Objective: To assess the efficacy of inhaled nitric oxide in improving pulmonary hypertension and gas exchange following oleic acid-induced acute lung injury.
Design: Prospective, pharmacologic study.
Setting: Surgical research laboratory at the University of Pittsburgh, Pittsburgh, PA.
Subjects: Instrumented, intubated pigs weighing 16 to 27 kg.
Interventions: Intravenous oleic acid and inhaled nitric oxide.
Measurements and main results: All pigs treated with intravenous oleic acid (0.11 mL/kg) developed a severe lung injury with pulmonary hypertension, accompanied by impaired oxygenation, intrapulmonary shunting, and increased extravascular lung water (p < .05 compared with baseline). Following nitric oxide inhalation, although pulmonary hypertension decreased in a dose-dependent fashion, no amelioration in pulmonary gas exchange was observed, as reflected by PaO2 and intrapulmonary shunt. Plasma nitrite and nitrate concentrations, the stable end products of nitric oxide metabolism, did not increase following nitric oxide exposure in this model of severe lung injury.
Conclusions: The effect of inhaled nitric oxide, restricted to relieving pulmonary vasoconstriction in this model of lung injury, may have limited benefit in improving pulmonary gas exchange when diffusion is impaired by severe lung injury and inflammatory thickening of the alveolar-capillary barrier. Nitric oxide inhalation may have better results when used at an earlier, less severe stage of acute lung injury.