Deep Stops Recreational Divers

[CandiveOz]

But as nice as it sounded, it just doesn't work in practice, does it? In fact, it's actually harmful.

Well that's the million dollar question really. The minimal research done on deeper stops at recreational levels is still in question. I've been trying to source all the studies myself and posted a question here.Deep stops for recreational diving

The original post was created by @scubadada back in 2010 and there is still nothing definitive since. Is it harmful on recreational NDL dives? Well, I have a dive profile to 30 metres that just hits the NDL limit at 15 minutes on the Galileo Sol. The PDIS recommendation was 12 metres for 2 minutes. Once the PDIS was completed, the computer reported an NDL of 88 minutes. This increased to 118 min at 10 metres and further increased the shallower the depth. Multilevel dives are common in Rec diving and divers don't see these as dangerous so I fail to see the difference. If I get time, I'll post the dive profile graph. A picture is worth a thousand words.

 

[rsingler]

Harmful as in if I hang out for two minutes on my ascent like my PDIS recommends, even though I'm far from a NDL, that I could get symptoms of DCS? Is there evidence this has happened?

Very much doubt it. It was Communism that I believe has been shown to be harmful, not deep stops, yet. Poor attempt at humor.
And you're absolutely right, I've never seen "evidence."

But here's the thing. I'm old, and with lots of scar tissue from one thing or another, and who knows what sort of hidden arteriosclerosis in my tissues. Poorly perfused tissues begin to approximate a "slow compartment", in some senses. So I've decided for me (since the science is still pending), that some of those "undeserved" DCS hits out there might have been due to offgassing limitations from compartments like my hypothetical scar tissue. So if I can decrease slow tissue loading by not lingering at depth unless I want to (as opposed to an artificially imposed profile dependent stop), then I think I'm better off.

I can't prove it, but it makes physiologic sense to me, since shifting the integral of supersaturation away from faster compartments has been shown to not help.

But dive and let dive, ya know?

 

[Gareth J]

But here's the thing. I'm old, and with lots of scar tissue from one thing or another, and who knows what sort of hidden arteriosclerosis in my tissues. Poorly perfused tissues begin to approximate a "slow compartment", in some senses. So I've decided for me (since the science is still pending), that some of those "undeserved" DCS hits out there might have been due to offgassing limitations from compartments like my hypothetical scar tissue. So if I can decrease slow tissue loading by not lingering at depth unless I want to (as opposed to an artificially imposed profile dependent stop), then I think I'm better off.

I can't prove it, but it makes physiologic sense to me, since shifting the integral of supersaturation away from faster compartments has been shown to not help.

But dive and let dive, ya know?

Thats almost a circular argument. If your breathing efficiency is low, then potentially the extra stops will allow your 'system' to catchup and clear any required 'off gasing'.

I do remember being told if you cough during the ascent, stop ascending, get your breathing normalised before continuing the ascent.

 

[KenGordon]

Why wouldn't you, since they chose to use the name in their advertising? The problem is that no one really knows what it is, or how it varies across their product line.

By reading the description they provide, by diving the thing. And the are extremely careful not always call it Suunto RGBM and not ‘full RGBM’, as are all the manufacturers (except Atomic, or whoever Ron works for).

 

[CandiveOz]

So I've decided for me (since the science is still pending), that some of those "undeserved" DCS hits out there might have been due to offgassing limitations from compartments like my hypothetical scar tissue. So if I can decrease slow tissue loading by not lingering at depth unless I want to (as opposed to an artificially imposed profile dependent stop), then I think I'm better off.

I respect your decision.

 

[Gareth J]

By reading the description they provide, by diving the thing. And the are extremely careful not always call it Suunto RGBM and not ‘full RGBM’, as are all the manufacturers (except Atomic, or whoever Ron works for).

I would say that with regard to recreational dive computers, none of them run 'vanilla' algorithms, all have some extra padding/compensation features. So, as a user you have it is very difficult to know what is 'under the hood'. This can easily be demonstrated by the variability of 'No Stop Times', between the different computers, between manufacturers and even different models from a given manufacturer. These 'adjustments' have been to make them safer, basically more conservative. Compare the NS stops from the computers of the 80's (monitorII) to those on the market now.

The technical dive computers are generally much more transparent, e.g. running known algorithms. E.g 'Buhlmann', which the user then modifies with GF.
This has always been the great strength and weakness of technical diving computers. In an educated users hands an excellent tool, in an uneducated diver, potentially an issue (GF set to 100/100!).

 

[taimen]

By reading the description they provide, by diving the thing. And the are extremely careful not always call it Suunto RGBM and not ‘full RGBM’, as are all the manufacturers (except Atomic, or whoever Ron works for).

This is interesting and I have actually noticed the same.
With their latest "Suunto Fused RGBM" Suunto has actually started talking about "Wienke's Full RGBM" which is used when diving below 45 meters with trimix.
Thus they are now blending something with "full RGBM"

Page 12
http://ns.suunto.com/pdf/Suunto_Div...4375.32847960.1556699908-924026121.1551874233

This isn't really a no-stop recreational profile. But anyway it looks like Suunto is still advocating something which looks like a deep stop model.

 

[taimen]

I find it interesting that Suunto now offers 4 different versions of the RGBM algorithm. The Fused and Fused 2 generate quite different deco profiles past 33 metres compared to Tech and the Standard RGBM. The "deep stops" tend to drop off using Fused according to my initial testing done in DM5.

That is probably due to "full RGBM" stepping in according to the brochure.
This profile which takes you out of water before GFhigh 100 and has deeper stops than 20/80 looks quite aggressive. I would love to see some data, but unfortunately Suunto has decided to release only sales material.

 

[rongoodman]

or whoever Ron works for).

What??

It sounds like you think Suunto should be able to have their cake and eat it too, so to speak. They were presenting their computers as running "RGBM" years ago, when it was clear that no available dive computer had the computational power to actually run the model. Now that the bubble models are going out of style, you're falling back to "they never said they were running RGBM, they said Suunto RGBM." Except now it turns out that they do claim to run actual RGBM, at least sometimes.

 

[CandiveOz]

Here is the PDIS dive profile I mentioned in post #101