The confounding effects of O2 on CO2-induced cerebrovascular reactivity as measured with BOLD MRI
Mikulis D, Fisher J, Han J, Prisman E, Rodrigues L, Poublanc J, Crawley A, Mardimae A, Slessarev M
University Health Network
Rapid cyclic changes in end-tidal partial pressures of CO2 (PETCO2) have previously been used to determine cerebrovascular reactivity (CVR) from BOLD MRI. However, the effects of variable end-tidal partial pressures of O2 (PETO2) on BOLD signal are unclear. We cycled PETO2 and PETCO2 to study the effects of variable PETO2 on BOLD signal during CO2-induced CVR. During high CO2 stimulus, increases in PETO2 resulted in an additional increase in BOLD signal beyond that due to CO2 alone. Hence, PETO2 should be carefully controlled during measurements of CVR with BOLD MRI.