Deco with too less air, options from the book

[h90]

I am terrible sorry for not answering in the forum. I had setting "Instant Email Notification" but didn't receive a single email so I thought no one is answering.

I'll answer tomorrow.......

 

[Chatterton]

I apologize for arriving so late to this shindig, but...

Technical dives should be made acording to the procedures that the certification agencies have developed. When they are followed, the inherent risk of decompression diving is reasonably managed. I assume we are all in agreement on this?

However, incidents have occured and continue to occur, where divers run out of breathing medium, and they are forced to surface before they have completed their required decompression. It does not happen every day, thank god, but on rare occasions it does happen. There was a recent fatality in Yap, where a pair of divers ran out of breathing gas and were forced to ascend, suffering serious DCS.

Obviously they made mistakes, and there is probably an opportunity for another great debate, however the point is that running out of gas for decompression can and does happen. Regardless if it is caused by bad planning, entrapment, getting lost, becoming entangled, or being involved with another diver with a problem, it actually can happen and it can be lethal.

Most divers will never see something like this, as it happens so infrequently. However it does occur more frequently than nuclear holocaust?

I thought the original question was both interesting and thought provoking. If you were in that situation, how would you expend your limited resources and why?

My answer would be to do my deep stops, without any padding (I don't like the MircoBubble Stop theory anyway), to minimize the chances of CNS involvement. Then breath everything I had, while still taking into consideration buoyancy issues and still hoping for salvation before I absolutely had to surface. If I had to take the hit, it would be simple bends, the lesser of two serious evils. Notice how I asume I am alone?

For me, all of this is a nice hypothetical discussion, as I have never been treated for DCS of any sort, and I have never surfaced out of gas, ever. Which of course does not imply I have never done anything stupid?

Diving is not only supposed to be fun, but it is a great opportunity to learn about science, history, and the human machine. Especially ourselves.

Cheers

JC

 

[texdiveguy]

John....always nice to read your input..... got your PM earlier and will let you know about May 09' dives. Alan

 

[h90]

Thanks everyone! I read everything and got a better understanding of everything.

 

[gmanstan]

I am a Noobee and just read to learn but after finishing these 9 pages there was so much personal Bull S#*t and Ego it was hard to see if anyone considered the original question which might be "what if in a well prepaired, well planed ,done by the numbers dive " you werent able to do all the Deco stops what would be the lesser evils and give a better survival chance ? Just theoritical but ,it was finally answered by a PROFESSIONAL, with a pro's point of veiw minus all the Flaming, non commital, self rightous answers. I know that you should never be in that situation . But never say never.What if "murphys law on steriods" happens and every fail safe and precaution went bad...Remember they never thought that Chernobyl would happen. Its nice to know what the what if worst case senario solution might be...I'll probably will never be at this level but always interested in people that take life to the extreme ouskirts of skill and technology..

 

[Rhone Man]

I am a Noobee and just read to learn but after finishing these 9 pages there was so much personal Bull S#*t and Ego it was hard to see if anyone considered the original question which might be "what if in a well prepaired, well planed ,done by the numbers dive " you werent able to do all the Deco stops what would be the lesser evils and give a better survival chance ? Just theoritical but ,it was finally answered by a PROFESSIONAL, with a pro's point of veiw minus all the Flaming, non commital, self rightous answers. I know that you should never be in that situation . But never say never.What if "murphys law on steriods" happens and every fail safe and precaution went bad...Remember they never thought that Chernobyl would happen. Its nice to know what the what if worst case senario solution might be...I'll probably will never be at this level but always interested in people that take life to the extreme ouskirts of skill and technology..

Cool. I am glad you were able rise above it all.

 

[imasinker]

I have a different take on the OP's question than Bismarck, although I may be off base. I don't see the question as reflecting someone who is trying to learn decompression theory and practice solely off the net, or from a single book, after which he/she will jump in the water, drop to 160 feet, and start using abbreviated decompression schedules (H90, if that is your intent, then I have to fully agree with Bismarck's reaction.). Rather, I see the post as an attempt to better understand something recently read, that does not intuitively make sense. Perhaps, the specific wording of the question creates a bit of a misimpression, and I don't know if English fluency plays any role here (h90, it would be helpful if you add a bit of meat to your profile, by the way). But, asking questions to better understand concepts, or to satisfy curiosity, should be part of what SB is all about. My read of the question is, 'THEORETICALLY, if for whatever reason, you find yourself in a situation where you cannot complete a decompression schedule as planned because of a gas availability issue, is it better to do the intended deeper stops as planned, realizing that you may have to cut short or eliminate some of the very shallow stops because you will run out of gas? Or, is it better to get shallow sooner, by cutting time at deeper stops, and use more of your available gas at a shallower depth?' A very reasonable question, certainly one that is frequently asked during technical dive training, but also one that is not by any means out of bounds for the curious recreational diver to ask. And, a reasonable answer is (as with so many things), 'It depends.' On the backgas you are using, on the amount of remaining gas you have available, on the dive environment, etc. In general, if you have a decompression obligation that you know you cannot meet, and the likelihood of having support resources available to alter that situation (e.g. you have no buddy, no support divers, whatever) is minimal / nonexistent, most divers will want to get as shallow as they reasonably can, as soon as you can, SAFELY. For example, if you are diving air as a backgas, you may be able to ascend to a shallower depth sooner (and spend more time and remaining gas at a shallower depth), than if you are diving a helium-based mix. But, that is a general precept, not an absolute statement. If I know I cannot complete my obligation, if I know I am low on gas, if I am still losing gas, for example, where do I want to be when I run out - at 90 feet, or 60 feet, or at 20 feet. I do not want to get bent by rapid ascent from depth, where I simply ignore planned deeper stops. But, I also do not want to drown or get bent attempting a CESA from 90 feet. That is a matter of practicality. On the other hand, what stop depths will do me the most good, balancing higher air consumption at depth against the physics of gas diffusion / bubble formation? That is where running a series of simulations with decompression software can be informative. Using desktop decompression software as a learning tool is perfectly reasonable. It is NOT a substitute for appropriate training, it does not replace a good instructor, it is not a surrogate for reference texts, and it is possible to wrongly interpret the calculated information out of context, etc. I agree fully with Bismarck on that point. But, you can learn from posing a series of 'what if' questions and running simulations to see what answers you get.

Thank You! This is one of the most honest and informative posts I have read in a long time....

 

[grazie42]

Late to the party as well but...
First off, I would eliminate all the "feel goods"(at all levels), the stuff you add to your "safe profile" "just because" and go to my nominal plan.

If I still didn´t have enough gas, I would do the deep stuff first and skimp on the shallows.

-If am going to get DCS, I would rather get it at 10 or 20ft than 60ft.
-Like others have already posted, you are more likely to avoid a type II that way as well.
-Close to the surface, with good support there´s a good chance that you can go back down and complete your deco without ever presenting with symptoms.
-Depending on the dive you may have He in your bottom mix and so be diving a gas that is less forgiving than air of fast ascents, thus increasing your chances of issues deep even more.
-The way I read it, this scenario also presumes that no shallow deco gas is available and so your BG will give you better decompression benefits deeper than shallow.

Just a few thoughts...

 

["J" valve]

I agree wholeheartedly that playing the "what if" game is an essential safety tool for every diver. h90, seems to me, is just saying "should I find myself in this situation, what's the best decision I can make?" And for those of you out there who say you never ran short of breathing medium I say "BS". Either that or you've never had a gauge malfunction, an injured buddy who needed your assist at depth, a snarled anchor line that had to be freed, a dragging anchor that had to be resecured, a valuable piece of photo gear dropped as you ascended, a dramatic change in current or viz, a navigation error, a blown hose or 'o' ring, etc., etc. Sure, you plan for contingencies, save an ample reserve, put a hang off bottle on the ascent line, even carry extra emergency gas on your rig. But, sh** happens. Better to think ahead and plan for the worst case scenario than to pompously say "you should never make mistakes" and then find yourself in deep doodoo when it inevitably happens. The way we learn what not to do is sometimes by having done it.

 

[Tortuga68]

This gets my vote for the worst thread I have ever read on SB - 45 posts before someone actually addressed the OPs question in a concise, realistic & non-condescending manner