(224b) Occlusive Flow of a Red Blood Cell

When red blood cells (RBCs) move through narrow capillaries in the microcirculation, they deform as they flow. In pathophysiological processes such as sickle cell disease and severe malaria, RBC motion and flow are severely restricted. This can lead to vaso-occlusive crises with dramatic consequences. To understand the dynamics close to the threshold of occlusion, we used a combination of experiment and theory to study the motion of a single swollen RBC through a narrow glass capillary of varying inner diameter. By tracking the motion of the squeezed cell as it is driven by a controlled pressure drop, we measure the RBC velocity as a function of the pressure gradient as well as the local capillary diameter, and find the velocity of the cell varies with pressure head as a power-law that depends upon the lubrication gap between the cell and the capillary wall, consistent with a simple elasto-hydrodynamic model. Our study highlights the role of lateral confinement in the nearly arrested pressure-driven flow of soft confined objects and allows us to quantify the increase in the effective viscosity associated with this regime.