Estimation of Red Cell Filterability Using Two-Step Nickel Mesh Filtration System: A Feasibility Study of Tandem Filtration

Human red cell filtration using a single porous membrane is a standard technique to estimate red cell filterability (RCF) that is a surrogate of red cell deformability. However, there is still a gap between such instantaneous ex vivo red cell filtration and continuous in vivo red cell capillary flow. Therefore, two-step filtration system was designed to estimate RCF under the constant flow rate (1.29 ml/min) of red cell suspension with hematocrit of 3.0 % by monitoring pressure difference (ΔP(t)) across a couple of identical nickel mesh membranes with pore size of exactly 5.49 μm. ΔP(t) showed baseline positive pressure under the saline filtration, initial steep rise at the passage of the head of red cell suspension and the secondary linear rise during filtration of suspension in each step. The amplitude of steep rise in ΔP(t) reflects an increase in apparent viscosity of suspension (mPa·s), and the slope of secondary linear rising segment indicates the rate of plugging pores by red cells (s ^{− 1}). Comparison of RCF in each step provided us with a hint of rheologic behaviors of heterogeneous red cells showing variable deformability. Tandem filtration using two-step filtration system and our specific nickel mesh membrane is concluded to be feasible, and our prototype of this system is promising to estimate RCF with easy handling skills.