Features of the Dynamics of the Human EEG Spectrum at a Constant Level of Acute Hypoxia

Features of the Dynamics of the Human EEG Spectrum at a Constant Level of Acute Hypoxia:

Studies of 12 subjects using Fourier analysis addressed the EEG amplitude-frequency spectrum at a constant level of normobaric hypoxia (breathing an oxygen-nitrogen mix containing 8% oxygen for 25 min). Cluster analysis of the 16-channel EEG identified two groups of subjects differing in terms of relative spectral power (SP) in the EEG δ range averaged over the period of hypoxia. Six of the subjects of the group 1 (n = 7), with greater relative SP in the δ range during hypoxia showed dominance o δ activity in all subsequent 1-min segments and all leads starting after 6 min of hypoxia. Subjects of group 2 (n = 5) showed dominant α activity in the occipital leads overall for the 25 min of hypoxia. In sequential 1-min segments, the dominance of α activity in some subjects of this group changed to a dominance of δ and θ activity. These studies showed that the dynamics of the EEG amplitude-frequency spectrum at a constant level of hypoxia do not always correspond to sequential “slowing” of the EEG described in increasing hypoxia.