Exercise-induced bronchoconstriction
Exercise-induced Bronchoconstriction | |
---|---|
Other names | EIA |
Specialty | Pulmonology |
Symptoms | Shortness of breath on vigorous exercise |
Usual onset | Rapid, on exercise |
Duration | For the duration of activity and some time afterwards |
Causes | Moderate to high intensity exercise |
Exercise-induced bronchoconstriction (EIB) occurs when the airways narrow as a result of exercise. This condition has been referred to as exercise-induced asthma (EIA); however, this term is no longer preferred.[1] While exercise does not cause asthma, it is frequently an asthma trigger.[1]
It might be expected that people with EIB. would present with
Cause
While the potential triggering events for EIB are well recognized, the underlying pathogenesis is poorly understood.
Diagnosis
Exercise-induced
Spirometry
Objective testing should begin with spirometry at rest. In true exercise-induced bronchoconstriction, the results should be within normal limits. Should resting values be abnormal, then asthma, or some other chronic lung condition, is present. There is, of course, no reason why asthma and exercise-induced bronchoconstriction should not co-exist but the distinction is important because without successful treatment of underlying asthma, treatment of an exercise component will likely be unsuccessful. If baseline testing is normal, some form of exercise or pharmacologic stress will be required, either on the sideline or practice venue, or in the laboratory.[9]
Exercise testing
Treadmill or ergometer-based testing in lung function laboratories are effective methods for diagnosing exercise-induced bronchoconstriction, but may result in false negatives if the exercise stimulus is not intense enough.
Field-exercise challenge
Field-exercise challenge tests that involve the athlete performing the sport in which they are normally involved and assessing FEV1 after exercise are helpful if abnormal but have been shown to be less sensitive than eucapnic voluntary hyperventilation.[10]
Eucapnic voluntary hyperventilation challenge
The International Olympic Committee recommends the eucapnic voluntary hyperventilation (EVH) challenge as the test to document exercise-induced asthma in Olympic athletes.[11] In the EVH challenge, the patient voluntarily, without exercising, rapidly breathes dry air enriched with 5% CO2 for six minutes. The presence of the enriched CO2 compensates for the CO2 losses in the expired air, not matched by metabolic production, that occurs during hyperventilation, and so maintains CO2 levels at normal.[12]
Medication challenge
Medication challenge tests, such as the methacholine challenge test, have a lower sensitivity for detection of exercise-induced bronchoconstriction in athletes and are also not a recommended first-line approach in the evaluation of exercise-induced asthma.[13]
Mannitol inhalation[14][15] has been recently approved for use in the United States.
A relatively recent review of the literature has concluded that there is currently insufficient available evidence to conclude that either mannitol inhalation or eucapnic voluntary hyperventilation are suitable alternatives to exercise challenge testing to detect exercise-induced bronchoconstriction and that additional research is required.[16]
Treatment
Lifestyle
The best treatment is avoidance of conditions predisposing to attacks, when possible. In athletes who wish to continue their sport or do so in adverse conditions, preventive measures include altered training techniques and medications.
Some take advantage of the refractory period by precipitating an attack by "warming up," and then timing competition such that it occurs during the refractory period. Step-wise training works in a similar fashion. Warm up occurs in stages of increasing intensity, using the refractory period generated by each stage to reach a full workload.[17]
Medication
There is no evidence supporting different treatment for EIB in asthmatic athletes and nonathletes.
In May 2013, the American Thoracic Society issued the first treatment guidelines for EIB, recommending use of "a short-acting β2-agonist before exercise in all patients with EIB. For patients who continue to have symptoms of EIB despite the administration of a short-acting β2-agonist before exercise, strong recommendations were made for a daily inhaled corticosteroid, a daily leukotriene receptor antagonist, or a mast cell stabilizing agent before exercise."[19]
There is conflicting information about the value of
Research
A crossover study compared oral montelukast with inhaled salmeterol, both given two hours before exercise, showing that the drugs had similar benefit.[21]
A meta-analysis of preliminary research indicated that vitamin C may be useful to relieve respiratory symptoms such as cough during exercise.[22]
Prognosis
As evidenced by many professional athletes who have overcome EIB using some combination of accepted treatments, the prognosis is usually very good.[
References
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- ^ Rosenthal, Richard. "Eucapnic Voluntary Hyperventilation (EVH) A Test for the Presence of Asthma". Archived from the original on 2014-05-31. Retrieved 2014-05-30.
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- ^ "Froome surprised at controversy over in-race inhaler use". 10 June 2014.
- ^ theguardian.com. Retrieved 29 April 2016.
- ^ cnn.com. Retrieved 29 April 2016.