Influence of adhesion on measurement of viscoelastic characteristics of whole blood with resonant-acoustic method
The paper investigates the effect of blood adhesion on the amplitude-frequency characteristics of a piezoelectric sensor in the method of low-frequency piezothromboelastography. As a result of adhesion, a layer of blood cells can accumulate on the surface of the resonator needle immersed in blood, which changes its configuration and mass and, as a consequence, its amplitude-frequency characteristics. Experiments showed that the natural frequency of oscillations of the resonator needle decreases in direct proportion to the increase in the mass of adhered blood during coagulation. To confirm this pattern, we carried out a numerical experiment on a 3D-mathematical model of a piezoelectric sensor used in the piezotromboelastograph ARP-01M Mednord using the COMSOL Multiphysics® 4.2 software package and the finite element method. We calculated a change in the natural frequency of oscillations of the resonator needle relative to the mass of adhered blood, as well as their time dependence in the process of blood coagulation. We observed an increase in the mass of adhered blood during its coagulation starting from the third minute and reaching its maximum of 0.42 milligram in 15 minutes, which leads to a noticeable shift in the resonance frequency of the piezoelectric sensor towards lower frequencies.