The exercise induced asthma (EIA) is known as a transient airway obstruction caused shortly after vigorous exercise, being its main symptoms shortness of breath, coughing and wheezing. May be evidenced by the fall in forced expiratory volume in one second (FEV1) and other spirometric parameters.The development mechanism of this obstruction is not yet defined; however, many studies were performed to elucidate about the mechanisms of action of the EIA.
A classic feature of the EIA, still not completely understood,is the refractory period to new stimuli, that occurs for a few hours after exercise. If an asthmatic develops EIA and spontaneously recover within one hour, a new exercise results in marked reduction of the EIA by about 50% of patients. The exercise-induced bronchoconstriction is caused, in part, by leukotriene d4 released in the airways. Studies suggest that LTD4 released in the airways of patients with asthma, as a result of the exercise, stimulates the slow release of bronchodilator prostaglandins, as PGE2 that relaxes the bronchial and vascular smooth muscle.
The diagnosis of exercise induced asthma remains a challenge to be overcome. This,from the point of view of clinical diagnosis, and research. Studies show that 64% of patients with established diagnosis of Exercise Induced Asthma (EIA) had no history suggestive of asthma, and more, had normal function at rest. About 20% of children who experience a confirmed crisis do not complain about the symptoms.
A laboratory test is useful for evaluating the severity and treatment effects of the EIA, because standardized conditions for the exercise are used and may be reproduced. The duration of the exercise must be 6-8 minutes, achieving ventilation, at least 4 minutes, 40-60% of maximal voluntary ventilation. The diagnosis of EIA is confirmed by decreases in FEV1 or PEF 15% or more after 5-10 minutes of interruption of vigorous physical activity lasting 5-6 minutes, in which FC of 80-90% of the maximum is reached.
Symptoms triggered by exercise disappear spontaneously, after a variable period, usually one hour after its completion. However, a portion of them may manifest symptoms again, about four to ten hours after the initial trigger. This phenomenon is called the late phase of the EIA. This one, in turn, has characteristics similar to those of late phase reaction triggered by allergens.
To reduce the possibility of an attack, there are few tricks, as a good warming (which should be of low intensity at the beginning) and an adequate relaxation after exercise, adaptation of the duration and intensity of exercise on the severity of the particular case, the eviction of allergens and protection from the cold. You should always breathe through your nose, so that the air maintain a high moisture content before entering the airways. It also recommends avoiding exercise before the suspicion or diagnosis of a respiratory infection. Finally, some medications, when administered before exercise, can prevent a crisis, not considered “doping” since the situation is properly clarified.