EEG changes during five minutes of inhalation of a 33% xenon-O2 mixture

The effects on the EEG of inhalation of a 33% Xenon O2 mixture over a period of 5 minutes were studied in 18 human volunteers. This dosage is similar to that used in xenon CT studies. In 4 subjects no EEG changes were observed during the study. In the 14 other subjects, EEG variations were detected, the most prominent of which was an increase in beta power. No change was observed in theta and delta power. These findings seem to support an early induction (excitation) phase of anaesthetics. All changes disappeared rapidly following the termination of xenon inhalation. The effects reported are minimal and should not impair the clinical value of CBF measurements using the xenon CT method.