Info Why are tables not taught in OW classes anymore?

[Superlyte27]

Oh, there’s more than one. Here’s an example:

Ultrasound in the diagnosis of acute-phase decompression sickness

A 53-year-old man, who performed a 44-minute dive to a depth of 21 meters, felt severe abdominal pain with dyspnea after surfacing. An ultrasound stud…

www.sciencedirect.com

In 2010 DAN published an article titled “The Validation of Dive Computer Decompression Safety,” in which they stated:

But on the other side, you’d think that the incidence of decompression sickness would decrease with dive computer usage; it hasn’t. Apparently, unless something has happened since 2010, there is no standard for validation of dive computer algorithms. Please read this article, and the expert commentary toward the end of the article.

The Validation of Dive Computer Decompression Safety

There is a lack of hard data on the validation of decompression safety and the intersection of dive computers. Read more.

dan.org

SeaRat

Oh! Two whole articles. Like I’ve said, I’ve witnessed hundreds if not thousands of people screw up their ill conceived and erroneous dive plans based on tables. Between being a boat captain in the keys to a dive master all over to being an instructor at every level, WAY WAY more mistakes are made with tables based dive planning than with dive computers. But you keep beating that little drum. I’m sure you’ll catch up with technology sooner or later. Lol

 

[John C. Ratliff]

You understand how flawed your Mickey Mouse logic is right? Lol. Bad instruction can take place in a computer class or tables class. The difference is that the fundamentals of computer diving (any computer) can be mastered in 5 minutes of quality instruction. The same is NOT possible with tables. All things equal, ask a brand new diver which is easier, safer, quicker, and more reliable; their brain and their understanding of tables or the dive computer. The answer will shut this argument down. You know it. I know it. The newer divers reading this thread know it.

Dive computers are:
Easier: yes.
Safer: not necessarily.
Quicker: yes
More Reliable: Not so sure.

You haven’t read the entire DAN report I linked to above about dive computers. The four experts, some of whom have developed dive computers, state that there are needs for a standard to measure them against. So far, apparently there is none. Karl Huggins was one of the participants in this article, and he stated:

Huggins: The first step would be to establish an industry standard that all dive computer manufacturers could adhere to. Since the likelihood of the manufacturers doing human subject tests is low, a protocol along the lines of the following would have a better chance of implementation:

—Run the decompression algorithm against a set series of dive profiles with known risk.
—Run the profiles allowed by the decompression algorithm through an established decompression risk model.
—Verify that the dive computer hardware and software run the decompression algorithm properly.
—Publish the results of the tests along with the risk estimates from each test profile.

Apparently, this still has not happened.

SeaRat

 

[El Diablo]

Because they are unreliable and make almost impossible to follow the set dive profile. I was trained on the US Navy tables but basically only used them in class and assisting classes. After that my 2002 Suunto Stinger took over....

No one re-calculates and adjusts for their mid-dive changes increasing exposure and DCS risks.

Dive computers do those calculations real time, thousands of calculations per second, rendering diving tables obsolete.

 

[rongoodman]

I personally think they are useful so much in that they help a new diver understand what is going on, at an abstracted level of their computer. Teach them tables, then show them the magic and joy that is a dive computer.

We covered tables in my OW class but while not difficult, I remember them as being a series of strictly rote calculations. There was certainly no explanation of tissue loading or the mechanics of on- and off-gassing, so in no sense did they explain "what is going on".

 

[boulderjohn]

Are you sure? Here’s an explanation by DAN of a dive resulting in decompression sickness, without exceeding the computer’s algorithm.

The problem is that reliance upon dive computers has made a current population of divers dependent upon them, and not upon the knowledge of decompression limits, and why they were established in the first place. So today’s divers lack an understanding of the basics of why the no-decompression limits were set, and how some profiles, the computer deems safe, may not be. Divers of yesteryear would plan their dives before entering the water, go deeper first, then not tarry around a jigsaw dive profile. We also cautioned against diving to the “knife edge” of the no-decompression limits, as those limits were devised with the understanding that a certain percentage of Navy divers would get decompression sickness at the edge of the no-decompression limits.

SeaRat

I have no idea why using computers means that you no longer learn all those things. They are still part of the OW course.

 

[boulderjohn]

The simple truth is that you cannot do many of the popular dives today--or yesterday--with tables.

When I first started diving, I did all the dives my first couple of years in Cozumel, where you are required by law to follow a guide, and where those guides lead you on multi-level dives. The very first time I tried to use my tables, I saw how very impossible it was. Within a couple of years, the dive oeprator I was using was requiring all divers to use computers for that reason. That was a couple decades ago.

 

[tursiops]

The simple truth is that you cannot do many of the popular dives today--or yesterday--with tables.

When I first started diving, I did all the dives my first couple of years in Cozumel, where you are required by law to follow a guide, and where those guides lead you on multi-level dives. The very first time I tried to use my tables, I saw how very impossible it was. Within a couple of years, the dive oeprator I was using was requiring all divers to use computers for that reason. That was a couple decades ago.

How did people dive in Cozumel pre-computers?

 

[ofg-1]

I don't understand why this discussion has warranted this many comments. If you choose to teach tables, go ahead. If your agency doesn't require it, don't. If you get a good margin on computers, hell sell them all 3 of them. Next year, the computers will be different colors to match your fins.

Other than your computer, we are diving with technology that is at least 60 years old. For that matter, the original "bends o matic" computer is also. Why does a little more of it offend you?

So tables, slide rules and the abacus are more difficult to teach. Idiocracy was not originally meant to be a documentary..

 

[tursiops]

Possibly some of the confusion/dissention/angst in this thread are because people are conflating something being easy to teach or learn with something that is easy to use, with an overlay of understanding what is behind the curtain. Tables are much hard to use than a computer; what could be simpler than just looking at numbers on a display? Teaching how to use a table can be done by providing a lot of background on gas models and then introduce the table as a way to track all those compartments on and off gassing. Or it can be taught as a rote exercise in using side A this way then side B that way. Clearly, from the posts in this thread, lot so people "learned" tables by the rote method....no background understanding was included. On the other hand, computer use is not much aided by all that background on on and off gassing; there is no tactile column of numbers that is the analogy to going deeper and staying longer. Teaching and learning the computer is much more of a rote exercise...to its detriment. those who argue for "tables first, then get a computer" are perhaps actually saying, "Learn the background for the tables first, with the visual display of the table actually helping you do that, then learn how to push buttons on a computer to get more meaningful answers for a multi-level dive."

Sidebar: my wife -- also an instructor -- used to teach tables by analogy to a credit card: you spend and spend and spend (descend, stay at depth...all on-gassing), but you've got a credit-card limit (NDL) you can't exceed. You can pay off some of your debt (ascend, begin some off gassing), When you get to the surface you still owe some money (residual nitrogen). Unlike a credit card, your debt does down if you just stay at the surface for a while; nice! On your next dive (say) an hour later, you still owe some money so you can't spend as much as you could have on your first dive (NDL reduced by residual nitrogen).

 

[John C. Ratliff]

I have no idea why using computers means that you no longer learn all those things. They are still part of the OW course.

I was talking to what Dan's spokesman said, and you deleted that part of my post:

Are you sure? Here’s an explanation by DAN of a dive resulting in decompression sickness, without exceeding the computer’s algorithm.

… Two decades ago the maximum allowable total dive time if a diver reached 30m depth would have been around 20 minutes if the dive was planned using tables, as it commonly was. This dive profile may even have been permitted using multilevel planning techniques. But today, modern dive computers do the work for us and such a profile is considered a “normal dive”.

The risk of decompression sickness is thought to be low among recreational divers because the majority of dives come nowhere near the no-decompression limits. After two previous days of repetitive diving, this diver suffered an injury which was diagnosed as a serious case of decompression sickness, probably without violating the dive computer’s limits. That the diver made a safety stop was prudent, but of particular note is that there was oxygen onboard the boat, and the diver continued breathing oxygen on the way to the ER.

After multiple hyperbaric treatments the diver is 99 percent recovered, which is good news, though it should be pointed out that bilateral symptoms affecting all four limbs are not typical of decompression sickness.

Regardless, this case serves as a reminder that our dive computer may well keep recalculating our allowable limits but that does not mean we should dive to those limits. If 100,000 divers dive to the limits then, even though they did not “break the rules”, by probability alone some will get the bends.

Peter Buzzacott, MPH, Ph.D.

“Normal” Dive Resulted in Decompression Sickness

This case serves as a reminder that our dive computer may well keep recalculating our allowable limits but that does not mean we should dive to those limits.

dan.org

I am not against computers; I use one. But I do want divers to know more about their limitations. I worked in high tech, which allowed the chips that make them possible to be built.

SeaRat