Update on Exercise-Induced Asthma: A Report of the Olympic Exercise Asthma Summit Conference
William W. Storms, MD; David M. Joyner, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 3 - MARCH 97
In Brief: Exercise-induced asthma (EIA) can be easily overlooked and underdiagnosed, especially in school children or recreational athletes. It affects individuals of all levels of activity, from recreational sports to competition. This article summarizes the results of the Olympic Exercise Asthma Summit Conference, organized by the Sports Medicine Division of the US Olympic Committee. Making the correct diagnosis of EIA is very important and usually requires some form of pulmonary function testing. Because effective pharmacologic and nonpharmacologic treatment is available for this condition, patients should be followed until the condition is controlled.
Exercise-induced asthma (EIA) can affect any susceptible person who exercises, whether he or she is a school child, recreational athlete, or elite athlete. The importance of making the proper diagnosis should not be underrated, since patients who have undiagnosed EIA may not be able to participate in athletic activities. Typical symptoms are coughing, wheezing, chest tightness, and shortness of breath during or after exercise (1,2).
Some patients with EIA have no specific symptoms of asthma but have atypical symptoms such as stomach cramps, chest pain or discomfort, nausea, headache, or feeling out of shape. In addition to those who have asthma symptoms only with exercise, most patients who have chronic asthma have increased symptoms with exertion.
The Sports Medicine Division of the US Olympic Committee convened the Olympic Exercise Asthma Summit Conference in Colorado Springs in December 1994 to discuss the issues surrounding EIA (see "Participants in the Olympic Exercise Asthma Summit Conference" at the end of this article). The scientific findings and treatment recommendations from the conference are summarized below.
Pathophysiology of EIA
There are two main theories on the pathophysiology of EIA. The water-loss theory (3) holds that loss of water through the bronchial mucosa into the exhaled air during exercise results in local events in the lungs that cause bronchospasm. Heat and water are transferred from the respiratory mucosa into the air in the airways when large volumes of air are moved in and out of the lungs. This leads to changes in the osmolarity, pH, and temperature of the airway epithelium, which may trigger EIA.
The thermal expenditure theory (4) states that EIA is a direct result of heat transfer from the pulmonary vascular bed into the air during and after exercise. Respiratory heat loss occurs during exercise, with heat moving to the exhaled air. This transfer of thermal energy is followed by rewarming after exercise ends, with associated dilation and hyperemia of the bronchiolar vessels. The hyperemia then leads to EIA.
Other theories for EIA have also been proposed (1,2). One theory is that cold air leads directly to bronchoconstriction; another states that vigorous physical exertion leads to mechanical stimulation of the bronchi and surrounding tissues, leading to EIA. The osmolar theory holds that the hyperpnea of exercise causes changes in the bronchial mucosa, which lead to hyperosmolarity of the cells of the mucosa and submucosa and subsequently to EIA.
Prevalence and Aggravating Factors
The exact prevalence of EIA is unclear, but it appears to affect 15% to 20% of the general population (5-7). Olympic-caliber athletes were found to have a prevalence of up to 11% (5). A 1993 study (6) of a healthy military population found respiratory symptoms compatible with EIA in 31% of subjects. Rupp et al (7) reported that 29% of middle school and high school athletes had reductions in FEV1 compatible with EIA, but that not all were symptomatic.
The Sports Medicine Committee of the American Academy of Allergy, Asthma & Immunology has been collecting data on a questionnaire to predict EIA (8) These questions were put to individuals undergoing exercise challenges for a potential diagnosis of EIA. Affirmative answers to three questions independently contributed to predict a positive exercise challenge indicative of EIA: (1) Have you ever missed school or work because of chest tightness, coughing, wheezing, or prolonged shortness of breath? (2) Do you ever have chest tightness? (3) When you exercise, do you often have wheezing?
These are important questions to ask all school children and recreational and competitive athletes to make the diagnosis of EIA. However, questionnaires are not totally predictive of EIA because some individuals have negative answers on the questionnaire but a positive exercise challenge.
Many factors can influence the severity of EIA (table 1). First, the type of exercise is important, with free running being more asthmogenic than treadmill exercise, stationary cycling, or swimming. Workload—the work itself and the rate at which it is performed—is important. Environmental factors play a significant role; for example, cold, dry air can be a potent stimulus. Other environmental factors include air pollution, particulates, smoke, and allergens.
These potential aggravating factors for EIA are important for the athlete and the physician to know, since preventive therapy may reduce the severity of EIA. It may be best for recreational athletes or those in training to exercise indoors on very cold days and, if they have an allergy to pollen, to avoid outdoor exercise when pollen counts are high. Competitive athletes do not have a choice of when or where they compete, but they should be aware of the potential aggravating factors and adjust their medication appropriately to control these factors.
Diagnosis of EIA
The diagnosis of EIA (figure 1: not shown) is often made on the basis of a history alone, but the patient may not spontaneously seek medical attention for this condition. Reports of symptoms, therefore, may need to be elicited by questioning during school physicals or routine physical examinations.
If a patient reports possible symptoms but the history leaves the diagnosis in doubt, pulmonary function tests (PFTs) at rest should be performed. Abnormal PFTs indicate that the patient needs daily asthma therapy and preexercise treatment. Normal PFTs, however, dictate that the patient should be treated for EIA. If the diagnosis is in doubt, hand-held peak flow meters are useful for testing because they are portable and easy to use in the field.
If the diagnosis is in doubt after peak flow testing, or if pretreatment with an inhaled beta-agonist before exercise does not help, spirometry with flow-volume curves should be performed before and after exercise on different days with and without pretreatment with an inhaled beta-agonist. The pulmonary function measurement should be performed before exercise and at 1, 5, 10, and 25 minutes after exercise. If no symptoms occur with the exercise challenge, the patient should be tested with exercise in his or her own sport.
Asthma or EIA? An important distinction must be made: Does the patient have solitary EIA or mild, chronic, persistent asthma with exercise-induced exacerbations? This distinction is critical in regard to treatment, because nearly all EIA patients require only preexercise treatment, whereas those with persistent asthma require daily anti-inflammatory therapy plus preexercise treatment.
The distinction between solitary EIA and persistent asthma is best made by pulmonary function testing at rest. In the patient with solitary EIA, the results will be normal; in the patient with chronic persistent asthma, pulmonary function will be lower than normal. This testing can easily be done in the physician's office or clinic using a small computerized spirometer.
Extended warm-ups before exercise may help reduce the severity of EIA, but they do not replace pharmacologic therapy. Physicians can suggest that patients perform "subthreshold exercise" before their regular workout, carefully explaining that patients need to warm up vigorously at a level just below their maximum exercise level. For the recreational athlete who is jogging, for instance, this would mean stretching and walking, then starting slowly for the first 8 to 10 minutes. The term "subthreshold exercise" rather than "warm-up" is suggested when dealing with active patients because a warm-up can mean anything from stretching to sprinting for different people.
For patients who have a choice, exercising in a warm, humid environment is better than a cold, dry environment. Also, short-burst activities like tennis will tend to exacerbate EIA less than will prolonged, steady exercise like running.
A variety of medications are available for treating EIA (table 2), by either the inhaled or oral routes; it is important for the physician to know which are first-line drugs, second-line drugs, etc (see below) (9). It is particularly important to tailor drug therapy to the individual patient and his or her athletic event. For example, a wrestler participating in a 5-hour meet may have his EIA controlled best by salmeterol before the meet rather than repeated doses of albuterol. Not only are the correct medications important, but follow-up visits are crucial to ensure that the treatment is controlling the problem and to assess whether adjustments are needed.
The first drug usually chosen for control of EIA is a short-acting beta-agonist such as albuterol, metaproterenol sulfate, pirbuterol acetate, or terbutaline sulfate. The beta-agonist is administered via a metered-dose inhaler or dry powder inhaler about 15 to 30 minutes before exercise. The potential side effects are tremor and palpitations. An alternative is long-acting salmeterol (10), which can be given 30 to 60 minutes before exercise and may control EIA as long as 12 hours. Salmeterol is quite useful in school children, since it may be taken before school and should protect the patient for the entire day.
Cromolyn sodium or nedocromil sodium can also be given before exercise either alone or in combination with a beta-agonist (11). Some physicians use cromolyn or nedocromil as first-line therapy, and it can be effective in many patients. As a general rule, either cromolyn or nedocromil or a beta-agonist is the drug of first choice, and then a drug from the other class is added in combination if the initial single-dose therapy is not adequate.
Some athletes may require a higher dose of cromolyn or nedocromil to block EIA; the dose of either of these can be increased to four puffs immediately before exercise. If these measures are not adequate to control the EIA, workshop participants suggested that ipratropium bromide can be used on a trial basis as an additional preexercise treatment.
If the patient does not obtain control of EIA with the above therapy, then daily inhaled corticosteroids should be considered. At this point, however, the patient's asthma should be re-evaluated to see if the individual is suffering from chronic persistent asthma with exercise-induced exacerbation. If this is the case, then daily anti-inflammatory inhalers (cromolyn, nedocromil, inhaled steroids) should be used for maintenance management and an inhaled beta-agonist, cromolyn, or nedocromil before exercise.
If inhaled steroids are used, the dosage is 8 to 16 puffs per day of beclomethasone dipropionate or triamcinolone acetonide, or four puffs a day of flunisolide or equivalent doses of fluticasone propionate. For cromolyn or nedocromil, the dosage is two puffs four times a day. Daily oral theophylline (5 to 10 mg/kg/day in divided doses) might also be considered.
With either a recreational or an elite athlete, a specialist consultation should be considered if symptoms are not controlled with treatment. Other conditions can masquerade as EIA.
Recognizing the Underrecognized
Exercise-induced asthma is underrecognized and underdiagnosed, so physicians need to look for it in all patients, including school children. Appropriate treatment should prevent EIA in most patients, and those with asthma or EIA can participate in athletics, even at an elite level. For competitive athletes, the applicable sports governing organization should be consulted for its list of allowed and banned substances and pertinent regulations.
Dr Storms is an allergist in private practice in Colorado Springs and was co-chair of the Olympic Exercise Asthma Summit Conference. Dr Joyner is an orthopedic surgeon in private practice in Harrisburg, Pennsylvania, is the chair of the US Olympic Sports Medicine Committee, and was co-chair of the Olympic Exercise Asthma Summit Conference. Address correspondence to William W. Storms, MD, Asthma and Allergy Associates, PC, 2709 N Tejon St, Colorado Springs, CO 80907; e-mail to [email protected].
Copyright (C) 1997. The McGraw-Hill Companies. All Rights Reserved