Any reported cases of Ox Tox between 1.4 and 1.6?

[deepblueglow]

First off, I'm not looking to start a 1.4 vs 1.6 debate! The conventional wisdom of 1.2-1.4 for diving and 1.6 for deco is perfectly sound.

I've been poking around on this subject for a while now though, and what I can't find is how exactly the 1.4 idea came about. I know there are loads of cases of Ox Tox at 1.8 and above, and that it's known to be really insidious. There's a great anecdote in The Last Dive about a diver who thought 2.0+ was fine, he actually got away with it for a dozens of dives before it finally bit him and he didn't come back up.

Are there any documented cases in literature, or even just well known examples, where divers had a seizure somewhere below 1.6? Or has theory just advanced to the point where we can say that odds are, it will bite someone sooner or later?

 

[tursiops]

Some History On Nitrox

Copied or not, nice summary - Thanks. I know that NAUI sanctioned Nitrox training for recreational divers in 1992 (I believe this was the first Traning Organisation to sanction Nitrox diving). Umm, sort of. NAUI likes to embellish this story, it was more like 1997 when they adopted it as...

scubaboard.com

 

[Underwater Tourist]

Weren’t there two ladies who toxes at 1.6, which also added to the speculation that women might be more susceptible to oxtox?

I read it awhile back somewhere, made a mental note, and never came back

Could be totally wrong..

 

[tursiops]

Weren’t there two ladies who toxes at 1.6, which also added to the speculation that women might be more susceptible to oxtox?

I read it awhile back somewhere, made a mental note, and never came back

Could be totally wrong..

Sex and Sensitivity to Oxygen Toxicity

The most feared manifestation of acute oxygen toxicity is a loss of consciousness and tonic-clonic convulsions (seizures). The threat of oxygen-induced seizures in scuba diving becomes real when th…

thedivelab.dan.org

 

[DOBY]

There was an unexplained suspected Ox tox cave diving fatality back in 2007 were the pO2 was within the recommended 1.2-1.4ata range. Gas was Tmx 24/25 to max depth of 150 feet. Some cave divers went to using EAN30 instead of EAN32 for most 100-120ft deep cave dives after that.

2007-07-14 Incident – IUCRR

iucrr.org

 

[deepblueglow]

There was an unexplained suspected Ox tox cave diving fatality back in 2007 were the pO2 was within the recommended 1.2-1.4ata range. Gas was Tmx 24/25 to max depth of 150 feet. Some cave divers went to using EAN30 instead of EAN32 for most 100-120ft deep cave dives after that.

2007-07-14 Incident – IUCRR

iucrr.org

Scary stuff.

Seems like the exposure time was close to an hour. I think it's safe to assume that no recreational diver will ever be exposed to 1.4 for that long, but if me and my girlfriend follow through on our Tec plans, we're going 1.2...

 

[crofrog]

Scary stuff.

Seems like the exposure time was close to an hour. I think it's safe to assume that no recreational diver will ever be exposed to 1.4 for that long, but if me and my girlfriend follow through on our Tec plans, we're going 1.2...

Is the Extra NDL worth it for recreational dives?

Generally speaking, your gas supply and reserve will be the limiting factors…

At 100 feet, Nitrox 30 provides 30 minutes of no-stop time on the NOAA tables.

Your minimum gas for that dive is:
42 cuft = 0.75 cuft/min * 2 divers * 2.5 avg ATA * 11 min

If you have a low SAC rate of 0.45 cuft/min:

Your available gas is 80 cuft - 42 cuft = 38 cuft.

38 cuft / (0.45 cuft/min * 4 ATA) = 21 minutes of bottom time.

With a 100 cuft tank and the same SAC rate, you get 32 minutes.

These same trends continue as you go shallower.

Some will argue that these gas reserves are more than required. This has been discussed in many threads about “rock bottom” and minimum gas, but the goal is to bring two divers safely to the surface off a single air source, without cutting short or omitting the safety stop, ascending slowly, and allowing some problem-solving time on the bottom while accounting for an elevated breathing rate.

It is an intentionally conservative approach.

 

[Duke Dive Medicine]

First off, I'm not looking to start a 1.4 vs 1.6 debate! The conventional wisdom of 1.2-1.4 for diving and 1.6 for deco is perfectly sound.

I've been poking around on this subject for a while now though, and what I can't find is how exactly the 1.4 idea came about. I know there are loads of cases of Ox Tox at 1.8 and above, and that it's known to be really insidious. There's a great anecdote in The Last Dive about a diver who thought 2.0+ was fine, he actually got away with it for a dozens of dives before it finally bit him and he didn't come back up.

Are there any documented cases in literature, or even just well known examples, where divers had a seizure somewhere below 1.6? Or has theory just advanced to the point where we can say that odds are, it will bite someone sooner or later?

Here's one where a combat dive candidate was being tested on normobaric oxygen (100% O2 at atmospheric pressure). One important takeaway is the role of CO2 in CNS O2 toxicity.

Symptoms of central nervous system oxygen toxicity during 100% oxygen breathing at normobaric pressure with increasing inspired levels of carbon dioxide: a case report - PubMed

The greatest danger faced by divers who use oxygen-enriched gas mixtures is central nervous system oxygen toxicity (CNS-OT). CNS-OT is characterised by convulsions resembling grand-mal epileptic seizures, which may terminate in drowning and death. Elevated arterial levels of carbon dioxide (CO₂)...

pubmed.ncbi.nlm.nih.gov

Best regards,
DDM

 

[Kendall Raine]

Is the Extra NDL worth it for recreational dives?

Generally speaking, your gas supply and reserve will be the limiting factors…

At 100 feet, Nitrox 30 provides 30 minutes on the NOAA tables.

EANx 30 at 100 feet is PP02 of 1.21. The NOAA limit for 30% at 100 feet is ~210 minutes. Not sure where you got your number of 30 minutes.

 

[crofrog]

EANx 30 at 100 feet is PP02 of 1.21. The NOAA limit for 30% at 100 feet is ~210 minutes. Not sure where you got your number of 30 minutes.

30 minutes of NDL

Let me restate.

Running a ppO2 higher than 1.2 in most recreational diving settings does not make sense, because the increase in NDL does not offer a practical benefit because the dives are gas limited when diving in a single tank. In my view the increased risk of CNS oxygen toxicity is greater than the slightly increased risk of DCS from running a lower ppO2 and the corresponding slight increase in inert gas tissue loading.