Exercise-induced asthma.

Annotation: Exercise-induced asthma (EIA) is one of the issues in athletes that can and should be controlled. That control can negate EIA from factoring into ability to perform as well as the level of performance.

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Exercise-induced asthma (EIA) is a common disorder characterized by bronchospasm resulting from moderate to vigorous exercise. The prevalence of EIA is found to be 15 to 20% in the general population. However, as many as 80% of true asthmatics and 40% of people with allergic rhinitis or atopic disease will have EIA. Even at the highest level of competition, a significant portion of athletes will have EIA. Among the athletes making up the 1984 and 1996 US Olympic teams, 11% and 16% respectively were affected by EIA. This fact demonstrates that, if recognized and treated appropriately, EIA should not be a significant factor in determining one's level of physical ability.

The causes of EIA appear to be multifactorial. Cooling of the mucosa and increasing interstitial osmolarity in the bronchial tree have both been found to be triggers of bronchospasm by altering blood flow and smooth muscle contraction around the bronchus. Both may result from hyperventilation. Therefore, activities with high minute ventilation such as running and cycling are more asthmagenic than sports with lower minute ventilation such as baseball and golf. Cold, dry air also cools the bronchial mucosa and increases interstitial osmolarity, triggering bronchospasm. Thus, running outside in a cold dry environment is likely to trigger EIA.

The typical presentation of a patient with EIA is one who complains of shortness of breath, chest tightness, and coughing or wheezing during or after vigorous exercise (Table 1). In many cases, cough during or after exercise is the only complaint. These symptoms usually occur within 5 to 8 minutes of exercise and may actually be the most severe within the first 3 to 15 minutes after stopping exercise. The symptoms will usually resolve within 30 minutes after exercise cessation. Other presenting symptoms may include chest pain, abdominal pain, nausea, vomiting, and headache. Children often report that they do not participate in physical activity because they cannot keep up with the other kids. Finally, a small subset of people with EIA may have latent-phase bronchospasm that occurs 4 to 8 hours after exercise.

Factors influencing EIA are many and may be environmental, dietary, or pulmonary. Environmental influences that may exacerbate EIA include cold, dry environments. Warm, humid environments, such as those found in the South or around the swimming pool, may be somewhat protective and reduce the severity of symptoms. Air pollution may act as a type of chemical irritant to the airways and serve as a contributing factor to bronchospasm. For patients who have allergic rhinitis, areas and seasons with high pollen counts may increase the severity of symptoms.

Dietary factors include salt and lycopene intake. Patients with high dietary salt intakes found a reduction in symptom severity upon reducing salt intake. On the other hand, lycopene is an antioxidant found in tomatoes. When ingested in quantities of 30 mg per day, it was found to reduce the severity of EIA. Finally, recent viral respiratory illnesses often exacerbate EIA symptoms.

Making an accurate diagnosis of EIA is important not only to help people stay active, but also to provide appropriate medications. The diagnosis is usually made by formal exercise testing. Before testing, the patient should refrain from use of short-acting beta agonists for 6 hours and leukotriene inhibitors, long-acting beta agonists, and cromolyn for 24 hours. First, the patient undergoes basic spirometry to rule out any underlying pulmonary disease, or to ensure that baseline asthma is well controlled. Their forced expiratory flow at one second (FEV 1) should be within 85% of a predicted value based on age and gender. The patient then undergoes sustained vigorous exercise at 85 to 95% of their age-predicted maximal heart rate for a total of at least 6 minutes. Exercising much longer than 6 minutes may produce a refractory state and the diagnosis may be missed. Immediately after exercise and every 5 minutes thereafter, the patient undergoes repeat spirometry for a total of 30 minutes. A 10 to 14% decrease of the FEV 1 from baseline is suggestive for EIA. A decrease in FEV 1 of greater than or equal to 15% is diagnostic for EIA. EIA may then be categorized as mild (FEV 1 decrease of 15-20%), moderate (FEV 1 decrease of 20-40%), or severe (FEV 1 decrease of more than 40%) (Table 2).

Treatment of EIA is multifactorial. Both nonpharmacological and pharmacological treatments are beneficial and should be used together for best results. Aerobic conditioning has been found to reduce the severity of symptoms. Warm-ups 45 to 60 minutes before the main event may induce a refractory period. Warm-ups often include sprints and other activities that simulate the actual event. Nasal breathing warms and humidifies the air and should be performed as much as possible. In cold dry environments, the use of a scarf or surgical mask may help warm and humidify the air reducing the severity of symptoms. When the air pollution or pollen count is high, exercising indoors is indicated, if possible. Also, refraining from exercising during rush hour traffic is advisable. One should also refrain from exercise during viral respiratory illnesses because they are likely to exacerbate EIA symptoms. Finally, help children choose activities that are less asthmagenic, such as recreational swimming and baseball.

Many agents are helpful in the treatment of EIA (Table 3). The first line drug of choice is a beta agonist such as albuterol or salbutamol. The usual dose is 2 puffs 15 minutes before exercise. These agents have been found to be effective in 90% of patients. Salmeterol, a long-acting beta agonist, may be beneficial in preventing latent-phase EIA. Cromolyn sodium, 2 puffs 15 to 20 minutes before exercise, is also effective and may have particular benefit in patients with atopic disease. This medication may be used as a second agent in patients not fully controlled with the beta agonist. The leukotriene inhibitors are also used as first-line drugs. They must be taken at least one hour before exercise and may be used only on days of exercise. A steady state of this medication is not necessary for the treatment of EIA. The leukotriene inhibitors may be of special benefit for younger patients who have trouble coordinating inhaled medications or are embarrassed about the stigma of having to use a medication. Finally, in patients with underlying asthma and/or allergic disease, good baseline control with inhaled corticosteroids and antihistamines is paramount before the control of EIA.

As a final word on the treatment of EIA, some of the medications used in the treatment of asthma and allergies are considered banned substances by the International Olympic Committee and the NCAA. If the patient is participating in events sponsored by one of these institutions, the physician should periodically check the list of banned substances published by these institutions before prescribing medications. If the medication is on the banned substance list, the physician and athlete must submit a request for waiver before the use of any banned substance.

Table 1. Symptoms associated with exercise-induced asthma

              Cough
              Dyspnea
              Wheezing
              Fatigue
              Chest pain
              Nausea
              Headache

Table 2. Classification of severity of exercise-induced asthma

                  Decrease in FE[V.sub.1]
Severity          from baseline (%)

Mild              15 to 20
Moderate          20 to 40
Severe            40

Table 3. First line medications used to treat exercise-induced asthma

Proventyl/salbutamol    2 puffs 15 minutes prior to exercise
Cromolyn sodium         2 puffs 20 minutes prior to exercise
Salmeterol              2 puffs 30 minutes prior to exercise
                        Good for latent phase EIA
Leukotriene inhibitors  Taken by mouth at least 1 hour prior to exercise

Accepted May 21, 2004.

Mark Leski, MD

From Lexington Family Practice, Lexington, SC.

Reprint requests to Mark Leski, MD, Lexington Family Practice, 122 Powell Drive, Lexington, SC 29072.