<title>Measurement of erythrocyte deformability by the flow-channel diffraction method</title>

Abstract

Erythrocyte deformability, known as ability of red blood cell (RBC) to change shape during flow in the microcirculation, is the basic rheological property of erythrocyte. Many techniques have been proposed to measure RBC's deformability (e.g. micropipette aspiration, micropore filtration, high shear viscometer and rheoscope techniques). Perhaps one of the most elegant technique for measurements of RBC deformability is ektacytometry, technique based on laser diffraction, worked out by Bessis and Mohandas¹ and recently developed by others^2,3. The laser light scattered by erythrocytes subjected to a well-defined shear stress (z) can be analyzed with the ektacytometer to obtain information regarding the changes in cell shape due to fluid shear. Usually, in order to deform RBC with shear stress the rotating Couette chamber is used ^1-5. From the diffraction images the elongation index (E), as a quotient of minor and major axes of the elliptically transformed diffraction patterns, is calculated. However, one has to face a series of methodological problems ⁵: 1. Occurrence of turbulences and heat shear, 2. Control of gap width within the Couette viscometer and the intensity of transmitted light, 3. The determination of RBC elongation coefficients E from the diffraction patterns. Therefore, in order to get accurate results, we have used unconventional technique which consists of a simple laminar flow system made from two parallel Plexiglas plates (flow-channel diffractometer) and the computer analysis of the diffraction pattern.