Measurement of viscosity of biologic fluids by cone plate viscometer.

Abstract

Abstract Viscosity of a fluid is defined as the ratio of shear stress to sheer rate. Shearing occurs as the result of the internal friction of the fluid layers moving over one another during flow. For simple fluids this relationship is linear. The presence of colloidal suspensions or macromolecular substances usually cause marked alinearity of this shear stress-shear rate relationship. Biologic fluids such as blood, which contains protein and a colloidal suspension of cells, have been demonstrated to have anamolous flow properties, i.e., a nonlinear change in viscosity with a constantly increasing or decreasing shear rate. A cone plate viscometer capable of recording absolute values of shear stress and shear rate is described. The instrument permits the rapid analysis of small samples of fluid. Whole blood was shown to consistently demonstrate pseudoplastic (shear thinning) flow behavior. Samples of mucus from the respiratory tract also demonstrated the same characteristics at considerably higher values of viscosity.