Complexity and Topographic Analysis of EEG under Normal and Simulated High Altitude Acute Hypoxia Conditions

This study investigated hypoxia related changes in the human brain function through EEG analysis with the method of Lempel-Ziv complexity (LZC) and approximate entropy (ApEn). Meanwhile, multichannel human EEG signals were studied topographically in 3 healthy subjects under normal and different hypoxia conditions respectively. It was found that when subjects were at the simulated altitude of 3000m, the measure of LZC and ApEn increased in almost all channels. The results also show that after 15 days hypoxic training, the LZC measure and ApEn decreased obviously and almost the same as those in normal condition. This suggests that after hypoxic training, the subjects were almost adapted to the hypoxia environment. In addition, the complexity measure was calculated and compared in each sub frequency band. We propose that LZC and ApEn can be used to evaluate the effect of brain functional changes at different levels of hypoxia and hypoxic training is an effective means to prevent hypoxic fatigue.