Prediction of hematocrit and red cell deformability with whole body biological impedance

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Bioelectrical impedancemetry has been used to evaluate hemorheological parameters in vitro but whole body impedance measurements are also correlated to some hemorheologic factors, due to their close relationship with determinants of electric properties of blood. In previous studies, we have determined a set of predictive equations for hematocrit, whole blood viscosity and plasma viscosity in both sedentary and trained individuals. In this study we aimed at verifying those findings and investigating for other equations in a sample of 62 subjects whose body composition was assessed with a multifrequency bioelectrical impedancemeter using low intensity at the following frequencies: 1, 5, 10, 50 and 100kHz. Viscometric measurements were done with a falling ball viscometer. Hematocrit was measured with microcentrifuge. We confirm that hematocrit was correlated with impedance measurements at 50 kHz (r=-0.671, p < 0.01), and describe a new predictive equation for RBC rigidity index "k" calculated with the equation of Quemada, ("k" index = 0.0003 Z50 + 1.2815; mean difference: -0.0506; 95% confidence interval of -0.0134 to 0.00324) that is also correlated with impedance measurements at 50 kHz (r = 0.526, p < 0.01). Although the precision of these formulae is not sufficient for allowing true "predictions" of hematocrit and red cell deformability, these findings confirm that factors of viscosity are to some extent reflected by whole body electric properties.