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Revisit on the cerebrovascular responses to end-tidal CO2 fluctuations during spontaneous breathing as a surrogate of regional cerebrovascular reactivity assessment under hypercapnic challenge

Suk-tak Chan¹, Karleyton C. Evans², Tian-yue Song¹, Andre van der Kouwe¹, Bruce R. Rosen¹, Yong-ping Zheng³, and Kenneth K. Kwong¹
¹Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Biogen, Inc., Cambridge, MA, United States, ³Department of Biomedical Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong

CVR to endogenous CO2 at rest showed significant inter-subject variability and was substantially different from CVR to external CO2 challenge. Such inter-subject variability, not reduced by correction of respiratory effects, also showed up less prominently in CVR to endogenous O2 at rest.

Fig 1. Individual CVR maps show significant CVR changes under external CO2 challenges (n=11) (1st row). Individual CVR maps to endogenous maps showed significant inter-subject variability (2nd row). Such inter-subject variability was not reduced by correction of respiratory effects using RETROICOR (3rd row). CVR maps to endogenous O2 show less inter-subject variability than CVR maps to endogenous CO2 (4th row).