Effects of hyperoxia in the presence of acute lung injury

We employed a multiple-dose, oleic acid (OA) model to evaluate the susceptibility to oxygen toxicity of rabbits with acute lung injury (ALI). The rabbits were partitioned into four groups: ALI group (n = 8) received OA (0.04 ml/kg iv) and again at two consecutive 24-h intervals and breathed room air (RA); hyperoxic O2/ALI group (n = 8) underwent similar OA injection protocol and breathed an FIO2 greater than or equal to 0.96; oxygen group (n = 8) received identical injection protocol with normal saline (NS) and breathed an FIO2 greater than or equal to 0.96; and control (CTR) group (n = 5) received isovolume NS injections and breathed RA. Arterial blood pH and gas tensions were measured before and 24, 48, and 60 h after ALI. Surviving animals were killed at 72 h and body weight (BW) was determined at autopsy; then the lungs were removed and weighed (LW). The mortality for animals exposed to hyperoxia was significantly (p less than or equal to .02) greater than those breathing RA, regardless of the presence or absence of ALI. Blood pH was lower (p less than or equal to .05) in all animals but the CTR group. However, acidemia was significantly greater in both hyperoxic groups compared to animals in the CTR and ALI/RA. Inflation and deflation lung-thorax compliances were lower (p less than or equal to .05) and percent lung weight of terminal body weight (LW/BW) was higher (p less than or equal to .05) after hyperoxia with or without ALI compared to CTR animals regardless of FIO2.(ABSTRACT TRUNCATED AT 250 WORDS)