Influence of hyperbaric heliox environment at 31ATA on microvibration and electroencephalogram in four divers

Abstract

The simulated experiment of heliox dive to 31ATA in four subjects was performed for one month including the pressure holding for one week. In order to study the influence of hyperbaric environment on physical condition and level of consciousness, microvibration (MV) on thenar and eyelid and electroencephalogram (EEG) on T4 and O2 were measured at various atmosphere conditions. The power spectrum of MV and EEG were calculated: The peak frequency of power spectrum and the magnitude of power spectrum at the peak frequency were evaluated. The amplitude of MV increased after compression as compared with the value of pre-compression i.e., 1ATA, and the tendency was emphasized on eyelid MV at post-compression i.e., 1ATA, whereas the peak frequency of MV did not change significantly throughout the experiment. A remarkable hyperbaric effect was found in the evaluation of EEG peak frequency; The lowering of the peak frequency was recognized during the process of compression, pressure holding, and decompression. As the high pressure nervous syndrome (HPNS), especially during compression, was not recognized here, MV was not used as a detector of omen of HPNS, but the hyperbaric effect on skeletal muscle was found in ballistocardiogram component of MV due to the increase of the amplitude at post-compression. EEG denoted the lowering of level of consciousness during pressure holding, so that the result meant calling one's attention to the operation in hyperbaric environment of 31ATA.