The pathophysiology of small airway inflammation in asthma.

Histologic and imaging studies show that asthmatic inflammation occurs in small airways of the peripheral lung, even in patients with mild disease. Small airway inflammation leads to obstruction that can be detected as peripheral resistance, air trapping, and eosinophil infiltration and is manifested clinically as nocturnal asthma and frequent exacerbations. Inflammatory activity in the distal lung of patients may actually exceed that of the large airways. Anatomic changes in small airways are prominent in cases of fatal asthma.