VISCOELASTIC - THIXOTROPY OF BLOOD

It is well established that the theological properties of blood depend on the shear rate of the flow. At low shear rate of around 1 sec(-1) blood exhibits the property of a viscoelastic fluid. As the shear rate increases progressively, the blood transforms to thixotropic, pseudop lastic and then Newtonian fluid. In the shear rate range up to approxi mately 1 sec(-1), blood behaves viscoelastic and thixotropic. This tim e dependent, strain dependent and shear rate dependent theological beh avior of blood has been demonstrated experimentally in the literature. In this work, a theological equation is developed for the characteriz ation of both viscoelastic and thixotropic properties of blood. The eq uation is based on the Huang model of thixotropic property incorporate d into the viscous component of the relaxation modulus of the general Maxwell model. Experimental data of theological hysteresis of blood at low shear rate obtained by Bureau, Healy, Bourgoin and Joly was used to test the validity of representation of data by the developed equati on. Ten sets of hysteresis data were tested. They can be divided into two different studies. The first study compared normal blood from a he alth human subject and the pathological blood from a diabetic patient. The second study shows the effect of neuraminidase treatment on norma l blood. The shear rate ranges of hysteresis loops are 0 to 0.12 sec(- 1) and 0 to 1.02 sec(-1). Results show that our theological equation g ives excellent representations of 10 sets of hysteresis loops with div ersified theological behavior. Therefore the theological parameters in the equation can be used to compare normal blood behavior with that o f pathological and neuraminidase modified bloods. This method of param eter comparison may lead to the detection of serious pathological cond itions and be further developed to a clinical test. The method may als o monitor the effectiveness of drug treatment to a patient as the pati ents' blood sample theological parameters return to that of normal hea lthy human subjects.