Document Detail


Peripheral chemoreceptor contributions to sympathetic and cardiovascular responses during hypercapnia.
MedLine Citation:
PMID:  12564639     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We tested the hypothesis that integrated sympathetic and cardiovascular reflexes are modulated by systemic CO2 differently in hypoxia than in hyperoxia (n = 7). Subjects performed a CO2 rebreathe protocol that equilibrates CO2 partial pressures between arterial and venous blood and that elevates end tidal CO2 (PET(CO2)) from approximately 40 to approximately 58 mmHg. This test was repeated under conditions where end tidal oxygen levels were clamped at 50 (hypoxia) or 200 (hyperoxia) mmHg. Heart rate (HR; EKG), stroke volume (SV; Doppler ultrasound), blood pressure (MAP; finger plethysmograph), and muscle sympathetic nerve activity (MSNA) were measured continuously during the two protocols. MAP at 40 mmHg PET(CO2) (i.e., the first minute of the rebreathe) was greater during hypoxia versus hyperoxia (P < 0.05). However, the increase in MAP during the rebreathe (P < 0.05) was similar in hypoxia (16 +/- 3 mmHg) and hyperoxia (17 +/- 2 mmHg PET(CO2)). The increase in cardiac output (Q) at 55 mmHg PET(CO2) was greater in hypoxia (2.61 +/- 0.7 L/min) versus hyperoxia (1.09 +/- 0.44 L/min) (P < 0.05). In both conditions the increase in Q was due to elevations in both HR and SV (P < 0.05). Systemic vascular conductance (SVC) increased to similar absolute levels in both conditions but rose earlier during hypoxia (> 50 mmHg PET(CO2)) than hyperoxia (> 55 mmHg). MSNA increased earlier during hypoxic hypercapnia (> 45 mmHg) compared with hyperoxic hypercapnia (> 55 mmHg). Thus, in these conscious humans, the dose-response effect of PET(CO2) on the integrated cardiovascular responses was shifted to the left during hypoxic hypercapnia. The combined data indicate that peripheral chemoreceptors exert important influence over cardiovascular reflex responses to hypercapnia.
Authors:
J K Shoemaker; A Vovk; D A Cunningham
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Canadian journal of physiology and pharmacology     Volume:  80     ISSN:  0008-4212     ISO Abbreviation:  Can. J. Physiol. Pharmacol.     Publication Date:  2002 Dec 
Date Detail:
Created Date:  2003-02-04     Completed Date:  2003-08-13     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0372712     Medline TA:  Can J Physiol Pharmacol     Country:  Canada    
Other Details:
Languages:  eng     Pagination:  1136-44     Citation Subset:  IM    
Affiliation:
Neurovascular Research Laboratory, Room 3110, Thames Hall, School of Kinesiology, The University of Western Ontario, London, ON N6A 3K7, Canada. kshoemak@uwo.ca
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MeSH Terms
Descriptor/Qualifier:
Adrenergic Fibers / drug effects,  physiology*
Adult
Analysis of Variance
Carbon Dioxide / pharmacology
Cardiovascular System / drug effects
Chemoreceptor Cells / physiology*
Female
Hemodynamics / drug effects,  physiology*
Humans
Hypercapnia / chemically induced,  physiopathology*
Hyperventilation / chemically induced,  physiopathology
Male
Chemical
Reg. No./Substance:
124-38-9/Carbon Dioxide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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