Physical Principles of the Method of Low-Frequency Piezothromboelastography for Studying Rheological Properties of Whole Blood

The paper expounds physical principles of the low-frequency piezothromboelastography method for studying viscous properties of whole blood and diagnosis of the hemostatic potential. A mathematical model of ultrasonic vibrations in a viscous fluid has been developed. An ARP-01M “Mednord” piezothromboelastograph is used to carry out a numerical experiment to study the operational modes of a piezoelectric sensor and its applicability for measuring the dynamics of the viscous properties of whole blood. It is shown that the piezoelectric sensor reaches the optimal operational mode with the configuration of the needle-resonator in the form of a rectilinear rod with a loop. The maximum sensitivity in measuring the amplitude-frequency signal characteristics with a recording piezoelement is observed at 2.95 kHz. A numerical experiment studying the influence of a viscous medium on changes in the amplitude-frequency characteristics of vibrations of the needle-resonator of the piezoelectric transducer with allowance for the viscous friction force magnitude has been performed. The viscous properties of water and glycerin are used as an example. Calculations have been performed for two limiting magnitudes of the viscous force encompassing the interval of changes of the whole blood viscosity in the process of coagulation. It is demonstrated that the method has sufficient sensitivity to changes in the viscous characteristics of blood and to the dynamics of changes of these characteristics during coagulation and hence, has high measurement accuracy.