In an operating theatre, electro medical equipment (EME) may fail and cause health hazards as the passing of a weak but hazardous current (leakage current) through the heart of the patient during surgical interventions. This occurs evidently during their use, when connected to the patient. The related values of leakage currents can be estimated by an electrical circuit model. To obtain the circuit of a surgical layout, the electrical models of medical location supply power system, human body and EME involved in a determined surgical intervention ought to be drawn. The present work focuses on the method to obtain the model of EME. The idea is to model by circuits each leakage current measurement set-up performed in accordance with the international standard IEC 60601-1. To assign the values to the model parameters, it is necessary to obtain also some information on the EME as the values of insulation impedances and the feasible leakage current paths inside it. The case of a commercial defibrillator is taken as an example to show the feasibility of the method. The comparison between the leakage currents simulated by the circuit and the ones measured is here presented. The agreement is satisfactory. An estimation of the model sensitivity due to the uncertainty in the knowledge of the parameters has been performed too, by using the Monte Carlo method. The extension of this approach to draw the model of other EME is also considered in view of the realization of a surgical layout circuit.
Applied part, defibrillator circuit model, electrical safety, medical equipment, microshock risk, leakage currents.
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