Radial Traction and Small Airways Disease in Excised Human Lungs1,2

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Abstract
We studied 47 excised human lungs in order to examine the relationship between the number of alveolar attachments surrounding bronchioles 2 mm or less in diameter and the presence of small airways disease and overall lung function. Expiratory pressure-volume curves, the FEV1, and the single-breath nitrogen washout were obtained from 11 lungs without emphysema and 36 lungs with various degrees of emphysema. The lungs were subsequently inflation-fixed at 20 cm H2O. Gough sections were used to measure emphysema. Six to 10 blocks of tissue were cut at random from a midsagittal slice of lung tissue for the small airways and alveolar attachment study. We measured the inside diameters of all nonrespiratory bronchioles (2 mm or less in diameter) and made corrections for shrinkage during processing. The number of alveolar attachments on the outside wall of the bronchioles cut in cross section were obtained from all the sections observed. The mean number of alveolar attachments per bronchiole was determined for each lung. The histopathologic features of the bronchioles were evaluated by the method of Cosio and coworkers (2). We found a positive correlation between the number of alveolar attachments and the percentage of predicted FEV1 (r = 0.328, p < 0.03) and the percentage of predicted closing capacity (r = 0.553, p < 0.01). There was a negative correlation of the mean number of alveolar attachments and the small airways fibrosis score (r = −0.344, p < 0.02). A correlation also existed between the number of alveolar attachments and the mean internal bronchiolar diameter (r = 0.561, p < 0.001). We conclude that the alveolar attachments and elastic recoil are related to the size and function of the small airways.