Regional pulmonary function in sarcoidosis

In 26 subjects with a confirmed histological diagnosis of thoracic sarcoidosis regional lung function was studied with Xenon 133. All subjects also underwent overall lung function studies including CO steady state (TCO SS) and single breath (TCO SB) diffusing capacity. Regional ventilation (Vr) was on the average increased in stages I (isolated hilar adenopathies) and II (pulmonary infiltration) and appeared normal in stage III (pulmonary fibrosis). Regional perfusion (Qr) was on the average normal in stages I and II and decreased in stage III. There were no appreciable differences between average values in stages I and II. Abnormalities of Vr and Qr were frequently found in individual cases. A distinction was made between the total number of abnormalities and deficiency abnormalities. The total number of abnormalties was high in all three stages. Deficiency abnormalities were relatively rare in stages I and II, and frequent in stage III. The correlation between radiological and regional functional abnormalities was low. TCO SB/VA was found significantly lower (P less than 0.005) in subjects with regional deficiency abnormalities (mostly perfusion abnormalities). These data probably indicate that a lowered diffusing capacity may be due to the loss of pulmonary capillaries and not only to ventilation - perfusion disparities.