Info Why are tables not taught in OW classes anymore?

[scubadada]

Yeah, but we know you are weird because you don't use any air....so can't possibly uptake much nitrogen.....

Ha, and I thought nitrogen uptake was independent of breathing rate. None of the divers in the DSAT validation were as old as me, or you

 

[John C. Ratliff]

I have two words for anyone considering backup tables, backup computer.

Okay, now I’m curious; how if your computer dies on the first dive of the day, do you program that first dive into the backup computer?

SeaRat

 

[John C. Ratliff]

As has been demonstrated over and over and over and over and over again on ScubaBoard, if your first dive was multilevel with a computer, it will be a rare case when you can use tables to plan the second if your computer fails. Your first dive would likely be off the tables, so you wouldn't be able to dive with tables until the next day.

Not if you are diving a single steel 72 or even an AL80. I think that the assumption is with a high pressure, high capacity cylinder or twins (either back-mounted or slung).

SeaRat

 

[Nick_Radov]

You don't think that almost 40 years of successful use represents validation?

No, not for the circumstances I described above. Any of the tables or computer models in common use today empirically seem to work well enough for up to two dives in a series with a good surface interval. For three or more dives in a series there has been very little solid research. Even when the models seem to "work" I suspect it's more because the free parameters have been tweaked than due to any alignment with what's actually happening in divers' bodies.

I know that for divemasters and guides in resort areas doing multiple dives per day every day nonstop, minor DCS hits are pretty common. These incidents don't get reported anywhere, they just breathe some oxygen or grab another tank and do IWR. The ones who get hit repeatedly quit and do something else. So, we don't have any good data and even the anecdotal reports aren't representative of the general diver population.

The problem with pretty much all of the current tables and computers is that they "allow" repetitive dives after short surface intervals. Rather than drilling OW students on table usage, it would be more beneficial to teach them the basics of bubble mechanics and circulatory system physiology. Give them a qualitative understanding of why it's important to allow enough time for bubbles to clear even when they're being pressured to hurry up.

 

[scubadada]

Okay, now I’m curious; how if your computer dies on the first dive of the day, do you program that first dive into the backup computer?

SeaRat

Oh, come on John, I wear them both all the time. I lived in Portland for 8 years, but never dived in the Clackamas River. I did catch some great salmon and steelhead while I lived there.

 

[Bigbella]

In other words, they use the tables even when the tables can't be used. Isn't that a different way to say they wing it and dive with no guidance at all? Aren't you just jumping in the water and hoping for the best? Since the tables don't work in those cases, what is the benefit to knowing how to use them?

Let's just say, for the sake of argument, that they're called diving for the day, after their Teric has crapped out; and that they'll snorkel, for the benefit of the sharks, and pick up diving the following morning, with the use of tables.

Neither dive tables or the fanciest of Canuck computers are any measure of physiology, eh; they're best guess models, dependent upon any number of factors, not including the fitness or even more commonly, the unfitness of the diver, whether you've spent two hundred or twelve hundred dollars.

We all must have been stupid-lucky back then -- and all in great shape.

My first fifteen years of diving were before the advent of computers; and those whom I knew who eventually contracted DCS, exclusively did so, much later, pushing limits on computers, not tables . . .

 

[tursiops]

This is just a bit unfair, I think.

For three or more dives in a series there has been very little solid research.

Counter examples are Liveaboards and Bonaire; 3-4-5-6 dives a day. Bonaire typically as treated maybe 5-6 dives a week in their chamber....out of how many dives on the island each week?

Even when the models seem to "work" I suspect it's more because the free parameters have been tweaked than due to any alignment with what's actually happening in divers' bodies.

Isn't that saying the same thing? That is, tweaked to more accurately represent what the body is doing?

I know that for divemasters and guides in resort areas doing multiple dives per day every day nonstop, minor DCS hits are pretty common.

Mostly I see Suuntos....old ones.

The problem with pretty much all of the current tables and computers is that they "allow" repetitive dives after short surface intervals.

The RDP was designed apriori for shorter surface intervals, and the NDLs adjusted to allow that.

 

[tursiops]

My first fifteen years of diving were before the advent of computers; and those whom I knew who eventually contracted DCS, exclusively did so, much later, pushing limits on computers . . .

I started on tables too. For many years. It is much harder to push the limits with tables; computers make it easy. The problem is pushing the limits, not inherently computers.

 

[scubadada]

...The problem with pretty much all of the current tables and computers is that they "allow" repetitive dives after short surface intervals. Rather than drilling OW students on table usage, it would be more beneficial to teach them the basics of bubble mechanics and circulatory system physiology. Give them a qualitative understanding of why it's important to allow enough time for bubbles to clear even when they're being pressured to hurry up.

Hi Nick

I'm quite curious, you haven't said, what do you dive?

Our computers adjust NDL based on the previous dive and the SI. I suppose the tissue graphs are also useless since the decompression algorithm does not reflect the human body. The dissolved gas algorithms are quite successful in avoiding DCS.

Teaching students bubble mechanics and circulatory physiology are going to help them in what way?

One thing is for sure, the less exposure at depth, the less the risk of DCS. The risk with all available computers is small.

 

[scubadada]

I started on tables too. For many years. It is much harder to push the limits with tables; computers make it easy. The problem is pushing the limits, not inherently computers.

I dived Navy tables 1970-80, no more than a couple dives per day. Of course, these were shore dives in Southern California