PURPOSE OF THE STUDY.
Exercise-induced bronchospasm (EIB) is defined as acute, reversible bronchoconstriction induced by exercise. Two variations have been described: one with symptoms occurring during exercise and another with symptoms occurring after exercise. How often does each of these patterns occur in children with EIB?
The study included 30 Children with asthma (mean age 12.3 years) and a history of exercise induced symptoms.
Participants underwent an exercise test of 12 minutes at 80% predicted maximum heart rate on a treadmill inside an ice rink where the air was cold and dry. Pulmonary function was measured before and each minute during exercise and at 1, 3 and 5 minutes after exercise. If EIB occurred (fall in FEV1 >15% from baseline), exercise was terminated and albuterol administered.
EIB was revealed in 19 of the 30 subjects. In 12, EIB occurred during exercise between 6 and 10 minutes (mean, 7.75 minutes) with a mean fall in FEV1, 1 minute after cessation of exercise, of 34% from baseline (range, 17%–54%). In 7, EIB did not occur until immediately after exercise with a mean fall in FEV1 of 21% (range, 17%–34%).
In the majority of children with EIB in this study (ie, 12 of 19), bronchoconstriction started during, and not after, a submaximal exercise test.
There are clearly 2 patterns of EIB: 1 where patients develop symptoms during exercise and another where the symptoms do not begin until shortly after exercise. These 2 patterns may correlate with the 2 proposed mechanisms for EIB: (1) exercise induced drying of the respiratory mucosa leading to degranulation of mast cells and (2) exercise induced airway cooling followed by vasodilatation in the airways on rewarming. Also, exercise induces the release of several bronchodilating mediators, such as Prostaglandin E2 and nitric oxide, and deep inspirations themselves may protect against bronchoconstriction. Thus there is a balance between bronchoconstrictor and bronchodilator influences. If the bronchoconstrictor influences predominate during exercise, this would cause symptoms during exercise. If the bronchodilator influences are able to compensate for the bronchoconstrictor influences during exercise, the symptoms would not occur until after exercise. Also of interest is the fact that in 11 of 33 children with asthma, who complained of exercise-induced asthma symptoms, the symptoms could not be reproduced by this exercise challenge. Some of these children may not have asthma, or may not have EIB, but it may also be that the conditions of the exercise challenge were not the same as those that induce symptoms during a “real life” challenge such as a soccer game. Such patients may still warrant a trial of preexercise albuterol or inhaled corticosteroids.
- Copyright © 2012 by the American Academy of Pediatrics