Non-Invasive Estimation Of Metabolic Flux And Blood Flow In Working Muscle: Effect Of Blood-Tissue Distribution
Muscle oxygenation measurements by near infrared spectroscopy (NIRS) are frequently obtained in humans to make inferences about mechanisms of metabolic control of respiration in working skeletal muscle. However, these measurements have technical limitations that can mislead the evaluation of tissue processes. In particular, NIRS measurements of working muscle represent oxygenation of a mix of fibers with heterogeneous activation, perfusion and architecture. Specifically, the relative volume distribution of capillaries, small arteries, and venules may affect NIRS data. To determine the effect of spatial volume distribution of components of working muscle on oxygen utilization dynamics and blood flow changes, a mathematical model of oxygen transport and utilization was developed. The model includes blood volume distribution within skeletal muscle and accounts for convective, diffusive, and reactive processes of oxygen transport and metabolism in working muscle. Inputs to the model are arterial O2 concentration, cardiac output and ATP demand. Model simulations were compared to exercise data from human subjects during a rest-to-work transition. Relationships between muscle oxygen consumption, blood flow, and the rate coefficient of capillarytissue transport are analyzed. Blood volume distribution in muscle has noticeable effects on the optimal estimates of metabolic flux and blood flow in response to an exercise stimulus.
KeywordsMetabolic Flux Oxygen Transport Near Infrared Spectroscopy Muscle Oxygenation NIRS Measurement
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- 11.T.K. Tran, N. Sailasuta, U. Kreutzer, R. Hurd, Y. Chung, P. Mole’, S. Kuno, and T. Jue, Comparative analysis of NMR and NIRS measurements of intracellular PO2 in human skeletal muscle, Am J Physiol Regul Integr Comp Physiol 276: R1682–R1690 (1999).Google Scholar
- 13.T. Hamaoka, K. Mccully, V. Quaresima, K. Yamamoto and B. Chance, Near-infrared spectroscopy/imaging for monitoring muscle oxygenation and oxidative metabolism in healthy and diseased humans, Journal of Biomedical Optics 12(6), 062105, 2007.Google Scholar
- 14.M. Wolf, M. Ferrari and V. Quaresima, Progress of near-infrared spectroscopy and topography for brain and muscle clinical applications, Journal of Biomedical Optics 12(6), 062104, 2007.Google Scholar