Pathology of emphysema in chronic obstructive pulmonary disease.

Emphysema is an almost constant finding in the lungs of chronic obstructive pulmonary disease patients. Several types of emphysema are recognized by pathologists, but only the centrilobular (CLE) and panlobular (PLE) emphysemas are found in association with smoking. In this review, the morphological and functional differences between CLE and PLE are described, and it is suggested that they could arise as different abnormalities as a result of the same insult, cigarette smoke. In CLE: 1) the destruction of the lung is uneven and originates around the airways; 2) the membranous bronchioles are thicker, narrower and more reactive than in PLE; 3) lung compliance is low or normal and does not relate to the extent of the emphysema; and 4) the decrease in flow is related mainly to the degree of airway abnormality and not to the losses of elastic recoil. In contrast, in PLE: 1) the destruction of the lung is even; 2) the small airways appear less narrowed and less inflammed than in CLE; 3) the compliance of the lung is increased and related to the extent of the emphysema; and 4) the decrease in flow is related mainly to the loss of elastic recoil and not to the abnormalities in the airways. The authors would propose that centrilobular emphysema and panlobular emphysema are distinct entities, centrilobular emphysema an airborne disease related to airway reactivity, panlobular emphysema a blood-borne disease related to abnormalities in lung protective mechanisms against inflammatory insults.