Power Spectral Analysis of the Neonatal Primate Electroencephalogram during Acute Hypoxemia

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Abstract
The effect of acute graded hypoxemia on the EEG of 5 prematures and 5 full term Macaca nemestrina in the neonatal period was determined using power spectral analysis, a technique that obviates the limitations of visual inspection. The EEG of selected epochs was analyzed by a Fast Fourier Transform program (POWER) during the 20 min of each trial of hypoxemia and compared with simultaneous arterial O2 tensions. Levels of hypoxemia were graded as profound (PaO2 [arterial partial pressure] = 15-25 Torr), severe (PaO2 = 26-35 Torr), moderate (PaO2 = 36-50 Torr) or mild (PaO2 = 51-75 Torr). The EEG during normoxemia had a band width of 0.5-10 Hz and a peak power at 1-3 Hz. During mild hypoxemia, an increase in power in the delta range (0-3.5 Hz) occurred in the oldest animals. At moderate hypoxemia, the youngest animals showed a depression of absolute power in the delta band. A slowing of the EEG and decrease in power in the theta frequency range (4-8 Hz) followed when severe hypoxemic levels were reached. During profound hypoxemia, all animals at each postnatal age exhibited a significant decrease in EEG power at the delta and theta frequencies (P < 0.025) except 3 wk old full term animals in which there was no significant change in the delta band. These results clarify and extend previously reported effects of hypoxemia on the neonatal EEG.