A new simple cone-plate viscometer for hemorheology

The aim of this work was to evaluate a new automatic cone-plate viscometer (LBY-N6, PRECIL, Beijing, China) which was designed for clinical measurements of blood and plasma viscosities. Standard calibrating oils of viscosity varying from 1.85 to 20.5 mPas (conforming to ASTM Standard) were used to test the precision and reproducibility of the device. Then the viscometer was used to measure blood and plasma viscosities. The results were compared with those obtained with a conventional Couette viscometer and a capillary viscometer. The results showed that this new viscometer gave good values of viscosity for standard oils with relative errors lower than 10% at shear rates ranging from 20 to 200 s(-1). It also had a good reproducibility (standard deviations < 3% in most cases). Only the results at low shear rates (< 10 s(-1)) were less identical. As for blood, the relative difference between the results given by LBY-N6 and those obtained by Low Shear 30 was less than 10% at high shear rates. This difference decreased with shear rate and could be partly caused by viscoelastic and thixotropic properties of human blood. A small difference between the values of plasma viscosity obtained by LBY-N6 and the capillary viscometer AMTEC was also observed. In conclusion, this new viscometer can be used a routine tool to determine quickly plasma and blood viscosities in clinical practice at shear rates higher than 20 s(-1).