[On the compression rate for inhibiting high pressure nervous syndrome under high pressure helium atmosphere]

Bennett (1975) reported that signs and symptoms of the High Pressure Nervous Syndrome (HPNS) appeared including nausea, dizziness, tremors of the hands and arms, increased slow wave activity in electroencephalogram, especially in the theta band (4-7 Hz) with depression of alpha (8-13 Hz) and beta (20 Hz and higher) on compression with oxygen-helium to depths greater than 500 ft (16 ATA). Earlier studies have indicated that the HPNS may be controlled by use of an increased nitrogen partial pressure, slowing compression rate or excluding subject who has higher susceptibility to HPNS. For determining the effect of slowing compression rate, it was changed to new compression profile of linear compression to 31 ATA with intermediate stops in SEADRAGON-VI carried out at JAMSTEC in 1983. All divers to compressed to 31 ATA using the new rate complained few and slight signs and symptoms involved HPNS than ever experienced.