Does 100% O2 on deco provide a greater benefit than other deco mixes?

[100days-a-year]

Is there any valid reason to increase or decrease 02 exposure in relation to Dysbaric Osteonecrosis?
I'd seen a 1 line reference somewhere of 02 potentially exacerbating the risk of DON but nothing concrete,but tons of info on nitrogen exposure.That would be my only real concern as a few minutes more or less of deco are not worth worrying over and I'm not really worried about oxtox the little time I spend at high P02s.

 

[Patoux01]

the PO2 of pure O2 is unforgiving at 20 feet which is where you'll spend much of you deco time: you can't accidently go any deeper during your deco stop but you'll have less overall run time.

Ahem, how does one "accidentally go deeper during a deco stop" ?

 

[BenjaminF]

Ahem, how does one "accidentally go deeper during a deco stop" ?

Where is that popcorn...

 

[kensuf]

Ahem, how does one "accidentally go deeper during a deco stop" ?

You're kidding, right?

I kicked a guy out of an AN/DP class a week ago because he couldn't maintain buoyancy during a series of simulated stops. He wouldn't inflate enough gas in his rig to maintain buoyancy, so he constantly sculled, as soon as he got even the slightest bit task loaded, he stopped sculling and sank.

Getting task loaded and losing buoyancy control happens more often than you think. I've done "insta-buddy" tek dives with people throughout the Caribbean that had poor buoyancy and trim, but had a card from an instructor somewhere. My wife recently looked at some videos of me and a few other guys on a wall at 100m and her first reaction was "they seem to be working really hard to hover but you're not, why are they kicking so much???"

As for the guy I kicked out, the time to fix his buoyancy problems was going to slow the progression of the other two students, so I asked him to come back in a couple of weeks to work one on one with me and sent him some video footage of himself (along with an email with several suggestions).

 

[Patoux01]

No I am not kidding.

I'm pretty strict when it comes to "more serious" diving (ie not just backgas deco), where I'll expect my teammates to be solid, in the same way I hope they expect me to be.
Now, I prefer skipping a dive or going solo than cringing all dive long.
There's basically only the GUE guys and those for which I know the instructor that I'd go do deco dives with without first doing a fun dive. Ironically, most of the guys at GUE are not fine diving with me .

I dive because it's relaxing, when I see people kicking non-stop for over an hour, it tends to have the opposite effect on me, ruin my dive and sometimes even my day . If I engage on dives where I know the divers' skills might be low, at least I don't have my hopes up for a completely relaxing dive, and sometimes they'll even want to learn a bit on how to improve.

 

[Michael Guerrero]

Is 100% O2 substantially better than 90% or 80%

Better, yes. Substantially, not from a washout perspective for the most common deco diving. If you have access to a booster, probably not a reason to use anything but O2, unless you have significant wave motion concerns. If you don't, then less than O2 can get you the volume you need for a dive and some backup.

 

[lv2dive]

See the links below for the best article/summary I can remember finding on the subject of Dysbararic Osteonecrosis (DON).

The second article (listed first below) speaks to some of what you are asking. In general, my conclusion (after re-reading the links) would be that a higher PPO2 from O2 deco in recreational diving isn't going to impact risk of DON. ("Prolonged exposure" in the quote below is referring to much longer dives than we are discussing in this thread).

Just MHO, I've no Medical knowledge /background.

A quote from the first link: "What general conclusions can be drawn? First, DON seems to be related to inadequate decompression and may be exacerbated by prolonged exposure to high partial pressures of oxygen and/or rapid rates of compression. It is exceedingly rare in recreational divers. For the normal, conservative sports diver DON is not a concern..."

Dysbaric Osteonecrosis Part 2 | DIVER magazine

Dysbaric Osteonecrosis Part 1 | DIVER magazine

Is there any valid reason to increase or decrease 02 exposure in relation to Dysbaric Osteonecrosis?
I'd seen a 1 line reference somewhere of 02 potentially exacerbating the risk of DON but nothing concrete,but tons of info on nitrogen exposure.That would be my only real concern as a few minutes more or less of deco are not worth worrying over and I'm not really worried about oxtox the little time I spend at high P02s.

 

[Fathom044]

Ok this question speaks of lack of training. Please take a deco class to address this question. Short answer is yes!

 

[sportxlh]

Ahem, how does one "accidentally go deeper during a deco stop" ?

Should have clarified. Most of the diving in the area is drift diving, so deco is drifting too. No anchor line or mooring ball line to assist. His point was that if one gets task loaded from messing with an improperly deployed reel or a tangled reel line or a dropped spool or distracted by a loud passing freighter (which are scarey as hell when they pass nearby since you feel like your brain is about to vibrate loose in your head) or with nasty wave action near the gulf stream, the situation with 100% O2 at 20 feet is unforgiving if you don't maintain buoyancy and a diver mistakenly starts to descend. He didn't think that saving a couple of extra minutes run time with anything beyond 50% was worth the risk for the type of diving that was typically done in the area. That's all he was pointing out and its obviously his opinion: not gospel.

 

[DevonDiver]

His point was that if one gets task loaded from.....

..... then they're diving beyond their capabilities. End.