Document Detail

Critical capillary PO2 and the role of lactate production in oxyhemoglobin dissociation during exercise.
MedLine Citation:
PMID:  10659163     Owner:  NLM     Status:  MEDLINE    
During exercise, O2 transport from capillary to myocyte is not diffusion-limited until end-capillary PO2 reaches its lowest value (critical capillary PO2). Critical capillary PO2 is reached at the mid-level of the subject's work capacity, not at Vo2 max. Femoral vein lactate does not increase until the critical capillary PO2 is reached. The increase in lactate is essential once the critical capillary PO2 is reached because the increase in H+ that accompanies the increase in lactate, through the "Bohr Effect", becomes the mechanism for oxyhemoglobin dissociation. Both normal subjects and patients with chronic stable heart failure have a critical capillary PO2 between 14 and 22 mm Hg. The pattern of femoral vein (end capillary) PO2 change as VO2 increases, describes the Vo2 at which O2 becomes diffusion limited and the extent to which new muscle capillary bed is recruited as Vo2 increases above the lactate threshold.
K Wasserman
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Advances in experimental medicine and biology     Volume:  471     ISSN:  0065-2598     ISO Abbreviation:  Adv. Exp. Med. Biol.     Publication Date:  1999  
Date Detail:
Created Date:  2000-04-11     Completed Date:  2000-04-11     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0121103     Medline TA:  Adv Exp Med Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  321-33     Citation Subset:  IM    
Division of Respiratory and Critical Care Physiology and Medicine, Harbor-UCLA Medical Center, UCLA School of Medicine, Torrance 90509, USA.
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MeSH Terms
Acidosis, Lactic / metabolism
Blood Gas Analysis
Capillaries / metabolism
Cardiac Output, Low / metabolism*
Exercise / physiology*
Femoral Vein / metabolism
Lactic Acid / biosynthesis*
Oxygen / metabolism*
Oxyhemoglobins / metabolism*
Reg. No./Substance:
0/Buffers; 0/Oxyhemoglobins; 50-21-5/Lactic Acid; 7782-44-7/Oxygen

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

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