dive computers vs dive tables vs WKPP practices

[chrisch]

One technology development that is here today is the "programmable" personal dive computer. The VR3 is such an example that allows new algorithms to be updated to the memory. The website doesn't give too much detail but EPROM is my guess.
Sadly the price makes it too much for my limited budget, but I would like something like this for trimix dives up to about 50m. My buddy is my wife so we need to buy two and that is enough money for a couple of week's diving so I am hoping the price drops...
There are a whole host of views about the VR3 and its competitors and they have been discused on other threads - pls don't repeat here!!

The CONCEPT though is surely a sound one? Allowing for future developments in algoriths, models and the like as well as changing the M-values for the individual diver as s/he ages and goes through the life process and/or loses/gains weight.

My concern would be available memory. I would need to know a lot more before shelling out $1,000 x 2.

Chris

 

[KLD]

A couple of others out there include:

1) -- Suunto VYTEC for rec/light deco air and nitrox
diving;

2) -- HydroSpace EXPLORER for fullup, mixed gas, tech,
deco diving;

plus Mares, Dacor, and Zeagle are updating for next product
offering. Plus Steam Machines for RB diving.

J-factors enter into modified M-value reductions in the
Suunto, Mares, and Dacor meters (dissolved gas), while phase
volume and bubble number reductions enter into the
HydroSpace, Steam Machines, and Zeagle meters
(dual phase). But they have not been completely linked
nor systematized.

BW

One technology development that is here today is the "programmable" personal dive computer. The VR3 is such an example that allows new algorithms to be updated to the memory. The website doesn't give too much detail but EPROM is my guess.
Sadly the price makes it too much for my limited budget, but I would like something like this for trimix dives up to about 50m. My buddy is my wife so we need to buy two and that is enough money for a couple of week's diving so I am hoping the price drops...
There are a whole host of views about the VR3 and its competitors and they have been discused on other threads - pls don't repeat here!!

The CONCEPT though is surely a sound one? Allowing for future developments in algoriths, models and the like as well as changing the M-values for the individual diver as s/he ages and goes through the life process and/or loses/gains weight.

My concern would be available memory. I would need to know a lot more before shelling out $1,000 x 2.

Chris

 

[chrisch]

The Suunto all have extra "conservatism" if you want it. The HS I have not seen - but just downloaded the simulator so I will have a look. Sadly it too is $1200.
Hmmph.
But the point is a good one - I think there are some very good thing to come soon. The more interest there is in "shallow" (<55m) trimix the better...............

Chris

 

[Scuba]

BRW, please help clarify a few points.

RGBM (full up) is rolled over data (RGBM Data Bank) in
maximum likelihood for certain model parameters. We extract
them from profile data. Data is tec, deco, extreme, mixed gas
etc diving. Not recreational diving, which, in all due respect,
tells us virtually NOTHING in model correlations. The rec DCS
incidence rate is in the noise -- like 1/100,000, which is really
statistically insignificant.

Most statistics I've seen show a DCS incidence rate of aproximately 1-5/10,000 for rec. diving. What is the basis for the difference?
I don't recall ever seeing any meaningful statistics for tec diving incidence of DCS. Do you have such data? What is the tec DCS incidence rate?

(we thus wonder about rec DAN
PDE, and their focus on rec computer downloads for their data.
The new generation of RGBM rec computers with deep stops, will
be useful now to them, we believe. WKPP, C & C (us), NAUI Tec
are real weight calibration points over tec diving).

Seems to me usefull data can be obtained from any dive computer, not just the ones with RGBM algorithm.

Are you, or someone else you're aware of, collecting RGBM and other rec dive data from the general diver population which can be used to statistically compare different algorithms? Tec?

 

[Dr Deco]

Hi scuba:

The incidence rate for DCS will depend on the number of “hits” divided by the number of dives. The “hits” can be arrived at by the number of calls to DAN. This, however, does not account for the number of divers with mild joint pain or niggles who do not call. This will also not account for those mild hits that appear and remit within an hour or so and are dismissed as “a sprain” by the diver. The calls to DAN will probably be more heavily weighted toward neurological problems, also.

The denominator is the more difficult part. It is virtually impossible to know the number of divers in the USA during a given week. The number of divers in the whole world is virtually impossible. Thus, people will make an educated guess. The various estimates used will vary the incidence rate.

No matter how you cut it, the incidence of DCS in recreational diving is small. I am not at all familiar with rates for technical divers, as I personally have little interaction with this segment of the diving population.

Dr Deco (on vacation this week).

 

[MikeFerrara]

Hi scuba:

The incidence rate for DCS will depend on the number of “hits” divided by the number of dives. The “hits” can be arrived at by the number of calls to DAN. This, however, does not account for the number of divers with mild joint pain or niggles who do not call. This will also not account for those mild hits that appear and remit within an hour or so and are dismissed as “a sprain” by the diver. The calls to DAN will probably be more heavily weighted toward neurological problems, also.

I think these are important points. In technical diving we p[ay attention to how we feel before and after dives and in relation to how we've felt after other dives. We adjust our approach to decompression accordingly subjective though it may be.

Recent model developers like BRW have I think paid attention to the reports of the guys actually doing the dives. One example of this is the data base on the v-planner site. If I remember right reference to this is also made in "Technical Diving in Depth" by BRW.

DAN seems far more occupied with issues like diving after flying and the results of no stop dives. Admittedly these are of concern to a larger number of divers. As BRW points out the incedents of DCS on shallow short dives doesn't seem to say anything at all about the effectiveness of a model when used on longer and/or deeper dives especially when we throw in multiple gasses and stratagies for their use.

Another area I feel needs lots of attention is the effects of O2. There's a lot there that obviously just isn't understood. We routinly use methods that seem to work but have little science, that I know of, to back it up. It seems to work but we don't know why. Maybe it's just luck but if we wait for science to catch up we won't be able to dive. By the time some one figures out why our O2 exposure management methods work I'm pretty sure that I'll be way to old to care.

 

[BlueDevil]

Firstly I would like to say that this has been one of the best threads I have read on any diving forum. Thanks to those with expertise who given their valuable time to help educate the rest of us.

Hills is the prime example
and mover. I have some personal letters from him that I will
share with this forum that are historical gems.

Dr.BRW, you mentioned earlier about the letters you have from Hills. I would be very interested to see them as I would like to have a better understanding of his role in deep stop theory, and I am sure there would be others who would also be interested. Have they been posted to this forum, or if not could that be done? I am sure some room could be made available somewhere on this site for such "historical gems"!

THANKS, BD

 

[Scuba]

The incidence rate for DCS will depend on the number of “hits” divided by the number of dives. The “hits” can be arrived at by the number of calls to DAN. This, however, does not account for the number of divers with mild joint pain or niggles who do not call. This will also not account for those mild hits that appear and remit within an hour or so and are dismissed as “a sprain” by the diver. The calls to DAN will probably be more heavily weighted toward neurological problems, also.

Which would indicate that if we count unreported, minor and subclinical DCS hits, the incidence rate is probably much higher than the currently assumed rates. Many divers are not concerned or dismiss subclinical DCS. While there may not be any conclusive evidence of long term effects, likewise there is no evidence proving otherwise. I, for one, practice the example given by MikeFerrara, posted below, for my rec. dives.
While it appears that most subclinical DCS hits are temporary injuries from which most divers fully recover. I am concerned about any possible long term effects that may result from repetitive minor injuries.

While tec. divers take on greater risks, I would guess there are many tec. divers who through greater knowledge, prudent planning and execution, surface from a tec. dive with less residual nitrogen than a rec. diver. These same tec. divers may have placed a lesser strain on their body during the dive than many a rec. diver. It is not always the case where the diver with a lesser decompression risk practices safer diving, as you have said many times Dr Deco. This is a very important point all rec divers should be aware of.

I think these are important points. In technical diving we p[ay attention to how we feel before and after dives and in relation to how we've felt after other dives. We adjust our approach to decompression accordingly subjective though it may be.

Does anyone know if the generally seen figures for DCS incorporate what could be charactirized as undeserved hits or are these filtered out when found?

 

[BlueDevil]

Does anyone know if the generally seen figures for DCS incorporate what could be charactirized as undeserved hits or are these filtered out when found?

Undeserved hits are generally defined as those in which the diver was within accepted table/computer limits but still got hit. A very substantial number of bends cases are therefore "undeserved" (can't remember the figures but ? >50%). I figure that if these were filtered out of the stats then the data would be completely invalid.

 

[Scuba]

I made a mistake. I meant to say "deserved". Those in which a diver takes a hit during or after a dive in which he is known to have violated the deco model parameters.