Don’t base diagnosis of exercise-induced bronchoconstriction on symptoms alone – but do have patients use inhaled short-acting beta-agonists and do warm-ups before exercise, according to new clinical practice guidelines issued May 1 by the American Thoracic Society.
The guidelines define exercise-induced bronchoconstriction (EIB) as "acute airway narrowing that occurs as a result of exercise."
Considering the high prevalence of EIB, which also affects people without asthma, "evidence-based guidelines for its management are of critical importance," said Dr. Jonathan Parsons, the lead author and chair of the committee that drafted the guidelines, in a statement.
Dr. Jonathan Parsons
The recommendations "synthesize the latest clinical evidence and will help guide the management of EIB in patients with or without asthma, and in athletes at all levels of competition," added Dr. Parsons, associate professor of internal medicine and associate director of the Ohio State University Asthma Center, Columbus.
The EIB guidelines cover pathogenesis, environmental triggers, diagnosis, treatment, and screening (Am. J. Resp. Crit. Care Med. 2013;187 [doi:10.1164/rccm.201303-0437ST]). Also included is a section on exercise, asthma, and doping – with reminders about which EIB drugs are banned in competitive sports (most beta-agonists) and which are allowed (short-acting inhaled albuterol and inhaled steroids).
Although the guidelines can apply both to adolescents and adults, they cannot be applied reliably to young children, Dr. Parsons noted in an interview.
EIB prevalence among people with asthma is not known, but the estimated prevalence among people who have not been diagnosed with asthma is as high as 20%, according to the ATS. EIB is more prevalent among athletes, affecting 30%-70% of Olympic and elite athletes. Environmental factors likely play a role, such as pollutants emitted from ice surfacing machines in indoor ice rinks, high trichloramine levels in the air of indoor pools, and cold, dry air.
An EIB diagnosis should not be based on symptoms, which are variable, nonspecific, and have poor predictive value. Instead, diagnosis should be made based on changes in lung function provoked by exercise, using serial lung function measurements after a specific exercise or a hyperpnea challenge. Assessing the effects of exercise on forced expiratory volume in 1 second (FEV1) is preferred.
The guidelines grade EIB as mild, moderate, or severe, depending on the percent fall in FEV1 from baseline. They also offer information on alternatives to exercise testing.
The authors rate pharmacologic and nonpharmacologic therapies based on the quality of the supportive evidence. Their first recommendation – administration of an inhaled short-acting beta-agonist (SABA) before exercise – earns a "strong" recommendation based on "high-quality" evidence. Patients typically take SABAs 15 minutes before exercise.
Because of the potential for serious side effects, the authors recommend against daily use of an inhaled long-acting beta-agonist (LABA) for EIB – a strong recommendation based on moderate-quality evidence.
For patients who use an inhaled SABA but continue to have symptoms or need to use the inhaled SABA "daily or more frequently," treatment options before exercise include a daily inhaled corticosteroid (ICS), a daily leukotriene-receptor antagonist, or a mast-cell–stabilizing agent.
"We generally add a daily inhaled ICS or a daily leukotriene-receptor antagonist first, with the choice between these agents made on a case-by-case basis depending upon patient preferences," the guideline authors note. Mast-cell–stabilizing agents and inhaled anticholinergic drugs "play a secondary role," they added. There is also a role for antihistamines in patient with continued symptoms despite treatment, but not for patients without allergies.
Nonpharmacologic measures include interval or combination warm-up exercises before planned exercise, which the guidelines recommend "for all patients" with EIB – a strong recommendation, based on moderate quality evidence. The guidelines cite evidence showing a lower reduction in FEV1 after exercise among people with EIB who engaged in "interval, low-intensity continuous; high-intensity continuous; or combination warm-up" before they exercised.
Another nonpharmacologic recommendation is use of a mask or another device that warms and humidifies the air when patients exercise in a cold climate.
While there is not much evidence supporting dietary modifications, patients interested in this approach can try a low-salt diet, or take fish oil or vitamin C supplements. However, the use of lycopene is not supported, based on the available evidence.
"Our overall recommendations regarding therapy leave a lot of options for the individual patient, which should be discussed with the patient’s physician and tried and evaluated on an ongoing basis," the authors concluded.
The mainstay of treatment "remains maintaining good control of underlying asthma (if present) and preventing or treating symptoms of EIB with SABAs."
The EIB practice guidelines were supported by the ATS and approved by the ATS board of directors. Dr. Parsons’ disclosures include having received lecture fees from AstraZeneca, GlaxoSmithKline, Merck, and Schering Plough. All but one of the other authors disclosed financial relations with a wide range of pharmaceutical companies.