PADI tables finally going away?

[DA Aquamaster]

And using the 720 minute compartment is even more conservative. Should we do that? Is conservative always good? If we say that divers should wait 6 days between dives, we can pretty much be sure that residual nitrogen is gone, but is that necessary? I think you would agree that we want to use a protocol that keeps us safe and still allows us to dive. The question is this: where do we draw the line.

The research by the group that created the RDP (and our own Doc Deco--Michael Powell--was part of the team) determined that for dives within the recreational limits imposed by the table (with some exceptions), the 60 minute compartment was more than adequate for safe diving. The exception is for multiple dives that fall within the WX and YZ rules, for which they made special rules.

Do you have access to research that shows their studies were wrong? If so, you should go to the Ask Dr. Decompression forum and tell Michael about that research. I am sure he will be interested in learning why they were wrong.

Don't get twitchy about it - I am not arguing one way or the other regarding the efficacy of the PADI RDP for recreational diving - I own one, have never used it, probbaly never will and I don't have a dog in the fight, but at the same time I do not want other readers to get the wrong impression about the RDP. If it is more conservative than the US Navy tables it is in terms of the shorter NDL's, not the faster washout.

I was instead suggesting that the way you constructed your paragraph regarding increased conservatism in using the 40 versus 60 minute compartment tends to bleed the "more conservative" concept into the washout rate concept implying the 6 hour out on the RDP is more conservative than the 12 hour out on the US Navy tables.

But you pretty much confirm that is not the case in your last post when you mention the need for a special set of rules for multiple dives that fall in WX and YZ, so again, we agree.

 

[boulderjohn]

Don't get twitchy about it - I am not arguing one way or the other regarding the efficacy of the PADI RDP for recreational diving - I own one, have never used it, probbaly never will and I don't have a dog in the fight, but at the same time I do not want other readers to get the wrong impression about the RDP. If it is more conservative than the US Navy tables it is in terms of the shorter NDL's, not the faster washout.

I was instead suggesting that the way you constructed your paragraph regarding increased conservatism in using the 40 versus 60 minute compartment tends to bleed the "more conservative" concept into the washout rate concept implying the 6 hour out on the RDP is more conservative than the 12 hour out on the US Navy tables.

But you pretty much confirm that is not the case in your last post when you mention the need for a special set of rules for multiple dives that fall in WX and YZ, so again, we agree.

Didn't mean to be twitchy. Sorry.

Let me state my explanation more clearly for all. (and I know you understand it.)

The Navy tables are based on the 120 minute compartment, leading to some long surface intervals. Navy divers frequently did long and deep dives. PADI's research showed that for recreational dives, the 40 minute compartment could safely be used instead. This leads to much shorter surface intervals than the Navy tables. In order to be more conservative than their research suggested they needed to be, they used the 60 minute compartment. This still leads to shorter surface intervals than the Navy tables do.

 

[The Chairman]

Some food for thought: Wikipedia: Human Reliability

Human error has been cited as a cause or contributing factor in disasters and accidents in industries as diverse as nuclear power (e.g., Three Mile Island accident), aviation (see pilot error), space exploration (e.g., Space Shuttle Challenger Disaster), and medicine (see medical error). It is also important to stress that "human error" mechanisms are the same as "human performance" mechanisms; performance later categorized as 'error' is done so in hindsight (Reason, 1991; Woods, 1990): therefore actions later termed "human error" are actually part of the ordinary spectrum of human behaviour. The study of absent-mindedness in everyday life provides ample documentation and categorization of such aspects of behavior. While human error is firmly entrenched in the classical approaches to accident investigation and risk assessment, it has no role in newer approaches such as Resilience Engineering.

It's not that the tables are prone to being wrong: we are even without narcosis! Add a little bit more N2 and we become bovine in nature. In addition, tables don't have alarms to remind us that we are exceeding a limit, but computers do. Tables are not nearly as interactive or versatile as a computer. They can't read your depth, measure your time or record your depth against time. I wonder how many of you don't set your alarm clock when you have a very important meeting? I wonder how many of you would tell your son or daughter not to rely on such a contrivance?

Moreover, how many of you have always had a perfect accounting with their bank when they reconciled? How many have never bounced a check? How many friends do you know who have never bounced a check? Ever? No, tables aren't math, but they are based on algorithms, which is math. They are prone to a variety of errors, including fat fingers, erroneous data and being ignored. We are the weakest link in using tables.

Me? I am going to continue to teach my students how to use computers and minimize their use (if any) of tables. It has nothing to do with me being lazy or over dependent on electronics. It has EVERYTHING to do with me wanting to train my students to use the best tool for the job. They can pick up how to use tables IF they ever get into tech diving.

 

[gcbryan]

Why not teach both?

 

[Kevrumbo]

Not even an issue: gotta know this table (http://wrigley.usc.edu/hyperbaric/hugi.pdf) and a few others, if you want to volunteer here: Welcome to the University of Southern California Catalina Hyperbaric Chamber

Ain't no digital computer controlling the hyperbaric chamber, nor tracking the N2 loading of patient, tender & physician here --it's all manual analog, base 60 arithmetic, and dive & treatment tables.

A good grounding in fundamental dive tables will always serve you, especially when that dive computer goes kaput. . .

 

[The Chairman]

Why not teach both?

For the same reasons I don't teach underwater demolition, how to rebuild a regulator and underwater basketweaving to open water students. Sure, if a student has an interest in any of those subjects (except UDT), I can help them gain mastery after the basic class. But really, tables aren't needed by them to go diving and have a great time. I would rather spend more time on skills they will actually use to have a safe and enjoyable dive, like trim and the frog kick.

For me, diving open water with tables is as anachronistic as diving with vintage Scuba Gear. Sure, you can dive with a double hose reg, duck feet and no BC, but I don't enjoy it! I much prefer modern gear that works the way I want it to. You can be sure I won't be training my OW students in them so they will have a feel for the "good ol' days". Go and listen to those vintage divers and they will tell you how much "better" the old stuff is. Many of us simply shake our heads and hide our smiles. They can believe it's "better", but I am going to side with technology on this. I don't dive to validate the process: I dive to have fun!

Earlier I identified technophobia as one possibility for this resistance to change and I feel I need to add neophobia and metathesiophobia as well. While I am sure that these are not full blown phobias for most, they certainly seem to be tendencies among the diving public. Human error and inattention will almost always be the major cause of diving injuries including DCS. Task loading people, especially students, seems the best way to induce these mistakes. I'm all for taking the guess work and drudgery out of this fun sport. Learning the tables won't make you a "better" diver nor will it increase your fun significantly. Why push them until you have to?

I wonder how many of you have ABS brakes or traction control on your cars? You allow your CAR to decide how you are going to brake during an emergency? Say it ain't so, Joe! It gets back to that task loading issue. When you are confronted with an emergency, you might very well forget to feather that pedal. You certainly won't feel the one wheel breaking loose first but I bet a sensor did. It's kind of like being narced with the perceptual narrowing. But who knows? Your knowledge of tables might help your driving too!

 

[lord.harshil]

I'm not all that experienced as a diver with less than 100 dives and only about half those dives using a dive computer but this is what I feel :

There are a few factors to consider here :

Time taken to teach and allow students to master both tables and computers and weather clients want to spend all this time learning them.

From what I've seen and experienced so far on the East Coast of Peninsular Malaysia, most new divers either don't understand the importance of tables, computers and DCS etc or they don't care. They just seem to want the fancy plastic card which, in their opinion, by default makes them safe divers and they just want to follow a DM / Instructor and swim with the fishes, pun not intended

I think its not very smart of them to do this, but then again, hey they're adults (most are older than 20 yr old me) and they have been told about the risks and at the end of the day its their choice. For me personally, I use a dive computer because its a lot easier and versatile than using tables. You rarely stay at a constant depth when diving reefs in Malaysia so I like using a computer in these cases. Having said this, I know about the NDL limits for each dive from the tables before I jump in the water in the unfortunate (and i hope RARE event) that my dive computer fails.

My advice to friends and clients alike, use a computer for its ease and simplicity but know the tables as well. If they choose to ignore this advice and they find themselves in a chamber, well, thats their problem to deal with then.

 

[DA Aquamaster]

I wonder how many of you have ABS brakes or traction control on your cars? You allow your CAR to decide how you are going to brake during an emergency? Say it ain't so, Joe! It gets back to that task loading issue. When you are confronted with an emergency, you might very well forget to feather that pedal. You certainly won't feel the one wheel breaking loose first but I bet a sensor did. It's kind of like being narced with the perceptual narrowing. But who knows? Your knowledge of tables might help your driving too!

That's a good analogy. I remember when they first came out as on our patrol cars - we discovered that they would cycle during hard braking on washboarded areas of gravel roads. This was unfortunate as the areas where cars normally brake on gravel are the areas that get washboarded the most since the braking forces contribute to the washboarding of the road. This discovery was made when several officers flew right off curves during high speed pursuits because the cycling brakes offerred basically no speed reduction on washboards. Great on ice, not so great on gravel.

So, I'd argue that while most drivers liek ABS and benefit from it, drivers who really know how to drive tend not to be the world's biggest ABS brake fans. Personally, I owe my life to NOT having ABS brakes. I was post law enforcement by then when I t-boned a car that pulled in front of me on the highway. I walked away from what should have been a fatal accident because I was able to lock the brakes, break the rear end loose and spin the car in order to aborb the energy along front and side of the car rather than head on. Talk about training taking over, but it would most likely not have worked in the time available with ABS brakes.

I'm not technophobic - I enjoy a dive computer as much as anybody (as a backup to solid deco and gas planning) and I certainly enjoy flying instrument approaches a lot more with a flight director or HSI than with just an artificial horizon or partial panel. But the point is I know how to do it with much less reliance on technology when the technology fails.

You are entirely correct that knowing the tables is not required as long as the diver has a working computer, but at a minimum they need to know what to do when it fails and they need to know enough to be abel to determine when it is feeding them false information and teaching tables is one of the quicker and easier ways to address both.

 

[Puffer Fish]

Well stated Pete.

Some food for thought: Wikipedia: Human Reliability



It's not that the tables are prone to being wrong: we are even without narcosis! Add a little bit more N2 and we become bovine in nature. In addition, tables don't have alarms to remind us that we are exceeding a limit, but computers do. Tables are not nearly as interactive or versatile as a computer. They can't read your depth, measure your time or record your depth against time. I wonder how many of you don't set your alarm clock when you have a very important meeting? I wonder how many of you would tell your son or daughter not to rely on such a contrivance?

Moreover, how many of you have always had a perfect accounting with their bank when they reconciled? How many have never bounced a check? How many friends do you know who have never bounced a check? Ever? No, tables aren't math, but they are based on algorithms, which is math. They are prone to a variety of errors, including fat fingers, erroneous data and being ignored. We are the weakest link in using tables.

Me? I am going to continue to teach my students how to use computers and minimize their use (if any) of tables. It has nothing to do with me being lazy or over dependent on electronics. It has EVERYTHING to do with me wanting to train my students to use the best tool for the job. They can pick up how to use tables IF they ever get into tech diving.

 

[Puffer Fish]

The problem with the antilock brakes was not ABS, it was a design flaw in the original US designs...which has been corrected. It was a pulse rate issue.. long since corrected.

Note: it was us car makers being cheap, as they had the European data that showed how fast was needed.

Your second example is interesting, because there is a very easy way to do the same thing...even with antilock brakes. However, it is the classic "I am safer without seatbelts, because...." story.

Lastly, there are conditions that no human can control...just review some of the test video on them... one set of wheels on slippery, one on pavement, and no human can control the braking because it requires different actions on different wheels.

Stability control (the next generation adding to ABS) is now considered to be the single biggest life saver benefit... more than twice that of ABS.. but ABS is first needed to make it work.

You are not safer without ABS.. not even close. Yet there are still people that believe this is not true...

That's a good analogy. I remember when they first came out as on our patrol cars - we discovered that they would cycle during hard braking on washboarded areas of gravel roads. This was unfortunate as the areas where cars normally brake on gravel are the areas that get washboarded the most since the braking forces contribute to the washboarding of the road. This discovery was made when several officers flew right off curves during high speed pursuits because the cycling brakes offerred basically no speed reduction on washboards. Great on ice, not so great on gravel.

So, I'd argue that while most drivers liek ABS and benefit from it, drivers who really know how to drive tend not to be the world's biggest ABS brake fans. Personally, I owe my life to NOT having ABS brakes. I was post law enforcement by then when I t-boned a car that pulled in front of me on the highway. I walked away from what should have been a fatal accident because I was able to lock the brakes, break the rear end loose and spin the car in order to aborb the energy along front and side of the car rather than head on. Talk about training taking over, but it would most likely not have worked in the time available with ABS brakes.

I'm not technophobic - I enjoy a dive computer as much as anybody (as a backup to solid deco and gas planning) and I certainly enjoy flying instrument approaches a lot more with a flight director or HSI than with just an artificial horizon or partial panel. But the point is I know how to do it with much less reliance on technology when the technology fails.

You are entirely correct that knowing the tables is not required as long as the diver has a working computer, but at a minimum they need to know what to do when it fails and they need to know enough to be abel to determine when it is feeding them false information and teaching tables is one of the quicker and easier ways to address both.