Pathology of chronic obstructive pulmonary disease.

This gathering of new observations about chronic obstructive pulmonary disease, collected under the loosely defined heading of "pathology," creates a certain air of excitement. Vascular engorgement in concert with muscle contraction produces small airways narrowing in asthma, but not in chronic obstructive pulmonary disease. Stenotic small airways can be visualized in three dimensions. Fibrosis may be an integral part of emphysema, stretching its definition somewhat. Microvascular injury seems to produce emphysema. The protease-antiprotease theory of emphysema has competition from the inflammation-repair-fibrosis sequence seen in other organs. The mystery of why some smoker's lungs remain unaffected by tobacco smoke is further documented but unsolved; neuroendocrine cells and their neuropeptides may be important.