Use of dielectric properties of human tissues in the analysis of lightning injuries

Abstract

This paper focuses on the use of dielectric properties of human tissues in analysing injuries as a result of the lighting short stroke current. The lightning short stroke current is decomposed into its frequency components and the effects of these frequency components on human tissues are analysed. The dielectric properties of nineteen types of human body tissues are examined and the correlations between the impedances of these tissues and the lightning stroke current pathway are investigated. The human tissues are modelled as cylindrical structures using a FEA (Finite Element Analysis) approach and simulated using the COMSOL Multiphysics software suite. The results obtained from the simulations include: current density, complex impedance and total absorbed power of the tissues. Only the first short stroke of the lightning flash is considered as the test parameter. The direct strike mechanism of lightning injury is examined in this paper with the possibility of including other mechanisms of lightning injury in the future. The first short stroke of the lightning flash is modelled using a double exponential model and exhibit a 4 kA 1.8/30µs waveform. This waveform consists of frequencies up to 100 kHz. The skin and bone marrow is found to have the most varying impedances within this frequency range and the heart is found to be the organ with the least impedance. The results from the simulations depict physical properties of real human tissues and hence are valid in the analyses of lightning injuries.