A condition which results from breathing Helium under high pressures. Early symptoms of HPNS are sometimes seen as shallow as 300FSW but more commonly over 600FSW. The severity also depends on the mix of breathing gases, Nitrogen can often moderate the affects of HPNS. The early symptoms include muscle tremors, followed by changes in electroencephalogram (EEG) readings, impaired motor and problem solving skills. Other symptoms can include euphoria, nausea, vomiting, lack of appetite and drowsiness. Symptoms sometimes moderate or entirely disappear with continued exposure.