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Exercise-Induced Asthma

Author: Anthony J Saglimbeni, MD, Staff Physician, Family Practice Residency, Medical Director, Center for Sports Medicine, O'Connor Hospital; Private Practice
Contributor Information and Disclosures

Updated: Nov 1, 2007

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• Overview
• Differential Diagnoses & Workup
• Treatment & Medication
• Follow-up

• References
• Keywords

Introduction

Background

Exercise-induced asthma (EIA) is a condition of respiratory difficulty that is triggered by aerobic exercise and lasts several minutes. Symptoms of EIA may resemble those of allergic asthma, or they may be much more vague and go unrecognized, resulting in probable underreporting of the disease. (See also the Medscape Asthma Resource Center and the eMedicine article Asthma.)

Exercise-induced urticaria, or anaphylaxis, is often presumed to be related to EIA, even though this condition is extremely rare and unrelated. EIA is related to histamine release.^1,2,3 Only 500-1000 cases of exercise-induced urticaria have been reported in the literature. In this condition, there is an early stage of exercise-related fatigue and itchiness, followed by early onset of urticaria and angioedema, which is initially mild.⁴ If progression occurs, there is choking, stridor, nausea, vomiting, and even hypotension. A late stage that is marked by headache may also occur. As implied by the alternative name of anaphylaxis, EIA can be life threatening; however, this can be prevented by exercise modification or avoidance of certain conditions (see Sport-Specific Biomechanics, below).

(See also the eMedicine articles Exercise-Induced Anaphylaxis [in the Pediatrics section], Urticaria [in the Allergy and Immunology section], and Angioedema [in the Emergency Medicine section].)

Frequency

United States

EIA affects 12-15% of the population. Ninety percent of asthmatic individuals and 35-45% of people with allergic rhinitis experience EIA, but even when those with rhinitis and allergic asthma are excluded, a 3-10% incidence of EIA is seen in the general population.³

EIA seems to be more prevalent in some winter or cold-weather sports.⁵ Some studies have demonstrated rates as high as 35% or even 50% in competitive-caliber figure skaters, ice hockey players, and cross-country skiers.^6,7

Functional Anatomy

The problem in EIA occurs distal to the glottis, in the lower airway. Bronchoconstriction is involved that is distinguishable from laryngospasm, which can occur in other exercise-related conditions. One such example is the condition known as vocal cord dysfunction in which there is paradoxical narrowing of the vocal cords during inspiration, resulting in stridor that is often misconstrued as audible wheezing.^8,9 Normally, the vocal cords open with inspiration. (See also the eMedicine article Vocal Cord Dysfunction.)

Sport-Specific Biomechanics

EIA usually affects individuals who participate in sports that include an aerobic component. The condition can be seen in any sport, but EIA is much less common in predominantly anaerobic activities. This is likely due to the role of consistent and repetitive air movement through the airways (seen in aerobic sports), which affect airway humidity and temperature. EIA triggers an unknown biochemical and neurochemical pathway, resulting in the bronchospasm, which manifests as the symptoms of the disease.

Although the exact mechanism of EIA is unknown, there are 2 predominant theories as to how the symptom complex is triggered. One is the airway humidity theory, which suggests that air movement through the airway results in relative drying of the airway. This, in turn, is believed to trigger a cascade of events that results in airway edema secondary to hyperemia and increased perfusion in an attempt to combat the drying. The result is bronchospasm.

The other theory is based on airway cooling and assumes that the air movement in the bronchial tree results in a decreased temperature of the bronchi, which may also trigger a hyperemic response in an effort to heat the airway. Again, the result is a spasm in the bronchi.

Many authors think that there may be a combination of the above 2 theories that takes place, but the biochemical or physical pathways that mediate these responses are unclear. Evidence may even exist to support the idea that the resulting cascades are not the inflammatory pathways to which we attribute allergic asthma.

Likewise, certain sports and their environments predispose individuals with asthma to experience EIA. Sports played in cold and dry environments usually result in more symptom manifestation for athletes with this condition. On the other hand, when the environment is warm and humid, the incidence and severity of EIA decrease.

Clinical

History

Patients usually present complaining of exercise-related respiratory symptoms. This complaint is much more common among children and younger athletes but can be seen at any age.

• Symptoms during or following exercise include the following^1,3 :
  • Chest tightness or pain
  • Cough
  • Shortness of breath
  • Wheezing
  • Underperformance or poor performance on the field of play
  • Fatigue
  • Prolonged recovery time
  • Gastrointestinal (GI) discomfort
• Symptom denial may be seen due to the following:
  • Peer pressure
  • Embarrassment
  • Fear of losing position on the team
  • Misinterpretation as postexercise fatigue
• Contributing factors consist of the following:
  • Cool temperatures
  • Low-humidity environment
  • Poor air quality
  • High pollen counts
  • Coincident respiratory infection
  • Poor physical conditioning
• Exercise factors can include the following:
  • Aerobic exercise appears to be much more problematic than anaerobic exercise.
  • Duration of aerobic activity greater than 8-10 minutes provokes EIA.
  • High-intensity aerobic exercise also provokes EIA.
• Time interval between sessions of aerobic exercise
  • Refractory phase
    • Starts less than 1 hour after initial aerobic exercise
    • Lasts up to 3 hours
    • The refractory phase results in as little as one half the degree of bronchospasm as in the first episode.
    • Occurrence is unpredictable and intermittent
    • The warm-up period can be used in an attempt to ensure that competition occurs during this refractory phase.
    • The mechanism is unknown but is believed to involve the following possibilities: depletion of mast cell mediators, release of endogenous catecholamines, and release of endogenous protective prostaglandins.
  • Late-phase response
    • This phase occurs 3-9 hours after the initial exercise challenge, and unlike the refractory phase, the late phase manifests as an increase in symptoms, with cough, wheezing, or shortness of breath.
    • This response is much more common in children and is more likely to occur if severe early exercise-induced bronchospasm (EIB) is present.
    • This late-phase response is usually less severe than the early response.

Physical

The patient's physical examination is often unremarkable in the clinical setting; a higher yield is obtained on the field or after an exercise challenge.¹⁰ Exercise challenge, for the purpose of the physical examination, may be informal. For example, the clinician may have the athlete come to the office wearing athletic clothing and run on a treadmill or around the parking lot for 10 minutes, which is then followed by another pulmonary examination.

• The physical examination should include the following areas:
  • Skin (note any signs of atopic disease)
  • Head, ears, eyes, nose, and throat (note any evidence of acute infection, chronic infection, allergic/atopic disease)
  • Pharynx (note any mucus, cobblestoning, erythema)
  • Nose (note the presence of enlarged turbinates, erythema, congestion)
  • Sinuses (note the presence of tenderness)
  • Lungs (note the presence of rales, rhonchi, wheezes, a prolonged expiratory phase)
  • Heart (note the presence of murmurs, an irregular rhythm)

Causes

The causes of EIA can be divided into the categories of medical, environmental, and drug related. Eliminating some causes can diminish—but may not eliminate—the athlete's symptoms. EIA may also exist without the presence of any of these causes.

• Medical
  • Poorly controlled asthma results in increased patient symptoms with exercise.
  • Maximizing control of the patient's baseline asthma, when present, is critical in the treatment of EIA.¹
  • Poorly controlled allergic rhinitis also results in increased patient symptoms with exercise.
  • Secretions resulting from hay fever can aggravate both allergic asthma and EIA.
  • Viral, bacterial, and other forms of upper respiratory infections also aggravate the symptoms of EIA.
    • Controlling the secretions of these illnesses, as with allergic rhinitis, can make the EIA symptoms much more tolerable.
• Environmental
  • Excess of pollens or other allergens in the air can exacerbate the allergic and exercise-induced forms of asthma.
    • Pollutants in the air are irritants to the airways and can lower the threshold for symptomatic bronchospasm.
  • The chemicals used in certain sports for environmental maintenance can predispose individuals to wheezing and worsen EIA symptoms. These chemicals include the following:
    • Chlorination in pools
    • Insecticides and pesticides used to maintain playing fields
    • Fertilizers and herbicides used to maintain playing fields
    • Paints and other decorative substances to enhance the appearance of playing fields
• Drugs – Asthmogenic agents include the following:
  • Beta-blockers (β- blockers)
  • Aspirin
  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Diuretics
  • Zanamivir

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