Acute hemodynamic effects of controlled oxygen therapy in decompensated chronic obstructive pulmonary disease.

The acute effects of controlled O2 therapy on hemodynamics and blood gases were investigated in 22 patients with decompensated chronic obstructive pulmonary disease (COPD). An inspired O2 fraction (FIO2) of 0.24 and 0.28 given to the first 12 patients markedly improved arterial and mixed-venous blood oxygenation with no (FIO2 0.24) or slight (FIO2 0.28) aggravation of hypercapnia, but did not change O2 delivery to the tissues. Higher FIO2 values of 0.35 and 0.40 in the next ten patients improved blood oxygenation even more, together with an increase in O2 delivery to the tissues and a significant aggravation of hypercapnia. All four FIO2 values reduced cardiac output without changing pulmonary vascular resistance. These results suggest that in patients with decompensated COPD, low-flow O2 improves oxygenation by diffusion rather than convection. On the other hand, controlled O2 therapy does not appear to be an immediately effective pulmonary vasodilating treatment in these patients.