[Effects of hyperbaric oxygen on the acute lung injury induced by oleic acid in rats]

To explore the effect of hyperbaric oxygen (HBO) on acute lung injury (ALI) induced by oleic acid (OA) in rats.

Eighty healthy Sprague-Dawley (SD) rats were randomly divided into four groups. In OA group (n=30), ALI was produced by injection of OA 0.15 ml/kg through tail vein. Ten rats were randomly selected and sacrificed after injection of OA at the time of 4 hours, 3 days, and 7 days, respectively. In OA plus HBO group (n=20), rats received HBO intervention in a special box with oxygen of 2.5 atm (1 atm=101.325 kPa) for 90 minutes. Ten rats were randomly respectively sacrificed at 3 days and 7 days. In simple HBO group, 20 rats were sacrificed at 3 days and 7 days of HBO intervention, respectively. Other 10 rats were assigned as control group. Blood, lung specimens were collected after sacrifice. Serum contents of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and IL-6 were measured. Gross changes and pathological findings of the left lung were recorded. The wet to the dry weigh (W/D) of the right lung was determined.

Partial pressure of oxygen in arterial blood (PaO2, mm Hg, 1 mm Hg=0.133 kPa) fell from 107.70+/-5.37 to 57.40+/-2.63 in OA group. Congestion, bleeding and edema could be seen grossly. They could also be found under microscope with disappearance of normal structure, and accumulation of fluid in interstitium with inflammatory cell infiltration and hyaline membrane formation were also found. Lung W/D ratio was increased as compared with the control group (6.94+/-0.44 vs. 4.59+/-0.44, P<0.05). A marked increase was found in serum TNF-alpha, IL-1 beta, IL-6 levels [TNF-alpha (microg/L): 18.52+/-1.20 vs. 5.27+/-0.61, IL-1 beta (microg/L): 13.73+/-1.37 vs. 6.13+/-1.51, IL-6 (microg/L): 14.51+/-1.21 vs. 11.14+/-0.89]. After HBO therapy for 3 days and 7 days, PaO2 (mm Hg, 3 days: 79.20+/-1.68 vs. 59.00+/-2.70, 7 days: 94.30+/-3.77 vs. 74.00+/-3.85) and lung W/D (3 day: 7.43+/-0.73 vs. 9.82+/-0.99, 7 days : 6.75+/-1.14 vs. 8.77+/-1.60) of HBO group were ameliorated to varying degrees compared with OA model group (P<0.05 or P<0.01). HBO therapy for 3 days could lower levels of IL-1 beta (microg/L) in the serum (6.46+/-1.99 vs. 9.09+/-1.09, P<0.05).

It is suggested that HBO treatment for ALI in rats had effects of improving arterial blood gases and the lung water transport, and inhibiting inflammatory mediators production.