Freediving and O2 toxicity

trux · Mar 18, 2008

unobreath said:
That was on trimix not standard air.

No, it was a deep air record - see more about it here: World Record Trimix Dive 2003 by Mark Andrews on DeeperBlue.net - Fanatical About FreeDiving, Scuba Diving, Spearfishing & Technical Diving or here: channel4.com - Superhuman - Mark Andrews, or here: 150 Meter Deep Air Record Set

With trimix he went much deeper - that's what the first article on DB is about (but mentioning the deep air record too).

EDIT: Dan Manion appears to have made another deep air record: 525 f / 161 m. He survived a blackout, and sustained significant injury when he was badly bent on a subsequent air dive to 300 f /92 m (source: Mix timeline, reference also here: a q u a C 0 R P S F 0 R U M). Other sources speak though about 148m for Manion, so I am not sure whether he did two different records, or if one of them is inocrrect or invalid.

dave · Mar 19, 2008

unobreath said:
The max pp02 to where CNS 02 toxicity is possible is different for a wet diver than it is a dry diver.
1.3-1.6 wet
2.6-2.8 dry (chamber)

.

I think you mean minimum, not maximum. But whatever, it is nothing like as clear cut as that. What you have posted are maximum allowable ppO2s as are quoted in commercial diving regulations
O2 seizures to seem to happen at lower ppO2s in water than dry, but the main reason higher ppO2s are allowed in dry environments is that an O2 seizure is not too much of a problem in the dry, and the decompression/ therapy benefits outweigh the risks. By my understanding O2 seizures are essentially random events, that become progressively more common as you increase ppO2 and exposure time. Although 1.6bar is the advised maximum, in practise 2bar rarely causes problems , 10m always used be regarded as the safe limit on pure O2 rebreathers (before the advent of mixed gas rebreathers many navies used them to 20m for short excursions, but then losing the odd diver in a war is an acceptable risk)
One of the best references is "Oxygen and the Diver" by Kendall Donald. It is mainly based on research done on British Navy divers during the second world war, when it was perfectly acceptable to make experimental subjects fit and foam at the mouth. For some reason that tends to be frowned on these days so there is very little recent research data based on humans.

cheers
dave
Spearguns by Spearo uk ltd finest supplier of speargun, monofins, speargun and freediving equipment

unobreath · Mar 20, 2008

dave said:
I think you mean minimum, not maximum. But whatever, it is nothing like as clear cut as that. What you have posted are maximum allowable ppO2s as are quoted in commercial diving regulations
O2 seizures to seem to happen at lower ppO2s in water than dry, but the main reason higher ppO2s are allowed in dry environments is that an O2 seizure is not too much of a problem in the dry, and the decompression/ therapy benefits outweigh the risks. By my understanding O2 seizures are essentially random events, that become progressively more common as you increase ppO2 and exposure time. Although 1.6bar is the advised maximum, in practise 2bar rarely causes problems , 10m always used be regarded as the safe limit on pure O2 rebreathers (before the advent of mixed gas rebreathers many navies used them to 20m for short excursions, but then losing the odd diver in a war is an acceptable risk)
One of the best references is "Oxygen and the Diver" by Kendall Donald. It is mainly based on research done on British Navy divers during the second world war, when it was perfectly acceptable to make experimental subjects fit and foam at the mouth. For some reason that tends to be frowned on these days so there is very little recent research data based on humans.

cheers
dave
Spearguns by Spearo uk ltd finest supplier of speargun, monofins, speargun and freediving equipment

Its at those partial pressure's that 02 becomes toxic at depth in water and in chamber. In other words at those partial pressures CNS 02 toxicity can occur. But like you said it is not cut and dry. It affects different people at different partial pressures just like any other diving related illness.

Pulmonary 02 toxicity has to do with exposure time. As during long chamber treatments or long durations on a 100% 02 rig, such as a LAR V or like the civilian version the dolphin, it is something we have to keep an eye out for as it is not fun to deal with and can be potentially dangerous to your health . It feels like a burning sensation in the lungs.

But 02/CO2 limits are classified for military rebreathers for obvious reasons.

As for experiments to where foaming at the mouth is happily accepted, NEDU in panama city is where scientists are more than happy to bend us for the benefit of science. It is not uncommon there to seriously injure someone if not kill them for the greater good of humanity or so they say. I have only been there a few times for short durations but have co works that have been used as "test" subjects.

Most of the studies are just not publicly published.

Freediving and O2 toxicity

trux

~~~~~

dave

Dicentrarchus labrax

unobreath

Beach Bum

Freediving and O2 toxicity

trux

~~~~~

dave

Dicentrarchus labrax

unobreath

Beach Bum

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