Document Detail

Insensitivity of VO2max to hemoglobin-P50 as sea level and altitude.
MedLine Citation:
PMID:  9128901     Owner:  NLM     Status:  MEDLINE    
O2 uptake in the lungs, and therefore arterial oxygenation, is favored by a low Hb-P50 but this inhibits tissue O2 extraction, raising the question of optimal P50 during maximal exercise when VO2 is limited by O2 supply. Using a model of the lungs and muscles connected by the circulation so that O2 transport is simultaneously considered in both sites, sensitivity of VO2max to P50 was determined at three altitudes: PB = 760, 464 and 253 Torr, encompassing sea level and Mt. Everest. At Pb = 760 Torr, VO2max peaked at P50 = 30 Torr, was 99.4% (of that at 30) at normal P50 (26.8) and exceeded 95% (of that at P50 = 30) over the P50 range from 24 to 43 Torr. Optimal P50 at PB = 464 Torr was 25 Torr, VO2max at P50 = 26.8 was reduced only 0.1% and exceeded 95% over the P50 range from 19 to 41 Torr. At Pb = 253, optimal P50 was 20 Torr, VO2max at P50 = 26.8 was reduced only 0.4% and exceeded 95% over the wide P50 range from 15 to 47 Torr. While this analysis shows that technically, optimal P50 falls with altitude, VO2max is insensitive to P50 over a range that widens with altitude, so that P50 changes over a realistic interval would not measurably affect VO2max.
P D Wagner
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Respiration physiology     Volume:  107     ISSN:  0034-5687     ISO Abbreviation:  Respir Physiol     Publication Date:  1997 Mar 
Date Detail:
Created Date:  1997-07-11     Completed Date:  1997-07-11     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0047142     Medline TA:  Respir Physiol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  205-12     Citation Subset:  IM; S    
Department of Medicine, University of California, San Diego, La Jolla, USA.
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MeSH Terms
Atmospheric Pressure*
Exercise / physiology
Hemoglobins / physiology*
Models, Biological
Oxygen Consumption / physiology*
Pulmonary Gas Exchange / physiology
Grant Support
Reg. No./Substance:
0/Hemoglobins; 37220-04-5/hemoglobin P

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