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Abstract #4116

Interpreting patterns of BOLD responses to carbon dioxide through flow resistance

James Duffin1,2, Olivia Sobczyk3, Adrian P Crawley4, Julien Poublanc4, Paul Dufort3, Lashmi Venkatraghavan5, David J Mikulis3,4, and Joseph A Fisher1,2,3

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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