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Transcranial Doppler Estimation Of Cerebral Blood Flow And Cerebrovascular Conductance During Modified Rebreathing, Jurgen A.H.R. Claassen, Rong Zhang, Qi Fu, Sarah Witkowski, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO2 (PETCO2) under steady-state conditions. However, the cerebral blood flow (CBF)-PETCO2 relationship is nonlinear, even for moderate changes in CO2. Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and PETCO2. Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O2 to maintain arterial oxygen saturation constant. To minimize effects of changes …