Geometric Considerations in Modeling Oxygen Transport Processes in Tissue
Numerical solution of partial differential equations describing transport processes in capillaries and tissue is used for calculation of oxygen transport to brain tissue. Calculation is based on a three-dimensional network model which covers inhomogeneities in capillary blood flow in a relation of 27:1, This study was performed in order to obtain information about the influence of the main physiological parameters on oxygen tension frequency distribution pattern. Following results were obtained: a)Increase (or decrease) of the oxygen consumption rate in tissue to about twice (or half) of the normal case for cerebral grey matter causes an extreme left (or right) shift of the oxygen tension frequency distribution = histogram with a decrease (or increase) in venous oxygen tension from 35 to 18 (or 61) mmHg. b)A decrease of capillary blood flow at the input of the network in steps of about 15% from the normal value causes a stepwise left shift of the oxygen tension frequency distribution with venous oxygen tensions from 35 to 22 (or 13) mmHg. c)An increase of the critical oxygen tension from 1 to 10 mmHg causes a considerable right shift with an increase of the venous oxygen tension from 35 to 49 mmHg.
Theoretical oxygen tension frequency distributions are compared with experimental results which have been measured in rat brain cortex by means of oxygen micro-sensors. The frequently observed low oxygen tension values are discussed on the basis of mutual parameter changes in blood and tissue.
KeywordsOxygen Tension Oxygen Consumption Rate Flux Line Capillary Blood Flow Cerebral Grey Matter
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