In cases where the asthma diagnosis is questionable, the UI experts recommend further testing to identify the true cause of exercise-induced shortness of breath.
"Asthma usually responds well to treatment, and people with asthma who are well treated can have normal exercise tolerance," said Miles Weinberger, M.D., professor of pediatrics in the UI Roy J. and Lucille A. Carver College of Medicine and director of the Pediatric Allergy and Pulmonary Division at Children's Hospital of Iowa. "However, if the asthma medication doesn't work and the patient has normal lung function when measured before exercise, it is probably not asthma.
"If a patient is not responding to the simplest measure, such as use of a bronchodilator inhaler, and there are no other asthmatic symptoms, the exercise-induced shortness of breath, also known as dyspnea, requires further detailed evaluation," he added.
Weinberger and his colleagues examined 142 patients who were troubled by exercise-induced dyspnea (EID) but did not show other signs of asthma or were not responding to asthma medications. The team monitored respiration and heart function continuously while patients exercised on a treadmill vigorously enough to reproduce their usual symptoms. Sophisticated equipment allowed breath-by-breath analysis of oxygen use, carbon dioxide production and other important lung capabilities. A significant drop in a major measurement of lung function, called the "one-second forced expiratory volume," confirmed a diagnosis of asthma.
Under these conditions, exercise testing reproduced the symptoms troubling the patient in 117 cases, Although EID had previously been attributed to ast
Contact: Jennifer Brown
University of Iowa