Effect of inhaled nitric oxide on pulmonary function in cystic fibrosis

Concentrations of nitric oxide (NO) have been found to be reduced in both t he upper and lower airway of patients with cystic fibrosis (CF). As NO modu lates bronchomuscular tone, low NO levels may contribute to the obstructive lung disease in these patients. To assess whether increasing inspiratory N O concentrations has any impact on lung function, we have studied 13 CF pat ients aged 14-38 years in a clinically stable condition and nine healthy co ntrols. NO was applied via a mixing chamber for 5 min with NO concentration s of 100 parts per billion, 1 and 40 parts per million. Spirometry was perf ormed at baseline and after inhalation on each occasion. There were no clinical side-effects at any NO concentration and no changes in oxygen saturation were observed. Lung function remained unchanged in all subjects throughout the study period. Sputum nitrate and nitrite concentra tions before and after inhalation of high NO concentrations (40 ppm) in eig ht CF patients did not show any significant changes, even though a tendency to higher nitrate levels was observed (399+/-231 vs. 556+/-474 mu moll(-1) ). Therefore, inhaled NO at either the physiological levels present in the upper airway of normal individuals or those used therapeutically to treat p ulmonary hypertension has no immediate effect on bronchomuscular tone in pa tients with cystic fibrosis. (C) 1999 Harcourt Publishers Ltd.