Document Detail

Hemodynamics and muscle sympathetic nerve activity after 8 h of sustained hypoxia in healthy humans.
MedLine Citation:
PMID:  17873026     Owner:  NLM     Status:  MEDLINE    
Hemodynamics, muscle sympathetic nerve activity (MSNA), and forearm blood flow were evaluated in 12 normal subjects before, during (1 and 7 h), and after ventilatory acclimatization to hypoxia achieved with 8 h of continuous poikilocapnic hypoxia. All results are means +/- SD. Subjects experienced mean oxygen saturation of 84.3 +/- 2.3% during exposure. The exposure resulted in hypoxic acclimatization as suggested by end-tidal CO(2) [44.7 +/- 2.7 (pre) vs. 39.5 +/- 2.2 mmHg (post), P < 0.001] and by ventilatory response to hypoxia [1.2 +/- 0.8 (pre) vs. 2.3 +/- 1.3 l x min(-1).1% fall in saturation(-1) (post), P < 0.05]. Subjects exhibited a significant increase in heart rate across the exposure that remained elevated even upon return to room air breathing compared with preexposure (67.3 +/- 15.9 vs. 59.8 +/- 12.1 beats/min, P < 0.008). Although arterial pressure exhibited a trend toward an increase across the exposure, this did not reach significance. MSNA initially increased from room air to poikilocapnic hypoxia (26.2 +/- 10.3 to 32.0 +/- 10.3 bursts/100 beats, not significant at 1 h of exposure); however, MSNA then decreased below the normoxic baseline despite continued poikilocapnic hypoxia (20.9 +/- 8.0 bursts/100 beats, 7 h Hx vs. 1 h Hx; P < 0.008 at 7 h). MSNA decreased further after subjects returned to room air (16.6 +/- 6.0 bursts/100 beats; P < 0.008 compared with baseline). Forearm conductance increased after exposure from 2.9 +/- 1.5 to 4.3 +/- 1.6 conductance units (P < 0.01). These findings indicate alterations of cardiovascular and respiratory control following 8 h of sustained hypoxia producing not only acclimatization but sympathoinhibition.
Renaud Tamisier; Brian E Hunt; Geoffrey S Gilmartin; Mathew Curley; Amit Anand; J Woodrow Weiss
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Publication Detail:
Type:  Controlled Clinical Trial; Journal Article; Research Support, N.I.H., Extramural     Date:  2007-09-14
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  293     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-11-08     Completed Date:  2008-01-07     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H3027-35     Citation Subset:  IM    
Pulmonary and Sleep Research Laboratory, Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
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MeSH Terms
Anoxia / physiopathology*
Blood Pressure*
Heart Rate*
Middle Aged
Muscle, Skeletal / innervation*,  physiopathology*
Sympathetic Nervous System / physiopathology*
Grant Support

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

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