Document Detail

Regional brain blood flow in man during acute changes in arterial blood gases.
MedLine Citation:
PMID:  22495584     Owner:  NLM     Status:  MEDLINE    
Despite the importance of blood flow on brainstem control of respiratory and autonomic function, little is known about regional cerebral blood flow (CBF) during changes in arterial blood gases.We quantified: (1) anterior and posterior CBF and reactivity through a wide range of steady-state changes in the partial pressures of CO2 (PaCO2) and O2 (PaO2) in arterial blood, and (2) determined if the internal carotid artery (ICA) and vertebral artery (VA) change diameter through the same range.We used near-concurrent vascular ultrasound measures of flow through the ICA and VA, and blood velocity in their downstream arteries (the middle (MCA) and posterior (PCA) cerebral arteries). Part A (n =16) examined iso-oxic changes in PaCO2, consisting of three hypocapnic stages (PaCO2 =∼15, ∼20 and ∼30 mmHg) and four hypercapnic stages (PaCO2 =∼50, ∼55, ∼60 and ∼65 mmHg). In Part B (n =10), during isocapnia, PaO2 was decreased to ∼60, ∼44, and ∼35 mmHg and increased to ∼320 mmHg and ∼430 mmHg. Stages lasted ∼15 min. Intra-arterial pressure was measured continuously; arterial blood gases were sampled at the end of each stage. There were three principal findings. (1) Regional reactivity: the VA reactivity to hypocapnia was larger than the ICA, MCA and PCA; hypercapnic reactivity was similar.With profound hypoxia (35 mmHg) the relative increase in VA flow was 50% greater than the other vessels. (2) Neck vessel diameters: changes in diameter (∼25%) of the ICA was positively related to changes in PaCO2 (R2, 0.63±0.26; P<0.05); VA diameter was unaltered in response to changed PaCO2 but yielded a diameter increase of +9% with severe hypoxia. (3) Intra- vs. extra-cerebral measures: MCA and PCA blood velocities yielded smaller reactivities and estimates of flow than VA and ICA flow. The findings respectively indicate: (1) disparate blood flow regulation to the brainstem and cortex; (2) cerebrovascular resistance is not solely modulated at the level of the arteriolar pial vessels; and (3) transcranial Doppler ultrasound may underestimate measurements of CBF during extreme hypoxia and/or hypercapnia.
C K Willie; D B Macleod; A D Shaw; K J Smith; Y C Tzeng; N D Eves; K Ikeda; J Graham; N C Lewis; T A Day; P N Ainslie
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-04-10
Journal Detail:
Title:  The Journal of physiology     Volume:  590     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-07-24     Completed Date:  2012-11-30     Revised Date:  2013-07-16    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3261-75     Citation Subset:  IM    
School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan Campus, Canada, 3333 University Way, Kelowna, BC Canada V1V 1V7.
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MeSH Terms
Anoxia / blood*,  ultrasonography
Blood Flow Velocity / physiology
Blood Gas Analysis
Brain / blood supply*
Carotid Artery, Internal / ultrasonography
Cerebral Arteries / ultrasonography
Hypercapnia / blood*,  ultrasonography
Hypocapnia / blood*,  ultrasonography
Regional Blood Flow / physiology
Ultrasonography, Doppler, Transcranial
Vasoconstriction / physiology
Vasodilation / physiology
Vertebral Artery / ultrasonography
Comment In:
J Physiol. 2012 Jul 15;590(Pt 14):3217   [PMID:  22826302 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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