High-pressure nervous syndrome (HPNS – also known as high-pressure neurological syndrome) is a neurological and physiological diving disorder that results when a diver descends below about 500 feet (150 m) while breathing a helium–oxygen mixture. The effects depend on the rate of descent and the depth. HPNS is a limiting factor in future deep diving.
"Helium tremors" were first widely described in 1965 by Royal Navy physiologist Peter B. Bennett, who also founded the Divers Alert Network. Russian scientist G. L. Zal'tsman also reported on helium tremors in his experiments from 1961. However these reports were not available in the West until 1967.
The term high pressure nervous syndrome was first used by Brauer in 1968 to describe the combined symptoms of tremor, electroencephalography (EEG) changes, and somnolence that appeared during a 1,189-foot (362 m) chamber dive in Marseille.
Read more about High-pressure Nervous Syndrome: Symptoms, Causes, Prevention
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