A kinetic measurement of red cell deformability: a modified micropipette aspiration technique.

A kinetic measurement of the red cell deformability is developed, modifying the micropipette aspiration technique of BRAASCH (1971). The sedimented human red cells on a slide-glass are individually aspirated into a micropipette by negative pressure (delta P), and the decreasing "velocity (v)" of the applied electric current, due to the aspirating cell, is taken as a measure of the "easiness" of the cell to enter into the small orifice of the micropipette (inner diameter, 2 R congruent to 3 micrometer). An empirical relation, v infinity (pi r2) . (delta P) . ("deformability"), is obtained. In order to test the validity of the method, some factors influencing the deformability are studied: i.e., the "velocity" decreases as lowering temperature; the "velocity" of the glutaraldehyde-pretreated cells and of both in vivo and in vitro aged cells decreases. Therefore, the parameter, "velocity (v)," reflects the deformability well. In addition, if a few assumptions could be allowed, v would be related to the Young's modulus of the membrane.