Do Dive computer get you bent more than tables?

[tombiowami]

Lost Yooper- and yet a piece of the pie must fall on the divers getting bent, IMO.

From my reading with the DAN info, I think all but the tiniest sliver of pie would go to the diver. Everyone is taught the basics, but then choose to ignore or push the limit. On reading the stories of what happened it is pretty rare that the "undeserved hit" comes about.

Of course I am one of those personal responsibility types...

A lot of them were combinations of events, any one of them not too bad, but all put together, spell disaster. I always think of the Rouses, and how they violated rule after rule after rule.


Tommy

 

[The Chairman]

missing were ascent speeds. Dan even re-iterated that we should be doing 30ft/min (9 meters/min), but how many divers really do that. I always hear my alarm going off at least once a dive so I am constantly adjusting to slower. So many of us were taught that 60 ft/min (18 meters/min) was A-O-K, that I do not think the lessons have come home. Stone, you are too right! We are our own worst enemy!

 

[blacknet]

Hello,

Even when I was taught the 60f/m rule I was using something around 15.

Ed

 

[Lost Yooper]

Tommy,

I'm a big personnal responsibility guy too. I have to be considering the type of diving I do. If you don't follow established rules, procedures, and standards , then you should be responsible. Unfortunately, it's some of those rules, procedures, and theories that are taught or ignored that is the problem. PADI still says it recommends a 30FPM ascent rate with 60FPM being the max. This is partly what I mean, 30FPM should be stress as the max, not 60FPM.

If the majority of those getting hurt and killed are new divers, what does that say about their readiness out of OW? Where's the standards and screenings that should be going on? This is why I place a lot of blame on the agencies and industry as a whole. It has become an accepted practice throughout this industry to certify students with bare minimum standards. The students don't know the difference, so how can they be blamed?They think they're ready since that's what their instructor/agency said, but most are not, IMO. Sure, most live through it, but...

Many things are simply not stressed enough such as predive and post dive activities (hydration, exercise, etc), buoyancy control, and buddy skills. Students with obvious preconditions, such as obesity, are being passed through OW and being told they will be safe. Couple all this with a computer with a less-than-optimal deco program which divers trust whole heartedly, and I think you've come up with a pretty good recipe for an increased risk of DCS.

Students/divers are placing 100% trust in an industry who's primary ambition is to make a lot of money. There's enough blame to go around, but I place a good deal of blame on those who are supposed to be trusted -- the industry as a whole -- who are breeding divers who, all to often, have a false sense of security in their training, equipment, and diving practices.

Mike

 

[Piscean]

So I have been reading this and the BSAC (British Sub-Aqua Club) Incident report and would like to say that that suggests that there is no clear correlation between level of training and incidents. Infact if you read the reports it seems that the incidents are mostly due to people exceeding their limits (i.e. their training level, fitness, etc.) rather than being inherently under trained. I was recently on a trip for example where a Divemaster got bent (badly bent - neurologically bent) and there were lots of open water/ advanced open water divers on that trip who didn't get bent. Only one data point of course, so utterly useless statistically speaking.

I agree though, the physical activity thing seems to be totally understressed in dive classes.

Now, as far as tables and computers are concerned, it seems to me that it depends a lot on how you dive with them. For example, do a 100 ft dive for 20 mins. That is the limit of the PADI RDP. Then ascend at 30FPM or less and do a 3 min stop at 15 ft and surface at less than 30FPM. Should be OK according to the table. However, my Suunto Cobra will not let me dive that long, it only lets me go to 100 ft for 17 mins so if I follow that to the limit then ascend in the same way, I must be safer than with the tables, no matter what the other factors.

If I dive to 100 ft for 10 mins, then ascend to 50 ft for 10 more minutes and surface as before, I have followed the tables (because max depth counts) but will be safer than in the previous example. If I use my computer in this case though I can stay much longer at 50 ft before I get to the limit. In which case it seems to me that I will probably be more likely to get DCI by using my computer.

These are only two examples, I have ignored the wheel for simplicity, but I hope that it is obvious that there are an almost infinite number of dives, some of which are safer with a computer, some are safer with the tables and some are dangerous with either.

In conclusion, choose a conservative computer, don't push its limits, ascend slowly, spend a few extra minutes at your safety stop and relax while you are there. Finally it is better to pee in your suit than to be dehydrated.

Piscean.

P.S. Check out my friend's website: www.coltonscuba.com

 

[The Chairman]

Piscean...

Tables are a predicated on a "square" dive profile. Something that few divers do. The tables start timing the dive ON DESCENT, not when you get there as a computer does. Some tables (like NAUI) are still timing you UNTIL you get to your safety stop. So IF you add at least three minutes of "travel time" (hopefully it is FAR more) your computer jives with your tables. HOWEVER, I did a dive to 98 ft recently on EANx34... where I m-i-g-h-t have spent 5 or ten minutes at that depth. The rest of the time I was less than 80 ft. My computer compensated for this and I was down for 45 minutes (not the 22 min dictated by my NAUI table), and STILL had time till I hit my NDL. So prima fascea, the computer may seem more conservative than a table; it is surely NOT. It is just a more accurate and dynamic way to predict your nitrogen loading and off-gassing.

To err is human... to really fowl things requires the use of a computer.

 

[Lost Yooper]

Piscean,

I saw a study that showed 60% of fatalities in scuba occured with divers having less than 20 dives or something. It also showed a similar statistic for DCS incidents. This same study was also quoted in the DIRF book by GUE, but I saw the study a fews years ago. I don't have the specific info in front of me right now.

Assuming the study is a good average (which I would guess has gone up), then it would seem as though computers are not really to blame for the majority DCS incidents. It would seem to me that what is to blame is agency standards, diver ignorance, or diver neglect. I place more weight on the first two.

Mike

 

[bgonderi]

While computers are useful to allow you to extend your bottom time, as others have pointed out, this also places you closer to "the edge," and therefore increases your risk of injury somewhat.

I also think that new divers may become totally dependant on their computers without really understanding what the computer is doing. Case in point, in my basic OW class there was a couple that was having a lot of trouble with the tables. While working through their problems with the instructor, the husband mentioned "Well, this table stuff really doesn't matter since we'll be diving with computers."

Obviously, if his computer malfunctions and tells him he has 5 hours of bottom time left at 90fsw, he would probably happily cruise around until he ran out of air.

Kinda like the use of calculators in math classes in schools. The kids may be able to work complex math problems with them, but then they're unable to make change at the local fast-food establishment when the cash register goes down.

To quote Dirty Harry, "A man's gotta know his limitations."

 

[devjr]

I'm surprised at the attention that this statistic has received. I saw the DAN statement and paid it no attention at all because it means nothing standing on it's face.

DAN called me twice last year to follow up on my recovery from partial paralysis. However, there was no discussion in detail about the accident itself. Where are they getting the data? The computer I used was the old fashioned mechanical type which follows the US Navy tables. Unfortunately, I neglected to refer to it during ascent. I just looked at the time and pressure and came up, and certainly not at 30 feet/min, try a bit faster. Mea Culpa. I had used the DCP for hundreds of hours and finally had a bad hair day. The gauge's dial was slightly in the red.

In spite of my(ahem)advanced age and in spite of the minor violation, there is no doubt in my mind that I would not have been bent if I had stopped at shallow depth for a few minutes. Moreover, I would have gotten away clean if I had drank some water before diving. Also, the same if I had not spent the previous four hours freediving to 50' depths.

Thereafter, I bought a new Genesis Resource, and promptly put it in the pressure tank. I found that this computer only allows about 3/4 of the bottom time on a simulation which approximates the problem dive. I also confirmed this by running the new and old meters side by side. There is no way I would have been bent if I had followed the Resource. My understanding is that most of these electronic D meters are just as conservative as is the Resource.

If that be, then there is no way that accidents skewed toward computer users is the fault of the units themselves, that is as long as they are working as expected.

 

[Aquamore]

......... I think it's safe to say that it's unsafe diving practices that get divers bent
NOT tables and
Not Computers

Aquamore
(The thinking man's diver)