Respiratory Disorders Associated with Impairment of Gas Diffusion (Alveolo-Capillary Block Syndrome)

Abstract

The literature on those pulmonary diseases which are associated with qualitative changes in pulmonary diffusion is of relatively recent origin, though of course many fundamental contributions had been made before 1958. It is becoming increasingly clear that in many of these conditions the relationship between the measured impairment of pulmonary diffusion and the radiological appearances is by no means a direct one. Extreme examples of gross radiological change without much impairment of function may be found in alveolar microlithiasis and in some cases of sarcoidosis. More commonly the reverse situation applies, in which the pulmonary diffusing capacity is severely reduced in the absence of striking radiological change; and examples of this situation may be found in asbestosis, chronic diffuse interstitial fibrosis of the Hamman-Rich type, and also in certain patients with sarcoidosis. The originally described clinical syndrome associated with change in the quality of the pulmonary membrane has come to be modified to some extent by the recognition that in some patients of this type, particularly those with chronic diffuse interstitial fibrosis and alveolar proteinosis, there may be ventilatory obstruction leading to CO2 retention rather than to a low arterial pCO2.