Effects of a single dose inhaled corticosteroid on the dynamics of airway obstruction after exercise

Abstract

Rationale Exercise-induced bronchoconstriction (EIB) is defined as a transient narrowing of the airways induced by exercise. Repetitive measurements of spirometric parameters, such as FEV 1 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 FEV 1, and FEF 50 fell significantly after exercise within groups; the peak fall in FEV 1 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 FEV 1 and FEF 50 peaked 3 min after exercise and showed a subsequent partial recovery. The fall in the FEV 1/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 Rrs 6 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 Xrs 6 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. © 2011 Wiley-Liss, Inc.