Asthma exacerbations are extremely high risk for asthma patients and impose a great cost burden on healthcare providers. Perhaps equally important is the evidence that full symptomatic recovery from exacerbation can result, nevertheless, in persistent decreased lung function after recovery. To this issue, Paul O’Byrne inventories current therapies directed specifically at preventing or mitigating asthma exacerbations in this month’s issue (J Allergy Clin Immunol 2011;128: 257-263).
O’Byrne notes that exacerbations are thought to be precipitous, emergent events. In fact, they have a gradual development over approximately a week as symptoms increase and lung function decreases until the point of urgent intervention. Additionally they are frequently associated with upper respiratory infections (URI) caused typically by human rhinovirus (HRV) or allergen exposure in atopic patients. The author notes that URI or allergen exposure alone is not sufficient to elicit exacerbation and other conditions are required, therefore, prevention is targeted at risk mitigation.
The author discusses inhaled corticosteroids (ICS) as the primary intervention aimed at reducing airway inflammation, and subsequently, risk of infection or reactivity. ICS have a positive effect on airway eosinophilia, a primary cause of inflammation, but O’Byrne notes that slightly less than half of asthma patients have airway neutrophilia that doesn’t respond to ICS therapy. Symptom rescue is managed through use of short- and long-acting bronchodilators, used separately or in steroid + long-acting bronchodilator combination products. O’Byrne comments on recent research supporting the use of the combination product budesonide + formoterol for maintenance as well as exacerbation, noting that budesonide + formoterol was as effective as oral steroids for common outcomes, such as nighttime awakenings and albuterol rescue use.
O’Byrne discusses the beneficial effects of anti-leukotriene therapy, especially in pediatric asthma patients. Anti-IgE antibody therapy is helpful in allergic asthma and inner city children with asthma, though anti-IL-5 antibody therapy for reducing airway eosinophilia in refractory asthma has not yet proven unequivocally beneficial. Finally, the author discusses bronchial thermoplasty for refractory asthma, which has approval in only a few countries.
Editor's note: Readers interested in learning more about asthma exacerbations may want to consult the August 2009 supplement, Supplemental Recommendations for the Management and Follow-up of Asthma Exacerbations, written by representatives of the American Academy of Allergy, Asthma & Immunology, the American Academy of Emergency Medicine, and the American Thoracic Society. The supplement is available for free download at: http://www.jacionline.org/issues?issue_key=S0091-6749(09)X0009-6.
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