Inexpensive but not going to get me bent?

[Web Monkey]

DAN minght have stats on who got bent with what kind of computer and/or tables but I've never seen it anywhere.

I wonder if they would part with that info?

Terry

that thousands of divers have used the haldanean computers on many thousands of NDL dives, and I feel pretty certain that if there was some inherent safety issue with the computers on this type of dive, single tank (usually AL80) at recreational depths, someone would have said something about it; there's simply too much liability at stake. The key here is the type of usage; single tank, recreational depth, sensible profiles.

 

[Snowbear]

.... I feel pretty certain that if there was some inherent safety issue with the computers on this type of dive, single tank (usually AL80) at recreational depths, someone would have said something about it; there's simply too much liability at stake....

Some people have said this. No matter how it's presented though, It's pretty much always dismissed as a "closed-minded technophobe rant" with a justification such as the one here tacked on: "...No, I'm *not* looking for a computer to replace my brain, but for backup - I don't intend to turn my brain off entirely, but I would still like a *safe* backup..."

Funny thing is (to me anyhow), once I opened my mind to the possibility that there actually might be a simple way to achieve longer, safer dives without using the computer to tell me how to run it, I actually learned something. Even if I get distracted (no, I'm not even close to perfect and yes I make mistakes.... lots of them :11: ), the inherent conservatism of the system and "shaping the curve" of the dive as you go is so simple once you figure it out that it pretty consistantly gives me longer, safer dives that leave me feeling better at the end of the day than I ever felt when I used my Vyper as most people do, even using it in air mode while diving nitrox.

The best part is, there really isn't much math involved. I'm still not that great at nailing my "everage depth" as Uncle Pug seems able to do within a foot or 2, but that'll come as I keep practicing it

 

[BlueDevil]

The sort of argument that you present is what almost pushed me to get a more conservative computer. The thing that kept me from doing so, though, is the fact that thousands of divers have used the haldanean computers on many thousands of NDL dives, and I feel pretty certain that if there was some inherent safety issue with the computers on this type of dive, single tank (usually AL80) at recreational depths, someone would have said something about it; there's simply too much liability at stake. The key here is the type of usage; single tank, recreational depth, sensible profiles. I would venture a guess, and this is just a guess, that almost all DCS incidents (about 1 in 23,000 according to stats I've read) in this type of diving are due to diver error; most likely dehydration, rapid ascent rate, possibly heavy exertion immediately after diving. This would be the only explanation I could think of that would account for a lack of corrolation between computer algorithm and DCS in recreational diving. With that in mind, I bought the atmos, as I really like the interface, reputation for reliability, and the price was right.

Some more stats for you:

1. DAN America data shows that around 72% of bent divers were using computers

2. DAN America data from 1997 indicates that 93.7% of such cases were diving within the limits of their computer!!

So we can say that the majority of divers that get bent are using computers and that the majority of those are within the limits required by their computer for that dive.

(The fact that most bent divers are using computers shouldn't be any great surprise since the majority of dives are conducted using computers these days.)

To keep things in perspective, of course, the overall incidence of DCS is not that high. Most dives will be completed uneventfully, sometimes even those dives that exceed the limits. However DCS can and does happen, and the results (eg permanent paralysis) can be devastating. With that in mind I think your comments about doing some extra safety stop time and not being in a rush to get out of the water are very wise.

 

[BlueDevil]

DAN minght have stats on who got bent with what kind of computer and/or tables but I've never seen it anywhere.

I wonder if they would part with that info?

Terry

I don't know if they have info on that issue in particular but you can certainly find some interesting stats through the DAN websites. DAN America and DAN Europe sites are definitely worth a look. There is some really good research on the DAN Europe site about the value of deep safety stops in recreational diving, which is well worth being aware of.

This link should give you links to various DAN sites.
https://www.diversalertnetwork.org/contact/international.asp#DAN Southeast Asia-Pacific

 

[asaara]

Do you own a thumb? Thats what its for

The buddy in question would probably normally be wearing a wetsuit, thereby preventing placement of the thumb where it would be most effective, should they not happen to agree with your suggestion. ;-)

Why can't I remember where it was that they were talking about pressure points...?

 

[halocline]

I'm trying to figure out how to quote 2 different posts in the same reply, but it seems to be beyond me, so....

Snowbear said: "Some people have said that" (referring to more people getting DCS with a liberal computer"

Blue Devil said: "DAN statistics show 72% of bent divers were using computers, in 1997 92.5% of those were within the computer limits" (paraphrase)



Okay, but we don't know which computers we're talking about; i.e the DAN stats offer nothing about the relative safety of the algorithms, only that following a computer is no guarantee that you'll avoid DCS. As far as Snowbear's comment, I know you're not presenting what people have said as fact; as far as I know there is simply no reliable information that clearly shows that conservative computers provide more safety against DCS; I agree that intuitively it makes sense that the more conservative a computer is, the less likely it SEEMS that you'd get bent following it's guidelines. But the stats simply don't support that claim, although it's certainly possible that in time, someone will do a study that shows the RGBM and/or Buhlman algorithms are safer for recreational diving than is the haldanean. If that were to happen, there would be alot of used aeris computers, including mine, on ebay!

 

[Snowbear]

Snowbear said: "Some people have said that" (referring to more people getting DCS with a liberal computer"

Not quite..... I was referring to the inherent safety of using a computer vs not.

I neither said nor implied anything about more people getting bent with a "liberal" computer.

 

[asaara]

Some more stats for you:

1. DAN America data shows that around 72% of bent divers were using computers

2. DAN America data from 1997 indicates that 93.7% of such cases were diving within the limits of their computer!!

So we can say that the majority of divers that get bent are using computers and that the majority of those are within the limits required by their computer for that dive.

Ok, that's the kind of data I was looking for, but a bit more recent than 1997, entirely willing to take anecdotal evidence here, say if of that 93.7%, 60% were on one kind, 20% on another, 5% on a third, etc. - who's setting the limits *outside* what will bend a statistically average diver, and how far outside? Was the "within limits" all with the computer functioning normally, or was there machine error that wasn't related to the algorithims going on? A "conservative" computer relative to the rest that still has, say, 40% of all bent divers using it within limits, because it malfunctions a lot, isn't necessarily going to be better than a "liberal" computer that is being used within limits by 10% of all bent divers that very rarely has problems.

...which brings us back around to batteries and parts and such. Anything currently popular but prone to breakage? They've all got user replacable batteries now, no?

And *do* any come with software that'll also work on a Mac?

 

[BlueDevil]

I'm trying to figure out how to quote 2 different posts in the same reply, but it seems to be beyond me, so....

Snowbear said: "Some people have said that" (referring to more people getting DCS with a liberal computer"

Blue Devil said: "DAN statistics show 72% of bent divers were using computers, in 1997 92.5% of those were within the computer limits" (paraphrase)



I agree that intuitively it makes sense that the more conservative a computer is, the less likely it SEEMS that you'd get bent following it's guidelines. But the stats simply don't support that claim

If there are no stats on this issue (at least that we aware of) then it is not possible to state "the stats simply don't support that claim". Non-existent stats can't be used to either support or refute any sort of claim.

The fact that we don't have access to stats that say liberal computers are not as safe as conservative ones cannot lead you to the conclusion that the stats don't support or deny this position. All we can say is that we don't know either way. In the absence of such stats it would not seem to me to be unreasonable or illogical to presume that conservative computers are safer than liberal ones until it can be proven othewise.

 

[BlueDevil]

Ok, that's the kind of data I was looking for, but a bit more recent than 1997, entirely willing to take anecdotal evidence here, say if of that 93.7%, 60% were on one kind, 20% on another, 5% on a third, etc. - who's setting the limits *outside* what will bend a statistically average diver, and how far outside? Was the "within limits" all with the computer functioning normally, or was there machine error that wasn't related to the algorithims going on? A "conservative" computer relative to the rest that still has, say, 40% of all bent divers using it within limits, because it malfunctions a lot, isn't necessarily going to be better than a "liberal" computer that is being used within limits by 10% of all bent divers that very rarely has problems.

I can only quote the figures that i have access to. I would be surprised if the 1997 figure would be substantially different from the current figure - ie I think we could guess that current figures would be somewhere in the same ball park. Even if we supposed the current figure was now say 80% (I just made that figure up for the sake of the argument - I have no reason to believe it would have changed that much) it would still represent a very high rate of bends from dives that computers are saying are quite safe.


Unfortunately the article I saw doesn't comment on what brand of computers were involved.

I can only presume that "within limits" simply means that the diver was either within the NDLs for their profile, or maybe, had completed any decompression requirements specified by that particular computer (in other words they had no outstanding decompression requirement at the time they surfaced). It would also be my guess that if the computer had obviously malfunctioned that they would exclude it from the stats, since you could not claim that the dive was "within limits" if the computer had clearly failed. (However this is my speculation since the article didn't state this explicitly)