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

Abstract

Background. Establishing regularities in postmortem intervals comprises one of the main tasks of the forensic science of death and cadaveric phenomena. The knowledge of these regularities is directly related to reconstructing the postmortem conditions and, consequently, to determining the postmortem interval. Objective. To analyze postmortem changes in cadaver tissues and dynamics of their impedance parameters under the conditions of natural biocenosis. Methods. The study involved the cadavers of model biological objects – eight pigs, aged one to two months, weighing up to 10 kg. Experimental studies of cadaver decomposition were carried out under natural biocenosis conditions, daily for 28 days with two replications. Changes in cadaver tissues during decomposition were recorded and analyzed. The subject of biophysical studies was the tissue impedance parameters of three diagnostic zones of the biological object: the musculocutaneous flap, the cartilaginous part of the third rib and the calcaneal tendon. Impedance measurements for each postmortem interval were performed at five studied current frequencies: 100 and 120 Hz, 1, 10 and 100 kHz. A total of 2,400 readings were taken. Statistical analysis of the study results was carried out by means of Statistica 8.0 (StatSoft Inc., USA). Results. Postmortem biological changes in cadaver tissues correlate with the nature of their impedance dynamics. The study of impedance under conditions of natural biocenosis established its identical dependence on the postmortem interval for all current frequencies of the study of all diagnostic zones of model biological objects: in the initial interval of 0–4 days, the impedance gives a “surge” followed by a smoother decrease. Cadaver tissues were recorded to indicate the presence of impedance dispersion in general in the studied frequency range and the absence of dispersion directly for high frequencies. Conclusion. Understanding the causes and essence of postmortem processes contributes to assessing and substantiating changes in any characteristics of tissues measured quantitatively, including impedance indicators, as well as to predicting the prospects of their use for specific practical purposes, in particular, for determining the postmortem interval.