ALBUTEROL TREATMENT BLOCKS EXERCISE-INDUCED RETENTION OF RESPIRABLE H₂O₂ AND BRONCHOSPASM IN CHILDREN WITH ASTHMA. ▴ 2330

H₂O₂ is a volatile oxidant which accumulates on the respiratory surface and is expired in increased concentrations in children with unstable asthma. Exercise can induce bronchospasm (EIB) in children with asthma and may also increase the synthesis of H₂O₂ by airway epithelial and inflammatory cells. We therefore studied whether albuterol pre-treatment, which blocks EIB, could preserve the respiratory clearance of H₂O₂ following exercise. Ten school-age children, 7 with stable asthma of moderate severity and 3 healthy controls, underwent paired treadmill challenge tests via a standard protocol. Before the tests, the children inhaled in random order either 2.5 mg albuterol or saline diluent. We measured lung function and the concentration of H₂O₂ in the expirate condensate collected during tidal breathing before and during recovery from exercise. In children with asthma pre-treated with diluent, exercise led to a mean decrease in FEV₁ of 8% and a two-fold increase in the mean expirate concentration of H₂O₂ (0.66 ± 0.51 to 1.34± 0.88 μM, p=0.05) during recovery. Following albuterol, exercise had no effect on FEV₁ and the expirate concentration of H₂O₂ fell from its pre-exercise value in children with asthma. In healthy children, exercise following albuterol or diluent had no effect on pulmonary function or the expirate H₂O₂ concentration. We conclude that EIB in children with asthma is associated with a net increase in the exhaled H₂O₂ burden. Albuterol blocks this response, possibly by preserving the distribution of ventilation and clearance of H₂O₂. Funded by Emory Pediatrics.