High-Pressure Nervous Syndrome

High-pressure nervous syndrome (HPNS – also known as high-pressure neurological syndrome) is a neurological and physiological diving disorder that results when a commercial diver or scuba 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

Symptoms of HPNS include :

• tremors
• myoclonic jerking
• somnolence,
• EEG changes,
• visual disturbance
• nausea, dizziness
• decreased mental performance