DCI in Thailand

[MoonWrasse]

Here's the Suunto Stinger manual:
http://media-server.amazon.com/exec...E1hbnVhbA==&file=TUFOVUFMMDAwMDI3NzM5LnBkZg==

And the Cobra manual:
http://www.suunto.com/media/suunto/manuals/en_US/cobra_manual_en_11855.pdf#search='suunto%20cobra%20manual'

Both are almost or are identical in setting personal adjustment.

What I'd take from this thread is to watch the dehydration, which is not always so apparent in the tropics, and adjust to P1 if I had diarrhea or was taking something like Pepto Bismo/Imodium. That's specific to my own experience, as I dive in the same local under similar conditions as the OP.

BTW I didn't find any mention of age as a factor in the manuals

 

[John C. Ratliff]

Here's the Suunto Stinger manual:
http://media-server.amazon.com/exec...E1hbnVhbA==&file=TUFOVUFMMDAwMDI3NzM5LnBkZg==

And the Cobra manual:
http://www.suunto.com/media/suunto/manuals/en_US/cobra_manual_en_11855.pdf#search='suunto%20cobra%20manual'

Both are almost or are identical in setting personal adjustment.

What I'd take from this thread is to watch the dehydration, which is not always so apparent in the tropics, and adjust to P1 if I had diarrhea or was taking something like Pepto Bismo/Imodium. That's specific to my own experience, as I dive in the same local under similar conditions as the OP.

BTW I didn't find any mention of age as a factor in the manuals

It wasn't in the manual, it was in their publication Suunto Reduced Gradient Bubble Model, which comes with their Diving Product Catalogue. This is an eight page handout that covers the RGBM, with the subtitle "SUUNTO'S PERSONAL ADJUSTMENT PROVIDES GREATER ACCURACY." In it, this is stated:

Just as it is possible to reduce the effect of the Suunto RGBM model it is similarly possibel to choose gradually more conservative parameters for decompression calculations, when adverse personal conditions exist. The principal personal factors that show a correlation with DCI suseptibility include: physical and dive itness; age, particularly fr divers over the age of 50; fatigue; cold water eposure, which can cause the bloood vessels at the body's extremities to close down and maintain the body's core temperature; pre-dive exercisee, which can create new gas nuclei; exercise during the dive with blood bringing additional nitrogen to muscle tissues; post dive exercise which can cause supersaturatedblood to course thorough the blood vessels; tight fitting equipment, which can cause DCI pain around a joint where the limb is pinched by the suit; hot showers or baths and sunbaking can all raise the skin temperature and reduce the capacity of the skin to hold nitrogen in solution; and dehydration, which effects the micro circulaton andtherefore the out-gassing of nitrogen after diving.

SeaRat

 

[MoonWrasse]

It wasn't in the manual, it was in their publication Suunto Reduced Gradient Bubble Model, which comes with their Diving Product Catalogue. This is an eight page handout that covers the RGBM, with the subtitle "SUUNTO'S PERSONAL ADJUSTMENT PROVIDES GREATER ACCURACY." In it, this is stated:


SeaRat

You'd have to predict your post dive activities in order to factor in some of those risks (post dive exercise, hot showers, sunbathing). The tropics expose northerners who are not used to the strong sun to increased risks of sunburn, divers or not.

Also I notice the lack of alcohol consumption as being listed a factor - I recall that post dive alcohol consumption can increase micro bubble creation. Every boat I recall being on has made available beer or stronger after one's last dive of the day.

 

[String]

It wasn't in the manual, it was in their publication Suunto Reduced Gradient Bubble Model, which comes with their Diving Product Catalogue.

Which can be found here:

http://www.dive-tech.co.uk/resources/suunto-rgbm.pdf

 

[String]

String, that's not quite the same, but I'll grant you that the two types of profiles are different.

They arent even similar - they're totally different dives with just about no commonality.

We are into the computer age, but the computers are based upon some of the same theories as the tables were based upon. There are some differences, however. Here's a few:

Actually the computers are based on the same algorithms in many cases. And all the tables are newer than the ones you

--In the old days, we taught "plan your dive, and dive your plan." Therefore, for the first dive to 28m, I would have stopped the dive at 20 minutes (one away from the "knife edge" of the no-decompression limits), and headed up.

It isnt a computer vs tables things. This is purely the limitation in the tables you have. Multilevel diving is possible to plot on tables or computers - computers just apply the same algorithm more accurately as they know the exact profile at all times.

--after the first dive to 28m for 20 minutes, if I had been planning it according to my 1990 NAUI Dive Tables, and I knew that I wanted to dive to about 27m the next dive, I would know that my RNT was 16 minutes, and I had 9 minutes of no-decompression limit bottom time at that depth. My plan would be for a bottom time 9 minutes would be in order.

All very well but that totally ignores the multi level factor of the dive. Youve just planned a totally different dive than the one that took place so its not a fair comparison.

Now we have the computers, but they are still only instruments. They can handle the multi-level dives like you mentioned, but they still have limitations.

Indeed but this isnt a computer vs tables problem. The padi wheel for example is a tables method of multi level dive planning.

My Suunto Cobra uses the Suunto Reduced Gradient Bubble Model, and it is pretty conservative. It also has "personal adjustments," and when I look at them, I see that I immediately fall inot one personal factor that shows an incleased DCI suseptibility: I am 60 years old.

Computers have "fudge factors" like that as do tables. Again this isnt a thing only computers have. Even tables state that other risk factors should be considered and added to suit the individual. The older the tables the more of an issue these were as the older ones tended not to be based on real theory and the individual samples used were young fit healthy individuals (certainly not your average diver)

"...age, particularly for divers over the age of 50" is listed as a factor. Suunto's handout shows on page 3 the depth in metres, along with the personal modes and the no-decompression limits that the RGBM model uses. For 28 meters (30 meters on their table in the handout), that limit is 18 minutes in PO mode, 14 minutes in P1 mode, and 12 minutes in P2 mode. I will probably set mine at least to P1 mode, unless I am tired, getting really cold, etc., in which case it will go into P2 mode.

These fudge factors arent really based on science (just as they werent on the tables), they simply add xx% time to stops or reduce NDL by xx%.

It uses the same algorithm my computer uses. The only thing i dont like about it for recreational use is the lack of deep stops so i pad all deep no-stop and all my planned decompression dives with deep stops otherwise just like the tables you use its a "bend then mend" strategy as opposed to gradual decompression. Thats for a different forum though.

From what I'm seeing here, this backup simply is not happening.

I cant see anything in his post to say he didnt have a planned backup on a slate,wheel or whatever so not sure where you got that from.

Concerning your analogy of the cow and the auto for the Dive Tables verses the Dive Computer, I think it a more like a car and an SUV with 4-wheel drive capability. The SUV can go off-road, just as a diver with a DC can do much of what he wants, and still figure his decompression. The car has to stick to roads, which is more like what diving the tables is like--you have to stick to the tables if you want to know your decompression limits.

Again the analogy i used is correct. Your method is comparing 2 totally different dives, Complaining a journey to a destination 200 miles east took longer than a journey to a different place 100 miles west etc. Computers have planning modes which allow EXACTLY the same level of dive planning as tables offered. In addition to this most divers i know (including myself) carry a slate of tables, backup timer and depth gauge to use in case the computer dies in the water. Just because he didnt stick to your (dated) tables doesnt mean he didnt stick to the proper decompression algorithm.

 

[John C. Ratliff]

It is interesting, my tables are out-dated, I'm not doing the calculations correctly for multi-level diving, but my methodology is far more conservative than these dives were. What is that saying about today's diving?

SeaRat

 

[String]

Its saying simply thing things move on, times change, techniques and theories improve rendering older ones obsolete.

In the same way the car replaced the horse and cart and electric light bulb replaced the candle.

 

[John C. Ratliff]

Its saying simply thing things move on, times change, techniques and theories improve rendering older ones obsolete.

In the same way the car replaced the horse and cart and electric light bulb replaced the candle.

It is true that diving techniques change over time, but it is not always for the best. The techniques and theeories have changed, but my impression is that this has led to an increase of decompression-related accidents such as the one documented in this thread. I did a seach on PubMed, and have at least one study that supports this contention:

http://www.ncbi.nlm.nih.gov/entrez/..._uids=14974786&query_hl=1&itool=pubmed_DocSum

The fact is that without dive computers, some of the dive profiles (including the one in this thread) would not be possible. This study states:

Change of occurance of type 1 and type 2 decompression sickness of divers treated at the Croatian Naval Medical Institute in the period from 1967 to 2000.

Andric D, Petri NM, Stipancevic H, Petri LV, Kovacevic H.

The Naval Medical Institute, Department of Undersea and Hyperbaric Medicine, Split, Croatia.

A significant change of occurrence (p=0.0343) of type 1 and type 2 decompression sickness (DCS) of divers in Croatia was observed in the period from 1991 to 2002 (type 1: n=26, 37.68% and type 2: n=43, 62.32%) compared with the period from 1967 to 1990 (type 1: n=93, 52.84% and type 2: n=83, 47.16%). The change was attributed to the extensive usage of diving computers and artificial gas mixtures which enable extended bottom times and deeper dives, thus putting divers at an increased decompression risk. The importance of the results of this report is in the fact that permanent neurological deficit occurs only after type 2 DCS. Injured divers with permanent loss after type 2 DCS are not fit for diving and require a long term medical care, thus becoming a significant public health problem.

There is a whole industry that has grown up which is geared toward this technical diving, and has a vested interest in maintaining that the newer techniques are an "improvement." This may not necessarily be true, and to dive safely with dive computers means that there needs to be a very intense knowledge of decompression theory, so that divers know when they need to modify the computers. The reason is that while the computers won't vary in their analysis of a given dive profile (unless changed by the diver), the diver's own physiology will vary, and suseptabilities wall also vary. The dive computer puts the diver much closer to the "knife edge" of decompression sickness than the use of Tables in the older way I was taught years ago. Divers need to be aware of this, and treat the dives and their computers in a very respectful way in order not to have an unscheduled trip to the recompression chamber.

SeaRat

 

[pt40fathoms]

Just a few observations and points I would like to make.

1) SUUNTO are know for being more conservative than most dive computers. The Stinger is one I would recommend to a parent who is looking for a dive computer that will help keep their young one from pushing the limits. When the Stinger tells you you have only 1 min of NDL remaining, many other brands would still allow you several additional minutes of bottom time.

2) Your profile's although not perfect, do not constitute a reverse profile. Your later dives were within 6 meters in depth, and is within the margin that defines a reverse profile.

3) Your surface intervals although over one hour, should have been 3 hours to account for your depth reaching that magic 30m mark combined your times being within 5 minutes or closer of the NDL. This, in conjuntion with the possibility of mild dehydration as you stated may been your case, is interesting to note.

Chances are that most of us on this board have done exactly what you have done without incident. However, it was close to the line and this time you got nipped in the butt. If you were on EAN32, you would have reduced your chances greatly, which is why when doing multiple dives over multiple days, Nitrox is the only logical choice. It's nice to see so many dive operations recognizing that fact and offering it.

Glad you recovered so well, and thanks for sharing your experience with us. It is appreciated and usefull to us all.

 

[Scuba]

Multi day repetitive dives has been shown to increase the risk of DCI. (Don't have the reference handy and I don't know if there is newer research in this topic)

The greater the number of dives, multi day/repetitive, the less tested and reliable the deco models become. From a safety point you can't go wrong being more conservative.

On this day all dives were basically treated the same, from first to last, by the rec book diving. In addition to some of the other suggestions, consider making subsequent dives more conservative. Decrease max. depth, time, increase length of safety stop, slow your ascent rate even more and use more stops in the shallows, spend a larger portion of the dive shallow, increase time between dives, reduce the number of dives per day, reduce the number of consecutive dive days.

There is something to be said for starting very conservative and then slowly expanding one's personal limits, as opposed to applying to oneself generalized limits statistically formulated for the most part using questionable data and analysis, and then finding they don't apply

You now have a limit and incidence of DCI reference point. However accurate or inacurate it may be, it's a personal guidepost that most divers don't have. Some divers gradually increase their limits while being very sensitive to what their body and mind is saying, in effect using a less precise and benign guidepost. If you would have sat out dive four because after three you were tired, you may not have gotten bent, or most likely it would have been less severe. This way you will miss more dives and may miss some dives requiring certain profiles significantly beyond those known to be safe. It's probably wise to increase the conservative factor in your diving, at least for awhile. Listen to your mind and body more closely, and when it asks for a brake, let it have it. This will increase the chance of having another dive another day.

I don't look back and regret the dives I have missed, because it was the right thing to do at the time. I'm comfortable doing this in order to decrease the chance of one day looking back and regretting doing a dive I shouldn't have done.