Nitrogen narcosis

Background

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

Clinical Features

• Insidious onset of symptoms similar to alcohol intoxication (or nitrous oxide inhalation)
  • Early stage: Euphoria, false sense of security, impaired judgement
  • Later stage: Impaired concentration and memory, paresthesias, hallucinations
  • Final stage: [Occurs at depths of at least 10-13ATM (333-429 feet)], lethargy and loss of consciousness
• Causes high risk of making bad decisions at depth (cause of up to 9% of diving deaths)

Differential Diagnosis

Diving Emergencies

• Barotrauma of descent
  • Otic barotrauma
  • Pulmonary barotrauma
  • Sinus barotrauma
  • Mask squeeze
  • Barodentalgia (trapped dental air causing squeeze)
• Barotrauma of ascent
  • Pulmonary barotrauma (pulmonary overpressurization syndrome)
  • Decompression sickness (DCS)
  • Arterial gas embolism
  • Alternobaric vertigo
  • Facial baroparesis (Bells Palsy)
• At depth injuries
  • Oxygen toxicity
  • Nitrogen narcosis
  • Hypothermia
  • Contaminated gas mixture (e.g. CO toxicity)
  • Caustic cocktail from rebreathing circuit

Diagnosis

• Clinical diagnosis

Management

• 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

Disposition

• Discharge

See Also

• Scuba diving emergencies