ABSTRACT
Asthma is characterized by airway inflammation and a reduction in airway caliber, both of which fluctuate over time. Bronchoconstriction can be precipitated by a wide range of stimuli, both organic and physical; it may be transient with a rapid return to previous lung function, or it may persist and be labeled an exacerbation. Exacerbations are a cardinal feature of asthma, reflecting one end of the spectrum of the fluctuations that are an inherent part of the disease.
