A study on rheological properties of blood and improvements with high-voltage plasma discharge
Authors:   , Jung Jin Mu , Cho Young I. 
Published: July 2021

Blood behaves as a shear-thinning non-Newtonian fluid where its viscosity varies due to both the deformability and aggregation of RBCs with the interaction with macro-molecules in blood plasma. The elevated whole blood viscosity (WBV), which indicates the increased frictional resistance between a moving blood and stationary vessel walls, has been suggested as one of the major determinants or risk factors of atherosclerosis diseases (i.e., cardiovascular diseases, stroke, and peripheral arterial diseases etc.) and microvascular disorders (i.e., diabetic retinopathy, nephrophathy, and neuropathy etc.) by causing both the endothelial injury of vessel walls and poor perfusion at capillaries. In order to investigate the shear-thinning non-Newtonian behavior of blood in regards to the effects of increased wall shear stress and impaired oxygen delivery on various diseases that might be caused by hyperviscosity, the present study was focused on the studies of rheological properties of blood by examining the WBV profiles over a pathologically wide range of shear rates using a scanning capillary tube viscometer (SCTV) and their improvements using high-voltage plasma discharge. Firstly, a new hematocrit-correction model using the Casson model was proposed to correct the measured WBVs of different blood samples with different hematocrits to a standard hematocrit of 45 %, a process which is needed to compare the effect of intrinsic rheological properties or other determinants on blood viscosity for different blood samples. Without the measurement of plasma viscosity, the new model showed about 4 to 6 times more accurate and less deviations than the conventional Matrai's model. Secondly, a new method of measuring the electric conductivity of whole blood was introduced for the purpose of hematocrit determination, demonstrating a simple but accurate hematocrit measurement by employing a low-frequency squarewave voltage signal in a conductance cell, without the usual error associated with the sedimentation of erythrocytes. Thirdly, a new physical treatment method with the application of highvoltage plasma discharges (i.e. DBD and corona discharge) followed by filtration of the coagulated particles was proposed. The results indicated that WBV could be reduced by 9.1 % and 17.7 % for systolic blood viscosity (SBV) and diastolic blood viscosity (DBV), respectively, from the baseline values when DBD-treated blood plasma was filtered prior to mixing with red blood cells. When treated with the corona discharge for 60 pulses, DBV and LDL concentration dropped by 30.1 % and 31.5 %, respectively, from the baseline values. Lastly, a new opaque standard viscosity fluid (SVF) was proposed using maltose with 55 % of concentration to replicate a shear-thinning non-Newtonian behavior of blood for different shear rates. The produced viscosity profiles from three different levels of SVFs provided low-, medium-, and high-standard viscosity fluids that can be used for the performance test of any blood viscometers over a wide range of shear rates. The applicability of new opaque SVFs was demonstrated by dye concentration test, repeatability test, and degradation test.