Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia.

@article{Coverdale2014CerebralBF,
  title={Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia.},
  author={Nicole S. Coverdale and Joseph S. Gati and Oksana Opalevych and Amanda Perrotta and Joel Kevin Shoemaker},
  journal={Journal of applied physiology},
  year={2014},
  volume={117 10},
  pages={
          1090-6
        }
}
To establish the accuracy of transcranial Doppler ultrasound (TCD) measures of middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) as a surrogate of cerebral blood flow (CBF) during hypercapnia (HC) and hypocapnia (HO), we examined whether the cross-sectional area (CSA) of the MCA changed during HC or HO and whether TCD-based estimates of CBFV were equivalent to estimates from phase contrast (PC) magnetic resonance imaging. MCA CSA was measured from 3T magnetic resonance images… 
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Impact of age on cerebrovascular dilation versus reactivity to hypercapnia
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The central hemodynamic response tohypercapnia compensated for a diminished dilatory response downstream from the MCA so that the CBF response to hypercapnia per unit of brain mass was not affected by age.
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