Nitrogen narcosis


  • Toxic effects of breathing nitrogen-containing gases while at depth
  • Called the "rapture of the deep"
  • Develops between 3-4ATM (99-132 feet)[1]
    • Rare at depths less than 30 meters (100 ft) unless breathing non-standard air mixtures
    • Similar to alcohol, frequent divers can develop subjective "tolerance" to the effects, but impairment remains[2][1]
  • Can be prevented by using nitrogen-free gas mixture (e.g. heliox), or mixtures with reduced nitrogen content (e.g. helium-nitrogen-oxygen)[1]
  • Risk factors = exertion during dive, cold conditions, alcohol intoxication before dive[1]
  • Other inert gases cause similar symptoms at depth - severity based on lipid solubility of the gas[3]

Clinical Features

  • Insidious onset of symptoms similar to alcohol intoxication (or nitrous oxide inhalation)[1][2]
  • Causes high risk of making bad decisions at depth, i.e. impairs diver's judgment therefore leading to drowning accidents (cause of up to 9% of diving deaths)[1][2]

Differential Diagnosis

Scuba Diving Emergencies


  • Clinical diagnosis


  • Ascent - symptoms completely reversed within minutes by ascending to a shallower depth, with no long-term effect
    • Therefore, consider other causes in patients with continued symptoms after ascent


  • Discharge

See Also

External Links


  1. 1.0 1.1 1.2 1.3 1.4 1.5 Grover CA, Grover DH. Albert Behnke: nitrogen narcosis. J Emerg Med. 2014 Feb;46(2):225-7.
  2. 2.0 2.1 2.2 Levett DZ, Millar IL. Bubble trouble: a review of diving physiology and disease. Postgrad Med J. 2008 Nov;84(997):571-8.
  3. Bove AA. Diving medicine. Am J Respir Crit Care Med. 2014 Jun 15;189(12):1479-86.