Detecting Peripheral Airway Response in Exercise-Induced Bronchoconstriction: The Role of Impulse Oscillometry

Background: Exercise-induced bronchoconstriction (EIB) is common in children with asthma, but whether it is a phenomenon of central versus peripheral airway reactivity is unknown. The purpose of this study was to investigate central and peripheral airway responses after an exercise challenge test among children with asthma. Methods: Sixteen children with asthma underwent exercise challenge testing on 2 separate visits: one without any medications (control) and another with pretreatment with 180 µg albuterol (bronchodilator). Central airway EIB was defined as a >10% reduction in FEV₁ after exercise assessed with spirometry. Peripheral airway EIB was assessed as a >40% increase in resistance between 5 Hz and 20 Hz with impulse oscillometry. Spirometry and impulse oscillometry were measured before the condition and periodically for up to 30 min after exercise. Results: Three of 16 children (19%) experienced only central airway EIB. Ten of 16 children (62%), including all 3 who experienced central airway EIB, experienced peripheral airway EIB. Among children who experienced EIB, resistance between 5 Hz and 20 Hz increased by 119.67 ± 102.56% after exercise during the control condition compared with an average decrease of -10.38 ± 34.97% during the bronchodilator condition, which suggests that albuterol was effective in preventing EIB (P = .003, paired t test). Conclusions: Peripheral airway EIB may occur frequently in children with asthma. Spirometry-based testing alone may miss peripheral airway EIB in some children. Impulse oscillometry could be used in conjunction with spirometry to detect peripheral airway EIB in children with asthma.