Hyperthermia modulates regional differences in cerebral blood flow to changes in CO2.The purpose of this study was to assess blood flow responses to changes in carbon dioxide (CO2) in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) during normothermic and hyperthermic conditions.  Eleven healthy subjects aged 22 ± 2 (SD) yr were exposed to passive whole body heating followed by spontaneous hypocapnic and hypercapnic challenges in normothermic and hyperthermic conditions.  Regardless of the thermal conditions, ICA and VA blood flows and MCA Vmean were decreased by hypocapnic challenges and increased by hypercapnic challenges.  Similar responses in ECA blood flow were observed in hyperthermia but not in normothermia.  These results indicate that hyperthermia is capable of altering dynamic cerebral blood flow regulation.
THERM