The impact of gas exchange measurement during exercise in pulmonary sarcoidosis

Abstract

Pulmonary sarcoidosis shows a remarkable heterogeneity of phenotypes ranging from bihilar lymphadenopathy to progressive fibrosis. Individual disease assessment is demanding and requires sensible, practical measures. We tested whether gas exchange measurements during exercise reflects disease activity and clinical course in sarcoidosis. In 149 patients with proven pulmonary sarcoidosis the alveolar-arterial oxygen pressure gradient (P(A-a)O(2)) during exercise was assessed and compared with chest X-ray typing, pulmonary function, single breath-diffusing capacity for carbon monoxide (DL(CO)), serological markers, cell composition of bronchoalveolar lavage fluid (BALF) and clinical course. Patients were categorized according to thresholds of P(A-a)O(2) during exercise. Chest X-ray typing, pulmonary function, DL(CO) and the need for immunosuppressive treatment differed between the disease categories based on P(A-a)O(2) during exercise (p<0.0001 each). Patients with an impairment of gas exchange during exercise also showed elevated levels of neopterin (p=0.002) and higher percentages of neutrophils (p=0.013) and eosinophils (p<0.0001) in BALF. Multivariate regression analysis showed that forced vital capacity (FVC) (p=0.009) and P(A-a)O(2) during exercise (p<0.0001) were independently associated with a prolonged need for immunosuppressive treatment (>1 year), but not DL(CO). About 50% (n=75) of the study population showed a normal spirometry. Even in this subgroup 23% had an impaired gas exchange during exercise, which correlated with chest X-ray types (p<0.0001) and the need for immunosuppressive treatment (p<0.005). Impaired gas exchange during exercise reflects disease activity and its extent and is associated with a prolonged need for immunosuppressive treatment during follow-up in patients with pulmonary sarcoidosis.