A Simple “Streak Length Method” for Quantifying and Characterizing Red Blood Cell Velocity Profiles and Blood Flow in Rat Skeletal Muscle Arterioles

OBJECTIVES: To develop a valid experimental method for quantifying blood flow in continuously branching skeletal muscle arterioles, and to derive an empirical relationship between velocity ratio (V(Max)/V(Mean)) and arteriolar diameter. METHODS: We evaluated arteriolar trees using IVVM of rat gluteus maximus muscle and developed a method to acquire single fluorescent-labeled RBC velocities across arteriolar lumens to create velocity profiles. These data were used to calculate the blood flow for 37 vessel segments (diameters: 21-115 μm). RESULTS: Mass balance at arteriolar bifurcations had 0.6 ± 3.2% error. Velocity ratios ranged from 1.35 to 1.98 and were positively correlated with diameter (p < 0.0001), and V(RBC) profiles were blunted with decreasing diameter. CONCLUSIONS: We present a means for quantifying blood flow in continuously branching skeletal muscle arterioles. Further, we provide an equation for calculating velocity ratios based on arteriolar diameter, which may be used by others for blood flow calculations.