Bioelectrical Impedance as a Technique for Estimating Postmortem Interval,,

Abstract

Estimation of postmortem interval (PMI) is a critical component of death investigation. A cadaver can be hypothesized to be a resistor-capacitor (RC) circuit the impedance (Z) of which changes in a quantifiable manner as the cadaver decomposes. This hypothesis was tested using bioelectrical impedance analysis (BIA) equipment to apply a current with a fixed amplitude at a single frequency to four cadavers over time and measuring two components of Z, resistance (R) and reactance (X ). Quadratic regression analysis between Z and accumulated degree days (ADD) showed a statistically significant parabolic relationship. The parabolic relationship poses an initial challenge to the use of the method, and additional research is needed to address this issue. However, the results of the reported research support the hypothesis that Z measured using BIA has a relationship to PMI.

Accuracy of Estimated Bioimpedance Parameters with Octapolar Segmental Bioimpedance Analysis

“…Studies have demonstrated that there are six current circuits (arm-to-arm, right-arm–left-leg, right-arm–right-leg, left-arm–left-leg, right-arm–right-leg, foot-to-foot) for the equipotential-based OS-BIA technique [ 28 , 29 ]; however, these circuits are not clearly defined, especially for the determination of reactance and the phase angle. Importantly, studies have reported additional body current circuits, such as right-arm–right-leg, left-leg–right-leg circuits, and impedance parameters in these current circuits can overlap and lead to distorted results in impedance values [ 1 , 37 , 41 ]. This overlap of the current circuits could be eliminated by positioning the arm to be adducted 90 degrees at the shoulder joint, so that the voltage between the measured and unmeasured volage electrode is equipotential.…”

Postmortem tissue changes and dynamics of their impedance parameters: a preclinical experimental study

“…С другой стороны, следует отметить, что при наличии дисперсии Z в целом в исследуемом интервале частот (от 100 Гц до 100 кГц), непосредственно для высоких частот (10 и 100 кГц) дисперсия практически отсутствует, т. е. коэффициент поляризации k п близок к единице для всех сроков ДНС в любых условиях. Известно, что дисперсия Z для высоких частот присуща только живым тканям и отсутствует у мертвых [22]. Именно в интервале высоких частот от 10 до 1000 кГц для живых тканей дисперсия импеданса определяется поляризацией фосфолипидов мембран клеток в поле внешнего электрического тока и дипольной поляризацией структурных образований в цитоплазме.…”