Nitrogen narcosis during deep diving

Nitrogen narcosis is caused by the increased partial pressure of nitrogen in compressed air at depth, resulting in increased nitrogen within nervous system tissues. Known as ‘rapture of the deep’, nitrogen narcosis produces changes similar to alcohol intoxication, including impairment of intellectual performance, deterioration in judgement, and personality changes. It usually only occurs at depths of greater than 30 metres (100 feet), which is why recreational scuba diving is limited to this depth.

The risk of nitrogen narcosis increases if the diver is cold, dehydrated or has consumed alcohol in the preceding 24 hours. Some medications can potentiate the effects of nitrogen narcosis (eg sedating drugs). The main danger is drowning as a result of impaired judgement. Symptoms resolve rapidly after ascent.

In screening people to determine if referral to a diving doctor is required to assess fitness to dive, ask if the person has any predisposing factors or a history suggestive of nitrogen narcosis; these warrant assessment by a diving doctor to clarify the diagnosis and to advise on the safety of further diving.