Fitting the determined impedance in the guinea pig inner ear to Randles circuit using square error minimization in the range of 100 Hz to 50 kHz.

Objective. Several lumped and distributed parameter models of the inner ear have been proposed to improve vestibular implant stimulation. The models should account for all significant physical phenomena that influence the current propagation, such as the electrical double layer (EDL) and medium polarization. The electrical properties of the medium are reflected in the electrical impedance; therefore, the study aimed to measure the impedance in the guinea pig inner ear and construct its equivalent circuit.Approach. The electrical impedance was measured from 100 Hz to 50 kHz between a pair of platinum electrodes immersed in 0.9% NaCl saline solution using sinusoidal voltage signals. The Randles circuit was fitted to the measured impedance in the saline solution in order to estimate the EDL parameters (C,W,andRct) of the electrode interface in saline. Then, the electrical impedance was measured between all combinations of the electrodes located in the semicircular canal ampullae and the vestibular nerve in the guinea pigin vitro. The extended Randles circuit considering the medium polarization (Ri,Re,Cm) together with EDL parameters (C,Rct) obtained from the saline solution was fitted to the measured impedance of the guinea pig inner ear. The Warburg element was assumed negligible and was not considered in the guinea pig model.Main results. For the set-up used, the obtained EDL parameters were:C=27.09*10-8F,Rct=18.75kΩ.The average values of intra-, extracellular resistances, and membrane capacitance wereRi=4.74kΩ,Re=45.05kΩ,Cm=9.69*10-8F,respectively.Significance. The obtained values of the model parameters can serve as a good estimation of the EDL for modelling work. The EDL, together with medium polarization, plays a significant role in the electrical impedance of the guinea pig inner ear, therefore, they should be considered in electrical conductivity models to increase the credibility of the simulations.

[The medical nurses: the factors of professional burning-out].

Nowadays, the professional burnout of paramedical personnel becomes a serious health care problem, resulting in productivity loss and medical care costs increase. The most effective mean to prevent the mentioned burnout is elimination of risk factors. The study purpose is to identify such factors (both positive or negative ones) and to quantify their contribution into development of professional burnout as exemplified by paramedical personnel in the Tomsk Oblast of Russia. The study sampling included 2,486 paramedicals as respondents. The sociological survey was carried out using questionnaire that included the Maslach Burnout Inventory tool and questions to assess corresponding factors of social, professional, economic and physical spheres of life. The study established high prevalence of high degree (29.57%) and extremely high degree (37.01%) of professional burnout in respondents. The following factors were associated with decrease in likelihood of burnout: advanced age (r = -0.089), married status (OR = 0.7; 95% CI 0.6-0, 9), higher number of children in family (r = -0.088), adequate sleep (r = -0.046), amount of time spent on sports per day (r = -0.167). The following factors were associated with increase in the likelihood of burnout: self-reported lack of sleep (OR = 2.1; 95% CI 1.8-2.5), frequent night shift work (r=0.082). The multiple linear regression analysis was applied with selection of model using the Akaike criterion: two mathematical models were formed for the integral value of professional burnout and its "Emotional exhaustion" sub-scale. The models described 15% and 20% of dispersion, respectively. The models allow both to quantify particular contributing factors to development of this syndrome and to develop programs of strengthening positive factors and mitigate negative ones. This will prevent development of professional burnout in paramedical personnel in the Tomsk Oblast.

Pathogenetic Role of Endothelial Dysfunction in Idiopathic Vestibulopathy.

Comparative analysis of the groups of patients with idiopathic bilateral vestibular hypofunction and a group of vestibulopathy patients with vertebrobasilar insufficiency demonstrated identity of the basic and additional diagnostic parameters in these syndromes as well as similarity in clinical diagnostic and anamnesis data. In all cases, functional assessment of endothelium-dependent vasodilation and selected biochemical marker sICAM-1 revealed endothelial dysfunction. Drug correction of endothelial dysfunction positively affected the manifestations of major and minor features of the syndrome, which confirmed the contribution of endothelial functional disturbances to the pathogenesis of bilateral vestibular hypofunction.

Electrophysiological Properties of Rat Vestibular Labyrinth and Their Effect on Parameters of Transmitted Voltage Pulses.

We propose a new approach to optimization of electrical stimulation of the vestibular nerve and improving the transfer function of vestibular implant. A mathematical model of the vestibular organ is developed based on its anatomy, the model premises, 3D-analysis of MRI and CT images, and mathematical description of physical processes underlying propagation of alternating electric current across the tissues of vestibular labyrinth. This approach was tested in vitro on the rat vestibular apparatus and had been examined anatomically prior to the development of its mathematical model and equivalent electrical circuit. The experimental and theoretical values of changes of the gain-phase characteristics of vestibular tissues in relation to location of the reference electrode obtained in this study can be used to optimize the electrical stimulation of vestibular nerve.