| Differential effects of acute hypoxia and high altitude on cerebral blood flow velocity and dynamic cerebral autoregulation: alterations with hyperoxia. | |
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MedLine Citation:
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PMID: 18048592 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We hypothesized that 1) acute severe hypoxia, but not hyperoxia, at sea level would impair dynamic cerebral autoregulation (CA); 2) impairment in CA at high altitude (HA) would be partly restored with hyperoxia; and 3) hyperoxia at HA and would have more influence on blood pressure (BP) and less influence on middle cerebral artery blood flow velocity (MCAv). In healthy volunteers, BP and MCAv were measured continuously during normoxia and in acute hypoxia (inspired O2 fraction = 0.12 and 0.10, respectively; n = 10) or hyperoxia (inspired O2 fraction, 1.0; n = 12). Dynamic CA was assessed using transfer-function gain, phase, and coherence between mean BP and MCAv. Arterial blood gases were also obtained. In matched volunteers, the same variables were measured during air breathing and hyperoxia at low altitude (LA; 1,400 m) and after 1-2 days after arrival at HA ( approximately 5,400 m, n = 10). In acute hypoxia and hyperoxia, BP was unchanged whereas it was decreased during hyperoxia at HA (-11 +/- 4%; P < 0.05 vs. LA). MCAv was unchanged during acute hypoxia and at HA; however, acute hyperoxia caused MCAv to fall to a greater extent than at HA (-12 +/- 3 vs. -5 +/- 4%, respectively; P < 0.05). Whereas CA was unchanged in hyperoxia, gain in the low-frequency range was reduced during acute hypoxia, indicating improvement in CA. In contrast, HA was associated with elevations in transfer-function gain in the very low- and low-frequency range, indicating CA impairment; hyperoxia lowered these elevations by approximately 50% (P < 0.05). Findings indicate that hyperoxia at HA can partially improve CA and lower BP, with little effect on MCAv. |
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Authors:
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Philip N Ainslie; Shigehiko Ogoh; Katie Burgess; Leo Celi; Ken McGrattan; Karen Peebles; Carissa Murrell; Prajan Subedi; Keith R Burgess |
Publication Detail:
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Type: Clinical Trial; Comparative Study; Journal Article; Research Support, Non-U.S. Gov't Date: 2007-11-29 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 104 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2008 Feb |
Date Detail:
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Created Date: 2008-02-11 Completed Date: 2008-04-04 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 490-8 Citation Subset: IM |
Affiliation:
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Dept. of Physiology, Univ. of Otago, Dunedin, New Zealand. philip.ainslie@stonebow.otago.ac.nz |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Acclimatization* Acute Disease Adult Altitude* Anoxia / blood, physiopathology* Blood Flow Velocity Blood Pressure Carbon Dioxide / blood Cerebrovascular Circulation* Cross-Sectional Studies Female Heart Rate Homeostasis Humans Hyperoxia / blood, physiopathology* Male Middle Aged Middle Cerebral Artery / physiopathology* Oxygen / blood Pulmonary Ventilation Respiratory Mechanics Severity of Illness Index Time Factors |
| Chemical | |
Reg. No./Substance:
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124-38-9/Carbon Dioxide; 7782-44-7/Oxygen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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