Periods of reversible airway narrowing in the presence of aeroallergens, irritants, or exercise. o Pathophysiology: an external trigger causes bronchial spasms, an inflammation response, and increased airway secretions. o Clinical presentation: chest is expanded, accessory muscles are used to help breathe, wheezing, crackling, decreased breath sounds due to poor air movement. FEV1 will be decreased but is reversible through use of recovery drugs.