Brain Blood Flow: Age and Gender

Participants will undergo a MRI scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory rate and PetCO2 will be measured.

Participants will undergo a TCD scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory and PetCO2 will be measured.