| The effect of oxygen on dynamic cerebral autoregulation: critical role of hypocapnia. | |
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MedLine Citation:
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PMID: 20056845 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Hypoxia is known to impair cerebral autoregulation (CA). Previous studies indicate that CA is profoundly affected by cerebrovascular tone, which is largely determined by the partial pressure of arterial O(2) and CO(2). However, hypoxic-induced hyperventilation via respiratory chemoreflex activation causes hypocapnia, which may influence CA independent of partial pressure of arterial O(2). To identify the effect of O(2) on dynamic cerebral blood flow regulation, we examined the influence of normoxia, isocapnia hyperoxia, hypoxia, and hypoxia with consequent hypocapnia on dynamic CA. We measured heart rate, blood pressure, ventilatory parameters, and middle cerebral artery blood velocity (transcranial Doppler). Dynamic CA was assessed (n = 9) during each of four randomly assigned respiratory interventions: 1) normoxia (21% O(2)); 2) isocapnic hyperoxia (40% O(2)); 3) isocapnic hypoxia (14% O(2)); and 4) hypocapnic hypoxia (14% O(2)). During each condition, the rate of cerebral regulation (RoR), an established index of dynamic CA, was estimated during bilateral thigh cuff-induced transient hypotension. The RoR was unaltered during isocapnic hyperoxia. Isocapnic hypoxia attenuated the RoR (0.202 +/- 0.003/s; 27%; P = 0.043), indicating impairment in dynamic CA. In contrast, hypocapnic hypoxia increased RoR (0.444 +/- 0.069/s) from normoxia (0.311 +/- 0.054/s; +55%; P = 0.041). These findings indicated that hypoxia disrupts dynamic CA, but hypocapnia augments the dynamic CA response. Because hypocapnia is a consequence of hypoxic-induced chemoreflex activation, it may provide a teleological means to effectively maintain dynamic CA in the face of prevailing arterial hypoxemia. |
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Authors:
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Shigehiko Ogoh; Hidehiro Nakahara; Philip N Ainslie; Tadayoshi Miyamoto |
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Publication Detail:
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Type: Comparative Study; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't Date: 2010-01-07 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 108 ISSN: 1522-1601 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2010 Mar |
Date Detail:
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Created Date: 2010-03-17 Completed Date: 2010-06-04 Revised Date: 2010-10-19 |
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: 538-43 Citation Subset: IM |
Affiliation:
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Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan. ogoh@toyonet.toyo.ac.jp |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adolescent Adult Anoxia / blood, physiopathology*, ultrasonography Blood Flow Velocity Blood Pressure Cerebrovascular Circulation* Heart Rate Homeostasis Humans Hyperoxia / blood, physiopathology*, ultrasonography Hypocapnia / blood, physiopathology*, ultrasonography Male Middle Cerebral Artery / physiopathology*, ultrasonography Oxygen / blood* Thigh / blood supply Time Factors Ultrasonography, Doppler, Transcranial Young Adult |
| Chemical | |
Reg. No./Substance:
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7782-44-7/Oxygen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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