Abstract #4116

Interpreting patterns of BOLD responses to carbon dioxide through flow resistance

James Duffin^1,2, Olivia Sobczyk³, Adrian P Crawley⁴, Julien Poublanc⁴, Paul Dufort³, Lashmi Venkatraghavan⁵, David J Mikulis^3,4, and Joseph A Fisher^1,2,3

¹Department of Physiology, University of Toronto, Toronto, ON, Canada, ²Departments of Anaesthesia, University Health Network, Toronto, ON, Canada, ³Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada, ⁴Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada, ⁵Department of Anaesthesia, University Health Network, Toronto, ON, Canada

The patterns of BOLD changes in response to a ramp CO₂ stimulus ranging from hypocapnia to hypercapnia can be classified into four types, based on the two linear slopes fitted to each range. We describe the physiology underlying the different response patterns using a simple model of two vascular beds competing for the same limited blood supply; deriving the sigmoidal resistance changes in each branch of the model from measured BOLD responses. We illustrate the use of the model to analyse the BOLD responses in an example patient.

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