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Mathematical Model of Mixed Venous SO 2 Transients at Onset of Exercise in Discrete Capillary Networks
Author(s) -
Fraser Graham Mathew,
Goldman Dan,
Kowalchuk John,
Ellis Christopher G
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1142.12
Subject(s) - skeletal muscle , capillary action , blood flow , venous blood , intravital microscopy , chemistry , outflow , diffusion , steady state (chemistry) , biomedical engineering , anatomy , microcirculation , cardiology , mechanics , medicine , physics , thermodynamics , meteorology
Increases in muscle O 2 consumption (VO 2 ) result in higher blood flow to accommodate changing metabolic demand. The time required for diffusion of O 2 within a muscle volume to support increased VO 2 causes tissue PO 2 and mixed venous SO 2 to lag behind VO 2 . The purpose of this study was to determine how diffusive transport affects time transients in venous SO 2 following increases in blood flow and VO 2 . A finite difference model was used to simulate O 2 transport in a discrete 3D microvascular network mapped from rat skeletal muscle using intravital video microscopy. Measurements were made in vivo to determine baseline simulation parameters for red blood cell supply rate (RBC SR), capillary inlet SO 2 , and VO 2 . Using the baseline solution as a starting point, exercise was simulated using simultaneous 6X step increases in VO 2 and RBC SR. Tissue PO 2 and capillary venous outflow SO 2 (cvSO 2 ) were recorded at 0.2s intervals until steady‐state (SS) was reached. SS mean tissue PO 2 decreased from 37.2 ± 2.7 at baseline to 18.2 ± 5.9 mmHg in simulated exercise. Figure I shows the cvSO 2 profile of blood as it exits the volume and the relative time course of the step change. This model demonstrates that despite instantaneous step increases in muscle VO 2 and microvascular blood flow, diffusive transport of O 2 in skeletal muscle imposes an observable time transient to cvSO 2 following the onset of exercise. Supported by CIHR MOP 102504 & NIH HL089125