A Comparative Study on Interspecies Blood Rheology*

Blood is a complex suspension of red blood cells (RBCs), white blood cells, and platelets in an aqueous plasma phase with several dissolved proteins. Despite a consistent makeup, with minor changes in constituent sizes and volume fractions, blood from different species exhibits significantly different rheological signatures. Blood from some species including horse, pig, and human exhibit a yield stress at low shear rates, while blood from other species including cow, sheep, and guinea pig exhibit no yield stress. This is attributed to the presence or absence of microstructural RBC aggregates at low shear rates. Moreover, blood samples across all species may exhibit unique transient behavior which enables insight into how blood evolved to the specific organism. In this work, we present new steady and transient rheological data on blood from several species. We show that a previously developed thixotropy model can be used to model blood rheology across species and discuss the similarities and differences. This study improves the understanding of how blood changes across species, which is important for drug clinical testing and elucidates the connection between physiology and blood rheology.