Oxygen therapy titrated to raise mixed venous oxygen content in COPD

Supplemental oxygen therapy delivered at concentrations which increase PaO2 greater than 60 mm Hg often has minimal effects on either pulmonary hemodynamics or the oxygen tension of mixed venous blood (PvO2). Since mixed venous hypoxemia has been shown to contribute to pulmonary vasoconstriction in experimental conditions and is a determinant of survival in chronic obstructive pulmonary disease (COPD), we evaluated the hemodynamic effects of oxygen therapy titrated to raise PvO2 in 12 COPD patients who underwent right heart catheterization. After room air measurements of mean pulmonary artery pressure, cardia output, and pulmonary vascular resistance, they were randomized to either supplemental oxygen therapy given to raise PaO2 greater than or equal to 60 mm Hg (group 1, n = 6) or to raise PvO2 greater than or equal to 36 mm Hg (group 2, n = 6). An oxygen-conserving nasal cannula and oxygen concentrator were used. Baseline PaO2, PvO2, and hemodynamics were identical in each group and hemodynamics after four hours and 48 hours of continuous oxygen therapy were unchanged. Ten patients were catheterized after four months of continuous oxygen therapy (group 1, n = 4; group 2, n = 6). Although PvO2 in group 2 had been raised to normal levels (39.2 +/- 1.2 mm Hg), there was no significant improvement in pulmonary hemodynamics. Our preliminary study suggests that oxygen titrated to raise PvO2 to the normal range has no greater hemodynamic effect than oxygen therapy as it is currently prescribed.