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. 2006 Jun;53(6):1016-23.
doi: 10.1109/TBME.2006.873394.

Quantitative EEG and effect of hypothermia on brain recovery after cardiac arrest

Hyun-Chool Shin  1 , Shanbao Tong, Soichiro Yamashita, Xiaofeng Jia, Romergryko G Geocadin, Nitish V Thakor
Affiliations

Quantitative EEG and effect of hypothermia on brain recovery after cardiac arrest

Hyun-Chool Shin et al. IEEE Trans Biomed Eng. 2006 Jun.

Abstract

In this paper, we provide a quantitative electroencephalogram (EEG) analysis to study the effect of hypothermia on the neurological recovery of brain after cardiac arrest. We hypothesize that the brain injury results in a reduction in information of the brain rhythm. To measure the information content of the EEG a new measure called information quantity (IQ), which is the Shannon entropy of decorrelated EEG signals, is developed. For decorrelating EEG signals, we use the discrete wavelet transform (DWT) which is known to have good decorrelating properties and to show a good match to the standard clinical bands in EEG. In measuring the amount of information, IQ shows better tracking capability for dynamic amplitude change and frequency component change than conventional entropy-based measures. Experiments are carried out in rodents (n = 30) to monitor the neurological recovery after cardiac arrest. In addition, EEG signal recovery under normothermic (37 degrees C) and hypothermic (33 degrees C) resuscitation following 5, 7, and 9 min of cardiac arrest is recorded and analyzed. Experimental results show that the IQ is greater for hypothermic than normothermic rats, with an IQ difference of more than 0.20 (0.20 +/- 0.11 is 95% condidence interval). The results quantitatively support the hypothesis that hypothermia accelerates the electrical recovery from brain injury after cardiac arrest.

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Figures

Fig. 1
Fig. 1
Time evolution of SE, WE and IQ for signal with time-varying frequency components and Gaussian distribution. (a) Time domain representation. (b) Comparison of SE, WE, and IQ.
Fig. 2
Fig. 2
Real EEG data for a rat which is recovered after asphyxic cardiac arrest. (a) EEG recording under normothermia (I) is 10 min (baseline), (II) is 7-min brain injury after cardiac arrest and (III) is recovery under normothermia (37 °C). (b) EEG recording under hypothermia (I) is 10 min (baseline), (II) is 7-min brain injury after asphyxic cardiac arrest, (III) is 45-min early recovery under normothermia and (IV) is recovery under hypothermia (33 °C).
Fig. 3
Fig. 3
SE and IQ for experimental EEG data for rats under normothermia and hypothermia after 5-, 7-, and 9-min asphyxia cardiac arrest (Each curve is the averaged result over 5 rats). (a) Comparison of SE under hypothermia to SE under normothermia for 5-min brain injury. (b) Comparison of IQ under hypothermia to IQ under normothermia for 5-min brain injury. (c) Comparison of SE under hypothermia to SE under normothermia for 7-min brain injury. (d) Comparison of IQ under hypothermia to IQ under normothermia for 7-min brain injury. (e) Comparison of SE under hypothermia to SE under normothermia for 9-min brain injury. (f) Comparison of IQ under hypothermia to IQ under normothermia for 9-min brain injury.
Fig. 4
Fig. 4
The quantitative EEG measures (SE or IQ) versus NDS (a) averaged SE versus NDS. (b) Averaged IQ versus NDS.
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References

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