ISSN:
1420-9071
Keywords:
Maximal O2 consumption
;
acute and chronic hypoxia
;
maximal cardiac output
;
hemoglobin
;
O2 dissociation curve
;
muscle morphometry
;
limiting factors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The present paper discusses the factors affecting maximal O2 consumption $$\left( {\dot V_{O_2 } \max } \right)$$ in hypoxia (4300 m above sea level) along the following lines: 1) In acute hypoxia, the fractional limitation to $$\dot V_{O_2 } \max $$ imposed by circulatory O2 transport (FQ′) is 50%, instead of 70% as in normoxia. This is due to the increase in the blood O2 transport coefficient (βb) as $$P_{O_2 } $$ decreases, as a consequence of the sigmoidal shape of the O2 dissociation curve of hemoglobin. The remaining 50% is assumed to be equally partitioned between tissue O2 transfer (Ft′) and mitochondria O2 utilization (Fm′). 2) In chronic hypoxia, FQ′=0.45, Ft′=0.20 and Fm′=0.35, as a consequence of reduced muscle fiber size and muscle mitochondrial density following acclimatization. 3) The relationship between $$\dot V_{O_2 } \max $$ and $$PI_{O_2 } $$ in both acute and chronic hypoxia reflects the O2 dissociation curve. 4) Acclimatization to chronic hypoxia does not have the function of preserving $$\dot V_{O_2 } \max $$ .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01936934
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