More conservative/"alternative" diving profiles?

[tursiops]

Amazing how many people spin themselves into a tizzy about whether to stop for a minute deep, and then bolt from their safety stop to the surface in 5-10 seconds.

Fixed that for you.

 

[dmaziuk]

Amazing how many people spin themselves into a tizzy about whether to stop for a minute deep, and then bolt from their safety stop to the surface in 20 seconds.

Just do the "safety" at 5 metres or deeper, it's much easier to take longer than 10 seconds coming up from there. A "deep safety stop": the best of all worlds.

 

[Subcooled]

My question is, does any agency recommend the "halfway stop"? or is this an old procedure?

The truth is always complicated.

Simply put:

To reduce fatigue means to reduce the amount of bubbles in your blood stream (cold is another factor, as is physical activity).

Remember: Diving is like drinking alcohol: you will allways take some damage from bubbles, but only if you take too much, then you cannot recover, and you need a recompression chamber. The bubbles are foreign objects... just like flu viruses. No surprise then that both get you tired. The more the worse.

Where should you stop? For how long? Or should you ascend very slowly without stops? Both strategies exist to give time to the excess nitrogen (or helium if you use that) to get out.

If you are cold and circulation is off (think of toes, fingers) then no off-gassing happens either, and once you get warm and blood starts to flow, you'll get bent... in that hot shower... So... This is complicated.

Whatever you do, try to ascend slowly. And it's not feet per minute but ATA per minute that is relevant. That is why we use as much time from 4 ATA (30m) as we use from 2 ATA (10m)... OK, that was not based on diving tables or deco models, but you get the idea. Meaning the closer to the surface you are the slower you need to ascend.

Also note that the bubbles (=bad) in the blood stream do not gain more gas at a depth of ~6m / 18 feet anymore because of surface tension of the bubbles. This is why people can dwell at 6 or 5 meters indefinitely, offgassing, and that's good for them.

Stopping at depth might or might not be beneficial. Please use the Subsurface app or similar to check your decompression heat map for various surfacing strategies.

Get up to -6m as fast as safely possible and then dwell at 5...6m depth for a long time. Stopping at 3m just means being a little bit more aggressive and getting up to -3m to wait for surfacing...

The so called "deep stops" are a way of controlling your ascent speed. Please note that if you stop at 1/2 depth, 1/4 depth, 1/8 depth... then you ascend the slower the shallower you are... which is the golden rule.

 

[modustollens]

Familiar with this article from DAN?

"How effective are deep stops at preventing DCS, whether called for by a bubble algorithm or when used by divers independent of what their computers suggest? To help shed light on this issue, we asked several experts for their opinions."​

Deep Stops
Alert Diver | Deep Stops

 

[JohnnyC]

The truth of the matter is that for recreational profiles and run times, it's not gonna make much of a difference. Really all you're doing is slowing your ascent. A slow multi-level bimble up to a safety stop depth is essentially doing the same thing. I dislike those settings in computers because they're generally useless, and depending on the computer may have adverse effects on repetitive no-decompression limits.

Staged decompression is a whole different animal. In the recreational context, turn it off and dive intelligently and don't worry about it. It's not gonna make a difference.

 

[NAM001]

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!

I can see pros and cons on this. Research says it is not an advantage to do this. Many recommend a slow steady ascent to prevent further on gassing. cproper ascents require depth control skills beyond what most basic OW grads provides the diver with. The most basic thing amount deco is that the greater teh presure delta the faster teh off gassing. Personally I do not see a harm in doing a deep stop because m ost likely wiht out a line you probably exceeded your ascent rate and that stop will allow you body a minute to catch up prior to further ascent. I always take a minute at 35 to 40. The critical tissues are alreaddy deeper than that any way. Slow tissues will continue to on gass but they are not vital for recreational ascents. The deeper stop allows one to get neutral again before making your way to the 20 ft SS. IMO there is more issues with blowing past a SS than taking a minute or so at a "deep stop" I see one post that mentioned an ascent from 140 and a 70 ft stop would continue ongassing. 140 ft is not a recreational dive so you can ignore that comment. your diving is going to be more about an 80 ft dive adn making a gather yourself stop at say 35 ft to position your self to go to 20 ft and be able to stop at depth when you have no like to ascend on.

Slow ascents increase on gassing time. fast ascents is a propblem in it self. the harm of a fast ascent rate in deeper depths is small compared to is shallow water. the last 20 ft is the zone that will get you ti is quite normal to ascend to 1/2 or 1/3 the depth asn stop. If you are questioning teh rate try to do an ascent from say 80 ft and maintain a 30 ft per minute rate. As a new diver I would guess one could not do it and would ascend much faster than that. If it were not for a ascent alarm most would not know their ascent was in the 60 area as opposed to the 30 max. The ascent rate is a factor that is used to compute NDL if you come up too fast you then had a ndl that was too long for the rate of ascent you did. Lack of good depth control is a great reason not to push your NDL. cutting your time short is a good way to buffer for an unintended too high of ascent rate. The idea of NDL is that NDL says how long you can stay at depth and using a 30 ft per min ascent rate will allow you to go directly to the surface. tghe slower you ascend tehlonger you can stay. the faster you ascend the less you can stay. You computer normally uses a default rate of 30 to calculate with. deviate from that and teh calculated results ar no longer valid. Now one thing in favor of not doing deep stops is that you have a safety stop that also will provide similar relief for a greater than 30 fpm ascent. I seldom see divers do an ascent directly to 20 ft and stop. I see them go directly to say 30 ft and use the next 10 ft to stablize themsaelves for the SS. that 30 ft stop serves the same function. In the days when ascent rates were 60 fpm the dep stop seems to be a much more valid thing to do. My opinion is that they are not necessary oif you have ascent rate control in your favor. If not then I would stop a bit short of SS depth get neutral and then proceed to 20 ft to insure not being to light and popping to the surface. There are rules for safety stops that are also geared for assumed 30 fom ascent rates. If you slowed to say 20 then there is a chance that a SS would never be needed. the price for that is in your air supply. For a new diver My recommendation is that if you do a dive to 100 ft and you ave a NDL of say 20 use no more than 15 of it and head up. those 5 minutes not used should be a good buffer to insure that even with a little of over ascent rate it can be handled at the safety stop with out concern of DCS problems on the surface.

 

[NAM001]

NAUI still recommends deep stops.

doesnt nauii have longer NDL's on their tables??? if I temember nauii is 22 min at 100 ft where many other tables allow 20. The deep stop would maybe be prudent with that extra exposure and preticularly on repeditive dives I an guessing.

 

[NAM001]

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.

I think it is too dive dependant to make it a rule of thumb.

 

[Eyegore]

Recent advice given to me by an instructor is to stop for one minute at half the depth of a dive, ascend another ten feet and stop again for one minute, go up another ten feet and stop for another minute, rinse and repeat to a 20' three minute stop. The example provided/discussed was for a no-deco dive to 100' and for we who are no longer spring chickens.