Conditions favoring its occurrence:
(1) elevated partial pressure of oxygen to > 1.6 atmospheres (rare if < 1.4 atmospheres). This is encountered only in divers or someone in a pressurized environment.
(2) elevation in carbon dioxide (from inadequate ventilation during heavy exertion, failure of carbon dioxide scrubbing, or presence of CO2 in breathing mixture)
(3) increased exertion or metabolic function. This may include shivering, strenuous exercise, thyrotoxicosis, stimulant overdosage.
(4) increased time of exposure
Symptoms (make the mnemonic VENTIDC):
(1) visual symptoms, including tunnel or blurred vision
(2) ear symptoms, with tinnitus (roaring, bells ringing, machinery-like)
(3) nausea or spasmotic vomiting
(4) twitching or tingling, affecting muscles in the face, lips or extremities
(5) irritability, plus confusion, agitation and anxiety
(6) dizziness, plus clumsiness, incoordination or unusual fatigue
(7) convulsions, and possibly loss of consciousness
where:
• DIVE CNS might be another mnemonic, with S for spasms replacing T for twitching and tingling).
