Deformation behaviour of stomatocyte, discocyte and echinocyte red blood cell morphologies in a uniform flow channel – A numerical study

The aim of the study is to investigate the deformation behaviour of red blood cells (RBCs) having different morphologies during its passage through a uniform flow channel. RBCs are vital for sustaining the life, and carry oxygen and carbon dioxide between lungs and body tissues. Less deformable RBCs can obstruct capillaries, require higher transit time to navigate the microcirculation and can lead to adverse post-transfusion outcomes. RBC deformability is linked with its morphology. Some pathophysiological conditions and hematologic disorders, stomatocytogenic and echinocytogenic agents, and in-vitro storage can change RBC morphology. A numerical study is employed with coarse-graining (CG) and smoothed particle hydrodynamics (SPH) methods to determine the minimum energy configuration of CG-RBC membrane, and to predict RBC behaviour during flow. Deformation behaviour of RBC is investigated for stomatocyte-II, discocyte and echinocyte-II morphology at different orientations to the flow direction. At a flow velocity comparable to an arteriole, RBC adopts the parachute shape profile irrespective of its initial morphology or orientation to the flow direction. Furthermore, the transit time for a RBC in its discocyte shape requires slightly more transit time whereas the echinocyte is the first to exit the flow channel, however, this difference in transit time for different morphologies is not significant. The study is capable of predicting stomatocyte, discocyte and echinocyte flow behaviour during their passage through microfluidic devices, ventricular assist devices (VADs) and blood cell separation etc., and currently being extended to capillary flow conditions. It is aimed to extend the current study to predict RBC morphology at altered extracellular ionic strength and pH conditions; to predict post-transfusion flow behaviour when stored at these modified extracellular conditions; and by this means to suggest improvements to existing additive solutions for in-vitro RBC storage.