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Abstract #0181

Robustly Accounting for Vascular Reactivity Differences Across Subjects Using Breath-Hold

Kevin Murphy1, Ashley D. Harris1, Richard G. Wise1

1CUBRIC, Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff, United Kingdom

Separating BOLD vascular and metabolic responses is often achieved using hypercapnic challenges. A simple way of elevating blood CO2 concentrations to measure vascular reactivity is breath-holding. Two aspects of this vascular reactivity measure are often neglected: breath-holds are usually modelled as blocks even though CO2 accumulates over time and increases in CO2 differ between subjects, both of which must be considered when using vascular reactivity as a calibration tool. This study determines that the appropriate model for the BOLD breath-hold response is derived from end-tidal CO2 traces and that individual differences in CO2 increases must be taken into account.