Oxygen therapy improves cardiac index and pulmonary vascular resistance in patients with pulmonary hypertension

Study objectives: We tested the hypothesis that breathing 100% oxygen could result in selective pulmonary vasodilatation in patients with pulmonary hypertension, including those patients who would not meet current Health Care Finance Administration guidelines for long-term oxygen therapy. Design, setting, and patients: From 1996 to 1999, 23 adult patients (mean +/- SEM age, 51 +/-4 years) with pulmonary arterial hypertension without left-heart failure underwent cardiac catheterization in a university teaching hospital while breathing air and then 100% oxygen. Measurements and results: Treatment with 100% oxygen increased arterial oxygen saturation (91 +/-1% to 99 +/-0.1%, p<0.05) and Pao(2) (64<plus/minus>3 to 309 +/- 28 min Hg, p<0.05). Treatment with 100% oxygen also decreased mean pulmonary artery pressure (56<plus/minus>3 to 53 +/-2 mm Hg, p<0.05) and increased cardiac index (2.1<plus/minus>0.1 to 2.5 +/-0.2 L/min/m(2), p<0.05). Calculated mean pulmonary vascular resistance (PVR) decreased from 14.1<plus/minus>1.4 to 10.6 +/-1.0 Wood units (p<0.05). Vasodilatation with 100% oxygen occurred preferentially in the pulmonary circulation (PVR/systemic vascular resistance, 0.53<plus/minus>0.04 to 0.48 +/-0.03; p<0.05). The magnitude of the PVR response to oxygen therapy was correlated only with decreasing patient age (r=0.45, p<0.05). Conclusions: Treatment with 100% oxygen is a selective pulmonary vasodilator in patients with pulmonary hypertension, regardless of primary diagnosis, baseline oxygenation, or right ventricular function. Development of disease-specific oxygen prescription guidelines warrants consideration.