Which deco stop to skip?

[ajduplessis]

@ John: Who said anything about surfacing?! Are you on strong medication?

amend and abandon are definitions. Read whats there and don't make you own assumptions, you look silly that way.

 

[boulderjohn]

@ John: Who said anything about surfacing?! Are you on strong medication?

amend and abandon are definitions. Read whats there and don't make you own assumptions, you look silly that way.

I'm not sure which of us is looking silly right now. I asked what Andy meant when he contrasted the two. He indicated one was unacceptable and the other was acceptable. I asked what the difference was. You gave me a lecture by giving me basic dictionary definitions that don't seem to relate to the way he used it. I applied the definitions you provided, and they did not seem to help. If you did not mean for them to be used the way you provided them, why did you provide them?

 

[nimoh]

I agree, it was silly to provide those definitions completely out of context.

if discussing abandoning a deco plan, based on the definition of abandon as giving up completely, that can only mean going to the surface, since doing nothing (i.e. hovering at depth) would be either continuing with the deco plan, or doing an alternate deco plan

 

[ajduplessis]

@John: First you assumed that DD indicated that Bühlmann profiles are unsafe (post 23). DD highlighted that for you in #25. His point was "why have one approach and then change/abandon that approach for something different" when the pooh hits.

You then ask asked "what the diff between abandon vs amend" I highlighted those for you. You see VPM try and fix things deeper, control ascent then use the shallows; where Bühlmann wants to get shallow quickly to off-gass, 2 different approaches. That's DD point. When the pooh hit you can make changes to the approach you trust and based you dive on. thats amending. Abandoning your "trusted" approach for something different is conflicting IMO. Yes a situation might force you into something else.

I go further to say that if you dramatically "amend" VPM approach it becomes something different like Bühlmann. Please see my comment below re surfacing assumption.


I modified my original response due to some bad wording/insults. That was not my intent.

---------- Post added April 25th, 2013 at 10:41 PM ----------

I agree, it was silly to provide those definitions completely out of context.

if discussing abandoning a deco plan, based on the definition of abandon as giving up completely, that can only mean going to the surface, since doing nothing (i.e. hovering at depth) would be either continuing with the deco plan, or doing an alternate deco plan

Abandoning a deco plan does not indicate surfacing. It indicate changing the deco approach/new plan; the old one is not going to work. Example: abandoning vpm plan because you dont have the deep gas does not mean SURFACE!! It means new approach, screw the deep stuff I have no gas, get shallow so I can use what I have. In this discussion we debate what to skip based on limited gasses/health issues or the likes, "get out before the cake is ready". If you have no gas, drown or surface.

 

[Diver0001]

Rhone Man and Diver0001... so you'd basically ditch any 'bubble theory' and opt for an old-school Haldanian 'bend and mend' in the shallows?

If a more modern algorithm (dual-phase/gradient/bubble) got/gets you up quicker in general, shouldn't that remain the same (quicker) model you'd follow, but make more aggressive to get you up much faster than ideal?

I'm assuming you're using such a model to begin with...?

Well that's the thing about deco theory, isn't it.

All we can really do with these kinds of scenarios when you're outside the envelop of what the thing was designed for is to to guess... or use intuition... if you follow Dilbert you'll realize that they're one in the same.

My guess/intuition, and apparently that of Rhone Man too is that if you're using a bubble model and you skip your shallow stops that you'll be hit worse than getting shallow, pushing the gradient and cutting the last stop short. Experiences of deep divers like Ellyatt seem to support this guess/intuition that skipping shallow stops is worse than skipping deep stops if you have to choose between which ****muffin you want to eat.

The fact is that none of us really knows. There's been no testing that I know of the compare how much supersaturation will differ with different models using different amounts of skipped deco from different kinds of profiles on different kinds of lost-gas scenarios as baseline variables.

The tone of your post suggests you intended to ridicule my guess/intuition. If you have a different guess/intuition then go ahead and present your case but playing the "know it all" card with me isn't what I find overly convincing.

I'm not saying his guess/intuition is necessarily right but I liked the logic of pushing the gradient, doing as much shallow deco as possible and hoping for the best better than avoiding bubbles for as long as possible and then skipping much of the shallow deco, which is the very thing Ellaytt "field tested" and proved beyond any shadow of a doubt was incredibly dangerous to say the least.

So yeah, we're way off in uncharted terrain here but go ahead and make a guess and try to try to convince people of your thinking if you want. Personally I'm not out to convince anyone of anything other than when I read the OP in this thread I had exactly the same thought that Rhone Man did.

Is that logic right? Who knows. The only correct answer to that is "maybe".

R..

 

[tracydr]

What about in a situation where the diver has developed pulmonary edema? What then? This situation has happened recently to a rebreather diver who barely made it through their decompression stops. What happens if they need to get immediately out of the water in order to receive cpap or worse, to be intubated?

 

[ajduplessis]

Getting the cake out before its baked is never good especially combined with heart disorders (well any serious medical problem). The problem is that it can develop suddenly and I dont know how anyone in the team is going to really know whats happened. If the diver is able to stay in the water complete the deco. Someone else needs to make a call if that not the case but things are not looking good.

 

[dumpsterDiver]

Moreover, if you are following a planned ascent and using a computer as backup, if you do shave time off your deep stops, the computer will adjust for you as you ascend. The computer can thus become your primary guide rather than the backup.

Are you sure this works with an dive computer? You can VIOLATE the computer, blow off the required deep stops and then all computers will happily go along with it and recalculate your adjusted deco plan after a violation? I find that hard to believe.

However, I DO believe the converse is probably true in most cases... You come up slower than the computer wants.... doing deep stops it did not predict and it will recalculate the correct deco. I have done that myself hundreds of times... as for the former... Not that I know of... Do you really have data to represent that violation of required deco stops won't cause "issues" with a dive computer?

 

[noladiver]

Skip whichever ones you don't feel like doing,
I usually put off the long ones till anther day so I can get to the bar sooner.
Sometimes I will give my buddy my deco obligation that way he can do it for me that way I can tan my cheeks on the boat.

 

[rjack321]

What about in a situation where the diver has developed pulmonary edema? What then? This situation has happened recently to a rebreather diver who barely made it through their decompression stops. What happens if they need to get immediately out of the water in order to receive cpap or worse, to be intubated?

Get shallow ASAP but "make up" for it by hanging and hanging and hanging. This way if your symptoms worsen you're not so far away from the surface before you drown in your own fluids. You might suffocate anyway, but being deep with worsening IPE seems alot worse to me than being closer to help.

For CCR divers in particular, I would say bailing out once you are in deco gas range might be a good idea, since most bailout deco gases have no He recirculating in the loop and most CCR divers aren't planning on a dil switch. Whatever you offgas on OC is "gone". Especially if they have 100% O2 along, get up to 20ft and go on that to accelerate your deco as much as humanly possible vs staying on the loop and hitting a 20ft ppO2 of 1.5 at most. No sense in limiting your offgassing by having any inerts in the loop if you don't have to.