Document Detail


Intermittent hypoxia reduces cerebrovascular sensitivity to isocapnic hypoxia in humans.
MedLine Citation:
PMID:  18206428     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The purpose of this study was to determine the changes in human cerebrovascular function associated with intermittent poikilocapnic hypoxia (IH). Healthy men (n=8; 24+/-1 years) were exposed to IH for 10 days (12% O(2) for 5min followed by 5min of normoxia for 1h). During the hypoxic exposures, oxyhemoglobin saturation (SaO(2)) was 85% and the end-tidal partial pressure of CO(2) was permitted to fall as a result of hypoxic hyperventilation. Pre- and post-IH intervention subjects underwent a progressive isocapnic hypoxic test where ventilation, blood pressure, heart rate, and cerebral blood flow velocity (middle cerebral artery, transcranial Doppler) were measured to determine the ventilatory, cardiovascular and cerebrovascular sensitivities to isocapnic hypoxia. When compared to the pre-IH trial, cerebrovascular sensitivity to hypoxia significantly decreased (pre-IH=0.28+/-0.15; post-IH=0.16+/-0.14cms(-1)%SaO(2)(-1); P<0.05). No changes in ventilatory, blood pressure or heart rate sensitivity were observed (P>0.05). We have previously shown that the ability to oxygenate cerebral tissue measured using spatially resolved near infrared spectroscopy is significantly reduced following IH in healthy humans. Our collective findings indicate that intermittent hypoxia can blunt cerebrovascular regulation. Thus, it appears that intermittent hypoxia has direct cerebrovascular effects that can occur in the absence of changes to the ventilatory and neurovascular control systems.
Authors:
Jordan S Querido; Jesse B Godwin; A William Sheel
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-11-17
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  161     ISSN:  1569-9048     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2008 Mar 
Date Detail:
Created Date:  2008-03-10     Completed Date:  2008-06-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  1-9     Citation Subset:  IM    
Affiliation:
School of Human Kinetics, The University of British Columbia, Vancouver, British Columbia, Canada.
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MeSH Terms
Descriptor/Qualifier:
Anoxia / physiopathology*
Blood Pressure / physiology*
Brain / blood supply
Cerebrovascular Circulation / physiology*
Heart Rate / physiology*
Humans
Male
Pulmonary Ventilation / physiology*

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