An animal model was used to study the effects of 85% oxygen pretreatment on the pulmonary toxicity of 100% oxygen exposure in rats. The hypothesis was that pretreatment of rat with 85% oxygen reduced mortality, decrease of compliance and pathologic changes.

32 rats were divided into 4 groups. Group 1 breathed 85% oxygen for 72 hours and exposured to room air for 24 hours. Group 2,3,4 breathed 85% oxygen for 72 hours and exposured to 100% oxygen for 24, 48, 72 hours respectively. After the exposure, survived rats were intubated through a tracheostomy, and inflation and deflation lung-thorax compliances were calculated. Lung weight per body weight ratios were obtained and the lung specimens got prepared to be examined microscopically.

Inflation and deflation lung-thorax compliances of group 2,3,4 were lower(P<0.05) compared to group 1. Lung weight per body weight ratios of group 2,3 were increased significantly(P<0.05) compared to group 1, but that of group 4 did not have any difference compared to group 1. Pulmonary pathologic findings did not show any significant differences between 4 groups. In group 3, 1 of 8 rats was died and in group 4, 2 of 8 rats were died.

We concluded that the pulmonary oxygen toxicity provoked by 100% oxygen exposure was partially prevented by pretreatment of 85% oxygen exposure. And more studies about the method of preventing pulmonary oxygen toxicity should be performed.