Exercise-Induced Bronchoconstriction

Definition and Pathophysiology

Exercise-induced bronchoconstriction (EIB) is defined as transient airway narrowing that occurs as a result of exercise, characterized by symptoms such as wheezing, cough, chest tightness, and dyspnea that typically occur after strenuous exertion, according to the American Thoracic Society 1, 2
EIB describes acute airway narrowing that occurs after exercise and can affect both individuals with and without underlying asthma, as stated by the American College of Chest Physicians 2
The term "exercise-induced bronchoconstriction" is preferred over "exercise-induced asthma" as it does not imply that exercise causes asthma or that the patient necessarily has underlying chronic asthma, recommended by the American Academy of Allergy, Asthma, and Immunology 2, 3
EIB is triggered by a period of high-intensity exercise or increased minute ventilation, causing a prototypical bronchoconstriction response that occurs predominantly after exercise cessation, as explained by the European Respiratory Society 1
Increased osmolarity stimulates mast cell degranulation, leading to the release of inflammatory mediators, such as histamine, tryptase, and leukotrienes, from eosinophils and mast cells, according to the American Journal of Respiratory and Critical Care Medicine 1

Elite athletes have a higher prevalence (30-70%) of EIB than the general population, as reported by the American College of Sports Medicine 2
Specific sports carry higher risk due to environmental exposures, such as ice rink athletes with a ~30% prevalence due to cold dry air and pollutants from ice resurfacing machines, according to the International Olympic Committee 1
Nordic skiers have a high prevalence of EIB due to inhalation of cold, dry air, as stated by the European Respiratory Society 1
Competitive swimmers have an 11-29% prevalence of EIB associated with trichloramine exposure, as reported by the American Academy of Pediatrics 1

Symptoms of EIB typically develop 5-10 minutes after exercise, peak 8-15 minutes post-exercise, and resolve within 30-90 minutes without treatment, according to the National Institutes of Health 1, 2
Common symptoms of EIB include chest tightness, cough, wheezing, and dyspnea, as listed by the American Thoracic Society 1, 2
Symptoms are often mild to moderate but can impair athletic performance, as stated by the American College of Sports Medicine 1
Severe episodes of EIB can occur rarely, potentially leading to respiratory failure, as warned by the European Respiratory Society 1

Diagnosis of EIB is established by changes in lung function after exercise, not based on symptoms alone, as recommended by the American Thoracic Society 1
Symptoms are neither sensitive nor specific for identifying EIB, according to the National Institutes of Health 1
A positive diagnosis of EIB requires a decrease in FEV1 of ≥10% after exercise and symptoms consistent with bronchospasm during or after exercise, as defined by the American College of Chest Physicians 1, 4
If spirometry is normal but EIB is suspected, additional testing is needed, such as an exercise challenge test or surrogate tests like eucapnic voluntary hyperpnea (EVH) or inhaled mannitol challenge, as recommended by the European Respiratory Society 1, 4

First-line treatment for EIB is short-acting β2-agonists (SABAs) 15 minutes before exercise, which provides protection in 80-95% of affected individuals, as recommended by the American Academy of Allergy, Asthma, and Immunology 5
For patients with persistent symptoms despite pre-exercise SABA, daily inhaled corticosteroids (ICS) or leukotriene receptor antagonists (LTRAs) like montelukast may be added, as suggested by the American Thoracic Society 5
Mast cell stabilizing agents or inhaled anticholinergic agents may be used before exercise, as recommended by the European Respiratory Society 2, 5
Avoid daily use of long-acting β2-agonists (LABAs) as monotherapy due to risk of serious side effects and development of tolerance, as warned by the American College of Chest Physicians 5

Warm-up exercise before planned activity, such as interval or combination warm-up, can help prevent EIB, as recommended by the American College of Sports Medicine 2, 5
Use of a face mask or scarf to warm and humidify air during cold weather exercise can reduce the risk of EIB, as suggested by the European Respiratory Society 2, 5
Dietary modifications, such as a low-salt diet, fish oil supplementation, or ascorbic acid (vitamin C) supplementation, may help alleviate EIB symptoms, as reported by the American Journal of Respiratory and Critical Care Medicine 2
Avoiding known triggers and high-pollution environments can help prevent EIB, as recommended by the American Thoracic Society 1
Choosing sports with lower minute ventilation when possible can reduce the risk of EIB, as suggested by the American Academy of Pediatrics 5