Efficacy of surface electrodes for the detection of electrocardiogram activity during deep accidental hypothermia

Experiments OR seven anaesthetised pigs were conducted where ECG was measured using sulface, needle apld epicardial electrodes during cooling of the pig to simulate deep accidental hypothemia. Data at four cooling conditions were examined: Control (skin at room temp, core 38c), Cool Skin (skin 2c, core 30c), Hypothermia and deep Hypothermia (skin 10c, core 15c). There was no significant change in the amplitude of ECG with cooling of the skin. However, there was a factor of 9 decrease in the ECG amplitude with decreasing core temperature. Core cooling slowly results in a decrease in the amplitude of the QRS complex and T wave, which is ultimately replaced by a IHz flutter, while the P wave remains relatively constant. This suggests that decreases in ECG amplitude is due to changes in the active bioelectricai behavior heart. rather than changes in the distribution of the ECG field in the body due to temperature dependant passive electrical impedance changes in the tissue.