Abstract #3858

Cerebrovascular Reactivity Assessment with O2-CO2 Exchange Ratio Under Brief Breath Hold Challenge

Suk-tak Chan¹, Karleyton C Evans², Tian-yue Song¹, Juliette Selb¹, Andre van Kouwe¹, Bruce R Rosen¹, Yong-ping Zheng³, Andrew C Ahn¹, and Kenneth K Kwong¹

¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, ²Biogen Inc., Cambridge, MA, United States, ³Biomedical Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong

Here we tested the hypothesis that the cerebrovascular responses to brief breath hold epochs were coupled not only with increased partial pressure of carbon dioxide (PCO₂), but also with decreased partial pressure of oxygen (PO₂). fMRI map of cerebrovascular reactivity (CVR) to breath-by-breath O₂-CO₂ exchange ratio covers similar regions as map of CVR to exogenous CO₂ challenge. Substantially fewer regions in fMRI map of CVR to endogenous end-tidal CO₂ satisfied statistical significance. Our results support the hypothesis that hypoxia and hypercapnia work synergistically to enhance cerebrovascular responses to breath hold.

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