Diving with gradient factors for a new recreational diver

[Capt Jim Wyatt]

I quit making "Deep Stops" over 10 years ago. The only evidence supporting Deep Stops was anecdotal and with the absence of empirical evidence it seemed like voodoo to me.

I dive 50/80 as my GF settings both on OC & CC.

 

[scubadada]

None of the Pelagic Pressure Systems computers, current or discontinued (Aeris, Aqua Lung, Hollis, Oceanic, Sherwood, Tusa), penalize you if you skip the safety stop or the deep stop. However, they will all lock you out in violation gauge mode if you do not satisfy an obligatory decompression stop.

 

[boulderjohn]

DAN Americas does not recommend deep stops for NDL diving.

Deep Stops

Could the implementation of a deep stop stave off decompression sickness. Learn more about the deep stop and DAN experts weigh in.

dan.org

 

[boulderjohn]

Why not? 15m stop for 3 min is "bad idea" when you went to 35m+? Plus I can ignore it, computer won't penalize me if I do...

I did not say it was a bad idea. I said it is not necessarily a good idea.

There is no research indicating that a deep stop provides any value in a NDL dive.

There is research indicating that it is a bad idea on a decompression dive.

 

[lowwall]

DAN Americas does not recommend deep stops for NDL diving.

Deep Stops

Could the implementation of a deep stop stave off decompression sickness. Learn more about the deep stop and DAN experts weigh in.

dan.org

That's not what the article says. They asked 5 experts for their opinion. One believes it is useful, the others say there is insufficient data to make a determination. Two of those add a No to the question. But that is a result of the phrasing of the question. None of them say there is evidence it will lead to negative outcomes.

Here is the relevant section:

"Should recreational divers staying within no-decompression limits be concerned about deep stops?

Mitchell: No. There is insufficient data to justify a deep stop approach in recreational, no-decompression diving. Divers should, however, pay careful attention to ascent rates, and the imposition of shallow safety stops is still considered beneficial.

Southerland: Recreational divers should be aware of the issue. If sufficient evidence becomes available, then a diver might be better off just upgrading the dive computer with a newer algorithm.

Gutvik: No. The recommended safety stop and a controlled, slow ascent rate are adequate for performing safe no-decompression dives. These dives will normally be either too shallow to consider deeper stop depths or too short for the deep stops to have an effect.

Bennett: There is no more reason for concern about deep stops than for the widely accepted shallow safety stop. Both were developed based on the reduction of bubbles in the blood vessels seen in research studies. The research on the deep stop is, in fact, more extensive and is based also on actual recreational dives. The deep stop at half the depth for 2.5 minutes significantly reduces not only bubbles, but also the critical gas supersaturation in the “fast” tissue compartments (like the spinal cord’s 13.5 minutes) without increasing the “slow” compartments usually related to limb pain. More recent research is concerned with the damaging effects of bubbles on the endothelial lining of blood vessels. Reduction of such bubbles will prevent this.

Doolette: Recreational diving within no-decompression limits conducted with a shallow safety stop has a good safety record. There is insufficient evidence to suggest a deep stop offers any advantage."

 

[boulderjohn]

That's not what the article says. They asked 5 experts for their opinion. One believes it is useful, the others say there is insufficient data to make a determination. Two of those add a No to the question. But that is a result of the phrasing of the question. None of them say there is evidence it will lead to negative outcomes.

When did I say they said it would lead to negative outcomes? I said they do not recommend them. Do you see a recommendation in there? I'm having trouble seeing it.

 

[lowwall]

Following up. The paper quoted above is from 2010. I did a quick check if DAN has more recent coverage of this and found from 2018

Deep Stop - Alert Diver Magazine | DAN Europe

I would like to know if deep stops are always recommended for recreational dives, if the depth of the deep stop must be half of...

alertdiver.eu

"The introduction of a deep stop at half of the maximum depth reached during recreational dives during the ascent phase seems to:

– significantly decrease inert gas bubbles detected by a Doppler scan after a dive

– reduce tension of inert gas in ‘fast’ tissues, which is an important fact to correlate with gas exchange happening in the spinal chord.

Authors of scientific publications regarding this topic concluded that a deep stop can decrease the likelihood of suffering from decompression sickness for recreational dives within the depth of 30 meters and without mandatory decompression stops."

 

[lowwall]

When did I say they said it would lead to negative outcomes? I said they do not recommend them. Do you see a recommendation in there? I'm having trouble seeing it.

OK. But that's splitting definitional hairs. "Does not recommend" when discussing a medical issue is understand to mean "that's a really bad idea."

 

[scubadada]

That's not what the article says. They asked 5 experts for their opinion. One believes it is useful, the others say there is insufficient data to make a determination. Two of those add a No to the question. But that is a result of the phrasing of the question. None of them say there is evidence it will lead to negative outcomes.

Here is the relevant section:

"Should recreational divers staying within no-decompression limits be concerned about deep stops?

Mitchell: No. There is insufficient data to justify a deep stop approach in recreational, no-decompression diving. Divers should, however, pay careful attention to ascent rates, and the imposition of shallow safety stops is still considered beneficial.

Southerland: Recreational divers should be aware of the issue. If sufficient evidence becomes available, then a diver might be better off just upgrading the dive computer with a newer algorithm.

Gutvik: No. The recommended safety stop and a controlled, slow ascent rate are adequate for performing safe no-decompression dives. These dives will normally be either too shallow to consider deeper stop depths or too short for the deep stops to have an effect.

Bennett: There is no more reason for concern about deep stops than for the widely accepted shallow safety stop. Both were developed based on the reduction of bubbles in the blood vessels seen in research studies. The research on the deep stop is, in fact, more extensive and is based also on actual recreational dives. The deep stop at half the depth for 2.5 minutes significantly reduces not only bubbles, but also the critical gas supersaturation in the “fast” tissue compartments (like the spinal cord’s 13.5 minutes) without increasing the “slow” compartments usually related to limb pain. More recent research is concerned with the damaging effects of bubbles on the endothelial lining of blood vessels. Reduction of such bubbles will prevent this.

Doolette: Recreational diving within no-decompression limits conducted with a shallow safety stop has a good safety record. There is insufficient evidence to suggest a deep stop offers any advantage."

Bennett was a coauthor of the DAN Europe publication. His comments are overreaching and not corroborated by additional study.

 

[boulderjohn]

Bennett was a coauthor of the DAN Europe publication. His comments are overreaching and not corroborated by additional study.

That's correct. He was also the only one of the experts on the panel to think they were good. That was one of two studies in that era that supported the idea, and neither is highly regarded today, except by DAN Europe.