Lung surface area in various morphologic forms of human emphysema.

The relation between lung surface area and the extent and morphologic type of emphysema was examined at autopsy in 69 men. It was found to be conceptually preferable to express the area as internal surface area per unit lung volume (specific surface area) rather than to use the more conventional, inversely related, mean linear intercept for comparison with other morphometric data. In the whole group, fixed inflated lung volume generally increased with increasing per cent involvement of lung parenchyma by emphysema, and total internal surface area decreased, but those changes were not so regular as the decline in specific surface area with increasing per cent emphysema (r=-0.574). Lungs with no emphysema had a significantly higher specific surface area than did lungs with very little emphysema (1 to 9 per cent), suggesting noticeable effects on the physical properties of lung by minimal degrees of this disease at high levels of inflation. The way in which specific surface area decreased with increasing percentage of emphysema was not noticeably different among patients with centrilobular, panlobular, or mixed forms of emphysema, although lungs with only centrilobular emphysema were much more common and had a significantly lower mean percentage of emphysema than did those with only panlobular emphysema; the prevalence and mean percentage of emphysema of the mixed group were intermediate. These observations, coupled with the association of older mean age with increasing percentage of emphysema, were interpreted as support for the concept that many examples of panlobular emphysema are derived from confluence of extensive centrilobular emphysematous lesions.