Document Detail


Central volume expansion is pivotal for sustained decrease in heart rate during seated to supine posture change.
MedLine Citation:
PMID:  11514297     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
B Pump; T Kamo; A Gabrielsen; P Bie; N J Christensen; P Norsk
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
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:
Created Date:  2001-08-21     Completed Date:  2001-09-20     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H1274-9     Citation Subset:  IM; S    
Affiliation:
Danish Aerospace Medical Centre of Research, Rigshospitalet 7805, DK-2200 Copenhagen, Denmark. bpump@post.uni2.dk
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological / 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:
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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