Bronchial allergen challenge in allergic children: continuous increase of nitric oxide in exhaled air 72 hours after allergen inhalation independent of bronchial obstruction.

BACKGROUND: Changes in fractional exhaled nitric oxide (FeNO) occurring after bronchial allergen challenges (BAC) are still not understood, neither are any possible associations between FeNO and forced expiratory volume in 1 sec (FEV(1)). The aim of the study was to compare the fluctuations of FeNO and FEV(1), which occur within 72 h of BAC in children sensitive to grass pollen. METHODS: Seventy-four children were divided into two groups based on their medical histories and the results of skin prick tests with 10 common allergens. Individuals in whom the test yielded a positive result to at least grass pollen (Group A, n = 57), and those with negative test results against all of the allergens applied (Group B, n = 17) were subjected to BAC. FeNO was measured at a baseline and at 1, 8, 21, and 72 h after the last dose of the allergen inhalation, whereas FEV(1) was measured at a baseline, hourly for 8 h after the challenge and at 21 and 72 h thereafter. RESULTS: Baseline FeNO in sensitive subjects (Group A) was significantly higher than in controls of Group B. In all grass pollen-sensitive subjects, even those that were free of a bronchial response, FeNO was markedly elevated compared to its baseline values, starting from the eighth hour onward, and still increased 72 h post-BAC, whereas FEV(1) returned to a baseline at the 72nd h post-BAC. The highest increase in FeNO was registered in individuals with a dual asthmatic response. CONCLUSIONS: An increase in FeNO in sensitive subjects starts a few hours later than the decrease in FEV(1). Consequently, measurements of FeNO seem to be useful in long-term monitoring of the allergic reaction triggered by a specific allergen.