Relation between hematocrit partitioning and red blood cell lingering in a microfluidic network

Despite increased interest in the effect of lingering red blood cells (LRBCs) on the heterogeneous hematocrit distribution in the microcirculation, quantitative data on LRBCs before and after the lingering event are still limited. The aim of the study was to investigate the relation between red blood cell (RBC) lingering and hematocrit partitioning in a microfluidic model of a microvascular bifurcation in the limit of low hematocrit conditions (tube hematocrit <10%). To this end, the classification of LRBCs was performed based on timing, position, and velocity of the RBCs. The investigation provided statistical information on the velocity, shape, and orientation of LRBCs as well as on their lateral distribution in the parent and daughter vessels. LRBCs traveled predominantly close to the centerline of the parent vessel, but they marginated close to the distal wall in the daughter vessels. Differently than the RBC flow observed in the smallest vessels, no influence of lingering events on the local hematocrit partitioning was observed in our experiments. However, importantly, we found that LRBCs flowing in the daughter vessel after lingering may be connected to reverse hematocrit partitioning in downstream bifurcations by influencing the skewness of the hematocrit distribution in the daughter vessel, which relates to the so-called network history effect.