Muscle bloodflow-O2 uptake interaction and their relation to on-exercise dynamics of O2 exchange

A computer model was developed to provide a theoretical framework for interpreting the dynamics of muscle capillary O-2 exchange in health and disease. We examined the effects of different muscle oxygen uptake (VO2m) and CvO(2) profiles on muscle blood flow (Q(m)) kinetics (Q(m) = VO2m/[CaO2 - CvO(2)]). Further, we simulated VO2m and Q(m) responses to predict the CvO(2) profile and the underlying dynamics of capillary O-2 exchange (CvO(2) = CaO2 - VO2m/Q(m)). Exponential equations describing VO2m, CvO(2) and Q(m) responses in vivo were used in the simulations. The results indicated that Q(m) kinetics were relatively insensitive to CvO(2) parameters, but directly associated with VO2m kinetics. The biphasic Q(m) response produced a substantial fall in CvO(2) within the first 15-20 s of the exercise transition (phase 1 of Q(m)). These results revealed that the main determinant Of CvO(2) (or O-2 extraction) kinetics was the dynamic interaction of Q(m) and VO2m kinetics during phase 1 of Q(m). (c) 2005 Elsevier B.V. All rights reserved.