Abstract #4329

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

Regional cerebraovascular reactivity (CVR) to endogenous carbon dioxide (CO₂) during spontaneous breathing (i.e. end-tidal partial pressure of CO2 (P_ETCO₂) measured at rest), was substantially different from that obtained under externally applied CO₂ challenge. Individual maps of CVR to endogenous CO₂ showed significant inter-subject variability while CVR maps under hypercapnic challenge did not. Such inter-subject variability was not reduced by correction of respiratory effects. In addition, the CVR to end-tidal partial pressure of oxygen (P_ETO₂) during spontaneous breathing shows less inter-subject variability. Our findings question the compatibility of using CVR during spontaneous breathing as a surrogate of CVR under hypercapnic challenge.

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