Structure and function in fibrosing alveolitis

Abstract

Lung volumes, maximal expiratory volume and flows, elastic recoil pressure, and impedances at various levels of the bronchial tree, as well as tissue impedance, were measured in 13 human lungs that demonstrated generalized fibrosis at autopsy. After fixation, mean internal chord of air spaces (Lma), transsection length of the alveolar walls (Lmw), and internal diameter (d) and density of membraneous bronchioles (n/cm2) were determined in the same lungs by use of morphometric techniques. The results of functional and structural measurements were correlated and compared with measurements obtained similarly in 10 normal lungs. This study shows that the functional alterations typical for fibrosing alveolitis can be attributed to the replacement of part of the parenchyma by fibrous tissue and to modifications of the mechanical properties of still-functional units. The lungs were characterized structurally by an increase of Lmw and d. In addition, in three lungs, an increase of Lma and a decrease of n/cm2 were observed. Functionally, these lungs demonstrated a pattern compatible with a mixture of fibrosis and emphysema.