Deep stops, Pyle stops, Gradient Factor

[MechDiver]

Correct me if I'm wrong here but I was under the impression that deep stops are for decompression diving where you actually have a "soft ceiling". I realize that every dive is technically a "deco" dive because as soon as we begin our ascent we are decompressing.
At the OW level all dives are taught as "non stop" or "no decompression" dives arn't they? This means that you could theoretically ascend directly to the surface at any point in the dive providing you have a nice slow ascent rate ???
Although the idea of deep stops has been around for ages, the term kind of implies that you are diving deep...45fsw is not really considered deep, or is it ???. I would think that this concept would be more apropriate to teach at the advanced level where you would be diving to depths below 80 and above 100.
On a multilevel dive profile I have always divided my max depth in half and used that depth as the second level for the dive, so I guess you could consider that a "deep stop" but there would be a point where my fast tissue compartments would begin to ongass again if I stayed at that depth for too long thus making the "deep stop" usless right ?
Please feel free to enlighten me if I'm missing something...

As you said, the word "deep" is relative. I consider anything past 150' deep, YMMV.
The purpose of the extra stop is safety, nothing more, nothing less, the same as the 15' stop. Some feel stopping for one minute at the 50% mark will help offgassing more so than the standard 3 minutes at 15'. True deep stops have their place, and are pretty much a necessary event when using trimix. In recreational diving, the stop promotes a slow ascent, buoyancy control, and thinking about your dive and your dive plan. All of which are beneficial.
And, as with the 3 minute stop, it is not mandatory. You can still ascend directly to the surface.

MD

 

[Tao of the Dive]

I think you are giving the students too much of a quandry to ponder in the quarry (Sorry, couldn't resist). Anyhow, it's my personal beleif is that you live/fight/dive the way you train. Consistency is the key, if you do something the same way every time, it not only becomes habit, but it becomes muscle memory, and it becomes reflex. The point, dive the same way, every time, and don't tell yourself, "well, it's just a 45ft quarry."

When we con ourselves into skipping things "just because it's..." we begin to take thing for granted.

 

[DepartureDiver]

Correct me if I'm wrong here but I was under the impression that deep stops are for decompression diving where you actually have a "soft ceiling". I realize that every dive is technically a "deco" dive because as soon as we begin our ascent we are decompressing.
At the OW level all dives are taught as "non stop" or "no decompression" dives arn't they? This means that you could theoretically ascend directly to the surface at any point in the dive providing you have a nice slow ascent rate ???
Although the idea of deep stops has been around for ages, the term kind of implies that you are diving deep...

No, deep stops refer to doing any stop deeper ... even a safety stop. While it may not be necessary after a 40' dive, the students are going to immediately go deeper on there own. I believe a dive to 60' for 40 minutes warrants the first stop being at 20'. This is close to 30' for simplicity calculations. Safety stops have been too shallow (especially for the deeper recreational dives). Plus novice divers need to start proper procedures early to avoid getting into bad habits and thinking stops are not necessary within recreational limits.

 

[diverbrian]

No, deep stops refer to doing any stop deeper ... even a safety stop. While it may not be necessary after a 40' dive, the students are going to immediately go deeper on there own. I believe a dive to 60' for 40 minutes warrants the first stop being at 20'. This is close to 30' for simplicity calculations. Safety stops have been too shallow (especially for the deeper recreational dives). Plus novice divers need to start proper procedures early to avoid getting into bad habits and thinking stops are not necessary within recreational limits.

You have mentioned the reason that my safety stops are normally at the 20 ft. end of the 10-20 ft. band that my Dive Computers use.

Actually, I think that the only U.S. Based recreational agency teaching this is NAUI. I heard that PADI was working on it. I work with SSI and the IC that runs the shop hasn't directed that this be taught (and I guarantee that he would if SSI changed their policy on this). But, then again, he teaches painfully slow descents/ascents .

 

[DepartureDiver]

and a dive to 100' should start a safety stop at 40' ... again close to the 1/2 depth of 50'

 

[diverbrian]

and a dive to 100' should start a safety stop at 40' ... again close to the 1/2 depth of 50'

Caribbean is great for this part as I might spend a couple of minutes at 100-120 to get a photo and spend the next twenty minutes or longer at 40 ft. taking photos of the reef.

 

[MHK]

I'm of the thought that deep stops are a good idea, but the current standards for them are a little screwy. I for one feel that a better guideline would be for dives over 60ft. in depth rather than 40ft.

Curious as to your thoughts on this issue. Any of you Instructors or AIs feel this way too?

Deep stops are an awesome tool, but often misunderstood, which is why at this point they aren't more widely recomended. The industry for the longest time promoted the use of 3 minutes at 15' and in this industry once something works it's way into the lexicon of diving it's nearly impossible to change.

That being said, for decades and decades the industry has relied primarily on the Buhlman model, which is essentially a nitrogen loading model. In very brief terms the Buhlman model subscribes to the theory that you want to get the diver to the shallow stop [ie; 15'] as quickly as you can [ ie; 60' fpm]
and then "treat" the diver there. You may often times hear people referring to Buhlman as a "bend and treat" model, and that is why.

Recently, ie; in the last 5 years or so, some very bright decompression modeler's like Weinke, Baker, Meiken et. al. have been developing a dual-phase model. Essentially what a dual-phase model means is that whereas Buhlman relies almost exclusively on tracking M-values by the amount of nitrogen a given tissue group can saturate a dual-phase model like RGBM or VPM tracks two things, hence the "dual"-phase. It tracks both bubble size and formation as well as tracking nitrogen tissue loading. The underlying theory behind the Bubble mechanics models is that it's best to control the growth or formation of the bubble and the way that is "treated" is by managing the shape of the ascent profile, and thus by extension reduce the bubble growth or the bubble accumulation. This is accomplished by slowing down your rate of ascent to 30' fpm and incorporating deep stops into your ascent rate strategy.

That brief overview is essentially why you see many of us incorporating "Deep Stops" into our profiles. The one problem that I've noticed as we've gone around the country teaching these principles is that all too many divers think that decompression theory is an exact science so they loose sight of the bigger picture. It's called "theory" for a reason. Whether you start your deep stops at 80% of your ATA's or 1/2 of your deepest part of your dive, or virtually any other ad hoc theory that I've seen advanced is nearly irrelevant. What is important is the shape of your ascent curve, but the industry often times fixates on reducing theoretical concepts to cute nuemonics, or easy to remember phrases like 3 minutes at 15'. I'd prefer to see instructors spending just a little bit more time teaching students about this. But I guess I'm in the minority ;-)


Hope that helps.

Regards,

Michael Kane

 

[pipedope]

If you make an extra stop it does a few good things.

It slows your overall ascent rate.
It gives you extra practice at bouyancy control and at being able to stop at a desired depth.

 

[DepartureDiver]

Deep stops are an awesome idea, but often misunderstood, which is why at this point thay aren't more widely recomended. . . . I'd prefer to see instructors spending just a little bit more time teaching students about this. But I guess I'm in the minority ;-)


Hope that helps.

Regards,

Michael Kane

Agreed ... thanks for digging yourself out of work for a little while to chime in.

 

[neophytediver]

MHK that helps a lot. Even more for me to consider. Like I said, I like the "idea" of deep stops, but feel that the way they're being executed is odd. I've always felt that ascent rate was just as important as making a safety stop, but it's something that isn't stressed as much. These are all things I will have to consider once my ITC starts and after I've taken my first students. Thanks!