title: CNS oxygen toxicity in closed-circuit diving: signs and symptoms before loss of consciousness.
abstract: BACKGROUND
  There is a dearth of information regarding CNS oxygen toxicity accidents in closed-circuit oxygen diving. The aims of the present study were to report the sensations and symptoms that accompany CNS oxygen toxicity accidents, and to evaluate whether loss of consciousness can occur without any warning signs.
  
  
  METHODS
  We documented 36 CNS oxygen toxicity accidents in closed-circuit oxygen diving. The full accident inquiry included the first report from the diving unit, an interview of the victim and his buddy by the researchers, and an examination of the diving equipment.
  
  
  RESULTS
  The symptoms that appeared before termination of a dive, as reported by the victim or his buddy, were as follows (in descending order of frequency): limb convulsions; hyperventilation; difficulty maintaining a steady depth; headache; and visual disturbances. The symptoms that appeared after detachment from the mouthpiece were, in descending order of frequency: headache; loss of consciousness; confusion; weakness; dizziness; and facial muscle twitching and limb convulsions. A high inspired CO2 [mean 4.2 kPa (29.9 mmHg)] was connected with loss of consciousness. No dive was terminated before at least two symptoms (mean 3.4) had been noted a minimum of 5 min before termination.
  
  
  CONCLUSIONS
  Symptoms that are accepted as being related to CNS oxygen toxicity, as well as others such as headache, difficulty maintaining a steady depth, hyperventilation, weakness, and a choking sensation, were more frequent among the O2 accident victims compared with divers who did not interrupt their dives.
  
  
  CONCLUSIONS
  Awareness of any unusual sensation can prevent a potentially dangerous situation from arising.
authors.affiliation: Israel Naval Medical Institute, IDF Medical Corps, Haifa, Israel. rarieli@netvision.net.il
authors.forename: R
authors.initials: R
authors.lastname: Arieli
authors.forename: Y
authors.initials: Y
authors.lastname: Arieli
authors.forename: Y
authors.initials: Y
authors.lastname: Daskalovic
authors.forename: M
authors.initials: M
authors.lastname: Eynan
authors.forename: A
authors.initials: A
authors.lastname: Abramovich
mesh_terms: D000059:Accidents; D002245:Carbon Dioxide / Q000032:analysis; D002490:Central Nervous System / Q000378:metabolism*; D004242:Diving / Q000502:physiology*; D006801:Humans; D010100:Oxygen / Q000009:adverse effects* / Q000097:blood*; D014474:Unconsciousness / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen