Single breath nitrogen washout in pulmonary sarcoidosis

In 35 patients with pulmonary sarcoidosis we explored the utility of single breath nitrogen washout as a means for detecting abnormalities in airway function and intrapulmonary distribution of air. Closing volume/vital capacity ratio (CV/VC) was 21% (predicted 12.5%) in patients with only hilar adenopathy (stage I). CV/VC was 21% (predicted 13%) in patients with hilar adenopathy and parenchymal infiltration (stage II). Abnormalities in CV/VC were less readily detectable in patients with parenchymal infiltrates only (stage III) or those with bullous lesions and lung retraction (stage IV). Closing capacity was abnormally high in 66% of the cases. The slope of the alveolar plateau (delta N2/L) increased with disease progression. Single breath nitrogen test provides useful information concerning the function of small airways and distribution of pulmonary ventilation in all stages of sarcoidosis.