Document Detail

Cardiorespiratory and cerebrovascular responses to hyperoxic and hypoxic rebreathing: effects of acclimatization to high altitude.
MedLine Citation:
PMID:  18378504     Owner:  NLM     Status:  MEDLINE    
We examined the cardiorespiratory and cerebrovascular responses to hyperoxic and hypoxic rebreathing at low attitude and high altitude. We measured ventilation, middle cerebral artery blood flow velocity (MCAv) and arterial blood pressure in conditions of eucapnia, hypocapnia (voluntary hyperventilation) and during hyperoxic and hypoxic rebreathing firstly at low altitude (1400 m) then again at high altitude (3840 m) in five individuals, following 9 days at altitude >5000 m. High altitude was associated with elevations in the blood pressure response to hyperoxic rebreathing, whilst cerebrovascular reactivity was reduced and ventilatory sensitivity was unchanged. During hypoxic rebreathing, whilst ventilatory and blood pressure reactivity were increased (vs. low altitude and hyperoxic rebreathing), cerebrovascular reactivity was preserved. In conclusion, at high altitude there was an enhancement in peripheral but not central chemosensitivity to CO(2); and during hypoxic rebreathing, marked elevations in blood pressure may restore some of the reduction in cerebrovascular CO(2) reactivity, potentially reflecting a pressure-passive relationship in the brain offsetting sympathetic-induced cerebral vasoconstriction.
Philip N Ainslie; Keith R Burgess
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-02-17
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  161     ISSN:  1569-9048     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-04-28     Completed Date:  2008-07-25     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  201-9     Citation Subset:  IM    
Department of Physiology, University of Otago, Dunedin, New Zealand.
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MeSH Terms
Acclimatization / physiology*
Anoxia / blood*
Blood Flow Velocity / physiology
Blood Pressure / physiology
Carbon Dioxide / blood*
Cerebrovascular Circulation / physiology
Hyperoxia / blood*
Middle Cerebral Artery / physiology
Pulmonary Ventilation / physiology*
Reference Values
Statistics, Nonparametric
Reg. No./Substance:
124-38-9/Carbon Dioxide

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