Pulmonary hypertension and right heart failure can complicate the management of the patient with advanced COPD. Attempts to treat this pulmonary hypertension with systemic vasodilators frequently result in a worsening of ventilation perfusion matching and an increase sense of dyspnea. This study will look at the effect of an FDA approved pulmonary vasodilator, iloprost, on gas exchange and pulmonary mechanics in patients with COPD. Ten clinically stable patients will be enrolled. They will report to the lab on the morning of the study and after an arterial line is placed, pulmonary function measurements and arterial blood gases will be obtained. Iloprost (2.5 mcg via nebulizer) will be administered and the effect upon arterial blood pressure, respiration and arterial saturation will be monitored. Pulmonary function tests (PFTs) and blood gases will be repeated after 30 minutes. Patients who remain clinically stable without evidence of a fall in arterial PO2 or systemic blood pressure would inhale a second dose of 2.5 mcg of iloprost. The patient will be monitored for a minimum of 2 hours after their last dose of iloprost. Primary outcome variable will be the alveolar arterial O2 difference while secondary outcomes will include PAO2, venous admixture, FVC and FEV1, DLCO and ventilatory equivalents for O2 and CO2. All comparisons will be made using Student's t-test with a Bonferroni correction. The number of study patients was chosen on the basis of a power analysis to provide an alpha of 0.05 at a level of 0.9.
