Deep diving accident

[TSandM]

If, in fact, this was an O2 hit at 15 feet, it will be at least the second oxtox event this year to occur at what are normally considered acceptable ppO2s, and it may be the third. The other two died. I'm beginning to think GUE's conservativism on ppO2s may be completely justified.

 

[Ayisha]

...I got an initial symptom (twitching lips, etc) suggesting a very high potential for oxtox.

This is good to know. What other symptoms might someone have who may be about to experience oxtox?

So if you were to experience those symptoms, you would switch to air if possible?

If you and a buddy are using only Nitrox (single tank) and have those symptoms, I guess you would start ascending and hope for the best?

Lynn, How conservative is GUE on ppO2? I plan the standard 1.4 that I was taught, but normally go a little shallower and for a little less time than the limits for the mix I'm using - normally 32%.

 

[shoredivr]

If, in fact, this was an O2 hit at 15 feet, it will be at least the second oxtox event this year to occur at what are normally considered acceptable ppO2s, and it may be the third. The other two died. I'm beginning to think GUE's conservativism on ppO2s may be completely justified.

IIRC, those other fatalities were after breathing 100% O2 shallower than 20 ft. I tried to get a discussion going a couple of months ago regarding this, with reference to postings over at TDS on the same topic. No interest at that time.

Ayisha, I think GUE mandates 1.2 after reading numerous DIR threads. I'm sure to be corrected if that's not the case.

A conclusion I'm beginning to draw is 100% O2 at shallow stops may be too risky, and perhaps 80% O2 has it's advantages. (Yes, it may mean less accelerated deco time; I'm trying to look at lessening O2 tox risk).

Anyone doing 80% O2 decos care to comment, i.e., had beginnings of O2 tox symptoms using 100% - twitching etc. - went to backgas with longer deco schedule to reduce oxtox and to end the dive, then on subsequent dives used 80% and didn't then notice these symptoms recur?

Has anyone found stats/studies on Oxygen toxicity accidents at 80% O2 at 20 ft or shallower stops? Thx

Of course, no such studies may exist

 

[wedivebc]

If, in fact, this was an O2 hit at 15 feet, it will be at least the second oxtox event this year to occur at what are normally considered acceptable ppO2s, and it may be the third. The other two died. I'm beginning to think GUE's conservativism on ppO2s may be completely justified.

I know of this and a cave incident, what is the third one?

 

[wedivebc]

A conclusion I'm beginning to draw is 100% O2 at shallow stops may be too risky, and perhaps 80% O2 has it's advantages. (Yes, it may mean less accelerated deco time; I'm trying to look at lessening O2 tox risk).

80% offers very little if any extra deco time using normal deco conventions. If you are using an O2 accelerated deco profile you must use O2 as there are no provisions for diong it with 80%

Anyone doing 80% O2 decos care to comment, i.e., had beginnings of O2 tox symptoms using 100% - twitching etc. - went to backgas with longer deco schedule to reduce oxtox and to end the dive, then on subsequent dives used 80% and didn't then notice these symptoms recur?

Has anyone found stats/studies on Oxygen toxicity accidents at 80% O2 at 20 ft or shallower stops? Thx

Of course, no such studies may exist

I think you will find 80% is not a common choice for deco gas so there is little evidence that is is safer. From a CNS tox perspective there would be no greater advantage to using 80% at 20 feet over oxygen at 10feet. Neither is optimal though.
80% does have it's advantages but not in this context.

 

[KMD]

The two divers were on their way to the surface and making decompression stops along the way, Lume said. During the stops, the diver seemed to be having a hard time keeping his buoyancy and was kicking hard to stay underneath, Lume said.

"He was inhaling more oxygen than he should," Lume said.

Anybody have any comments about how CO2 rentention might have been a contribuatory cause of this event?

Kevin

 

[TSandM]

Well, CO2 is known to be a cerebral vasodilator, and has been implicated in potentiating oxygen toxicity in divers. One wouldn't think that CO2 retention would be a big issue that close to the surface, with the reduced work of breathing there, but I suppose it's possible.

Dave, there was the woman whose death was pretty clearly an oxtox event, but wasn't there another cave diver a few months ago who had an unexplained death, where there was some rumor he had gone into seizures?

GUE used to recommend 1.4 for the working part of the dive, and 1.6 for deco, but they've gone to 1.2 and 1.4, I believe, and are even recommending that, for aggressive dives or dives with the potential for workload, 1.0 and 1.2 would be better.

 

[ageddiver]

Interesting. So GUE does not recommend the use of 100% O2 now? Or same gases and changes to the dive profile to maintain the lower PO2?

 

[Steve R]

Interesting. So GUE does not recommend the use of 100% O2 now? Or same gases and changes to the dive profile to maintain the lower PO2?

AFAIK, she's wrong there. We still use 1.6 for deco. Bottom is usually not greater than 1.2

Dave, I think she's referring to Jeff T. I don't recall much chat about the PPO and duration or any contributing factors though, unlike the first death.

 

[limeyx]

AFAIK, she's wrong there. We still use 1.6 for deco. Bottom is usually not greater than 1.2

Right bottom is *average* 1.2 with max of 1.4 allowed.

Also, I think all deco bottles (except O2) are equal to approx 1.2 average PPO2 (1.6 when you switch but I think when you average in the shallower stops -- certainly for the 50% bottle -- it's about 1.2 not 1.6)