[Changes in the amounts of elastic and collagenous elements of normal aged and emphysematous lung: use of a model of static pressure-volume relationships].

The possibility of a difference between the amount of elastic and collagenous connective tissues in normal and emphysematous lungs is controversial. I used an equation (MIN, 1995, reference 2) to compute the total amount of connective tissue in the pulmonary parenchyma from static pressure-volume relationships in 44 subjects divided into four groups. For normal nonsmokers, normal smokers, smokers with COPD, and subjects with emphysema, there was a unique relationship between the total, amount of connective tissues (sigma 0 = -0.82 Log(a) + 3.02 r2 = 0.201, p = 0.0029). Age was also significantly related to the modulus of elasticity: it appeared to increase 0.4% per year in nonsmokers and 5.4% per year in smokers with COPD. The ratio of collagen-to-elastin content in the lung parenchyma was taken to be 1.3 (from the results of recent studies), and little difference was found between normal smokers and emphysematous smokers in regard to collagen-elastin catabolism. In both groups the apparent yearly decrease in elastin content was about 1.6%, and the apparent yearly increase in collagen content was about 0.6%. Therefore, the damaging effects of emphysema on parenchymal connective tissues may be analogous to accelerated catabolism of parenchymal connective tissues in normal aging lungs.