e-NO peak versus e-NO plateau values in evaluating e-NO production in steroid-naive and in steroid-treated asthmatic children and in detecting response to inhaled steroid treatment.

SUMMARY. Airway nitric oxide (NO) production can be measured by chemiluminescence analyzer in children able to perform a single low exhalation. The aim of the present study was to evaluate whether exhaled NO (e-NO) peaks (first part of the exhalation) were as useful as e-NO plateaus (last part of the exhalation) in evaluating e-NO production in asthmatic children and in detecting responses to inhaled steroid treatment. E-NO peak, plateau, and rate of production values were measured in 100 atopic asthmatic children using a chemiluminescence analyser. Thirty-seven patients (mean age, 11.1 +/- 0.7 years) were receiving inhaled steroids (flunisolide, 0.8-1 mg daily) or beclomethasone (0.2-0.4 mg daily), while the remaining 63 (mean age, 12.0 +/- 0.4 yrs) were-steroid naive and treated only with inhaled beta(2)-agonists on an as-needed basis. Fifteen out of the 63 steroid-naive patients were reevaluated after a short course (3 weeks) of inhaled corticosteroid treatment (flunisolide, 0.8-1 mg daily, or beclomethasone, 0.2-0.4 mg daily). Regardless of the type of data analysis (peak, plateau, or rate of production), the e-NO values of the steroid-naive patients were significantly higher than those of inhaled steroid-treated patients (P < 0.01, each comparison). Similarly, in the subgroup of steroid-naive patients, the three methods were able to detect a decrease in e-NO levels by inhaled steroid therapy (P < 0.001, each comparison). Plotting the difference between e-NO peak and e-NO plateau values against their average, the peak e-NO concentrations were higher than e-NO plateau values. This difference was independent of the absolute e-NO concentration. The results of the two types of data analysis seems to agree more closely in steroid-naive patients than in steroid treated patients, or in the subgroup of steroid-naive patients who received a short course treatment with inhaled steroids. In steroid-treated subjects, the differences were up to five times higher for peak than plateau e-NO values. These data suggest that both e-NO plateau and e-NO peak values are useful in detecting airway NO production in atopic asthmatic children, but they cannot be used interchangeably. Because of possible nasal contamination in e-NO peak measurement, we prefer e-NO plateau levels for evaluating lower airway e-NO production.
(Copyright 2001 Wiley-Liss, Inc.)