Q: Cerebral blood flow (CBF) decreases by what percentage per drop of each mm Hg in the arterial partial pressure of carbon dioxide (PaCO2)?
Answer: 2%
The objective of the above question is to highlight the relationship between respiratory alkalosis (R-Al) and cerebral blood flow. Hypocapnia in R-Al causes cerebral artery vasoconstriction, resulting in reduced cerebral blood flow.
CBF decreases by 2% for every 1 mm Hg drop in PaCO2.
#pulmonary
#neurology
#acid-base
Recommended reads:
1. Yoon S, Zuccarello M, Rapoport RM. pCO(2) and pH regulation of cerebral blood flow. Front Physiol. 2012;3:365. Published 2012 Sep 14. doi:10.3389/fphys.2012.00365
2. Ito H, Kanno I, Ibaraki M, Hatazawa J, Miura S.Changes in human cerebral blood flow and cerebral blood volume during hypercapnia and hypocapnia measured by positron emission tomography.
J Cereb Blood Flow Metab. 2003 Jun;23(6):665-70.
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