Blood flow efficiency in response to red blood cell sphericity

The morphological properties of red blood cells, such as size and shape, play a crucial role in determining their flow properties. A typical abnormal shape can be found in several blood disorders, such as spherocytosis, ellipsocytosis, etc., where the cells have a spherelike or ellipselike appearance, instead of being biconcave. These shape anomalies can affect the ability of RBCs to deform and squeeze through narrow capillaries, leading to reduced blood flow and oxygen supply to tissues. This can cause tissue ischemia, which can lead to organ damage and dysfunction. We conduct numerical simulations in order to study the flow properties (such as flow rate, cell-free-layer, and RBCs hydrodynamic diffusion) by varying the shapes of the cells, from a biconcave one (healthy RBCs) to a spherical one, representing RBCs suffering spherocytosis disease. Our study highlights nontrivial effects, such as nonmonotonic behaviors of the flow rate as a function of asphericity, depending on the channel width. For example, for some channel width the usual biconcave shape is revealed to be optimal with respect to flow rate, whereas for other widths more inflated shapes are more efficient. This offers an interesting basis for the understanding of the mechanisms underlying blood flow deficiencies associated with shape anomalies, and may help evaluating the potential therapeutic strategies that might be used to alleviate the symptoms. As RBCs also serve as a classical model system for very deformable objects, our study reveals also some fundamental aspects of the flow of soft suspensions.