Is your deco mix killing you?

[Dr Stevil]

Originally Posted by Andrew H

I had the impression that oxidant as in anti oxidant was of the chemical type of oxidation ie loss of electrons, rather than an addition of oxygen per se.
Andrew

Oxidation may be either loss of electrons or the addition of oxygen, though the former is more widespread. either way, I'm more than happy with high ppO2 for my diving

[MattS]

AIUI

O2 like so many other drugs causes acute (short term) and chronic (long term) damage.

The acute damage is basically the convulsion. The process is thought to be caused by lipid peroxidation in the CNS. The thinking is that free radicals destabilise molecules in the lipid fats that make up the spinal chord, brain and other CNS tissues making the muscles they control go a bit loopy.

Free radicals are fairly short lived but continueing to breathe O2 at high pressures will allow them to build up faster than they die off. The more of these free radicals you have, the more likely a hit becomes. An air break provides time for the free radicles to effectively die off. The research into this process comes mainly from work on Alzheimers disease. Divers using Nitrox measure the risk of acute O2 poisoning using the CNS clock.

The chronic damage that hyperbaric O2 causes is a result of it's acidity. It burns the lungs to an extent which is relative to the pressure that you are breathing it at. The process is incremental with each exposure to high pressure O2 causing a little bit more damage. The sypmtoms of chronic O2 poisoning are respiratory problems and the like. There is not an awful lot you can do about it other than limit exposure times and give your lungs a chance to recover now and again. Divers using Nitrox measure the risk of chronic O2 poisoning using UPTDs or OTUs - different names for the same thing.

Now lets get chronic O2 poisoning in perspective. It is usually only a problem for people who routinely expose themselves to long periods breathing high pressure oxygen - saturation divers, chamber technicians and at the lower end of the risk group extreme technical divers. The rest of us just need to be aware of it and not do anything stupid.

Think about the last time you had your teeth x-rayed. The nurse would have hidden behind a lead plate to limit their x-ray dose while you get the full on exposure. It is highly unlikely that an average person will be damaged by the x-ray exposure they recieve in their lifetime. The nurse however is exposed many times a day and must take measures to limit the exposure to avoid x-ray poisoning. Unless you are doing hours of deco at high partial pressures you can pretty much ignore chronic O2 poisoning.

The chronic damage done by breathing Nitrox is a bit like drinking a cup of tea after your dive. A cup of tea contains a small amount of Aluminium which is pretty toxic stuff. However most of us manage a whole lifetime of drinking tea without developing symptoms of Aluminium poisoning - although I understand the risk is higher North of Watford Gap ;-)

[Andy Phillips]

I read the first line of this thread and thought ............. wait fot it ............. ah here's SteveW. In case any of you haven't worked it out. This is his field.

God bless you son,

Andrew

[MattS]

All due respect to SteveW

...(vitamin C) acts as a pro-oxidant, in this case by reducing Fe3+ to Fe2+, which in the presence of H2O2 leads to the production of OH. via the Fenton reaction.

His field appears to be somwhere near Greece ;-)

[Andy Phillips]

Only mentally only I thought it was more Lala land ----- sorry Steve.

Andrew

[Adrian Kelland]

Originally Posted by imported_andyp

Only mentally only I thought it was more Lala land

More like Toon Town

That's All Folks.

[Andy Phillips]

Originally Posted by Adrian Kelland

More like Toon Town

That's All Folks.

Not fair, funnier than mine.

Andrew

[Dr Stevil]

Originally Posted by MattS

His field appears to be somwhere near Greece ;-)

I give in, I don't geddit, "Greece" ?? Que???
confused of Toonland

[Adrian Kelland]

All Greek to me?

[Dr Stevil]

Originally Posted by Adrian Kelland

All Greek to me?

"clunk" Ah... sound of penny dropping, cheers Adrian, I was trying to think of something to do with the upcoming Olympics (Jeee-zus! hope they've got the security sorted out big style, I clearly remember the 1972 Munich massacre)