| Central volume expansion is pivotal for sustained decrease in heart rate during seated to supine posture change. | |
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MedLine Citation:
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PMID: 11514297 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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During prolonged, static carotid baroreceptor stimulation by neck suction (NS) in seated humans, heart rate (HR) decreases acutely and thereafter gradually increases. This increase has been explained by carotid baroreceptor adaptation and/or buffering by aortic reflexes. During a posture change from seated to supine (Sup) with similar carotid stimulation, however, the decrease in HR is sustained. To investigate whether this discrepancy is caused by changes in central blood volume, we compared (n = 10 subjects) the effects of 10 min of seated NS (adjusted to simulate carotid stimulation of a posture change), a posture change from seated to Sup, and the same posture change with left atrial (LA) diameter maintained unchanged by lower body negative pressure (Sup + LBNP). During Sup, the prompt decreases in HR and mean arterial pressure (MAP) were sustained. HR decreased similarly within 30 s of NS (65 +/- 2 to 59 +/- 2 beats/min) and Sup + LBNP (65 +/- 2 to 58 +/- 2 beats/min) and thereafter gradually increased to values of seated. MAP decreased similarly within 5 min during Sup + LBNP and NS (by 7 +/- 1 to 9 +/- 1 mmHg) and thereafter tended to increase toward values of seated subjects. Arterial pulse pressure was increased the most by Sup, less so by Sup + LBNP, and was unchanged by NS. LA diameter was only increased by Sup. In conclusion, static carotid baroreceptor stimulation per se causes the acute (<30 s) decrease in HR during a posture change from seated to Sup, whereas the central volume expansion (increased LA diameter and/or arterial pulse pressure) is pivotal to sustain this decrease. Thus the effects of central volume expansion override adaptation of the carotid baroreceptors and/or buffering of aortic reflexes. |
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Authors:
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B Pump; T Kamo; A Gabrielsen; P Bie; N J Christensen; P Norsk |
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Publication Detail:
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Type: Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: American journal of physiology. Heart and circulatory physiology Volume: 281 ISSN: 0363-6135 ISO Abbreviation: Am. J. Physiol. Heart Circ. Physiol. Publication Date: 2001 Sep |
Date Detail:
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Created Date: 2001-08-21 Completed Date: 2001-09-20 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 100901228 Medline TA: Am J Physiol Heart Circ Physiol Country: United States |
Other Details:
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Languages: eng Pagination: H1274-9 Citation Subset: IM; S |
Affiliation:
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Danish Aerospace Medical Centre of Research, Rigshospitalet 7805, DK-2200 Copenhagen, Denmark. bpump@post.uni2.dk |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adaptation, Physiological
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physiology Adult Arginine Vasopressin / blood Baroreflex / physiology* Blood Pressure / physiology Blood Volume / physiology* Carotid Arteries / physiology Heart Rate / physiology* Humans Hydrostatic Pressure Leg / blood supply, physiology Male Norepinephrine / blood Physical Stimulation / methods Posture / physiology* Supine Position / physiology |
| Chemical | |
Reg. No./Substance:
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113-79-1/Arginine Vasopressin; 51-41-2/Norepinephrine |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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