Two safety stops?

[boulderjohn]

When I did my first deep ocean dives, I was taught that there is little benefit to a very slow ascent during the deepest portion of the ascent from a deep dive. This allowed for higher ascent rates (up to 60'/min below 60' depth). Then to make a 2 min stop at 60' followed by a slower (max 30'/min) ascent to a 15 ft safety stop.

Could some of you more experience divers comment on what I was taught and still practice?

In addition to Lynne's very informative post, I will add that I read several years ago that deep divers have an unfortunate tendency to begin their ascent much too slowly. Having that thought in mind, I have noticed that in my experience it is definitely true. For some reason, I notice that divers starting their ascent from depth seem to want to go up at a snail's pace, well below 30 FPM. This is not intentional--they mean to go faster. In one case in which we analyzed the profile of the ascent of two divers who got bent, one of the things we noticed is that it took them almost 5 minutes to get ascend the first 50 feet prior to their first stop.

I have often felt like pulling my buddies upward during that point in my dive.

 

[danvolker]

Back in the early 90's when we were still doing air to 290 feet, we would ascend using Blow and go.... after 25 minutes on a wreck, we would collect, do buddy check, then everyone would fully inflate their BC at the same moment, and go from 290 to 100 in about 30 seconds or less. The thinking was that the biggest problem was incurring more deco obligation, and that the actual pressure change between 290 and 100 was not all that fast, even at blow and go speed.
You would sit at 100 for about 3 minutes, then do a 30 foor per minute ascent to 50 feet, stay there 10 minutes, then go to 40, etc....at the 20 foot stop we would often do pure O2, and then surface. Hundreds of these dives and non DCS.

This could not be done with Trimix, due to the helium bubbling much easier than air in your blood.

 

[DevonDiver]

Take a look at the ANDI ascent and descent procedures, particularly the Level 2 (rec): ANDI Ascent and Descent Procedures | Diving Techniques

 

[scubadada]

Interesting thread, not the 1st time this has been discussed on SB. The 2008 Decompression and the Deep Stop Workshop (UHMS, US Navy, DAN, NAUI, PADI) did not endorse deep stops for recreational diving. Deep stops may increase nitrogen exposure and accumulation. Multiple anidotes do not equal scientific data. The surrogate endpoint of "bubbling" correlates poorly with the development of DCS. Sounds a lot like the unproven benefits of nitrox. To each their own, I will remain a skeptical scientist though I could be convinced. An intriguing, modern decompression model argues against deep stops and in favor of the routine safety stop for recreation diving Modern Decompression

Remain critical, Craig

 

[Rhone Man]

I am personally not a big fan of deep stops - I prefer to take that proposed 2-3 minutes and spin out my ascent time to the primary safety stop / deco ceiling as the case may be. I certainly have no scientific basis for that, but it is just consistent with my own experiences.

But like all things related to deco theory, there is unfortunately so much we don't really know.

 

[The Chairman]

I do deep stops. 2 minutes at half of my max depth. I also do full five minute safety stops. If you read the first post again, he's talking about neural fluids. These have approximately the same half time as blood. While it's rare for a recreational diver to experience the bends, when they do it's a 95% chance that it will be Type II or a neural hit. So, in my personal risk assessment, I will dive in such a way that reduces that risk even further. Modifying my behavior to reduce Type I DCS is not logical. In fact, it would appear that we have those bases covered quite well. Ergo, I am going to modify my diving to reduce my risk of incurring Type II DCS which means allowing more time for the quick tissues to "catch up".

Remember, it only takes 5 half times to effectively saturate a tissue. Blood and neural tissues have a 3-5 minute half time, or so I have been told. So with a 25 minute dive, I have essentially saturated my blood and neural tissues. It only makes sense to adjust my diving to adequately off gas these tissues since they are the ones most likely to give me problems. Will the slower tissues be on-gassing during my deep stop? Sure. Who cares? I am not likely to get DCS and even more unlikely to get Type I DCS as a recreational diver diving within my NDL. If I am going to pad my buffer, I'm going to pad it with regards to Type II DCS. After all, have you ever heard someone complain about an "undeserved" hit that wasn't a Type II?

 

[Lorenzoid]

Is current thinking still that a deep stop can have the benefit of reducing fatigue believed to be caused by those sub-clinical bubbles? I would think that the possibility of simply reducing fatigue would be a major motivator for doing deep stops. (I admit I haven't read through the various links posted above, though I did see the spear gun post and Lynne's post.)

 

[The Chairman]

Is current thinking still that a deep stop can have the benefit of reducing fatigue believed to be caused by those sub-clinical bubbles? I would think that the possibility of simply reducing fatigue would be a major motivator for doing deep stops. (I admit I haven't read through the various links posted above, though I did see the spear gun post and Lynne's post.)

That's why I do them. I feel tons better after a dive with deep stops than I do without them.

 

[danvolker]

If I did 60 for 60 on air, I would feel better after diving if I had added a 5 to 8 minute stop at 10 feet. If I do that on a morning dive, I feel good enough to ride my bike for a couple hours in the afternoon at a zone 2 to 4 level. However, if I did this with no stop, when I got to the afternoon, I would sometimes feel low energy and more like watching TV.
So, I do the stop But NEVER a deep (30 foot) stop.

Same would be true for a maxed 100 foot dive. Just a 5 to 8 minute 10 foot stop.
If I actually wanted to PLAN a bike ride 4 hours later, I would bring a 20 cu foot bottle of pure O2 and do 8 minutes at 20 feet after each dive....then 4 hours later on the bike ride, my body would not even know that I had been diving earlier...for all practical purposes. The point being....if anyone here REALLY IS CONCERNED about micro hits or DCS issues on recreational profiles, then the option I recommend is gettin the training to be able to use an O2 pony(clipped stage stlye) --this is really incredibly easy....Anyone that I know that is a good enough recreational diver to have me happy about them diving with me...and smart enough to fit this criteria, should be able to follow the SIMPLE rule that you ONLY breath this at 20 feet deep, no deeper...and for 8 to 12 minutes. If a recreational diver can't hold a stop to a few feet plus or minus, they wont be in the gene pool I would consider diving with. If they can't remember and follow the simple directive that they can only breathe this at 20 feet, then they are the same people that would probably freak and hold their breath in an emergency ascent, and again, this is a gene pool I am not talking to in this thread What I am saying is that the training needed should be one day, maybe an hour long( in this day and age)...In the early days of tech, the training would be me telling you only breath this at 20 feet or shallower, and that is what you would do....it was so easy back then

---------- Post added March 26th, 2013 at 10:41 AM ----------

Come to think of it, one of the spearfisherman I used to dive with in the 80's and early 90's, Pat Frain ( maker of Ultimate Spearguns) used to have an O2 bottle on the boat, and would often suck O2 on the boat for 10 minutes after a dive.....prophylactically. He was a smoker, had no cardio fitness, and was older. This was his way of avoiding issues of micro hits or worse...and it worked for him.

 

[BDSC]

If I am worried about being fatigued after diving, I just get a good nights sleep before I go. Seems to work for me without any deep stops.