An objective approach using three indexes for determining fatal hypothermia due to cold exposure; statistical analysis of oxyhemoglobin saturation data

• We devised diagnostic criteria for fatal hypothermia using O2-Hb saturation.
• Our quantitative criteria yielded ⩾86% sensitivity and ⩾93% specificity.
• Refrigerator storage has no significant effect on O2-Hb saturation of heart blood.
• The method is useful for determining hypothermia in combination with conventional methods.

Analysis of oxyhemoglobin (O2-Hb) saturation levels in the left and right heart blood is useful in the assessment of exposure to cold surroundings before death. We quantified conventional subjective visual evaluation of O2-Hb saturation levels and developed useful diagnostic criteria for fatal hypothermia: O2-Hb saturation in the left heart blood (L-O2Hb) was ⩾36%, the O2-Hb saturation gap between the left and right heart blood (L–R gap) was ⩾13%, and the O2-Hb saturation ratio of the left to right heart blood (L/R ratio) was ⩾1.8. When we used L-O2Hb of ⩾36% as a basic criterion and applied a further criterion of an L–R gap of ⩾13% or an L/R ratio of ⩾1.8, these criteria registered a sensitivity level of ⩾86% and specificity level of ⩾93% for the diagnosis of fatal hypothermia. This method can be useful for determining fatal hypothermia in connection with conventional autopsy findings, as well as histological and biochemical markers.

Scatter plots of hypothermia (●) and control (□) cases, with L-O2Hb (oxyhemoglobin (O2-Hb) saturation levels in left heart blood) and L–R gap (difference in O2-Hb saturation levels between left and right heart blood) represented by the abscissa (%) and ordinate (%), respectively.Figure optionsDownload high-quality image (108 K)Download as PowerPoint slide