Modeling Red Blood Cell Deformation at Supraphysiological Strain Rates Using a Droplet Framework

Hemolysis remains a concern in mechanical circulatory support devices (MCSDs). Capturing flow-induced red blood cell (RBC) deformation is important to improve these technologies. Deformation models that are feasible for macroscale MCSD flows have not been calibrated with human RBC deformation data across multiple conditions. The purpose of this study is to modify and test a droplet deformation model that is applicable for MCSD flows for predicting human RBC deformation in silico.

In vitro human RBC deformation is studied in microfluidic flows in two suspension viscosities (2.05 and 4.17 cP) at MCSD relevant strain rates (5,000 - 200,000 s^-1 in shear flow; 330 - 13,160 s^-1 in extensional flow). Modifications are made to the deformation model's constitutive parameters to represent the observed RBC deformation in silico.

The calibrated model reproduces the unique RBC deformation behaviors observed in shear and extensional flows across a range of conditions. In silico shear deformation index data have mean absolute error (MAE) ≤ 0.15 compared to in vitro results for both viscosity conditions from 5,000 to 200,000 s^-1. Peak in silico extensional deformation data demonstrate MAE ≤ 0.11 compared to our in vitro results for both viscosity conditions from 670 to 1,300 s^-1, while MAE is higher (up to 0.17) for conditions at 330 s^-1.

The model adaptations successfully produce accurate RBC deformation results at MCSD relevant strain rates for two flow types and two suspension viscosities. The strengths of the model are in relatively high velocity gradient magnitudes and/or suspension viscosities where RBCs emulate liquid droplets.