oxtox

[spacemanspiff1974]

After all the lectures about oxygen toxicity in my advanced nitrox class, I'm wondering if anyone here has actually had oxygen toxicity.

I've had a pO2 of 1.6 on sufaded with no symptoms. Also, I remember seeing a picture of a guy in the early days of diving (1940's or so) where he went to around 70 feet on an O2 rebreather and lived.

So has anyone experienced this?

 

[Thalassamania]

After all the lectures about oxygen toxicity in my advanced nitrox class, I'm wondering if anyone here has actually had oxygen toxicity.

I've had a pO2 of 1.6 on sufaded with no symptoms. Also, I remember seeing a picture of a guy in the early days of diving (1940's or so) where he went to around 70 feet on an O2 rebreather and lived.

So has anyone experienced this?

I have not, but I watched the guy next to me in the chamber when we were doing an oxygen tolerance test go into convulsions (that was at 60FSW, a _ppO₂ of 2.8) but current data suggests that use of pure oxygen below 18fsw for more than a few minutes is Russian roulette.

 

[mania]

Here is one well known story:
JJ just posted this 'near miss' accounting and I thought I'd share it here - rec.scuba | Google Groups

Mania

 

[Hickdive]

Oxygen tolerence appears to vary between individuals and may well vary within individuals too.

We know that when Haldane was developing military rebreathers for the RN, volunteers were tested in chambers and it was not uncommon for them to tolerate pure O2 down to 100 feet. However, some volunteers blacked out at much shallower depths. That's why Haldane and Siebe Gorman developed systems that used O2 diluted with air (I suppose you could call it Nitrox) so that as many diver volunteers as possible could reliably dive with a minimum risk of oxtox balanced with the minimum risk of DCI.

We also know that Hans Hass regularly used pure oxygen rebreathers down to unprecedented depths in the Red Sea but he lost some colleagues to oxtox at depths considerably shallower that he regulalry tolerated. Jacques Cousteau recounts his one experience with an O2 rebreather in 'The Silent World' and he was lucky to survive. It was one of the reasons he sought out an alternative open circuit air-breathing system.

The NOAA exposure tables appear to have been calculated with zero risk in mind. That is to say at a max ppO2 of 1.6 bar no-one should be at significant risk of oxtox. That doesn't mean some people haven't been exposed to higher pressures without difficulty, it just means thats the maximum partial pressure NOAA have been unable to experimentally induce oxtox in humans.

Personally I'd rather not experiment with oygen toxicity and I'll stick to the NOAA guidelines.

 

[Gene_Hobbs]

The NOAA exposure tables appear to have been calculated with zero risk in mind.

Nice bit of history... We have to mention the amazing work from Kenneth Donald in the Royal Navy. His work on CNS manifestations in applied science is still unparalleled to this day. I mention this because his work is the main basis (later with that of Behnke and Lambertsen) for the CNS exposure limits set (not calculated) by all of the world's Naval forces as well as NOAA in the US. He PROVED that 'Oxygen tolerance varies between individuals as well as within the individual.'

More reading on Oxygen Toxicity:
RRR suggested reading list

and NOAA specific comments in:
DAN Nitrox Workshop Proceedings. - comments by Morgan Wells on how he set those limits.
REPEX: Development of repetitive excursions, surfacing techniques, and oxygen procedures for habitat diving. Technical Report 88-1A. - Hamilton et. al. development of proceedures
and more on REPEX

as for the OP's question: I have seen many seizures in treatments and hope to NEVER see one in the water. The are numerous reports of short spikes in pO2 and the US Navy has an 'excursion' limit for just that operational need (one of the references by Butler from the RRR list linked above).

 

[all4scuba05]

In the book The Last Dive, was a mention of a guy who liked diving with a higher po2 than recommended. He died while on one of those dives. It doesn't say someone saw him go into convulsions but you have to wonder, just as the author wondered.

 

[Hickdive]

We have to mention the amazing work from Kenneth Donald in the Royal Navy

I'm sure I had a link to one of his papers but I can't find it at the moment.

Anyway here's an interesting synopsis of his work;

http://www.frogkick.nl/files/oxygen_and_the_diver.pdf

I've got first editions of 'The Frogmen' and 'P Parties' in the attic, I must dig them out and re-read them.