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Interpretation of clinically significant changes in total cerebral blood flow (CBF) can be confounded by normal variability in flow measures. We assessed the effects of resting end-tidal CO2 (PETCO2) on inter-session variability in total CBF as measured with phase contrast MRI. Participants were scanned twice, 1-3 weeks apart, with PETCO2 clamped at resting physiology. Clamping PETCO2 at participants’ resting respiratory physiology does not notably improve inter-session variability in flow, which was found to be consistent with previously reported values. Furthermore, inter-session changes in resting PETCO2 did not help to explain noted variability in total CBF.
Johnson et al. (Wed,) studied this question.