The concept that abnormalities of the pulmonary membrane might alter its permeability to respiratory gases and thereby lead to disturbances in the diffusion of oxygen across the membrane was suggested many years ago, and it was suspected that impaired oxygen diffusion might be the main cause of cyanosis in some patients with pulmonary disease. With the development, more than a decade ago, of practical techniques for measuring the diffusion characteristics of the lungs, such abnormalities were indeed demonstrated in these patients.
In 1951, Austrian and his colleagues 1 introduced the term "alveolar-capillary block" syndrome to identify a group of clinical and physiological features found in some patients with diffuse pulmonary disease who had evidence of impaired pulmonary oxygen diffusion. The clinical features which were considered to be characteristic of the syndrome included progressive dyspnea, tachypnea at rest and after exercise, cyanosis after exercise, fine rales at the lung bases, lack
Eldridge F. The Alveolar-Capillary Block Syndrome. AMA Arch Intern Med. 1960;105(5):665-667. doi:10.1001/archinte.1960.00270170003001