Abstract #0762

Graded hypercapnia-calibrated BOLD: Beyond the iso-metabolic hypercapnia assumption

Ian D Driver¹, Richard G Wise¹, and Kevin Murphy¹

¹CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom

We propose a method for correcting for bias introduced by an iso-metabolic assumption in hypercapnia calibrated BOLD studies. A graded hypercapnia design and an assumption of linear CMRO₂ dependence on hypercapnia level are used to separate the calibration parameter M from CMRO₂ changes during hypercapnia. This method avoids intra-subject and experimental variability introduced by making a prior assumption of iso-metabolism or a CMRO₂ decrease with hypercapnia based on literature values. We implement this method using two distinct levels of hypercapnia, measuring lower M values than when making the iso-metabolic assumption, with a significant dose-wise reduction in CMRO₂ with hypercapnia level.

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