Background: Impulse oscillometry (IOS) is a good method for measuring airway resistance. It does not require special breathing skills and it can reflect different aspects of airway obstruction to those revealed by spirometry, which is an effort-dependent maneuver.

Objective: To evaluate the characteristics of airway obstruction in young asthmatics after an exercise bronchial provocation test (EBPT) using IOS.

Methods: Forty-seven young adults were enrolled in the study. All the participants underwent a methacholine bronchial provocation test (MBPT) and an EBPT for the evaluation of their asthma. IOS and spirometric parameters were collected at baseline and at 0, 5, 10, 20, and 30 minutes post-EBPT. The participants were divided into 2 groups according to MBPT positivity: an airway hyperresponsiveness (AHR) group and a no-AHR group.

Results: There were differences in the percent decrease in forced expiratory volume in the first second (FEV1) between the 2 groups at 5, 10, and 20 minutes after exercise. Resistance at 5 Hz (R5) increased in the AHR group but not in the no-AHR group at 5 and 10 minutes after exercise. Integration of reactance from 5 Hz to resonance frequency (area of reactance, AX) was also increased in the AHR group at only 5 and 10 minutes post-EBPT. ΔR5 and ΔAX at 5 and 10 minutes post-exercise were well correlated with the percent decrease in FEV1.

Conclusions: IOS parameters, especially ΔR5 and ΔAX, may be useful for performing objective evaluations and improving our understanding
of exercise-induced airway obstruction in young asthmatics.

Key words: Impulse oscillometry. Exercise-induced bronchoconstriction. Asthma.