Dynamics of Bioimpedance Parameters on Three Frequencies During Ultrafiltration

Abstract

Background/Aim. At present, methods based on the analysis of non-invasively measured parameters of electrical bioimpedance for the diagnosis of the patient's biohydrality are of interest. The purpose of this article is to investigate the dynamics of electrical impedance parameters (module, phase angle, active and reactive components) of the human body during ultrafiltration of programmed hemodialysis at three frequencies of 20 kHz, 100 kHz, 500 kHz. Equipment and Methods. For the research was used the hemodialysis system Fresenius Medical Care 5008C. This system provided the implementation of the ultrafiltration procedure profile. Also was used the hardware and software complex of monitoring bioimpedasometry TOR-M-1, adapted for hemodialysis procedure and conditions. Using these equipment the dependences of the modulus Z, the phase angle $ \varphi $, active R and the reactive X impedance components corrected to the body length of the patient H, the region of distribution of the bioimpedance vector relative to the tolerance ellipses and the dynamics of these parameters, depending on the volume of the ultrafiltrate and the profile of the ultrafiltration procedure were studied. Dynamics of bioimpedance parameters. It was found that during the ultrafiltration has a characteristic complex nonlinear behavior of the impedance parameters for each individual patient. The intensity of this nonlinearity increases with increasing frequency. It is expressively observed at higher frequencies of 100 kHz and 500 kHz. Interpretation of Impedance Dynamics with Tolerance Ellipses. The non-stationary oscillatory character of the parameter dynamics testifies to the complexity of the individual transient processes of redistribution of volumes of human water sectors in the process of hemodialysis and associated with changes in the ratio of intracellular, extracellular fluids and blood, the structural composition of the liquid. This causes fast flowing changes in active conductivity in the intercellular environment and reactive conductivity due to the action of polarization processes on the dielectric structures of biological tissues. Discussion and Conclusion. Measurements and cumulative analysis of the parameters of electrical impedance directly in the process of hemodialysis allows to objectively monitor the progress of the patient's functional state in real time with an assessment of the presence or absence of a `dry weight 'level, evaluate the nature of the processes of redistribution of intracellular and extracellular sectors of the body and blood, and the differences in the course of the process of ultrafiltration of patients. This can be the basis, if necessary, for promptly adjusting the ultrafiltration process. Widening of the impedance measurement bandwidth enhances the diagnostic capabilities of such monitoring and the timely correction of the ultrafiltration procedure.