The pathophysiology of airways disease

More than 10 million airway branches exist in the normal human lung. Radiographic visualization is < 1% of this total. Many diseases affect the airways, each pathologic insult ultimately resulting in obstruction to airflow. Normally there is little resistance to airflow in the small airways (<2 mm diameter); thus extensive disease may be present before it becomes clinically evident. Centrilobular emphysema is characterized by dilation and destruction of small air-ways, whereas bronchiolitis obliterans is characterized by concentric fibrous obliteration of small airways. High-resolution computed tomography, particularly comparison of images at full inspiration and full expiration, is the most sensitive radiographic method with which to image small airways disease.