Deep stops for recreational diving

[scubadada]

http://www.scubaboard.com/forums/technical-diving-specialties/472412-deep-stops-really-worth.html

I have been skeptical of the value of deep stops for recreational diving. This has been a controversial topic on SB with opinions polarized to one opinon or the other. Though the NEDU study is far from the usual recreational dive, I believe the principles apply.

 

[MB]

Wha??? Huh??? Controversial? Can somebody articulate the down side?

 

[DevonDiver]

Can somebody articulate the down side?

Deep stops are concerned with ascent, not descent.

 

[TSandM]

I'm not entirely sure the NEDU study applies to the typical recreational dive. As Doolette interprets the study, the problem with the deep stops profile is the increased supersaturation in the longer half-time compartments when you get shallower. Loading in those compartments on the typical NDL dive is going to be pretty minimal. Notice that the deco time on the deep stop profile the NEDU study used, when added to the 30 minutes of bottom time, almost would run you out of no-deco time just at the deco stop depths!

In addition, technical divers in general are counted upon to control ascent rates. Recreational divers often have problems with this, and the short NAUI "deep stop" at half maximal depth is probably a nice way to do some offgassing prior to the all too frequent lack of ascent rate control in the very shallow water. How many people do their careful 3 minute safety stop, and then take ten seconds to get from there to the surface?

 

[tomfcrist]

Funny enough, I was talking with A certain Noaa guy, and deep stops are not substantiated scientifically in no deco dives....however he also stated that the research for shallow stops (safety stops) suggested the best margins for safety lies somewhere between 5-7 minutes. He is baffled as to why every agency insists on saying 3 minutes or 3-5

 

[supergaijin]

Decompression Sickness

I believe it is a compromise between doing no stops and doing loooooong stops. My normal profiles include a type of deep stop, but this is more of a multi-level dive as opposed to 'stopping' during an ascent.

There are very few instances where a 'U' shaped profile is required in my neck of the woods.

 

[DevonDiver]

Funny enough, I was talking with A certain Noaa guy, .... He is baffled as to why every agency insists on saying 3 minutes or 3-5

Just a small point, but every agency doesn't...

Personally, I think that deep stops are pretty irrelevant for recreational, no-stop, diving. I also think we're unlikely to ever find a definitive answer, because the scale of potential benefits for no-stop divers is too small to justify specific study. Translating findings from studies conducted for technical diving is likely to be flawed; because factors effecting technical dives aren't present when significant on-gassing, at greater depth for longer duration, hasn't occurred.

The only real benefit to recreational deep stops is that it might provoke more recreational divers to view the overall issue of ascent from no-stop dives in a more considered and deliberate manner.

 

[PfcAJ]

I think a lot of folks do their 'deep stops' too deep and too long.

A 100' dive is probably not an average of 100'. Its probably more like 80-90, in my experience. Yet so many people will stop at 50', then they'll sit there for 2 mins (or longer). I think if you do that, its neutral-to-worse for you.

Now, a short pause at more like 40ft, and a 30fpm ascent past that makes a lot more sense in my mind.

 

[scubadada]

Deep stops were developed for technical diving, and, for the conditions employed in the high quality NEDU study, the deep stop strategy led to a statistically higher rate of DCS than the shallow stop strategy. The specific conditions of the study were carefully chosen for many reasons, including an expected rate of DCS that was high enough to possibly detect a difference, and that proved to be the case.

As mentioned in my opening post, the dives in the NEDU study look nothing like recreational dives. Deep stops were generalized to recreational diving with little to no data to support that decision. We're still without the evidence to judge the value of deep stops in recreational diving. A study similar to the one done by NEDU is simply not practical for recreational diving as the expected event rate is so low.

Personally, I'm very appreciative of the effort made by NEDU to shed light on this interesting topic. I will continue to do careful, controlled ascents and a safety stop from my recreational dives. The decision to add deep stops to recreational dives remains a personal one.

Good diving, Craig

 

[drbill]

I've done deep stops for decades... largely a result of the fact Catalina's submarine topography drops off quickly and as I ascend I always find something to film at different depths. So far in 51 years on SCUBA I have yet to get bent... so far, so good.