Exercise-Induced Bronchospasm - An Update.
Shelby Scott, M.D., FACSM, is part-time faculty at Natividad Medical Center in Salinas, CA, and associate clinical faculty at University of California-San Francisco School of Medicine. She practices Family Practice and Sports Medicine in the Santa Cruz area of California.
Exercise-induced bronchospasm (EIB) is a common condition characterized by a transient constriction of airways after 10 to 15 minutes of moderate exercise. The symptoms are chest tightness, cough, wheezing, or shortness of breath (1,2). Some people become so short of breath that they feel they are dying or having a myocardial infarction. It is important for health and exercise personnel to recognize the syndrome of EIB because people affected by this form of asthma, or airway constriction, often will avoid exercise. The chest tightness and other uncomfortable symptoms reach a peak 8 to 15 minutes after exercise cessation and can persist for up to an hour. These exercise-associated symptoms are a big disincentive for some clients to exercise (3). However, with proper recognition, the effects of EIB can be minimized or prevented.
One way to help clients is to question their postexercise symptoms and perceptions of their exertion. Ask them about the common symptoms of chest tightness, breathlessness, coughing, wheezing, or difficulty catching their breath. These symptoms may occur with any increase in exercise exertion during exercise or soon after exercise. Symptoms are usually directly related to the exercise intensity and commonly occur shortly after exercise (4). A questionnaire administered at intake of new clients can help to identify people with EIB. Once recognized, EIB can be treated and will cease to be an obstacle to exercise.
Exercise-induced bronchospasm is more prevalent than previously recognized (5,6). It is documented in 10% of competitive athletes and is more prevalent in competitive athletes than the general population (5-7). Recent studies have shown that many exercising adults, including college level athletes, are not aware that they have EIB. At Ohio State University, 107 athletes were tested for EIB using the preferred method of bronchospasm documentation for Olympic athletes-the eucapnic voluntary hyperpnea test. In this study, 39% or 42 of the athletes tested positive for EIB. Of this group, 86% or 36 of the athletes had no prior EIB. The prevalence of EIB was the same for athletes without symptoms as it was for athletes with symptoms (6).
A similar questionnaire-based study was performed looking at nonelite road running athletes (5). Based on a questionnaire of EIB symptoms only, 11% of the athletes exhibited symptoms of EIB. Despite a higher number of runners reporting symptoms, a very small fraction of the athletes sought medical attention for their symptoms or premedication before exercise. An earlier pulmonary function study of college cross-country runners had similar results, with 14% of athletes positive for EIB not previously diagnosed or using medications. Additionally, this study found that the incidence of EIB was greater than the number of runners expressing symptoms.
In the general population, approximately 90% of people with documented asthma and 40% of people with allergic rhinitis experience EIB. Of people with EIB, 9% neither have asthma or allergic rhinitis (6). Additionally, based on the studies previously cited, only half of exercising people with EIB may be aware of their problem. Anyone who has asthma or allergic rhinitis (airborne allergies like hay fever) should be evaluated. Additionally, if you suspect that a client has EIB, refer them to their primary treating physician for evaluation and reassure them that continuing exercise is safe and beneficial (1,2).
When clients are referred for medical evaluation, they should expect a thorough history and physical examination. Patients with known asthma or allergic rhinitis can expect a shorter visit that is focused on current symptoms, symptom triggers, and a review of current medications. Some medical problems that may mimic EIB are listed in Table 1. With a normal examination and historic symptoms of EIB, most clinicians will prescribe short-acting bronchodilators for a diagnostic trial (4). Older patients who have never been diagnosed with asthma or EIB may need to have a more comprehensive examination, including a chest X-ray, electrocardiogram, and treadmill stress test. For those with an uncertain diagnosis, the physician may perform pulmonary function tests and an exercise challenge test. Exercise challenges also may be used for clients who do not respond to bronchodilators or whose symptoms do not quantify the severity and responsiveness of people with known EIB.
Health and exercise professionals need to reassure people with EIB that exercise is safe. Multiple studies have shown that not only is it safe, but with conditioning, clients will have less severe symptoms and require less medication (1). Proper warm-up can minimize and sometimes prevent symptoms of EIB (Table 2). A refractory period, a time when people have resistance to EIB, happens after initial exercise and lasts for several hours. This can be used to the advantage of the athlete to completely prevent all symptoms. Because the severity of the EIB attack is related to the intensity of the exercise, a slow warm-up with 10 minutes of light cardiovascular exercise may help the athlete to exercise symptom free. Gyms can help lessen triggers by providing a warm and relatively humid environment for exercise. Dry cool air worsens the symptoms of EIB. For athletes who must exercise outdoors in cold weather, it's recommended that they warm up indoors then cover their nose and mouth to allow proper warming of the air while outside.
There are different medications available to treat EIB. Proper medical treatment lessens symptoms and can improve performance for competitive athletes. Most physicians prescribe a bronchodilator like a short-acting beta agonist (BA) to be taken 30 minutes before exercise. This is the most effective medicine for the prevention of EIB (4,8), with the effects lasting 2 to 4 hours. For athletes exercising for more prolonged periods, a long-acting BA will help to control symptoms for up to 12 hours (8,9). An inhaled long-acting BA also is useful for children as young as age 4 with EIB. The physical activity of children is less predictable. They may have short intermittent bursts of vigorous physical activity at unplanned times throughout the day.
Athletes with allergic rhinitis (hay fever) or asthma will have less EIB with proper treatment of their underlying condition. Antihistamines (antiallergy medicines) may control EIB in people with allergies. Most people with asthma are now treated using inhaled steroids combined with the long-acting BA. For most people, these initial steps will only reduce the symptoms, and they will need further pharmacological or medicinal treatments like the addition of short-acting BA to control their symptoms (Table 3).
Two other classes of medications are frequently used along with the BA to prevent EIB. Inhaled mast cell stabilizers cromolyn and nedocromil are the second most prescribed medications. These inhalers are not as effective against EIB as the BA (3,4). Like the other inhalers, they must be taken 10 to 20 minutes before exercise. The second class of medication is the antileukotrienes. Leukotriene receptor antagonists zafirlucast (Accolate) and montelukast (Singular) are available in the United States for the treatment of asthma. Their effects with EIB vary, so they do not have Food and Drug Administration approval for this use (4).
Once proper diagnosis and medical prevention of EIB is established, it is important to stress to the clients the importance of continuing with nonpharmacological treatments. Remind them to use a brief cardiovascular warm-up period, advise them to cover their nose and mouth with a cloth if they are exercising outdoors in the cold, and make sure they plan to stay hydrated before, during, and after exercise.
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