VIP and pulmonary arterial hypertension: In a small, prospective, controlled, intraindividual 3-month trial, administration of vasoactive intestinal peptide by inhalation (single 200-μg dose) to patients with PAH has shown a significant decrease in mean pulmonary arterial pressure, pulmonary vascular resistance, and dyspnea score and increased cardiac output, mixed venous oxygen saturation, and 6 min walk distance [90].