Ugh GUE goes tabular

[rjack321]

One more instance of precision misleadingly suggesting high accuracy.

 

[ucfdiver]

One more instance of precision misleadingly suggesting high accuracy.

It's a necessary evil if other agencies are teaching tables, students will need some form of exposure to dive planning with tables to work with other divers. As long as it's mixed with as much deco theory as can reasonably be absorbed in an intro to scuba course, I don't see an issue. Since these divers are breathing compressed gas for the first time, using muscles they haven't necessarily used, and have all the stress of being a new diver, I don't think they could use physical feedback to judge how their body is responding to their dive profiles. They're going to be exhausted just like we would if we were sub-clinically bent in the worst way even on a 30ft reef dive for 45 minutes...I was at first.

Just my opinion, but even teaching Boyle's law and how it relates to tissue loading and off-gassing in an overgeneralized form would be a huge improvement over what's currently out there. Even using a permeable membrane analogy with basic high school biology "experiments" where dye slowly enters and exits the membrane until both sides are in equilibrium as an example/visual would be GREAT for a new diver. Teach divers how staying 10ft off the bottom can add nearly 10min of dive time or more, as well as making them aware of sub-clinical symptoms to keep an eye out for, but leave them with something firm to hang onto (even if it's nothing more than a safe average that attorneys have agreed upon). Further levels of training should no doubt wean divers off of these tables into something more up-to-date with modern deco theory and/or algorithms.

What would you suggest?

 

[Ben_ca]

One more instance of precision misleadingly suggesting high accuracy.

+1 What was wrong with the old tables...

 

[rjack321]

Given the kinds of questions being asked on the GUE board I can imagine people sitting down and subtracting RNT from these new limits (and they should since they are pretty damn aggressive).

What would you suggest?

The air "table" they used to teach in DIRF,
100ft, 20min setpoint
-20% EAD for 32%

air:
40ft-170mins
50-60
60-50
70-35
80-30
90-25
100-20

Along with the repetitive dive guidelines for doubling the shallow stops with <90mins SIs and ignoring the previous dive with SIs >90mins.

Or the "120 rule". People have been diving without figuring RNT and junk like that for a decade plus. Its overly precise for mere theoretical accuracy in avoiding DCS.

 

[jjones9527]

Just my opinion, but even teaching Boyle's law and how it relates to tissue loading and off-gassing in an overgeneralized form would be a huge improvement over what's currently out there.

Don't you mean Henry's law?

 

[ucfdiver]

Don't you mean Henry's law?

No, I mean Boyles, pressure and volume...

Henry's law might give a more accurate description of the permeable membrane example, but I think the over-generalization of the balancing of internal and external forces would be enough, using boyles to kinda explain how higher pressures get into the tissues in the first place.

 

[jjones9527]

I must be missing something because I can't see how and increase in pressure and reduction in volume equates to more gas being dissolved in the tissues.

Boyles law is relative to something like bubble expansion on ascent, but thats about it as far as decompression is concerned.

 

[ucfdiver]

I must be missing something because I can't see how and increase in pressure and reduction in volume equates to more gas being dissolved in the tissues.

Boyles law is relative to something like bubble expansion on ascent, but thats about it as far as decompression is concerned.

I don't think I was even remotely suggesting that dissolved gas theory get introduced at the rec 1 level. I originally stated that Boyles law be used to demonstrate an oversimplified decompression concept.

Teaching that bubbles

• Always exist
• Are composed of inert gases (or nitrogen at the rec 1 level)
• Enter the body at a fairly steady rate (as it has to deal with volume), but realizing that 1cu ft of gas at 0ft is much less overall gas than at 33ft, so it's easier to pump more gas of equal volume into your body at depth.
• Increase in size as you ascend (decrease pressure).
• Cannot efficiently exit the body due to the permeability of the areas of the body which release them. Furthermore, as the bubbles grow, it becomes harder and harder for them to exit.

....is the most simple way I can think of to get a basic understanding of decompression theory. Sure, it's a generalization and has some inaccuracy, but we're trying to cut corners here...even Boyle's law it's self doesn't hold up at high pressures. Those of us who have had the misfortune of having to take college physics, chemistry, and biology will clearly want to read more in depth, but recreational courses have to be developed at a lower level than that.

If you have an idea how to explain the concept to a newly minted diver who might have very little mathematical or scientific background, and mainly desires to do recreational diving without decompression, I'd love to hear it...(and just to make sure my tone isn't misunderstood since we're online, I mean that in a friendly, non-trolling way-- I haven't heard many people or instructors accomplish this task well).

 

[TSandM]

I think the idea that GUE divers need to work tables so they can dive with people with other training is a bit silly. When was the last time you saw a recreational diver anywhere using tables? Virtually EVERYBODY buys a dive computer, and they never work tables again. Some agencies aren't even TEACHING tables any more.

I loved the old system, and I'm not sure what was broken that this is trying to fix. I'm not aware of any multitudes of people doing recreational dives by the old system getting bent.

Does anybody know whether these tables are max depth or average depth? If max depth, then there is a degree of conservativism built in already.

 

[jjones9527]

Teaching that bubbles

• Always exist
• Are composed of inert gases (or nitrogen at the rec 1 level)
• Enter the body at a fairly steady rate (as it has to deal with volume), but realizing that 1cu ft of gas at 0ft is much less overall gas than at 33ft, so it's easier to pump more gas of equal volume into your body at depth.
• Increase in size as you ascend (decrease pressure).
• Cannot efficiently exit the body due to the permeability of the areas of the body which release them. Furthermore, as the bubbles grow, it becomes harder and harder for them to exit.

Of that list, Boyles law only directly relates to number 4. ACUC's curriculum teaches Boyle, Dalton, Henry and Charles at the open water level. Rather than trying to relate Boyle in some obscure way to dissolving gas, we explain Henry to them. Its much easier to explain "as pressure increases the amount of gas that will dissolve in a liquid proportionally increases," rather than trying to relate gas compression due to a pressure increase resulting in greater inert gas dissolved in the blood.

Boyle = gas compression and expansion due to pressure changes
Henry = more pressure, more dissolved gas, less pressure, less dissolved gas

The two combined give a much better understanding of decompression mechanics rather than trying to cover all the bases with just one.