Ventilation–perfusion relationships in pulmonary arterial hypertension: Effect of intravenous and inhaled prostacyclin treatment

In seven patients with idiopathic or secondary pulmonary arterial hypertension (PAH), ventilation–perfusion (V˙A/Q˙) relationships were measured during a right heart catheterization using the multiple inert-gas elimination technique before and during intravenous infusion with epoprostenol (EPO), and following 5 months of 20 μg inhaled iloprost taken three times daily (ILO).Pre-treatment pulmonary vascular resistance (PVR) was 9.3 ± 5.0 mmHg/l/min and the dispersion of perfusion and ventilation for V˙A/Q˙-ratios was increased. EPO reduced PVR by 20%, and increased cardiac output, shunt, and mixed venous oxygenation (Sv¯O2). The arterial oxygen tension (PaO2PaO2) remained unchanged.Basal central haemodynamics did not change after 5 months of ILO. Fifteen minutes after ILO, PVR decreased by 20%, and the shunt, Sv¯O2, and PaO2PaO2 remained unaltered.ConclusionsIn secondary PAH with normal lung volumes, significant V˙A/Q˙ mismatching occurred. The PVR was reduced to a similar degree during EPO and after ILO, but only EPO increased the shunt and Sv¯O2. EPO and ILO did not significantly affect the PaO2PaO2.