Normobaric Hyperoxia Does Not Induce Significant Electroencephalogram Changes in Healthy Male Subjects

Abstract

ObjectiveHyperoxia can cause slowing and epileptic seizures in the electroencephalogram (EEG) when administered under hyperbaric conditions. Also hyperventilation and ensuing hypocapnia induce EEG slowing and may provoke epileptiform acitivity in patients with epilepsy. We aimed to study whether prolonged normobaric hyperoxia without hyperventilation has any effects on EEG. Methods Ten healthy, non-smoking men, aged 21-30 years, were recruited. Nineteen-channel-EEG was recorded continuously during breathing of 100 % oxygen through a tight 5 cmH2O continuous positive airway pressure –mask for one hour resulting in a mean end-tidal oxygen concentration of 91.1% (SD 1.8%). EEG-signal was analysed both visually and quantitatively after Fast Fourier Transformation. Total power and main frequency band powers (beta, alpha, theta, and delta) were calculated from the power spectrum, and compared between the baseline (before starting 100% oxygen) and after one hour breathing of pure oxygen. ResultsA slight reduction in posterior alpha band power and a simultaneous increase in anterior and lateral slow EEG activity occurred during oxygenation, but none of the changes remained significant after adjustment for multiple statistical comparisons. No epileptiform or other adverse activity occurred in the EEG. ConclusionsIn healthy subjects, normobaric oxygen, even when administered in high concentrations, does not cause significant EEG slowing or produce any other, possibly harmful changes in the EEG.