Measurement of human red blood cell deformability using a single micropore on a thin Si/sub 3/N/sub 4/ film

The filtration method for the evaluation of the red blood cell (RBC) deformability has been further refined to simulate the deformations encountered in the reticuloendothelial system (in particular the spleen). The core of the measuring system is a very thin (0.4 mu m thick) filter that consists of a single micropore (diameters down to 1 mu m) on a Si ₃N ₄ film which has been constructed using silicon microfabrication techniques. Individual RBC deformability is quantified by measuring the cell pore passage time. From one blood sample 200 passage times were analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. The effectiveness of the system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability. It is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 mu m when the pore length is very short.