Deep Stops Increases DCS

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Wow, RBW all over again...

Ok, I pulled up the paper, which is one that I've read in the past, and which comports with what I've already stated.

Quoted from Andrew's paper in 2007, "While there is some theoretical reasoning behind the adoption of deep decompression stops and some empirical and historical evidence that they may be of value, the available studies do not support their introduction.", emphasis added.

and..."It would seem that, from the available evidence, decompression profiles where more time is spent deep do not always reduce decompression stress as might be expected. This may be especially true of dives involving mixed gases and inert-gas switching. While accepting that stops deeper than those prescribed by the Buhlmann model may be optimal for safe decompression from significant depth, several workers in the field are now questioning the validity of deep stops as generated by ‘bubble’ models.", emphasis added.

The studies Andrew cites to substantiate his conclusion are:

36 Gerth WA, Gault KA, Doolette DJ. Empirical evaluation of the efficacy of deep stops in air decompression dives. Undersea Hyperb Med. 2007; 34 (suppl): 231-2....this is the NEDU study,which apparently some think is irrelevant because they don't understand how science works...

37 Gutvik CR, Mollerlokken A, Brubakk AO. Difference in bubble formation using deep stops is dependent on length of bottom time; experimental findings and theoretical support. Undersea Hyperb Med. 2007; 34 (suppl): 230-1.

38 Brubakk AO, Gutvik C. Optimal decompression from 90 msw. In: Lang MA, Smith EB, editors. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24. Washington DC: Smithsonian Institution; 2006. p. 39-46.

39 Imbert JC. Commercial diving: 90 msw operational aspects. In: Lang MA, Smith NE, editors. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24. Washington DC: Smithsonian Institution; 2006. p. 103-18.

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I think he makes a sound argument. And let's not forget, anything less than a GF Lo of 100 is a "deep" stop when considering Bhulmann.
 
Wow, RBW all over again...

Yes, I guess so. I laughed. A lot.

Michael, the summary at the end of the Fock paper has also been "celebrated" because it highlights his strong opinions about ... well, he says it better.

[blah blah blah] explosion of technical diving over the last 10 years. It is now common for recreational divers to conduct dives to over 50 msw, and dives to in excess of 100 msw [blah blah]. Many of the divers conducting these dives have little formal training or education in decompression theory beyond the basics taught in their technical diving courses and yet may be extremely opinionated and vocal in internet forums on the subject, based solely on their diving experience. It is rather alarming to see the almost zealous way in which deep stops have been incorporated into the recreational market given the paucity of good evidence as to either the benefit of such stops or a validated method of incorporating them into diving practice.
 
I switch off 18/45 and 15/55 to 50% nitrox all the time.

Why are you using so much nitrogen in these mixes? Why are you using trimix at all above 430'? Is it just to save money?
 
This again?

keeping the END below 100' is pretty darn safe.
 
If you are ok with "pretty darn safe" that is your choice. How much money are you saving by using trimix instead of heliox?
 
If you are ok with "pretty darn safe" that is your choice. How much money are you saving by using trimix instead of heliox?

Thermal conductivity is also a consideration with HeO2. It’s not like these guys are in hot water suits like sat divers. Trimix has always been primarily a cost savings tactic, even with the Hannes Keller 1000' bounce dive in 1962. We commercial guys do get spoiled when the client pays the gas bill and hot water is pumped down the umbilical.
 
If you are ok with "pretty darn safe" that is your choice. How much money are you saving by using trimix instead of heliox?

Depends on the dive. For 300 gas were using 10/85. Not much nitrogen in that mix.

What gas do you use for a 200ft OC dive?
 
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