Respiratory function in recent pulmonary sarcoidosis with special reference to small airways

Abstract

This study was designed to evaluate airway dysfunction in relation to duration of disease in patients with pulmonary sarcoidosis for less than two years. Twenty four subjects with recent disease were compared with nine subjects with disease of more than two years' duration. They underwent lung function testing (lung volumes, lung transfer factor for CO and pulmonary mechanics). Small airway function was assessed using frequency dependence of compliance, closing volume, nitrogen single breath test and flow-volume curves breathing air and helium-oxygen mixture. Airway dysfunction was seen in pulmonary sarcoidosis even in some patients with recent disease and it became more evident in disease of longer duration. The results suggest small airway involvement. The frequency of airway dysfunction is difficult to evaluate, varying from estimates of 0% using flow-volume curves to 79% with frequency dependence of compliance. This apparent discrepancy could be explained by the consequences of parenchymal involvement leading to inhomogeneities in distribution of compliance, and of elastic lung recoil. We conclude that patients with recent sarcoidosis are probably affected by intrinsic small airway disease, but an increase in elastic recoil often conceals its consequences. The airway disease may not be apparent using conventional function tests and published predicted values.