Inhaled Nitric Oxide Attenuates Hyperoxic Lung Injury in Lambs

ABSTRACT: Cytochrome P450 (CYP) inhibition with cimetidine reduces hyperoxic lung injury in young lambs. Nitric oxide (NO), also a CYP inhibitor, has been shown to either aggravate or protect against oxidant stress depending on experimental context. The ob-jective of this study was to determine whether NO, like cimetidine, would protect young lambs against hyperoxic lung injury, and whether its effect was associated with CYP inhibition. Three groups of lambs were studied: 1) room air exposure, 2) 95 % O2, and 3) 95 % O2 plus inhaled NO. After 72 h, hyperoxia alone resulted in a significant increase in arterial PCO2 and number of polymorphonu-clear leukocytes in bronchoalveolar lavage (BAL), and a significant decrease in arterial/alveolar O2 tension (a/A). The addition of inhaled NO significantly decreased the hypercarbia and BAL polymorpho-nuclear cellular response associated with hyperoxia but had no beneficial effect on a/A ratio. There were no significant differences i