differences between algorithms

[halocline]

Dr. Deco;

Forgive me if this question has been asked and answered on this forum. On the computers and analizers forum, there have recently been some threads about "liberal" vs "conservative" computers and their relative safety for recreational diving. After I did a little bit of research (DAN site and here on scubaboard) it appears to me that there has been no study which would provide any evidence that the more conservative computers, like suunto, provide any added margin of safety from DCS, from a statistical perspective. My WAG (you probably know what that stands for) is that in recreational diving scenarios, i.e single tank, depths less than 130ft, the variable causes for incurring a DCS hit, like ascent rate (or gas management problems that result in an unplanned rapid ascent), dehydration, exertion after diving, personal susceptability to DCS, etc... are all much larger contributors to possible DCS cases than are differences between the algorithms, and this would explain the lack of any data that point to an increased occurrance of DCS by users of a particular computer algorithm. Do you have an opinion on this?

Thanks!

 

[cudachaser]

Totally agree...the ascents are critical

 

[Charlie99]

1. DCS is a relatively rare event in recreational diving. That means that overall data is scarce.

2. What counts is your dive profile, not what your computer says. Or to put it another way --- if you aren't exiting the water at the limits of the computer, then what specific algorithm you are using isn't all that relevant.

------------

Statements along the lines of "Diving nitrox on air tables doesn't add any safety" have been made by many. The challenges in proving enhanced safety from nitrox are similar to that of proving enhanced safety from more conservative algorithms.

 

[halocline]

Right, I think we're all in agreement with the idea that control over your profile and good profile planning are important for diving safety. What I'd like to know is, is there any evidence or factual information regarding relative safety of the various algorithms?

 

[Dive-aholic]

There must be otherwise the manufacturers wouldn't use those algorithms for liability reasons. Call the manufacturers. They might be able to help you with what you're looking for.

 

[wedivebc]

There must be otherwise the manufacturers wouldn't use those algorithms for liability reasons. Call the manufacturers. They might be able to help you with what you're looking for.

What is a manufacturer going to tell you? "Our algorithm is the best, all the other will get you bent" is about all that will result in.

 

[Dive-aholic]

What is a manufacturer going to tell you? "Our algorithm is the best, all the other will get you bent" is about all that will result in.

True, but they should also be able to supply the algorithm their program is based on. They may not offer it, but if you push enough, you'll get it. Or just read the manual and see what it's based on. Then do an Internet search.

 

[limeyx]

Totally agree...the ascents are critical

Yup -- definitely got to ascend -- at some point

 

[BigJetDriver]

Folks,

As we know, ALL diving is decompression diving. In diving that is called No Decompression Limit (NDL) diving, the decompression is taken care of by (1) limiting the time, and thereby the dose, of inert gas, and (2) controlling the off-gassing via the ascent rate.

We also know that we cannot reduce the occurrence of Decompression Sickness (DCS) to zero, no matter what we do. We simply try to get it as low as possible. We do, however, have statistical outliers in any grouping, and we call these "unexpected" DCS cases.

All of the commercially available recreational decompression models have, if I am not mistaken, a statistical occurrence rate of DCS around 0.05%. That is extremely low, and the low occurrence overall of actual DCS cases world-wide in any one year, given the amount of diving that goes on, bears that out.

So, in essence, it does not matter if you are using a straight Buhlmann-ian model, or some form of tweak to that, or a dual-phase model, the statistics remain in the same range.

 

[Jamdiver]

Thanks for that BigJetdrive, I had actually been wondering about overall occurence of DCS among divers.