Structure and function of small airways in health and disease.

During the last two decades, great strides have been made in our 
understanding of the functional aspects of airflow in the periphery of 
the lung. It seems that the small airways are the important 
site of obstruction in a variety of chronic respiratory disorders associated 
with airflow obstruction. This review deals with the anatomic and functional 
aspects of small airways in normal and diseased lungs. In particular, 
the basis of obstruction or narrowing that is not dependent on 
intrinsic airway lesion is reviewed. The variety of pathologic changes in 
small airways observed in these diseases are outlined along with physiologic 
tests that are currently used to detect dysfunction at a stage 
long before they produce symptoms or alter standard tests of lung 
function. 