Effects of indomethacin and PEEP on oleic acid induced pulmonary oedema in rabbits

This study was designed to determine whether indomethacin, a suggested treatment for adult respiratory distress syndrome (ARDS), would inhibit the efficacy of positive end-expiratory pressure (PEEP) in an animal model of ARDS. Functional residual capacity (FRC), alveolar-to-arterial oxygen difference (A-aPO₂) and total lung water were measured in rabbits: 30 controls and 30 with oleic acid induced pulmonary oedema. Within each group, four treatments were administered: diluent (n = 12), PEEP (n = 6), indomethacin (n = 6), or PEEP + indomethacin (n = 6). Lung injury was induced at 30 mins and treatment commenced at 45 min. Oleic acid caused a significant increase at 3 h in % increase in A-aPO₂ from baseline (105 ± 12%) attenuated by PEEP (59 ± 17%) and indomethacin (57 ± 7%), with the combination of PEEP + indomethacin preventing a significant increase (26 ± 9%). PEEP increased FRC in both saline and oleic acid animals; this was not reversed by indomethacin. Oleic acid caused an increase in total lung water (5.16 to 6.58 ± 0.16 g), not influenced by any treatment. These findings suggest that indomethacin did not inhibit the efficacy of PEEP in this model of ARDS.