(190br) Blood Rheology across Species: Differences and Similarities

Blood is a complex suspension primarily composed of deformable red blood cells in an aqueous plasma phase. As a fluid, blood exhibits a unique viscoelastic and shear thinning behavior when subjected to flow. Additionally, blood from certain species also exhibits thixotropy, a time dependent viscosity. This arises as a result of microstructure aggregates which the red blood cells can form under low stresses. Understanding and modeling the rheology of blood is important due to the fact that a number of cardiovascular diseases have been linked to changes in the rheology of blood. Additionally, by having more accurate models for blood rheology, we can improve flow simulations which have a wide range of applications. Despite almost always containing the same constituents as human blood, blood from different species may demonstrate drastically different rheological characteristics. Understanding these changes and having a universal model for blood from all species is critical for a physiologically based model and may help to remove one of the barriers in drug scaleup – moving across species.

In this work, we present steady and for the first time a rich selection of transient rheological data on blood from a variety of species, including guinea pig, chicken, human, sheep, pig, horse, and cow. The measurements were obtained following a previously developed protocol for handling blood samples and performing rheological measurements [1]. Using the data, we can fit our constitutive, microstructure-based thixotropy model previously developed for human blood rheology [2]. Through modeling the rheological data for blood from different species, we are able to identify the components of blood rheology that are constant across species and the components which differ most significantly as well as demonstrate the universality of the blood thixotropy model. This also enables us to make the connection to the underlying microstructure phenomena, namely the extent to which the red blood cells from different blood samples will form aggregates and the mechanics of the aggregates if they are present.

By applying our model to blood from different species we are able to not only better understand how blood changes across species but also better understand human blood rheology and the impact that changes in the individual constituents will have. Various factors change across species including the red blood cell size, shape, and deformability; electrostatics; and plasma protein concentration. By measuring animal blood in addition to human blood, we can better understand how these components affect the bulk rheology and improve relations between the physiology of blood and the bulk rheology. Blood is just one of many biofluids that are shared across species, and by understanding the interspecies differences in blood, we can hopefully extend this analysis to other biofluids.

This work is supported by the National Science Foundation, award number CBET 1510837.

[1] Horner J. S., A. N. Beris, D. S. Woulfe, and N. J. Wagner, Clin. Hemorheol. Microcirc., (In press).

[2] Horner J. S., M. J. Armstrong, N. J. Wagner, and A. N. Beris, J. Rheol., 62(2), (2018).