Characterizing the Response of Skeletal Muscle Microvasculature to Imposed Oxygen Variations

Abstract

Computational modeling of the oxygen regulatory system has shown how signals conducted upstream from capillaries change the flow pattern in the arteriole tree. The simulation showed that the hemodynamic response to higher frequency oscillations (period 30 sec) is attenuated relative to lower frequency oscillations (period 90 sec). To test this prediction in vivo, a custom O2 gas chamber is used to supply O2 at the surface of exposed skeletal muscle and a sequence of 3 oscillations (1st and 3rd 30 sec period, 2nd 90 sec period, see figure) were generated. The hemodynamic response in capillaries to this stimulus was quantified using intravital video microscopy and a functional image analysis system (RBC velocity and hematocrit to yield RBC supply rate, SR). The RBC supply rate response supported the results from the computational model for the 1st and 2nd sine oscillation. The SR response to the higher frequency oscillation was attenuated to ~60‐70% of the lower frequency stimulus. However, the 3rd sinusoidal oscillation showed no response to the O2 signal suggesting that other factors need to be included in the model. Overall, the model and experimental results support the hypothesis that regulation of O2 supply involves a conducted signal along the arteriolar tree controlling both flow resistance and distribution of RBCs at bifurcations. (NIH R33 HL089094).