Mild emphysema is associated with reduced elastic recoil and increased lung size but not with air-flow limitation.

Thirty-nine excised human lungs were examined to identify early changes in the small airways, their size distribution, and their elastic recoil in relation to mild degrees of emphysema. Elastic recoil measurement, single-breath nitrogen (SBN2) tests, and FEV1 were obtained from 18 lungs with no emphysema and 21 emphysematous lungs with no greater than Grade 5 emphysema score. The mean number of alveolar attachments per brochiole was determined from all the bronchioles cut in cross section. When the 2 groups of lungs were compared, the percentage of predicted elastic recoil of the nonemphysematous lungs was significantly greater at 50, 70, 80, and 90% of TLC than in the mildly emphysematous lungs. The TLC of the emphysematous lungs (% of predicted) was also significantly greater than in the nonemphysematous lungs. Pigment of the small airways was the only pathologic feature that was significantly greater in the emphysematous lungs than in the nonemphysematous lungs. Size distribution in the small airways was similar except for the airways zero to 0.2 mm, which were more frequent in the emphysematous lungs. When data from both groups were combined, elastic recoil was shown to be related to both the number of alveolar attachments (p less than 0.03) and the mean diameter of the small airways (p less than 0.01). We conclude that structural and functional changes in lungs with mild emphysema include reduced elastic recoil, increased lung size, and some size distribution changes in the small airways. Mild emphysema is not associated with air-flow limitation.