More conservative/"alternative" diving profiles?

[A_Buhlmann]

When I took PADI's OWD course. The instructor told us the basic profile for recreational dives with the safety stop, ascent rate and everything else...

I was reading NOAA's Diving manual, which recommends to do a stop at half the max depth of the dive for 2.5 minutes, plus the safety stop at 15 ft for another 3 minutes.

My question is, does any agency recommend the "halfway stop"? or is this an old procedure?
I think I read about one decompression theory(don't remember which) that talked about this to reduce fatigue. Is there any advantage?
Thanks!

 

[Marie13]

I’d suggest getting a copy of Deco for Divers (make sure it’s the second edition) by Mark Powell if you haven’t read it before.

 

[MaxBottomtime]

Most are no longer using the deep stop theory as it adds to ongassing. The only way to reduce fatigue is to slow your ascent. After a safety stop, take at least another minute or two to ascend from fifteen feet.

 

[EFX]

I can't speak for agencies as a whole but the dive shop who instructed me, PADI and then SSI, taught us dive plans using the PADI and SSI tables, neither of which inserted deep stops. The shop instructed us to follow our dive computers if not using the tables. Some computers will insert a deep stop if necessary. My Mares Puck which runs the RGBM (reduced gradient bubble model) algorithm inserts a deep stop if the NDL went below 5 minutes. The length of the deep stop was user selectable at either 1 or 2 minutes. The NOAA recommendation of 2.5 minutes seems excessive to me. What is the copyright date of the NOAA reference you're citing? Does a more recent version still recommend the same procedure?

 

[Eric Sedletzky]

There is some new science that suggests deep stops can cause more harm than good with continuing gas loading in some tissue compartments while offgassing in others, but the overall effect is more negative than positive.
I guess it depends on the max depth.
A 2.5 minute stop at 70’ from a 140’ dive would seem to me to just be more accrued bottom time, not really any deco benefit. Whereas a 2.5 minute stop at 40’ from an 80’ dive seems ok I guess. It seems like 2.5 minutes is a little excessive. We used to do a series of 1 minute stops starting at 70’ for some deep dives back in the day.
I don’t dive deep anymore and I stay way within my NDL’s so any stop other that 15’ is a little pointless for me.
I’m going to defer to the experts here, I’m sure they will be piling in shortly.

 

[TMHeimer]

I read an article on deep stops a few years ago. It's outdated, but the conclusion was that people disagreed on whether a deep stop is a good idea or not.

 

[formernuke]

I wonder just brainstorming here if the time at depth affects this. AKA a 5 minute dive at 130, deep stop makes no difference or actually does more ongassing compared to 30 minutes at 130 assuming no gas switching ( I know this is not done just a extreme example) where deep stops would off gas because of the higher initial loading.

 

[tursiops]

I was reading NOAA's Diving manual, which recommends to do a stop at half the max depth of the dive for 2.5 minutes, plus the safety stop at 15 ft for another 3 minutes.

Which version of the NOAA Dive Manual, and which section/pages?

 

[sea_ledford]

NAUI still recommends deep stops.

 

[A_Buhlmann]

Wow, thanks for all the responses! I'm referencing NOAA's Diving Manual, 4th edition. Its a bit old, but I can't afford the newer edition right now. I have the "Deco for Divers" book.
I just watched a DAN lecture about the bubble model vs gas loading models( ). He cites my question, but the main focus remains at more deep/tec dives...
I guess the Science is not all sorted out, with various studies giving diverging results.
According to the diffusion model, the "deep stop" will add gas to the tissues( especially slow tissues). So the deep stop would be bad.