Researchers from the University of Iowa Hospital report on evaluations of children with exercise-induced dyspnea (EID) who were seen in their pediatric allergy and pulmonary clinic from 1996 to 2003. They retrospectively analyzed the results of treadmill exercise tests performed on 142 patients with EID when other symptoms and signs of asthma were absent, or if the use of inhaled β2-agonists had failed. The mean age of study patients was 14 years, with an age range of 6 to 21 years and male-female ratio of 0.7:1. The mean duration of symptoms was 30.2 months (range <1 to 192 months). Patients with chronic lung disease, cardiac diseases, or abnormal initial pulmonary function were excluded from the analysis. Sixty-nine percent (98/142) of study children had been previously diagnosed with asthma by their primary care referring physician, and 71% (101/142) had been treated with standard asthma medications. Criteria were established for restrictive abnormalities, physical conditioning, exercise-induced hyperventilation, and normal physiologic limitation. Endoscopy was performed if stridor and/or decreased maximal inspiratory flow were present.
All 142 patients underwent exercise treadmill testing; symptoms of EID were reproduced in 82%. Exercise-induced asthma (EIA), defined as the etiology for the EID if the exercise test resulted in reproduction of symptoms in association with a decrease in FEV1 of at least 15%, occurred in only 11 (8%) patients. Eight of these 11 had been previously diagnosed with asthma. In 25 (18%) patients, dyspnea did not occur on the treadmill, while 74 children (52%) demonstrated only normal physiologic exercise limitation associated with the reproduction of EID. Other diagnoses included restrictive abnormalities in 15, vocal cord dysfunction in 13, laryngomalacia in 2, hyperventilation in 1, and supraventricular tachycardia in 1. The authors conclude that although asthma is the most common cause of EID, other causes should be considered when signs and symptoms of asthma are absent, or if there is no benefit from pretreatment with an inhaled β2-agonist.
Dr. Dubik has disclosed no financial relationships relevant to this commentary.
Dyspnea is the unpleasant awareness of “running out of air.” The subjective experience of breathing difficulty is a complex psychophysiologic sensation of an excessive increase in the perceived labor of breathing. Most of the patients referred to these researchers were suspected by their primary care physicians to have EIA. EIA is a common cause of dyspnea but other entities can mimic asthma by producing EID. Screening by physical examination and medical history alone does not accurately detect exercise-induced bronchospasm.1 Further pulmonary evaluation, including running on an exercise treadmill, can help sort out the diagnosis. Only a small percentage (8%) of the referred patients in this study were found to have EIA, thus demonstrating the importance of considering other etiologies of EID. The finding of restrictive physiology as a cause of EID was particularly interesting. These patients had minor chest wall abnormalities and...