OTU's and CNS

[ziggyngizmo]

Hi everyone,

Looking back over my DSAT planning tables and realised that there are 2 ways to monitor pulmonary oxygen toxicty - OTUs and CNS%. Why is this? Is it something to do the speed of oxygens action on different tissues (similar in a way to fast and slow tissues for nitrogen.)?

Thanks

[nigelH]

Looking back over my DSAT planning tables and realised that there are 2 ways to monitor pulmonary oxygen toxicty - OTUs and CNS%. Why is this? Is it something to do the speed of oxygens action on different tissues (similar in a way to fast and slow tissues for nitrogen.)?

Nope.
Two almost unrelated effects:
OTUs are nasty oxygen rotting your lungs so you cough and weeze.
CNS is nasty oxygen messing up your nervious system so you have convulsions and blackouts.

[NotDeadYet]

Nope.
Two almost unrelated effects:
OTUs are nasty oxygen rotting your lungs so you cough and weeze.
CNS is nasty oxygen messing up your nervious system so you have convulsions and blackouts.

Or to put it another way, CNS is what you should worry about and OTU's are the ones you shouldn't. You have to go some to get anywhere near the OTU limits and even if you do then you'll feel like you're getting a cold. I've had the full dose in a day and it gave me a bit of a cough. Exceed the CNS limits, convulsion, dead, no warning.

Cheers,

Stuart

[Gene_Hobbs]

Bill Hamilton wrote a nice review of this for SPUMS in '97.

Hamilton Jr, RW. (1997) Tolerating oxygen exposure. South Pacific Underwater Medicine Society Journal. Volume 27 Number 1. RRR ID: 6038

For anyone that is interested, this is a great review/ overview of the history of oxygen in diving:

Acott, Chris J. (1999) Oxygen toxicity: A brief history of oxygen in diving. South Pacific Underwater Medicine Society Journal. Volume 29 Number 3. RRR ID: 6014

[nickb]

You have to go some to get anywhere near the OTU limits and even if you do then you'll feel like you're getting a cold. I've had the full dose in a day and it gave me a bit of a cough.

It's worth thinking about on multi-day trips though. A week diving the arse out of the cruisers etc. in Scapa using O2 for deco would get you there quite easily. I've come back feeling like my lungs had been fried.

With the amount of deco I usually expose myself to, I don't normally have to worry about air-breaks but would think about reducing my O2 exposures for that sort of trip next time.