Wednesday, July 05, 2006

CNS toxicity in closed-circuit oxygen diving: symptoms reported from 2527 dives.

CNS toxicity in closed-circuit oxygen diving: symptoms reported from 2527 dives.

There is a report in the journal "Aviation Space & Environmental Medicine for May, 2006 that you might find interesting. The study was done by a group at the Israel Naval Medical Institute in Haifa, Israel and led by Dr.s Arieli, Shochat and Adir.
< rarieli@netvision.net.il > The following is an abbreviated abstract of the article:

INTRODUCTION: Little work has been done on the problem of oxygen toxicity in divers '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.

METHOD: We collected 2527 dive reports from 473 closed-circuit oxygen divers, 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%.

DISCUSSION: 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).

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