Power Spectrum and Cross Power Spectral Density Based EEG Correlates of Intensive Care Delirium

Full montage EEG recordings of 15 ICU patients (altogether 23 recordings) were analysed to find EEG correlates of delirium. CAM-ICU assessment results were used as the reference. Time period from 7 to 30 minutes at the beginning of the recordings was analysed in 10 sec segments with 5 sec overlap. Relative power in the conventional frequency bands of the EEG signal at 20 electrode locations with common reference was calculated. In the state of delirium the relative power of frequencies above 8 Hz was lower; this effect was predominantly observed at central and parietal lobes. Also, the absolute cross power spectral density of 20 - 30 Hz was significantly lower in delirium between almost any two electrode locations.