Clinical and physiologic features of some types of pulmonary diseases with impairment of alveolar-capillary diffusion: The syndrome of “alveolar-capillary block”

Abstract

1. 1. Twelve additional cases with various diffuse diseases of the lungs characterized physiologically principally by interference with the diffusion of oxygen across the alveolar-capillary septum have been studied. 2. 2. The patients in this group included two with pulmonary granulomatosis following exposure to beryllium; one with pulmonary granulomatosis of the Boeck's sarcoid type; one with pulmonary granulomatosis of undetermined etiology, in which the granulomatous lesion contained unusually large numbers of foreign body-type giant cells and bi-refractile crystals; one patient with scleroderma; three patients with pulmonary fibrosis of unknown etiology (in one case after exposure to beryllium, in two cases associated with granulomas in other organs), and four cases in which a diagnosis could not be made. 3. 3. The pattern of pulmonary dysfunction consisted of (1) reduced lung volumes, (2) maintenance of a large maximum breathing capacity, (3) hyperventilation at rest and during exercise, (4) normal or nearly normal arterial oxygen saturation at rest but a marked reduction of the arterial oxygen saturation after exercise, (5) normal alveolar oxygen tension, (6) a reduced oxygen diffusing capacity and (7) pulmonary artery hypertension. 4. 4. In some severe cases the dead space-like ventilation and the venous admixture-like perfusion was increased. These findings have been interpreted as an indication of the inhomogeneous nature of the pathologic process. 5. 5. The clinical findings have been analyzed in the light of the physiologic data and the evolutionary trends, both clinical and physiologic, have been described. 6. 6. Because the major pathologic changes are localized in the alveolar capillary septa and because the major physiologic defect is a reduction of the permeability of the alveolar capillary membrane for oxygen, the name “alveolar-capillary block” has been tentatively offered to describe this syndrome.