL group (instillation of LPS in tracheal exposure), 8 rats in each group. The operation time among groups was recorded. The levels of arterial oxygen partial pressure (PaO2) and oxygenation index were detected on 24 hours after instillation of LPS. The wet/dry weight ratio (W/D) of pulmonary tissue, protein content of bronchoalveolar lavage fluid (BALF), levels of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in serum, and diffuse alveolar damage (DAD) scores were estimated and compared. Results The operation time in the EC group, IC group, EL group and IL group were (212 ± 24), (296 ± 53), (233 ± 44), (321 ± 56) s, respectively. The operation time among four groups showed significant difference (F = 9.808, P < 0.001), and the operation time was much shorter in the EC group and EL group than in the IC group and IL group (all P < 0.05). The levels of PaO2, oxygenation index, pulmonary W/D ratio, protein content of BALF, TNF-α, IL-6 and DAD scores all showed significant differences among four groups (F = 124.752, 123.920, 73.775, 65.922, 48.342, 419.548, 655.623; all P < 0.001). Compared with the EC group and IC group, the levels of PaO2 [(104 ± 10), (105 ± 9), (54 ± 3), (53 ± 4) mmHg] and oxygenation index [(498 ± 48), (502 ± 43), (261 ± 17), (255 ± 21) mmHg] were much lower, and the pulmonary W/D [(4.14 ± 0.16), (4.36 ± 0.18), (5.53 ± 0.31), (5.58 ± 0.29)], protein content of BALF [(0.39 ± 0.07), (0.34 ± 0.05), (2.19 ± 0.13), (2.15 ± 0.11) g/L], TNF-α [(177 ± 38), (186 ± 51), (414 ± 61), (440 ± 74) ng/L], IL-6 [(104 ± 11), (113 ± 28), (584 ± 42), (603 ± 56) ng/L] and DAD scores [(0.90 ± 0.29), (0.82 ± 0.38), (11.65 ± 0.89), (12.23 ± 0.97)] were much higher in the EL group and IL group (all P < 0.05). Conclusion It is simple and effective to establish a ARDS rat model by instillation of LPS with endoscopic assisted endotracheal intubation. Key words: Lipopolysaccharides; Endoscopes; Acute respiratory distress syndrome; Rats