Lack of effect of increased inspired oxygen concentrations on maximal exercise capacity or ventilation in stable heart failure

Recent uncontrolled studies have suggested improved maximal exercise capaci ty and decreased exercise ventilation in heart failure after administration of increased inspired oxygen concentrations. To study the responses furthe r, 16 patients performed staged, symptom-limited cycle ergometry with humid ified 21% and 60% inspired oxygen concentrations using a randomized, double -blind, crossover study design. Serial measurements of minute ventilation, heart rate, blood pressure, leg blood flow, and arterial and venous lactate and oxygen content were obtained. Exercise time did not change between the 2 tests (595 +/- 179 seconds and 602 +/- 181 seconds For 21% and 60% oxyge n concentrations, respectively). Similarly, measurements of the ventilatory response to exercise and of leg blood flow were not different between the 2 oxygen concentrations. Although hemoglobin oxygen saturation increased fr om 96.7 +/- 2.1% to 97.9 +/- 1.5% at rest, at both rest and maximal exercis e there was no statistically significant difference in arterial or venous o xygen content. This study failed to demonstrate any physiologic or function al benefit from the administration of increased oxygen concentrations to pa tients with stable heart failure. (C) 1999 by Excerpta Medico, Inc.