This is used to eliminate Nitrogen narcosis and to control the affects of Oxygen toxicity, by eliminating the Nitrogen and reducing the Oxygen in the breathing mix. Another benenfit is reduced effort of breathing due to the lower density of helium. There have been some reports of divers feeling jittery when using heliox, and as dives go beyond about 300 FSW, classic symptoms of HPNS can begin to appear. In rebreather diving this is usually the product of a poorly functioning scrubber . However, the condition is not limited to rebreather users.
Typical symptoms are a shortness of breath and a headache.
In extreme cases the final result is unconsciousness and eventual death from lack of Oxygen. Skip breathing , hard work at depth, dead air spaces in the breathing loop and other problems can lead to hypercapnia. Hyperoxic and Hyperoxia - In general, these terms relate to a more than a normal amount of Oxygen. Hyperoxia is the physiological condition associated with breathing too high of a partial pressure of Oxygen. The human body has a limit on both the partial pressure of Oxygen it can tolerate and the long term dosage of Oxygen.