Effects of supplemental O2 inhalation on cerebral oxygenation during exercise in patients with left ventricular dysfunction

Abstract

Background: It has been recently reported that cerebral oxyhemoglobin (O2Hb) decreases during exercise in nearly 50% of patients with dilated cardiomyopathy. The present study evaluated whether the inhalation of supplemental O2 diminishes the decrease in cerebral O2Hb during exercise. Methods and Results: Ten patients with a left ventricular ejection fraction <50% and a clearly observable decrease in cerebral O 2Hb during preliminary exercise testing underwent 2 additional symptom-limited incremental exercise tests: 1 while breathing room air (control) and the other while breathing 50% O2. In the latter test, the switch from room air to 50% O2 was performed, on average, at 43.0±14.2 W. Cerebral O2Hb was continuously monitored during exercise using near-infrared spectroscopy. In the control exercise test, cerebral O2Hb gradually decreased as the work rate increased in all the subjects. When the subjects breathed 50% O2, this decrease in cerebral O2Hb was diminished. The change in cerebral O2Hb from rest to peak exercise during the test under 50% O2 was significantly higher than that during the control test (-0.23±1.89 vs -2.47±1.57 μmol/L, p=0.002). Similarly, the change in the cerebral tissue oxygenation index was significantly higher in the test under 50% O 2 (0.45±4.46 vs -3.33±3.06%, p=0.023). Conclusions: Impaired cerebral oxygenation during moderate to heavy intensity exercise in patients with left ventricular dysfunction can be offset by breathing supplemental O2.