Deep Stops Increases DCS

[tomfcrist]

What part of the fact that this study was not scientifically controlled don't you get?

 

[PfcAJ]

However I can assume you can do basic division...hell I bet there is a calculator laying around you can use.

Take 10 random dive buddys, and find out how many times they have been bent collectively. Divide that by their collective dive count(just deco).....I'll bet it's less than 3.4%...

you have zero clue about experimental design and research statistics.

 

[LiteHedded]

as I dont think you've waded through the other big thread (where he answers questions like yours) and i'm fairly confident he's not stopping by here to answer all the same questions for internet laypersons again, here is a link to his description of the study:

Rebreather World - View Single Post - Deep stops debate (split from ascent rate thread)

what variable wasn't controlled to your satisfaction?

 

[tomfcrist]

Really?

The example I just posted is just as scientific as arbitrarily adding stop time to a deco dive...which is what this study did.


Is hydration critical to deco?

How did they asses the hydration levels of these divers? Self reporting? Real scientific.

 

[LiteHedded]

Really?

The example I just posted is just as scientific as arbitrarily adding stop time to a deco dive...which is what this study did.


Is hydration critical to deco?

How did they asses the hydration levels of these divers? Self reporting? Real scientific.

have you read his post? it wasn't arbitrary. it was done using BVM(3) to match the shallow stop schedule (VVal-18 Thalmann Algorithm)

 

[tomfcrist]

Right. They decided on a shallow stop schedule and kept fudging numbers on the deep schedule until all stops added up to 174. They knew by doing this that the incidence of DCS should be higher on the deep stops model due to the ridiculous amount of time that created at the deeper stops. If they didn't know that, they had tunnel vision.

The problem with adding time to these two models and focusing on the overall deco time is that when you add time in the shallow schedule, the majority of it is distributed in the top 30ft.

When you do the same thing to the deep schedule, you add so much time to the deeper stops that you cannot recover from the additional gassing of the slow tissues by the time you should be able to surface.

If you cannot see the difference between a 70' stop for 2 minutes and one for 17 minutes...I guess we have nothing left to talk about here.

 

[PfcAJ]

Do you have any data to support your statements?

 

[LiteHedded]

again, because you haven't read it i guess....

I want to talk about the schedules we tested in some detail, because these have been the source of a lot of confusion and misdirection in various forums. Clearly they do not look like technical diving schedules - they are not, they are deep air decompression schedules. In selecting the test pair of schedules, there were two principal criteria. First, they had to result in some DCS so there was something to compare. Second, they had to be long, so that they could have substantially different stop depth distribution, i.e. the deep stops schedule should require a substantial amount of time at deep stops, so any deep stops effect (good or bad) can manifest. There is no point in testing, for instance, two 90-minute decompression schedules where one has five or ten minutes of time spent at deeper stops – I would happily move five or ten minutes around in a 90-minute schedule and not expect it to make a any detectable change in my risk of DCS. Remember that the purpose of a decompression stop (deep or shallow): we stop to limit gas supersaturation and thereby limit bubble growth, and we stay to washout inert prior to moving to the next stop. The staying is important, the amount of gas washout that occurs in the course of one, two, or five minutes is relatively inconsequential.

The final test pair of schedules was the result of hundreds of hours of analysis and even a workshop attended by many people working in the field of decompression (acknowledged in NEDU TR 11-06).

people smarter than you (and me. no offense intended) looked at these schedules before the study. calling it arbitrary is nonsensical

 

[tomfcrist]

Lite headed.....your first quote does nothing but support what I have been saying this entire time...this study has no meaning whatsoever for 99.9% of the tech diving community. The benefits of deep stops are manifested during short durations, while the disadvantages are manifested on long stays.

He even says that these are not tech diving schedules...no kidding.

 

[PfcAJ]

The outcome of the study is simple. For a given ascent time, distributing the stops deep produces an increased incidence of DCS relative to the control (shallow stops schedule).