Adding to a safety stop

[Rooster59]

Thanks for all the replies.

I looked at some of the deep stop lit (Pyle, etc.) and I saw both pro and con. I choose not to do a deep stop as there's not a lot of agreement with that.

The dive profile I am talking about is my typical boat dive, coming up from 60-80 feet and getting back on the boat. I've noticed lately that some of the divers come up pretty fast, and I'm not sure they take the full safety stop if the conditions are rough. Some divers ascend pretty fast from the stop depth to the surface.

My computer (Nitek Trio) starts a safety stop when you get shallower than 20', but starts over again if you drop below 20. I go to 16 feet and hold that for 3min until the stop clears. I can hang there without going below 20ft if the conditions are rough. I'm going to keep doing the 10ft for 2min after the SS if I have the gas. From 30ft and shallower I may start going with a 20fpm or 5ft/15sec ascent rate. I'm thinking that being more careful with ascent rates and adding the additional stop at 10ft may someday keep me out of trouble.

But then again spreading grape jelly on your mirror keeps elephants out of your bedroom.

 

[diver 85]

Enjoy the beautiful sights(assuming you're @ a beautiful-----sight)for as long as you can........

 

[tbone1004]

also keep in mind sometimes a 10ft stop isn't "safe" depending on the surface conditions, unfortunate the trio resets if you drop below 20ft, but hanging out at 10ft after 3-5mins at 15ft isn't going to do a whole lot for you, an extra few mins at 15 will net similar results if there isn't anything pretty to look at at 10ft and you have the potential of getting a bit motion sick from surge due to surface conditions.

 

[igor p]

There is recent research reported by DAN to support this. In a nutshell... for "recreational" no-deco dives, deep stops may cause more harm than good. A preferred method is, as Kharon suggests, a nice slow and steady ascent rate. For deco dives, it's another story and deep stops might well be desirable.

Since the OP was asking about safety stops and no-deco dives, then deep stops probably are NOT the way to go... especially since the dive itself isn't all that deep presumably.

Could yoy please direct me to that study. .

Igor P

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[Lorenzoid]

Could yoy please direct me to that study. .

Igor P

There was a recent SB thread discussing this topic: http://www.scubaboard.com/forums/technical-diving-specialties/497187-deep-stops-increases-dcs.html

The first post in the thread has a link to a study conducted by the Navy Experimental Diving Unit. This is not DAN, so it may not be the same research that Stoo mentioned.

 

[Duke Dive Medicine]

There was a UHMS abstract done by Richard Walker and colleagues that said there was no difference in probability of DCS between last O2 deco stops at 10 vs 20 feet. It's linked below.

[abstract] THE EFFECT OF FINAL OXYGEN DECOMPRESSION STOP DEPTH ON DCS RISK: 20 FSW VS. 10 FSW.

I know this doesn't translate directly to safety stops, but I doubt there would be much difference between safety stops at 16 fsw and 10 fsw. You would likely get the same effect by simply extending your safety stop at 20 fsw.

Best regards,
DDM

 

[igor p]

Exactely correct. It is not. NEDU is one thing and DAN another. DAN study supports deep stops.

Name of study:
A deep stop during decompression from 82 fsw (25m) significantly reduces bubbles and fast tissue gas tensions.


Here is some other toughts showing how very different scientists think.

https://www.diversalertnetwork.org/default.aspx?a=news&id=514

And finaly in mentioned thread in the last post you can see corelation paper of different decompression algorithms to databank with known exit.

Best

Igor P

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[Duke Dive Medicine]

The DAN study supports deep stops for the particular dive profile that was used in the study, but you can't generalize the results to all dive profiles. As DoctorMike has already pointed out, a diver can still be on-gassing at a point halfway between the bottom and the surface depending on the depth and bottom time of the dive.

Best regards,
DDM

 

[igor p]

The DAN study supports deep stops for the particular dive profile that was used in the study, but you can't generalize the results to all dive profiles. As DoctorMike has already pointed out, a diver can still be on-gassing at that point depending on the depth and bottom time of the dive.

Best regards,
DDM

Yes sure, you are correct.
This is why the deep stop needs to be inserted carefuly, just long enough to relax the fast tissue and not more. Something like described in the study. I would say minute or two should be enought for dives in NDL.
If folowing dive computer, you will notice it (d computer) takes in account the added time at the deep stop in calculation and if neaded adds some minutes to shallow stops if yow fall in deco regime otherways normal safety stop will be requested.

Best,

Igor P

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[Duke Dive Medicine]

Yes sure, you are correct.
This is why the deep stop needs to be inserted carefuly, just long enough to relax the fast tissue and not more. Something like described in the study. I would say minute or two should be enought for dives in NDL.
If folowing dive computer, you will notice it (d computer) takes in account the added time at the deep stop in calculation and if neaded adds some minutes to shallow stops if yow fall in deco regime otherways normal safety stop will be requested.

Best,

Igor P

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igor,

I think we might be misunderstanding one another. If you perform a deep stop and the computer adds decompression on the shallow end, it's telling you that you have taken on inert gas at your deep stop, which is defeating the purpose. Am I reading your post correctly?

Best regards,
DDM