title: CNS toxicity in closed-circuit oxygen diving: symptoms reported from 2527 dives.
abstract: BACKGROUND
  Oxygen toxicity is a problem in diving and can have fatal consequences in the water. Various aspects of oxygen diving have been studied in dry hyperbaric chambers, but there is a lack of information on in-water diving using closed-circuit oxygen apparatus.
  
  
  METHODS
  We collected 2527 dive reports from 473 closed-circuit oxygen divers (a mean of 5.2 reports per diver), and analyzed the relationships between various symptoms and their dependence on depth and diving time.
  
  
  RESULTS
  No CNS oxygen toxicity-related symptoms were reported at a depth of 2 m seawater (msw), but their proportion increased at depths from 3 to 6 msw. We found that CNS oxygen toxicity-related symptoms appeared in 2.5% of dives conducted at a Po2 of 119 kPa. The main symptoms and signs reported were headache: 4.5%; nausea: 2.6%; hyperventilation: 2.6%; heavy breathing: 2.4%; dizziness: 1.6%; hiccups: 1.5%; bloody sputum: 1.4%; cold shivering: 1.1%; tinnitus: 0.9%; difficulty maintaining a steady depth: 0.9%; disorientation: 0.6%; tiredness: 0.5%; tingling in the limbs: 0.4%; hearing disturbances: 0.4%; a choking sensation: 0.4%; extreme effort: 0.4%; and loss of consciousness: 0.3%.
  
  
  CONCLUSIONS
  Environmental factors, light vs. dark and temperature, had no effect on symptoms. The number of symptoms increased with diving time. Divers who experienced amnesia, facial twitching, hearing disturbances (p < 0.001), and disorientation (p < 0.014) were prone to suffer loss of consciousness. It was found that some divers are more sensitive to oxygen than others (p < 0.0001).
authors.affiliation: Israel Naval Medical Institute, IDF Medical Corps, Haifa, Israel. rarieli@netvision.net.il
authors.forename: Ran
authors.initials: R
authors.lastname: Arieli
authors.forename: Tzippora
authors.initials: T
authors.lastname: Shochat
authors.forename: Yochai
authors.initials: Y
authors.lastname: Adir
mesh_terms: D000402:Airway Obstruction / Q000209:etiology; D003221:Confusion / Q000209:etiology; D004242:Diving; D004244:Dizziness / Q000209:etiology; D005221:Fatigue / Q000209:etiology; D006261:Headache / Q000209:etiology; D006311:Hearing Disorders / Q000209:etiology; D006469:Hemoptysis / Q000209:etiology; D006606:Hiccup / Q000209:etiology; D006801:Humans; D006985:Hyperventilation / Q000209:etiology; D008889:Military Personnel; D009325:Nausea / Q000209:etiology; D010100:Oxygen / Q000009:adverse effects*; D010292:Paresthesia / Q000209:etiology; D012768:Shivering; D013997:Time Factors; D014012:Tinnitus / Q000209:etiology; D014474:Unconsciousness / Q000209:etiology; D014939:Work of Breathing
chemical_list: D010100:Oxygen