A constitutive equation for whole human blood was developed using a power law functional form. This power law equation contains two parameters, the consistency index and the non-Newtonian index for the fluid. Viscometric data, utilizing a cone and plate viscometer, were obtained from anticoagulated blood samples of known hematocrit levels and chemical compositions. A multiple regression technique with apparent viscosity as the dependent variable was used to determine the consistency index and the non-Newtonian index.

A model including only the shear rate as the independent variable was found to be lacking any substantial degree of significance. When hematocrit was added as an independent variable, the degree of fit increased considerably.

Of the chemical variables examined, the least significant, as far as effects on viscosity is concerned, were the plasma lipids. The proteins, fibrinogen and globulin were found to have a much greater effect on viscosity than the protein, albumin. The best constitutive equation involving the chemical composition of blood was found to include the shear rate, the hematocrit level, and a variable which is the sum of fibrinogen and globulin. This model produced a statistically significant increase in the correlation between experimental and theoretical data compared with the best two variable model.