| Role of the autonomic nervous system in the reduced maximal cardiac output at altitude. | |
| | |
MedLine Citation:
|
PMID: 12070214 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
After acclimatization to high altitude, maximal exercise cardiac output (QT) is reduced. Possible contributing factors include 1) blood volume depletion, 2) increased blood viscosity, 3) myocardial hypoxia, 4) altered autonomic nervous system (ANS) function affecting maximal heart rate (HR), and 5) reduced flow demand from reduced muscle work capability. We tested the role of the ANS reduction of HR in this phenomenon in five normal subjects by separately blocking the sympathetic and parasympathetic arms of the ANS during maximal exercise after 2-wk acclimatization at 3,800 m to alter maximal HR. We used intravenous doses of 8.0 mg of propranolol and 0.8 mg of glycopyrrolate, respectively. At altitude, peak HR was 170 +/- 6 beats/min, reduced from 186 +/- 3 beats/min (P = 0.012) at sea level. Propranolol further reduced peak HR to 139 +/- 2 beats/min (P = 0.001), whereas glycopyrrolate increased peak HR to sea level values, 184 +/- 3 beats/min, confirming adequate dosing with each drug. In contrast, peak O(2) consumption, work rate, and QT were similar at altitude under all drug treatments [peak QT = 16.2 +/- 1.2 (control), 15.5 +/- 1.3 (propranolol), and 16.2 +/- 1.1 l/min (glycopyrrolate)]. All QT results at altitude were lower than those at sea level (20.0 +/- 1.8 l/min in air). Therefore, this study suggests that, whereas the ANS may affect HR at altitude, peak QT is unaffected by ANS blockade. We conclude that the effect of altered ANS function on HR is not the cause of the reduced maximal QT at altitude. |
| | |
Authors:
|
Harm J Bogaard; Susan R Hopkins; Yoshiki Yamaya; Kyuichi Niizeki; Michael G Ziegler; Peter D Wagner |
Related Documents
:
|
10694114 - Blood volume: importance and adaptations to exercise training, environmental stresses, ... 17173514 - Acetazolamide improves cerebral oxygenation during exercise at high altitude. 7698854 - Cardio-pulmonary function of cyclists competing on an ascending mountain course between... 8543384 - Estimation of the degree of acclimatization to high altitude by a rapid and simple phys... 1319684 - Control of fructose 2,6-diphosphate in muscle of exercising fasted rats. 21611824 - Comparisons of local and systemic aerobic fitness parameters between finswimmers with d... |
Publication Detail:
|
Type: Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
|
Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 93 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2002 Jul |
Date Detail:
|
Created Date: 2002-06-18 Completed Date: 2002-12-17 Revised Date: 2007-11-14 |
Medline Journal Info:
|
Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
|
Languages: eng Pagination: 271-9 Citation Subset: IM |
Affiliation:
|
Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla 92093, USA. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Acclimatization
/
physiology Acetylene / diagnostic use Adrenergic beta-Antagonists / pharmacology Adult Altitude* Autonomic Nervous System / physiology* Cardiac Output / physiology* Female Glycopyrrolate / pharmacology Heart Rate / physiology Humans Male Muscarinic Antagonists / pharmacology Oxygen Consumption / physiology Propranolol / pharmacology Stroke Volume / physiology |
| Grant Support | |
ID/Acronym/Agency:
|
HL-17731/HL/NHLBI NIH HHS; M01 RR-00827/RR/NCRR NIH HHS |
| Chemical | |
Reg. No./Substance:
|
0/Adrenergic beta-Antagonists; 0/Muscarinic Antagonists; 525-66-6/Propranolol; 596-51-0/Glycopyrrolate; 74-86-2/Acetylene |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Airway and tissue mechanics in a murine model of asthma: alveolar capsule vs. forced oscillations.
Next Document: Altered frequency responses of sympathetic nerve discharge bursts after IL-1beta and mild hypothermi...