Optimal cell transport in straight channels and networks

TL;DR

This paper investigates how particle flux in channels depends on volume fraction and particle properties, revealing an optimal hematocrit for blood flow and highlighting the complexity of network optimization.

Contribution

It introduces a combined simulation and modeling approach to identify optimal cell volume fractions and explores their dependence on vessel size and cell mechanics.

Findings

Existence of an optimal volume fraction for cell transport.

Blood's hematocrit in healthy individuals is near this optimal value.

Pathological conditions can significantly deviate from optimal hematocrit.

Abstract

Flux of rigid or soft particles (such as drops, vesicles, red blood cells, etc.) in a channel is a complex function of particle concentration, which depends on the details of induced dissipation and suspension structure due to hydrodynamic interactions with walls or between neighboring particles. Through two-dimensional and three-dimensional simulations and a simple model that reveals the contribution of the main characteristics of the flowing suspension, we discuss the existence of an optimal volume fraction for cell transport and its dependence on the cell mechanical properties. The example of blood is explored in detail, by adopting the commonly used modeling of red blood cells dynamics. We highlight the complexity of optimization at the level of a network, due to the antagonist evolution of local volume fraction and optimal volume fraction with the channels diameter. In the case of the blood network, the most recent results on the size evolution of vessels along the circulatory network of healthy organs suggest that the red blood cell volume fraction (hematocrit) of healthy subjects is close to optimality, as far as transport only is concerned. However, the hematocrit value of patients suffering from diverse red blood cel pathologies may strongly deviate from optimality.