Lung function and the response to exercise in systemic sclerosis.

Cardiopulmonary function has been studied at rest and during graded exercise in 11 patients with systemic sclerosis. All patients had multi-system disease, five complained of breathlessness, and four had radiographic evidence of pulmonary fibrosis. All patients had gross effort intolerance. Lung volumes were reduced in half the patients, as was the transfer factor for CO when corrected for lung volume. Airway resistance was normal. Four patients hyperventilated on exercise, but the tidal volume was normal; three developed arterial desaturation during exercise. Six patients had an excessive elevation of blood lactate on exercise and three of these had evidence of muscle disease. Analysis of the exercise data suggested that in seven patients cardiac output and dead space were normal. In four patients there was a pattern of normal cardiac output, increased dead space, and increased venous admixture, suggesting ventilation/perfusion imbalance. There was no correlation between the results of the physiological tests and the extent of clinical involvement with the disease. The possible reasons for this and for the effort intolerance are reviewed.