Spiegel Incident

[iztok]

True science is defined as being able to consistently produce the same results from an experiment. That will never apply to DCS, yet so many will firmly grip their own algorithms or believe that because the computer says I am ok, that I am not really in this wheelchair of chamber. Amazing.

IVS, you forget one "little" thing that you have to have the same conditions in order to produce the same result. Two different persons, two different dive profile, two different times etc.. do not make same conditions.

However statistically we can do something about it.

 

[Blue Sparkle]

Also, Andrew took longer to ascend. Their recollection is "about one minute" longer, but we don't have any way to know for sure (because, given what happened, it's easy - in my experience - to recollect times like that inaccurately). So let's say it was two minutes later. Would that partially explain Andrew's more minor DCS hit?

I know neither of their ascents were ideal, but was Andrew's "better" enough to account for some of the difference?

I guess the other question I have here is, was this level of DCS unusual given Matthew's dive profile and quick ascent? I understand that no two people are the same, but wouldn't anyone making the same exact dive be "expected" to take a hit? I don't ask this rhetorically; I really don't know and would like to.

B.

 

[sydney-diver]

True science is defined as being able to consistently produce the same results from an experiment. That will never apply to DCS, yet so many will firmly grip their own algorithms or believe that because the computer says I am ok, that I am not really in this wheelchair of chamber. Amazing.

That's not the case at all, there's plenty of branches of science and engineering which deal with uncertain parameters. That hardly makes it not "true science".

Also what do you suggest we follow if we don't trust our algorithms? I don't see any alternative - they've been rigourously tested and tuned over the years to prevent DCS at a very high confidence level (i.e. say 99%, I don't know the actual number and it probably varies from algo to algo).

 

[TSandM]

I'm not sure you have to implicate a PFO. If, as has been described, the ascent got out of control, it wouldn't have taken much breath-holding to create an arterial gas embolism situation (see the "Five things I learned about DCS" thread).

But speculating and arguing about the final mechanism of injury here is spending our time on precisely the wrong thing. The place for scrutiny is at the beginning of the cascade, the place where the accident could have been avoided. I know I'm harping on this, but this happened either because there was an inadequate or erroneous dive plan to begin with (or no plan), or because an adequate and safe plan was disregarded in the water. There was no equipment malfunction or unexpected environmental condition that played any significant role here. For novice divers reading this thread, the lesson is to create a plan that includes consideration of gas supply and decompression issues, and then dive it.

 

[boulderjohn]

. I know I'm harping on this, but this happened either because there was an inadequate or erroneous dive plan to begin with (or no plan), or because an adequate and safe plan was disregarded in the water. There was no equipment malfunction or unexpected environmental condition that played any significant role here.

I fully agree, and there have been several posts that have tried to get at this.

If our very helpful friend (skdevlieger) can find out what the plan was, it would be extraordinarily helpful. How did the divers know how much time to spend at what depths for their decompression? Or were they diving at the maximum depth until hey ran low on air and then ascending according to...well, what theory?

 

[scubafanatic]

...I'm still trying to get over NO COMPUTERS !!! ??? ...personally I won't get into the water without at least TWO computers......I'll never understand that omission.....

 

[iztok]

...I'm still trying to get over NO COMPUTERS !!! ??? ...personally I won't get into the water without at least TWO computers......I'll never understand that omission.....

While a lot of us who do rec dives use computers a lot of advanced/tech divers dive without one (depth gages, bottom timers and tables).

You can plan and execute dives w/o computer just fine.

 

[DandyDon]

This has become entirely too much to read. Is there going to be a Cliffs Notes version available once it's all said and done?

It's a discussion thread; that's what we do on the SB forums. The incident will probably be included in the annual DAN Accident report that comes out in a couple of years. I think all of the mistakes would be covered in any OW course plus a Boat Diving course tho.

...I'm still trying to get over NO COMPUTERS !!! ??? ...personally I won't get into the water without at least TWO computers......I'll never understand that omission.....

Many divers do not use computers; to dive safely without one, the diver should plan the dive well, then follow the plan, tracking NDL times manually on the fly, perhaps with the waterproof card issued in OW class. It's done. I wouldn't do it, but some do; I wear two too, but it can be done without. It'd become increasingly difficult to do so safely while following a camera like I do, or a spear gun.

My general impression may be inaccurate here, but I get the idea that the family, owning water front property and boats at home and in Florida, got certified years ago, did not see a need for continuing education or DAN magazine and accident coverage for their family diving & hunting, got into habits that they'd gotten away with for years - which included leaving an untended boat while all aboard went in together, but managed to get away with their family approach until the boys got new air tanks that increased their back gas from 78 cf to 119, with a 7# increase in weighting need.

It kind of sounds like their general dive plan was to surface before they ran out of air? Anyway, with 53% more back gas, the boys could stay down longer than they ever had - and they used almost all of their back gas to do so, perhaps unknowingly crossing NDLs. Whether weighting was the cause or not, there was a buoyancy problem with uncontrolled ascent. Down too long, up too fast.

 

[iztok]

Wow, I just used my Suunto dive planner using HP119 as a template and 0.8 SAC rate (high). If I try to simulate depth of 130ft and profile where one starts getting up at slightly under 500psi it gets about 27 minutes of bottom time.

Which puts one in quite big deco obligation (according to Suunto algorithm).

According to it one would have to have about 66min total time before surfacing (obviously one would run out of air before that).

If I change SAC to .7 I get 31 min bottom time and almost 80min total dive time. (And running out of air before hitting 10ft deco ceiling.)

Scary.

 

[japan-diver]

Its a common misconception but activity levels or breathing rates do not affect nitrogen absorption. Only thing that matters is pressure (depth) and time.

This statement is just wrong!! Gas absorption is affected by more things than pressure and time- (if these were the only two variables DCS would be much more predictable). Nitrogen saturation is effected by perfusion of the tissues (perfusion will be effected by workload- blood pressure,body composition, etc...), temperature (Henry's Law), time at depth, partial pressure, breathing rate and activity will effect CO2 levels which also have effects on absorption and elimination of nitrogen.

N2 tissue saturation is not a simple pressure and time curve