Jean J. Chen1, G. Bruce Pike1
1McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, Quebec, Canada
The effect of CO2 on cerebral metabolism is of great interest, since hypercapnia is routinely used in calibrated BOLD-based δCMRo2 estimation and assumes that CMRo2 remains unchanged during hypercapnia-induced blood flow increase. Certain anesthetized-animal studies, however, have put this claim under question, necessitating its verification in humans and under the conditions customary of calibrated BOLD. We report, for the first time, on steady-state global δCMRo2 measurements in awake humans during graded hypercapnia and hypocapnia. Our results show that under the mild levels of end-tidal CO2 changes commonly used in calibrated BOLD, there is negligible global δCMRo2.