Changes in cerebral blood flow and vasoreactivity to CO2 measured by arterial spin labeling after 6Â days at 4350Â m

► Cerebral blood flow (CBF) and vasoreactivity (CVR) may change at high altitude. ► Arterial spin labeling (ASL) was used to clarify these cerebral hemodynamic changes. ► CBF was increased and CO2 CVR decreased immediately after 6 days at 4350 m. ► Significant hemodynamic changes persist at sea level following a high altitude stay.