Effects of a single dose inhlaed corticosteroid on the dynamics of airway obstruction after excercise

Rationale: Exercise-induced bronchoconstriction (EIB) is defined as a transient narrowing of the airways induced by exercise. Repetitive measurements of spirometric parameters, such as FEV1 and expiratory flows, and forced oscillation technique (FOT) measurements can be used to analyze the dynamics of EIB. A single high dose of fluticasone propionate (FP) protects against EIB. The aim of the study was to analyze the effect of FP on the dynamics of exercise-induced airway narrowing as measured with FOT and spirometry. Methods: Twelve children performed an exercise challenge on 2 separate days, 4 hr after inhalation of 1 mg FP (pressurized metered dose inhaler) or a placebo. Before and after the exercise flow-volume loops as well as the FOT (frequency range: 4–32 Hz) were measured. Results: The FEV1, and FEF50 fell significantly after exercise within groups; the peak fall in FEV1 after FP was significantly smaller than after placebo (respectively, 19.3 ± 14.6% and 29.2 ± 14.8%, P = 0.03, 95% CI: 0.9–18.8%). The fall in FEV1 and FEF50 peaked 3 min after exercise and showed a subsequent partial recovery. The fall in the FEV1/FVC ratio showed a later peak fall (12 min after exercise). The resistance increased while the reactance decreased significantly after exercise. FP significantly decreased the maximal increase in Rrs6 when compared to the placebo (respectively 176.5 ± 59.1% and 201.0 ± 63.8%, P = 0.05, 95% CI: 0.5–48.7%). The maximal decrease in Xrs6 was not significantly affected by FP (P = 0.06). Conclusion: Repetitive spirometric and FOT measurements after exercise show a rapid narrowing and steady recovery of the patency of the conducting airways, and indicate a delayed and prolonged recovery of the smaller airways. A single high dose of inhaled FP seems to employ its effect mainly in the conducting airways.