Abstract #0053

Influence of end-tidal CO2 on cerebrovascular reactivity mapping: within-subject and across-subject effects

Jill Britt De Vis¹, Xirui Hou¹, Peiying Liu¹, Zheyu Wang², Siyuan Cheng², Yang Li¹, Harshan Ravi³, and Hanzhang Lu¹

¹Division of MR Research, Johns Hopkins University, Baltimore, MD, United States, ²Johns Hopkins University, Baltimore, MD, United States, ³National Institutes of Health, Bethesda, MD, United States

The relationship between end-tidal (Et) CO₂, and the output measure, BOLD signal, is highly non-linear, due to both physiological non-linearity between cerebral blood flow (CBF) and CO₂ as well as biophysical non-linearity between CBF and BOLD. In this study, we found that, across subjects, baseline EtCO₂ and ΔEtCO₂ inversely influenced the measured CVR values. Therefore, these factors should be taken into account when comparing CVR between groups or patients. However, these inter-subject differences appear to have an independent physiological underpinning, as manipulations of these factors within the subject did not seem to have an effect on the measured CVR values.

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