Imitators of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is described by transient narrowing of the airways after exercise. It occurs in approximately 10% of the general population, while athletes may show a higher prevalence, especially in cold weather and ice rink athletes. Diagnosis of EIB is often made on the basis of self-reported symptoms without objective lung function tests, however, the presence of EIB can not be accurately determined on the basis of symptoms and may be under-, over-, or misdiagnosed. The goal of this review is to describe other clinical entities that mimic asthma or EIB symptoms and can be confused with EIB

Dose-responses over time to inhaled fluticasone propionate treatment of exercise- and methacholine-induced bronchoconstriction in children with asthma

When treating bronchial hyperresponsiveness to so-called direct and indirect stimuli, distinct pathophysiological mechanisms might require differences in dose and duration of inhaled corticosteroid therapy. To test this hypothesis in children with asthma, we investigated the time- and dose-dependent effects of 2 doses of fluticasone propionate (FP, 100 or 250 mu g bid.) in improving exercise- (EIB) and methacholine-induced bronchoconstriction during 6 months of treatment, using a placebo-controlled parallel group study design. Thirty-seven children with asthma (aged 6 to 14 years; forced expired volume in 1 sec (FEV1) greater than or equal to 70% predicted; EIB greater than or equal to 20% fall in FEV1 from baseline; no inhaled steroids during the past 4 months) participated in a double-blind, placebo-controlled, 3-arm parallel study. Children receiving placebo were rerandomized to active treatment after 6 weeks. Standardized dry air treadmill exercise testing (EIB expressed as %fall in FEV1 from baseline) and methacholine challenge using a dosimetric technique (expressed as PD20) were performed repeatedly during the study. During FP-treatment, the severity of EIB decreased significantly as compared to placebo within 3 weeks, the geometric mean % fall in FEV1 being reduced from 34.1% to 9.9% for 100 mu g FP bid, and from 35.9% to 7.6% for 250 mu g FP bid (P <0.05). These reductions in EIB did not differ between the 2 doses and were sustained throughout the treatment period. PD20 methacholine improved significantly during the first 6 weeks as compared to placebo (P <0.04) and steadily increased with time in both treatment limbs (P = 0.04), the difference in improvement between doses (100 mu g FP bid, 1.6 dose steps; 250 mu g FP bid, 3.3 dose steps) approaching significance after 24 weeks (P = 0.06). We conclude that in childhood asthma, the protection afforded by inhaled fluticasone propionate against methacholine-induced bronchoconstriction is time- and dose-dependent, whereas protection against EIB is not. This suggests different modes of action of inhaled steroids in protecting against these pharmacological and physiological stimuli. This has to be taken into account when monitoring asthma treatment. (C) 2000 Wiley-Liss, Inc