Decompression Stop Guidelines - What we have to do if got deco alert?

[Diving Dubai]

@The Chairman and @boulderjohn, agree 100%. Lead by example and make the important things important.
I would add to explain why things are important. It's not just to pass the class. Too often what was seen and done in class is quickly over written by what is seen on "real dives" and in an effort to not look like a newb. If people understand why they are doing something they are more likely to not discard it.

Agreed. Slightly OT but in the pool last week the Instructor was demonstrating and then getting the students to carry out the LPI hose disconnect, after explaining why.

You could see the look on some of the students faces "this is an unlikely event" kinda look

The instructor (obviously picking up on this) turned to me and asked if I'd ever has an LP go into free flow in real life (knowing the answer) I told them yes and why. They paid more attention the second time around...

 

[Patoux01]

Working hard during the "Champagne Minutes" is never great. I'd much rather hang under the boat watching the fish and other divers for a little longer....

I don't think "champagne minutes" are at the exact moment when you ascend. IIRC it's more like 15-20 minutes later. But I've been wrong before... Can't seem to find the paper that talks about it (divers monitored through doppler over time after they get out of the water, there was a sharp increase after the dive I think).

 

[boulderjohn]

you may well right and im not disagreeing - id add on a few extra minutes too if was riding the NDL up -but im wondering what data is available to justify taking this position or is it subjective (ie i feel better)
Lets say an OW diver reads "stay within the NDL" and follows that to the letter, is there any literature "pre deco procedures training" to say that they should add on more minutes?

I don't know of any literature, but there is a bit of common sense involved.

Start with the idea that the concern is with going to the surface before having off-gassed enough to avoid DCS. The idea is that a 3 minute safety stop should allow enough off-gassing to be safe. Yes, it should. But what if it isn't quite enough because I pushed things a bit? If I stay another minute or two, I have extended the safety margin. It might not be necessary, but it can't hurt, either.

 

[scubadada]

I also tend to be conservative. I always do a safety stop, generally 3 minutes, 5 minutes if I've come within a few minutes of deco. I pad my shallow stop by 3-5 minutes after clearing light deco.

So far, so good, have never had DCS, and intend on keeping it that way.

 

[Storker]

Anecdote: A couple of years ago, some divers in the local community participated in a study. Basically, they did a 2-hour chamber dive to 18m/60ft, decompressed according to the then-current standard table and were monitored for some hours with ultrasound imaging of arterial bubbles.

According to the rumor mill, one of those divers got bent and had to take chamber ride. He was also the only one who thought that is was a good idea to start mowing his driveway for heavy, wet snow as he came home after being studied.

 

[gfaith]

I don't think "champagne minutes" are at the exact moment when you ascend. IIRC it's more like 15-20 minutes later. But I've been wrong before... Can't seem to find the paper that talks about it (divers monitored through doppler over time after they get out of the water, there was a sharp increase after the dive I think).

Mark Powell addresses this in "Deco for Divers" and you are correct the silent bubbles appeared at 15 minutes during surface intervals.

The test was 30m dive for 25 minutes: first group direct ascent with no SS.. Lots of Silent Bubbles @ 15 minutes after surfacing; bubbles still detected 120 minutes in SI.

Second group 2 minute @ 3m SS ... Less Silent bubbles but still appearing @ 15 minutes after surfacing. Bubbles less than group 1 but still detected at 120 minutes during SI.

Third group.. 1minute @6m..then 4minutes@3m.. no silent bubble spike @ 15 minutes and zero bubbles after 45 minutes in surface interval.

 

[Patoux01]

Thanks for that. I keep forgetting I bought that book.

 

[The Chairman]

I don't think "champagne minutes" are at the exact moment when you ascend. IIRC it's more like 15-20 minutes later.

Exertion can precipitate the event. I don't think it's a linear correlation either.

So far, so good, have never had DCS, and intend on keeping it that way.

48 years of diving and DCS free thus far. Safe diving is no accident.

 

[scubadada]

...48 years of diving and DCS free thus far. Safe diving is no accident.

You've got a year on me, here's to both of us continuing our streaks

 

[Patoux01]

Exertion can precipitate the event. I don't think it's a linear correlation either.

People doing the right thing for the wrong reason is not necessarily good if you ask me.

Adding a safety stop when you're drifting with no knowledge of where your boat is and are cold (not necessarily an uncommon scenario in some areas) might not be the safest thing to do.