Mathematical modeling of oxygen transport in skeletal muscle under conditions of high oxygen demand

Persistent Link:
http://hdl.handle.net/10150/280434
Title:
Mathematical modeling of oxygen transport in skeletal muscle under conditions of high oxygen demand
Author:
McGuire, Brooke Jamie
Issue Date:
2003
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Maximal oxygen consumption rates in exercising skeletal muscle are studied using a Krogh-type cylinder model. Effects of the decline in oxygen content of blood flowing along capillaries, intravascular resistance to oxygen diffusion, and myoglobin-facilitated diffusion are included. Parameter values are based on human skeletal muscle. The model is used to predict oxygen consumption rates in exercising skeletal muscle, based on transport processes occurring at the microvascular level. The dependence of maximal oxygen consumption rates on oxygen demand, perfusion, and capillary density (defined as number of capillaries per unit cross-section area of muscle) is examined. When demand is high, model results show that capillary oxygen content declines rapidly with axial distance and radial oxygen transport is limited by diffusion resistance within the capillary and within the tissue. Under these conditions, much of the tissue is hypoxic and consumption is substantially less than demand. Predicted consumption rates are compared with experimentally observed maximal rates of oxygen consumption. Capillary densities in human skeletal muscle are estimated by using the model to determine the minimum number of straight, evenly spaced capillaries required to achieve experimentally observed oxygen consumption rates. Estimated capillary density values are generally higher than values obtained using either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction, and muscle biopsy samples typically are strongly contracted. These results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle. The model is also used to predict decreases in oxygen consumption in maximally exercising muscle due to reductions in the inspired partial pressure of oxygen. In general, observed reductions in maximal oxygen consumption rates due to hypoxic breathing conditions are larger than predicted by the model, suggesting that responses to hypoxia not currently included in the model, such as decreases in oxygen demand or in muscle blood flow, may be important in determining maximal oxygen consumption in hypoxic conditions.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Biomedical.; Health Sciences, Recreation.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Biomedical Engineering
Degree Grantor:
University of Arizona
Advisor:
Secomb, Timothy W.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMathematical modeling of oxygen transport in skeletal muscle under conditions of high oxygen demanden_US
dc.creatorMcGuire, Brooke Jamieen_US
dc.contributor.authorMcGuire, Brooke Jamieen_US
dc.date.issued2003en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractMaximal oxygen consumption rates in exercising skeletal muscle are studied using a Krogh-type cylinder model. Effects of the decline in oxygen content of blood flowing along capillaries, intravascular resistance to oxygen diffusion, and myoglobin-facilitated diffusion are included. Parameter values are based on human skeletal muscle. The model is used to predict oxygen consumption rates in exercising skeletal muscle, based on transport processes occurring at the microvascular level. The dependence of maximal oxygen consumption rates on oxygen demand, perfusion, and capillary density (defined as number of capillaries per unit cross-section area of muscle) is examined. When demand is high, model results show that capillary oxygen content declines rapidly with axial distance and radial oxygen transport is limited by diffusion resistance within the capillary and within the tissue. Under these conditions, much of the tissue is hypoxic and consumption is substantially less than demand. Predicted consumption rates are compared with experimentally observed maximal rates of oxygen consumption. Capillary densities in human skeletal muscle are estimated by using the model to determine the minimum number of straight, evenly spaced capillaries required to achieve experimentally observed oxygen consumption rates. Estimated capillary density values are generally higher than values obtained using either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction, and muscle biopsy samples typically are strongly contracted. These results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle. The model is also used to predict decreases in oxygen consumption in maximally exercising muscle due to reductions in the inspired partial pressure of oxygen. In general, observed reductions in maximal oxygen consumption rates due to hypoxic breathing conditions are larger than predicted by the model, suggesting that responses to hypoxia not currently included in the model, such as decreases in oxygen demand or in muscle blood flow, may be important in determining maximal oxygen consumption in hypoxic conditions.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Biomedical.en_US
dc.subjectHealth Sciences, Recreation.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineBiomedical Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSecomb, Timothy W.en_US
dc.identifier.proquest3108931en_US
dc.identifier.bibrecord.b44829899en_US
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