Measurement of human blood viscosity by an electromagnetic spinning sphere viscometer.

We herein applied an electromagnetic spinning sphere (EMS) viscometer to the measurement of human blood viscosity for the first time. We collected blood samples from 100 healthy outpatient volunteers in order to analyse viscosity dependence on blood cell parameters and on the shear rate with a simple approximation formula [ηi (γ)\, = Ai γ(- pi) + η0]. Viscosity dependence on blood cell parameters was relatively high at a high shear rate, but became lower as the shear rate decreased. The approximation formula with appropriate parameters of Ai and pi nearly faithfully reproduced actual blood rheological behaviour with a standard deviation of 1.5%. The distributions of Ai and pi values were broad, suggesting that the pattern of viscosity dependence on the shear rate varied with individual differences. The results obtained using the EMS viscometer suggest that blood viscosity values are individual-specific and actual individual measurements are important for understanding rheological conditions.