Exercise-induced dyspnea in children and adolescents: if not asthma then what?

Exercise-induced dyspnea (EID) in children and adolescents is a common manifestation of asthma and is therefore commonly attributed to exercise-induced asthma (EIA) when present in otherwise healthy children.

To report the outcome of evaluations for EID when other symptoms and signs of asthma were absent or if there was no response to previous use of an inhaled beta2-agonist.

We reviewed the results of all exercise tests performed in otherwise healthy patients with EID during 1996 to 2003. Physiologic measures included preexercise and postexercise spirometry with the addition of oxygen uptake, carbon dioxide production, continuous oximetry, and electrocardiogram monitoring during most tests. EIA was diagnosed if symptoms were reproduced in association with a 15% or greater decrease in forced expiratory volume in 1 second from baseline. Endoscopy was performed if stridor and/or decreased maximal inspiratory flow were present. Criteria were established for restrictive abnormalities, physical conditioning, exercise-induced hyperventilation, and normal physiologic limitation.

A total of 142 patients met our criteria for inclusion. EID had been present in these patients for a mean duration of 30.2 months (range, <1 to 192 months) before evaluation and had been previously attributed to asthma by the referring physician in 98 of them. Symptoms of EID were reproduced during exercise testing in 117 patients. EIA was identified as the cause of EID in only 11 of those 117. Seventy-four demonstrated only normal physiologic exercise limitation; 48 of these 74 had normal to high cardiovascular conditioning, and 26 had poor conditioning. Other diagnoses associated with reproduced EID included restrictive abnormalities in 15, vocal cord dysfunction in 13, laryngomalacia in 2 (1 of whom had unilateral vocal cord paralysis), primary hyperventilation in 1, and supraventricular tachycardia in 1.

The diagnosis of EIA should be questioned as the etiology of EID in children and adolescents who have no other clinical manifestations of asthma and who do not respond to pretreatment with a beta2-agonist. Exercise testing that reproduces symptoms while monitoring cardiac and respiratory physiology is then indicated to identify causes of EID other than EIA.