Effect of electric field on erythrocyte sedimentation rate. IV. Volume fraction dependence of human red cells in plasma

We measured the volume fraction dependence of erythrocyte sedimentation for human red cells in autologous plasma while the volume fraction, H_ct, ranges from 0.220 to 0.650. A modified electrophoretic instrument was employed to investigate the electric effect of an upward DC field on erythrocyte sedimentation at a constant source supply of V s = 60.0 ± 0.5 V . The sedimentation curves all coincided well with the sigmoidal type equation, l = l max / { 1 + ( t 50 / t ) n } , at V S = 0 , or 60.0 V. Here, l_max is the length of plasma level, l, when the time, t, tends to infinity; t₅₀ is the elapsed time when the plasma level falls to l_max/2, and n is a constant (n > 0). A non-linear least-squares method was employed to fit experimental data. It was found that l_max decreased and t₅₀ increased with the increase of H_ct while n ranged from 1.53 to 3.95. The volume fraction dependence of sedimentation velocity, v_max, defined as the maximum slope of the sedimentation curve, fits well with an exponential-type curve, both at V S = 60.0 V and at V S = 0 V : v max = v S ( 1 − H ct ) exp ( − BH ct ) , where v_s is the velocity at infinite dilution and B is a phenomenological parameter. In the range of H ct = 0.220 – 0.650 , v_S and B are 326.1 mm/hr and 4.30, respectively, at V S = 60.0 V , while they are 130.4 mm/hr and 2.46, respectively, at V S = 0 V .