Failure of vasoldilator infusion to alter pulmonary diffusing capacity in systemic sclerosis.

PURPOSE: Patients with systemic sclerosis (SSc) do not exhibit a normal increase in the diffusing capacity for carbon monoxide (DLCO) on assuming the supine position. We sought to determine whether a potent prostacyclin derivative and vasodilator, iloprost, would reverse this defect. PATIENTS AND METHODS: Fourteen patients with SSc were enrolled in a randomized, double-blind, placebo-controlled study of iloprost. Patients were tested before and during 3 days of iloprost or placebo infusion with both upright and supine pulmonary function studies. RESULTS: The results of baseline pulmonary function studies including DLCO were not significantly altered by iloprost. Furthermore, iloprost did not alter the abnormal postural DLCO response. CONCLUSION: These results suggest that the pulmonary vascular defects seen in this group of patients are not a consequence of reversible pulmonary vasospasm.