Corticosteroids decrease exhaled nitric oxide in children with acute asthma.

Objectives: Nitric oxide (NO) produced in human airways seems to have both homeostatic and proinflammatory actions in the respiratory system. NO production has been shown to be higher in the exhaled air of asthmatic adults than in normal subjects. The aim of this study was to evaluate exhaled NO production during asthma exacerbation in children and the effect of a rescue course of oral steroid therapy.

Study Design: We measured NO in the exhaled air of 16 children (8 girls and 8 boys, aged 6 to 13 years) with an acute asthmatic episode before and after 5 days of therapy with prednisone, and in 16 healthy children. To measure NO, children inhaled NO-free air and, breathing at tidal volume, exhaled in a circuit from which a chemiluminescence analyzer sampled continuously. To assess the effect of acute changes in bronchial caliber on exhaled NO levels, we measured NO before and after a positive bronchodilation test result with albuterol in seven children with asthma whose disease was stable.

Results: In the group with acute asthma (forced expiratory volume in 1 second 62% +/- 4.4% predicted, mean +/- SEM), NO levels were significantly higher (31.3 +/- 4.2 parts per billion [ppb]) than in healthy children (5.4 +/- 0.4 ppb, p < 0.001). Administration of prednisone (1 mg/kg per day orally) for 5 days resulted in a mean decrease of 46% +/- 4% in exhaled NO concentrations (16.5 +/- 2.3 ppb, p < 0.001) compared with baseline, accompanied by a significant improvement in lung function (forced expiratory volume in 1 second 90.7% +/- 4.3% predicted). However, in patients with asthma exhaled NO levels remained significantly higher than in control children (p < 0.001) after steroid treatment. When exhaled NO was measured before and after a positive result after bronchodilator reversibility testing, we found no difference in exhaled NO levels (24 +/- 3.8 ppb vs 23.8 +/- 3 ppb; difference not significant). This demonstrates that inhaled albuterol and acute changes in bronchial caliber do not affect exhaled NO measurement.

Conclusions: These data show that children with asthma exacerbation have high levels of exhaled NO that rapidly decrease with oral steroid therapy. We suggest that measurement of exhaled NO may represent a noninvasive method of monitoring airway inflammation in children with asthma.