Theoretical predictions of maximal oxygen consumption in hypoxia: Effects of transport limitations

B. J. McGuire; T. W. Secomb

doi:10.1016/j.resp.2004.07.001

Theoretical predictions of maximal oxygen consumption in hypoxia: Effects of transport limitations

B. J. McGuire, T. W. Secomb

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

A Krogh-type model for oxygen transport is used to predict maximal oxygen consumption (V̇O2max) of human skeletal muscle under hypoxic conditions. Assumed values of capillary density, blood flow, and hemoglobin concentration are based on measurements under normoxic and hypoxic exercise conditions. Arterial partial pressure of oxygen is assumed to decrease with reductions in inspired partial pressure of oxygen (P _IO ₂), as observed experimentally. As a result of limitations of convective and diffusive oxygen delivery, predicted V̇O2max values decline gradually as P _IO ₂ is reduced from 150 mmHg to about 80 mmHg, and more rapidly as P _IO ₂ is further reduced. At very low levels of P _IO ₂, V̇O2max is limited primarily by convective oxygen supply. Experimentally observed values of V̇O2max in hypoxia show significant dispersion, with some values close to predicted levels and others substantially lower. These results suggest that maximal oxygen consumption rates in hypoxia are not necessarily determined by oxygen transport limitations and may instead reflect reduced muscle oxygen demand.

Original language	English (US)
Pages (from-to)	87-97
Number of pages	11
Journal	Respiratory Physiology and Neurobiology
Volume	143
Issue number	1
DOIs	https://doi.org/10.1016/j.resp.2004.07.001
State	Published - Oct 12 2004
Externally published	Yes

Keywords

Hypoxia
Krogh cylinder model
Maximal oxygen consumption
Oxygen transport

ASJC Scopus subject areas

Neuroscience(all)
Physiology
Pulmonary and Respiratory Medicine

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10.1016/j.resp.2004.07.001

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title = "Theoretical predictions of maximal oxygen consumption in hypoxia: Effects of transport limitations",

abstract = "A Krogh-type model for oxygen transport is used to predict maximal oxygen consumption ({\.V}O2max) of human skeletal muscle under hypoxic conditions. Assumed values of capillary density, blood flow, and hemoglobin concentration are based on measurements under normoxic and hypoxic exercise conditions. Arterial partial pressure of oxygen is assumed to decrease with reductions in inspired partial pressure of oxygen (P IO 2), as observed experimentally. As a result of limitations of convective and diffusive oxygen delivery, predicted {\.V}O2max values decline gradually as P IO 2 is reduced from 150 mmHg to about 80 mmHg, and more rapidly as P IO 2 is further reduced. At very low levels of P IO 2, {\.V}O2max is limited primarily by convective oxygen supply. Experimentally observed values of {\.V}O2max in hypoxia show significant dispersion, with some values close to predicted levels and others substantially lower. These results suggest that maximal oxygen consumption rates in hypoxia are not necessarily determined by oxygen transport limitations and may instead reflect reduced muscle oxygen demand.",

keywords = "Hypoxia, Krogh cylinder model, Maximal oxygen consumption, Oxygen transport",

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AU - McGuire, B. J.

AU - Secomb, T. W.

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N2 - A Krogh-type model for oxygen transport is used to predict maximal oxygen consumption (V̇O2max) of human skeletal muscle under hypoxic conditions. Assumed values of capillary density, blood flow, and hemoglobin concentration are based on measurements under normoxic and hypoxic exercise conditions. Arterial partial pressure of oxygen is assumed to decrease with reductions in inspired partial pressure of oxygen (P IO 2), as observed experimentally. As a result of limitations of convective and diffusive oxygen delivery, predicted V̇O2max values decline gradually as P IO 2 is reduced from 150 mmHg to about 80 mmHg, and more rapidly as P IO 2 is further reduced. At very low levels of P IO 2, V̇O2max is limited primarily by convective oxygen supply. Experimentally observed values of V̇O2max in hypoxia show significant dispersion, with some values close to predicted levels and others substantially lower. These results suggest that maximal oxygen consumption rates in hypoxia are not necessarily determined by oxygen transport limitations and may instead reflect reduced muscle oxygen demand.

AB - A Krogh-type model for oxygen transport is used to predict maximal oxygen consumption (V̇O2max) of human skeletal muscle under hypoxic conditions. Assumed values of capillary density, blood flow, and hemoglobin concentration are based on measurements under normoxic and hypoxic exercise conditions. Arterial partial pressure of oxygen is assumed to decrease with reductions in inspired partial pressure of oxygen (P IO 2), as observed experimentally. As a result of limitations of convective and diffusive oxygen delivery, predicted V̇O2max values decline gradually as P IO 2 is reduced from 150 mmHg to about 80 mmHg, and more rapidly as P IO 2 is further reduced. At very low levels of P IO 2, V̇O2max is limited primarily by convective oxygen supply. Experimentally observed values of V̇O2max in hypoxia show significant dispersion, with some values close to predicted levels and others substantially lower. These results suggest that maximal oxygen consumption rates in hypoxia are not necessarily determined by oxygen transport limitations and may instead reflect reduced muscle oxygen demand.

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