Failure of vasodilator 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 (DL_CO) 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, doubleblind, placebo-controlled study of iloprost. Patients were tested before and during 3 days of Uoprost or placebo infusion with both upright and supine pulmonary function studies. Results: The results of baseline pulmonary function studies including DL_CO were not significantly altered by iloprost Furthermore, iloprost did not alter the abnormal postural DL_CO response. Conclusion: These results suggest that the pulmonary vascular defects seen in this group of patients are not a consequence of reversible pulmonary vasospasm.