Safety stop

[Dr Deco]

Dear Murdock:

This is not question with an answer agreed upon by everyone. I can tell you my viewpoint. In the Haldane model, unless a given degree of supersaturation is exceeded, DCS will not occur. This model is known to not be correct since “silent bubbles” are present even in the absence of frank, clinical DCS.

Thus, there must be some degree of DCS with every decompression. We have “silent bubbles” causing “silent DCS.” The fact is that not all depressurizations produce large numbers of bubbles and these often last for but a few seconds.

Divers probably have a certain distribution of micronuclei in their bodies. In many cases, there simply are not enough nuclei for gas phase formation and DCS to occur under most conditions. Some divers are at the other end of the spectrum and possibly are near the “problem range” on some of their dives. These might be the ones who get “undeserved DCS” at one time.

Most times, bubble formation is a rarity and the effects of its presence are so small that one would not say that DCS occurred - - even in a subclinical way.

Dr Deco :doctor:

 

[chazpraz]

In a similar fashion, safety stops allow dissolved gas to move into the capillary system rather than being caught in growing tissue microbubbles. Since everything done by a diver on the way to the surface is decompression, a safety stop is just another form of it.

This is rather straightforward, but it is not necessarily simple to envision. :mean:

Dr Deco.

Thanks for your explanation of the benefits of the safety stop.

I have been "bothered" by the addition of safety stops since returning to sport diving after a fifteen year hiatus. Not because I think they are annoying but because I thought they were a voodoo solution to shortened surface intervals because of the increased number of divers at resorts such as cozumel. We used to spend a couple of hours on the beach before taking our second dive and now are lucky to get 45 minutes between dives. I have also noticed that depths have increased (100+ are fairly common now where they were restricted to one or two per visit in the past)

CP

 

[HammerNoMore]

First off, the reason we REALLY need safety stops is that we are too impatient. Our ascents are way, way too quick for our bodies. SOOOOO, to effectively slow you down (especially just before you make that last ascent) they stop you at 15 ft. Say you were at 66 ft and you came up at 30/min... it would take you only TWO minutes to get to 15 ft. THATS QUICK... now factor in that 3-5 minute safety stop, and your looking at an average of around 11 ft/min or less. Hmnnn... you could even ELIMINATE them thar safety stops IF you could ascend that slowly. Don't bet on it... do your safety stop and then take another two minutes... (5 minutes total). Your head and body will be glad you did!!!

The Deep Stops article in this months Alert Diver goes into great detail on this subject. The interesting part is that it start out by disussing the fact that over the last 20 years dive tables have been modified to give reduced times at depth but the DCI incidence rate has changed very little. The reason they give is that, while the tables have become more and more conservative, the ascent rate has changed very little.

Personally, if the conditions allow, I prefer a stepped approach. Dividing the depth in half or thirds for multiple stops.

 

[Snowbear]

The Deep Stops article in this months Alert Diver goes into great detail on this subject.

Amazing how stuff changes. It will be interesting to see what other procedural changes will be presented in the next 2 years

 

[ArcticDiver]

Amazing how stuff changes. It will be interesting to see what other procedural changes will be presented in the next 2 years

Why "2 years"? You got a whiff of something coming? If so what?

 

[HammerNoMore]

Why "2 years"? You got a whiff of something coming? If so what?

Well I know DAN has a lot of studies wraping up at the moment. The big one is the FAD study. Unfortunatly though they've already backed off of their liberal initial statements so I'm not expecting too much...

 

[Snowbear]

Why "2 years"?

That's a bit shorter than how long ago the thread was started - some thinking seems to have changed a bit since then, wouldn't you say?

 

[ArcticDiver]

That's a bit shorter than how long ago the thread was started - some thinking seems to have changed a bit since then, wouldn't you say?

Now if I had read the earlier post dates I would have known that.

 

[ColdH2Odvr]

Here’s a great graph from BRW’s last book (excellent, buy it!). If the VGE bubble count is an indicator of DCE probability then this graph pretty much answers the safety stop question.

http://www.rockisland.com/~dgrove/VGE_Bubbles.jpg

 

[pipedope]

Is decompression sickness something every diver will more than likely experience to some degree? It sounds like there's really no sure way to avoid it, just ways to minimize risk. Like driving a car on ice... you can be as careful as humanly possible, but you still might slide off the road.

Right?

If you dive then you might get DCI.
The only table that will eliminate all risk of DCI is the one where you don't dive at all.

So what do we do?

I read and study to learn the latest findings and thinking on deco and DCI. Then I pick tables/software that lets me plan dives with my acceptable level of risk.
I stay fit and hydrated as well as I can.
I use good diving technique, including slow ascents with safety stops.

Lastly, I watch for symptoms of DCI in myself and my buddy.

I am starting a personal campaign to get more divers to learn and use the 5 minute neurological exam;
http://wrigley.usc.edu/hyperbaric/neuro/neuro.htm

It is a good plan to do a 5 minute neuro on each other before the start of diving and at the end of the day. You can pick up things that your buddy is not noticing or is denying, and it gives you strong reason to call (or not if things are fine) DAN and EMS if you find a problem.

Remember, DCI is rare in sport divers but is possible even if you do everything right. Early treatment is the key to maximum recovery.