利用猪胸主动脉生物力学性能时序性变化推断死亡时间

Study on the postmortem interval estimation by timedependent changes of biomechanical of thoracic aorta in pigs

目的观察分析家猪尸体胸主动脉生物力学性状指标的变化规律,探讨其在死亡时间(PMI)推断中的应用价值。方法采集180根家猪的主动脉,在恒定温度、湿度下,于2～230h之间每间隔12h设置1个取检材时间点组;各组主动脉检材用电子万能材料试验机拉伸检测极限载荷、极限载荷变形、平均力、应力、应变,宽度和厚度等生物力学参数指标;应用多元逐步回归方法进行统计学分析。结果家猪死后230h内,随PMI延长,胸主动脉大体观呈自溶腐败性变色、瘫软、液化趋势。生物力学参数指标中,极限载荷、平均力和应力呈随PMI延长呈明显下降趋势,PMI间隔24h组间比较差异性均有统计学意义(P<0.05),校正决定系数分别为0.923、0.806、0.867,估计标准误差分别为±18.39h、±29.88h、±24.58h,PMI间隔24h组间比较差异性均有统计学意义(P<0.05),其它指标与PMI之间相关性不显著均P>0.05。结论死后230h内家猪胸主动脉的极限载荷、平均力和应力的死后时序性变化,与PMI呈明显的负相关性,可用于PMI推断,其中极限载荷效果最佳。

Objective To explore the timedependent changes in the biomechanical properties of thoracic aorta of pigs under the influence of autolysis and putrefaction after death, and to discuss its value to determine the postmortem interval （PMI）. Methods One hundred eighty aortas were taken from pigs slaughtered routinely and were put into artificial climate chamber with constant temperature and humidity. They were divided into different groups by 12 hours after death from 2 hours to 230 hours, and were sampled at every time point. The samples were immediately tested by electronic universal testing machine to obtain the biomechanical parameters, including limit load, maximum tension deformation, average pulling force, tensile stress, strain. Multiple stepwise regression was performed to determine the relationship between postmortem interval and biomechanical properties. Results During the PMI of 230 hours, the thoracic aortas gradually discolored, liquefied and became weak and thick under the influence of autolysis and putrefaction. Biomechanical properties of the thoracic aortas, including limit load, average pulling force and tensile stress decreased significantly with increasing PMI, and the difference of comparison among groups at the interval of 24 hours was obvious and statistically significant, with their Adjusted R Square of 0. 923, 0. 806 and 0. 867, respectively, and the estimated Std. Errors of ＋ 18.39h, _＋ 29.88h and ＋__ 24.58h, respectively. Conclusion Biomechanical properties, including limit load, average pulling force and tensile stress werestrongly negatively correlated with the PMI. They could be used to estimate the PMI up to 230 hours, and the limit load was the best indicator.