Studies of electrorheological properties of blood.

The electrorheological (ER) properties of blood indicate changes in the blood rheological behaviour due to imposition of electric field. The present work identifies and quantifies ER properties of blood at different shear rates and at different local structure of the flow field. A concurrent measurement system, based on a Contraves Low Shear 30 rotational rheometer was used in this study. It includes a pair of cylindrically shaped platinum electrodes, embedded into the wall of a resin replica of the Couette type flow chamber of the rheometer, constructed for conductivity measurement, and associated software (Data acquisition system). The relationship between the whole blood and plasma conductivity (the main active component of blood impedance) was studied in parallel with the changes in the rheological behaviour under steady and transient flow conditions. The time variation of blood conductivity at different flow regimes and the dependences of the apparent whole blood and plasma viscosity were investigated in the presence and absence of an electric field of 2 kHz. The results show that blood conductivity is strongly dependent on the blood factors considered and that any application using blood conductivity measurement should take into account the effect of flow, shear rates and hematocrit. The results also show that valuable information on the mechanical properties of blood can be obtained, in particular concerning the structuring and kinetics of "rouleaux formation".