Objective: To determine whether the variability in the effect of ipratropium bromide on the bronchial response to exercise among endurance athletes depends on their vagal activity. The hypothesis was that this would be the case.
Design: Participants served as their own controls in a double-blind, repeated-measures investigation.
Setting: Climatic chamber in an exercise laboratory.
Participants: Six well-trained healthy adult cross-country runners (three women and three men).
Interventions: Four exercise provocation tests at ambient temperature of 22 or -5 degrees C after inhalation of ipratropium bromide or placebo.
Main outcome measures: Vagal activity was assessed in each visit by a 4-second cycling test; airway response to exercise was measured by periodic pulmonary function testing.
Results: With ipratropium bromide, forced expiratory volume in 1 second (FEV1) increased by 5.3+/-1.4% at 22 degrees C and by 7.5+/-1.5% at -5 degrees C. The beneficial response of the large airways to ipratropium bromide versus placebo was positively related to vagal activity for FEV1 at -5 degrees C, for peak expiratory flow (PEF) at -5 degrees C, and for PEF at 22 degrees C.
Conclusion: The findings suggest that the beneficial large-airways response to ipratropium bromide may be related to vagal activity.
Clinical relevance: Information about vagal activity may help to determine whether an athlete is a suitable candidate for treatment with ipratropium bromide. This may offer more therapeutic possibilities, especially for those individuals who have a high vagal activity, such as endurance athletes.