Would you really know what was going on if your computer went into Deco...?

[MikeFerrara]

Thanks for providing some clarity to your position. Essentially what you have said is that you apply an unscientific and untested fudge factor to your dive planning.

If you're waiting for scientific proof as to what decompression works best all the time you had best avoid decompression for the time being.

This is akin to the "Kentucky Windage" rifle shooters use when they don't have any better data to aim their rifles. Sometimes it works, if you guess right. Other times it doesn't, if you guess wrong.

Exactly but in my case I'm always adding conservatism. However the cutting edge dives currently being done are shaving many (shallow) hours off the decompression that conventional tables call for. The theory is that more time spent deep reduces the amount of time needed shallow and maybe to a much greater extent than most realize. They are applying methods that have been used with success in the feild but the scientists haven't got it all figured out yet. Some amazing stretching of the O2 clock going on also (by using other control methods). The phisiologists seem to think it shouldn't work but it does. Eventually they'll figure out why.

Again, I hate to break it to you but the application od staged decompression is no where near an exact science. Your NDL is not a sharp reliable line and neither is the amount of required decompression that you owe at any given depth after any given profile. Those who aren't comfortable with this need to avoid significan't loading.

So, you are taking the accepted tables and applying a guess to them to plan your dive.

Acceptable to who? If you do something that works is it guess work the next time you do it? Another thing that you should realize is that a large amount of the information being used to develop and tweak modern models comes from the divers description of how they feel after their dives. Diver make the modifications that give better results and software developers make changes to incorporate those modifications (or at least to account for them)

That makes the dive plan guess work. This may work for you. But, to encourage others to dive by guesswork I think is at best misdirection.

That isn't what I'm doing here. I'm attempting to make divers aware that modern models like VPM, RGBM and the addition of gradient factors to halanian models are in common use. Adjusting those controls dramatically effects the schedule that the software provides. The software is designed for that. If you compare my Dplan schedule to commonly used tables/computers you'll see that I'm making my first stop at around 20% of the leading compartments critical tention verses the tables 100% and I'm exiting the water at about 80% of the leading compartments critical tension verses the tables 100%. What this means is that on dives that your tables or computer is happy calling a no-stop dive my software will call for manditory decompression.

Using such software you can set both to 100% if you choose. I don't know any one who chooses that though except those who are unaware of those options in the first place.

Here I've voiced my opinion that divers should become aware before incuring the decompression obligation in the first place.

On the other hand if you indeed do have a large enough data base from using your Fudge Factors on a wide variety of divers to make it statistically valid, then please publish the information. You owe it to the dive community to give them tools for better planning if indeed you have them.

I don't need to calculate decompression for a wide veriety of divers but rather only for me and those I dive with.

Reference what I said above about the use of field data in tweaking modern models. There are groups of divers providing data from their dives to those who study decompression. Check out Ross Hemingways data base on the vplanner site. Also do some reading on what groups like the WKPP have been doing (their not the only ones). Most of this knowledge hasn't yet made it's way into recreational computers yet though.

I'm trying to something for the community here by bringing attention to some of what's going on. Other than that, I don't really feel that I owe the dive community anything at all.

Or, when it is all said and done does all the language in your posts boil down to two sentences? "Use the dive tables or your computer with caution. Your dive may result in conditions different from those contemplated by the dive table or computer." If so I think that is what everyone else is saying too.

I'm saying a little more. I'm saying that I wouldn't use those computers or tables for staged decompression (or close) without understanding some of the more modern options. I haven't disagreed with those who have recommended caution. I've disagreed with those who suggested putting your computer into decompression to see how it works.

Every one,

Several agencies have began teaching deeper stops even for recreational profiles. The ones that I know of are GUE, NAUI and IANTD and if there isn't more I think there will be shortly.

Models like RGBM and VPM are becomming mainstream.
Applying gradient factors to haldanian models is an attempt to modify it to get similar results.

There are few who will argue the benefits of starting stops deeper even for modest decompression requirements.

Yet many of you are willing to decompress according to new computers and new tables using ancient theories.

ok

 

[flw]

I would agree with Mike F, although I confess I havn't really been following the thread. On the last liveaboard I was on, there were 12 of us all doing similar dives to 70-85m every day for 6 days.
I think only one pair followed exactly the same schedule as each other, otherwise we all had slightly different schedules, tweaked to our own personal comfort zone. Some used gradient factors, some vpm and some rgbm type models or vr3s. There was no way I'd have done some of the schedules personally, but they worked for the guys diving them, black magic I guess.
At the end of the week, no-one had managed to get bent, although we had the usual over dinner 'discussions' about it - what works for me, doesn't necessarily work for my buddy, although we're never apart by more than 6m or so in depth.
I'll often 'fudge' a schedule a bit to fit in with what I've actually done, but whilst I can justify to myself why I did it, there's not really a sound scientific argument to base it on.

 

[ArcticDiver]

OK, this thread started off with the question of whether someone would know what to do if their computer went into deco. That question has been answered and reansered and re-reanswered. To say it yet again: They'll know what to do if they have read and understood their computer's manual.

The rest of the thread has more to do with what we are willing to use for our planning than anything else. If anyone cares the points in this area have been made and remade. Like in a religious convesion I doubt that any of the discussion will change the mind of the truly evangelized. So, since we have answered the original question guess we'll let it rest for now.

As a last caution: Decompression diving(all dives are decompression dives) is an art based on science. Some science is good, some is bad, some is pure snake oil. Each diver has a responsibility to make his own decisions based on the best information he has. In the same way, be extremely wary of anyone, or anything where the proponent isn't willing to stand behind their product, or purports to have "inside", or "advanced knowledge" that they aren't willing to put their personal fortunes behind.

 

[Uncle Pug]

So, since we have answered the original question guess we'll let it rest for now.

Is that the royal *we* or are you speaking for everyone?

(I haven't been following your career all that carefully so I might have missed your credentials.)

15 pages of continued proof that computers do indeed rot your brain and you think this thread is over?

That will be the day... at best it will surface under another title.

 

[Genesis]

Is that the royal *we* or are you speaking for everyone?

(I haven't been following your career all that carefully so I might have missed your credentials.)

15 pages of continued proof that computers do indeed rot your brain and you think this thread is over?

That will be the day... at best it will surface under another title.

Now Pug, be honest here.

You can't have "rotted" what you didn't have in the first place.

I challenge you to find me an agency that actually teaches any part of decompression theory that has in any way any element of substance to any recreational diver.

You can't - because such an agency doesn't exist.

 

[flw]

The UK ones do, BSsac, SAA and Scotsac, although decompression diving in the UK is regarded as normal recreation diving

 

[Gary D.]

Now Pug, be honest here.

You can't have "rotted" what you didn't have in the first place.

I challenge you to find me an agency that actually teaches any part of decompression theory that has in any way any element of substance to any recreational diver.

You can't - because such an agency doesn't exist.

Depending on how you look at it they all do.

From the time you leave the bottom until you reach the surface is Deco time nomatter how fast or slow it may be. And they all teach how to do that.

Gary D.

 

[Scubaguy62]

You should know two things before intentionally going into deco; how to read your computer, and how to do deco. If you have no training in deco, you're flirting with disaster, considering that it is more likely than not that when you go into deco you're gas supply will be close to the minimum. This is no time to place "all your eggs in one basket" and risk mandatory deco stops without an adequate gas supply to complete them. However, if your last name is Trump, Gates, or Rockefeller, and/or you have a hyperbaric physician in your immediate family, by all means go ahead!

Rick

I'll second this - if you want to learn how to do deco, intentionally violating NDL's by just a little bit to see what happens isn't the way to do it. A minor violation probably won't kill you but it can sure spoil your day and may result in permanent injuries and no more diving, ever.

Dive safely.

 

[DandyDon]

OK, this thread started off with the question of whether someone would know what to do if their computer went into deco.

They'll know what to do if they have read and understood their computer's manual.

With that approach, the newbie who says "I know how to Scuba, 'cause I read the book and got all of the review questions right!" would be justified, huh? Practice is redundant...?!? :54:

don

 

[rcohn]

The statement you mane that recrestional computers have considerable conservatism is something we could debate. While they may have conservative NDL's the models commonly employed and the schedules generated for manditory decompression may not look so conservative when compare to a more modern model like VPM, RGBM or even Buhlman with gradient factor control. In an earlier post I described the situation where a freind was badly bent while his computer was very happy. He even did more decompression than his computer recommended. After comparing his schedule to those that I generated for the same dive I would not say his computer was conservative. I'd say it bent him on the initial ascent and then failed to treat him enough. It worked for his buddy though and maybe it would work for you...or not.

Conservatism isn’t really a matter for debate. It can be measured. Millions of dives are performed annually on computers. What is the accident rate? Does experience show that computer use is conservative or risky? The computer profile can be fed into the modeling software of your choice and the degree of conservatism can be measured. This will be limited by the model’s validity and the assumption that were made during its creation.

Conservatism is also dependent on the divers choices, the margin he stays above the NDLs, the ascent rate, the use of deep stops (some of us have been using them for several years), the length of the safety stops, the exertion during and after the dive. Rather than recommending technical mixed gas training (where many skills won’t be used) before recreational divers venture deeper, perhaps there should be training in techniques such as deep stop(s) (1/2 max depth?), minimizing exertion, and emergency deco profiles. Skills a recreational diver could actually use.

I’m sorry you friend was bent while using his computer within the limits. He is certainly not the first person to be bent while diving on a computer or tables. Are you suggesting no technical diver has ever been bent on a decompression schedule? As you know Dr. Deco would suggest that most sport divers are bent after they exit the water, are you certain the computer was at fault? Who do you blame if a technical diver on computer generated tables is bent?

Your statement that refering to the computer generated emergency decompression is based on what exactly? It's not a PLAN at all and that's the problem. It's a feature of the computer to bail you out after your failure to plan. The simple act of having to use it is a good arguement in favor of divers getting the training/skills that I recommended prior to doing those dives so that they can choose the way they want to decompress and have the skill and gas to execute the schedule.

You seem to be argueing in favor of divers ridin the edge of the "NDL" and relying on the computer to bail them out while I advocate the diver understanding the situation that they're in on such a dive and making informed decisions and being in control.

It’s no worse a plan, for a recreational diver, than a technical diver carrying a set of backup tables when he exceeds the original plan. If the technical diver is following his original plan he will never need the backup tables, it is only when he fails to follow his plan that these tables will be used. Your real issue is you don’t believe in dive computers. You think that using a program, whose inner working you don’t understand, on a computer at home is “safe”. While carrying one or more computers on your dive, that continuously monitor the actual conditions of your dive, is unsafe.

And, for the record, I’ve never argued that a diver should ride the edge of the NDLs nor do I ride the edge of the NDLs when I’m diving.

Do have some kind of proof that what you suggest is better? Are you suggesting that divers are better of at 100ft + without the trianing/skills I'm recommending?

Anyone can create safer divers by increasing the training standards. I might decide the GUE is unsafe and create a new agency that doubles the standards. Only Olympic level athletes could pass the physical tests. The classroom and in-water hour hours would double, and the exercises would exceed Navy SEAL standards. Maybe we would throw in hell week just for fun. I’d increase the safety ratios on deco and narcosis too. My agency’s divers would certainly be the safest in the world. Of course, there would be very few divers because almost no one could make it through the training.

The real question is what is the appropriate level of training and safety? How can we allow the greatest number of divers to safely participate in the sport of diving and enjoy the underwater world. IMO the accident statistics show the agencies do a surprisingly good job. There are many things I’d personally tighten up, starting with better swimming skills and actual basic freediving training prior to scuba. However, the statistics are generally good; it seems the current standards may be adequate in terms of water skills. Maybe they are adequate in terms of deep diving as well? More training (the right training) would always be better and should be encouraged, but the recreational diver training should reflect the conditions, equipment, profiles, and minimum standards appropriate to recreational diving, rather than those of technical diving.

What exactly is your motivation here?

You're using resort DM's as your knowledge base? Thats a joke right?

Trust me dives any one?

Ah Mike, you contempt for recreational divers and ignorance of the sites and conditions is showing. Many resort DMs have incredible skills. They may lead 500 or more dives a year. Some in challenging advance environments such as the Galapagos or Palau. They may have traveled and worked in a variety of locations. They deal with occasional divers who have inadaquate skills, with panicky divers, and with accidents. All of this builds the DM or instructor skill level. If you had ever dove at some of the exotic dive destinations you would know this.

I’ve witnessed one rescue at Grand Turk while diving with Oasis divers. Not a deep dive more like around 40 ft. A teenage girl, diving with her father, was feeding one of the groupers with fish food pellets. Not encouraged by Oasis divers but not prohibited either. The fish managed to nip her finger and draw a few drops of blood. She spit out her regulator and attempted to bolt to the surface. Everything so far I learned from my wife, I was looking in the opposite direction at the time, the rest I saw. Austin the DM, reached her quickly before she could travel far, got his reserve regulator in her mouth, and settled her down until she was successfully able to continue the dive. She also did her first night dive late that day and did fine.

Maybe I’ve been fortunate (and careful) but I’ve yet to meet a tropical divemaster who was a joke.

What’s my motivation? I get tired of the self-appointed biased experts who want to stand on a soapbox here and lecture everyone on what’s right and wrong in diving, and usually insisting that technical diving training, techniques, standards, and even objectives, are the only legitimate ways to dive. You are fond of forcefully expressing completely unsubstantiated opinions as though they were incontrovertible fact (e.g. the old frog kicking is the most efficient kicking post.). From your posts, you have no interest in recreational diving, and if I recall correctly, have never traveled to any of the popular dive destinations (I’m not counting Gilboa Quarry). Yet you leap at the chance to tell us your opinions on exactly what is wrong with recreation diving, how unsafe we all are, how incompetent all the DMs and instructors are, etc. Maybe if you want to be an authority on how recreational diving should be done, you might at least spend a week visiting a site like Grand Turk or on a liveaboard, to see what it is really all about.

ArcticDiver is the perfect example of my motivation; he reads the posts and arguments and decides for himself what you’re really all about. Then he (and the rest of us) can weight your copious advice appropriately.

Ralph