Had a not so fun experience, any ideas?

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Princess Chris

Registered
Scuba Instructor
Messages
33
Reaction score
33
Location
Wellington, New Zealand
# of dives
500 - 999
Ok so I had a rather unnerving experience acouple of weeks ago during a dive and for the life of me I cannot figure out what the cause of it was.
So I was diving a wreck (no penetration) at 40m, the plan was to descend down a mooring line on to the wreck spend a few minutes having a look then head up a slope to a shallow reef and finish off the dive there. I got a little distracted by a lion fish trying to eat a baby octo (who wouldn't?) and ended up going into deco. My computor beeped at me so I started my ascent in a calm and controlled manner and followed my comp instructions. This is when things got a bit screwy. At about 27m I had a strong feeling that I was going to lose consciousness. I managed to fight this off, signal to my buddy that I had a problem and pointed to my head. This continued for about 1/1.30 minutes. I maintained a safe ascent rate and made sure my buddy was right next to me. At about 20m I felt ok again just very confused.

This is not a new dive to me, I have done it several times with exactly the same profile. I wasn't in sick, tired, hungover or unfit. There is just one variable that I can't seem to figure out. Only thing different is that I went a little deeper than planned but still doesnt explain what happened.

If anyone could shed some light on the cause of the light headness then please let me know.
Thanks
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Did you test your tank for CO before your dive?

Excellent question. Does CO or CO2 effects abate at shallower depths? I'm wondering why he would have felt better at 20m.
 
Does CO or CO2 effects abate at shallower depths? I'm wondering why he would have felt better at 20m.

Very likely, because with all gas components, the partial pressures will be reduced at shallower depths. CO would be my first suspect.
 
Alert Diver | Carbon Monoxide: The Silent Killer

My interpretation of the article above is the symptoms of CO poisoning might well be reduced as depth is decreased. Assuming you don't pass out and drown before that happens!
That article just sucks, as it totally misses the risk of overworked, hot compressors burning their own lubricating oil. It gives lip service to a risk but no real solution.

Aside from that, you are partially right in that CO tainted gas would have a lessor effect at shallow depths on descent. It gets tricky on ascent as while PPO2 decreases as you go up, the CO already bound to your blood while at depth stays much longer so the effect can increase.

Could have CO tainted gas have caused the problem described in the original post? Maybe. There's only one way to tell, best done before the dive. It'd be possible now if the tank has not been drained or refilled and a CO tank tester could be obtained.
 
A touch of vertigo? It does happen sometimes when we lose our frame of reference and or brain gets mixed signals. An ascent is probably a likely time for this to occur.
 
I'd think CO would have had a longer effect, you might even have felt it coming on. I've had it above water and it just doesn't go away.

I'd purely guess vertigo too....

Any trouble equalizing, any full feeling in your ears after the dive?
 
Everyone on ScubaBoard has CO on the brain for every issue. Unless there is other evidence I would assume a simpler explanation.

You dove to 43m /141 feet and got seriously narc'ed! This is why is quickly cleared as you ascended rather than perishing from CO poisoning. Everyone gets narc'ed at different depths and experiences vary, but at 141 feet it might be expected.

Common symptoms of nitrogen narcosis:
  • poor judgement
  • short-term memory loss
  • trouble concentrating
  • a sense of euphoria
  • disorientation
  • reduced nerve and muscle function
  • hyperfocusing on a specific area
  • hallucinations
 
Everyone on ScubaBoard has CO on the brain for every issue.
No, not really, not at all. Not near enough. And others have suggested Vertigo, which is certainly a fitting possibility.

You dove to 43m /141 feet and got seriously narc'ed! This is why is quickly cleared as you ascended rather than perishing from CO poisoning.
His problem did not hit at 43/141 feet. He was almost halfway up. Narcosis doesn't fit.
At about 27m I had a strong feeling that I was going to lose consciousness.
 
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