up too fast? go back and do it again ???

[miked]

While talking to a non-diver, who was interested in the activity, and had many questions. This situation came up. I was not sure what the "best" answer would be, so I thought I'd throw the question out to the SB experts:

Suppose a diver realized that he had ascended too fast-(not to the surface-but en route to a safety stop-recreational diver-no mandated deco).
What would the best/safest course of action be, and Why??

[Also: would the answer depend on the depths involved? (i.e. is there a difference if you came up from 60' to 40' too fast, vs. from 100' to 60', etc.) or how "too fast" the ascent was??)]

options:
(pos and cons of each, if possible)

Descend, and come up more slowly?

Stay where you are, wait a few minutes, then continue to ascend at a proper rate?

Continue to the safety stop at a proper rate, then make a longer SS?

Or....?


For the sake of discussion, let's assume that gas supply/ NDL/ other factors are not an issue. Of course, we should never ascend too fast, but..what if ??



Thanks in advance,
Mike

 

[Lightning Fish]

Stay where you are, wait a few minutes, then continue to ascend at a proper rate?

Continue to the safety stop at a proper rate, then make a longer SS?

I would stop and get things under control and make sure I am okay. Then continue to my safety stop and extend it.

I don't see the point in descending again. How far would you descend? If you descend too far you will start on gassing again.

Bill.

 

[dpbishop]

Stop at the point where you realize your error and wait until your computer stops saying "ascending to fast!!". If you are diving without a computer than do half your safety stop at the current depth and half at 10 feet. The worst thing you can do if you suspect a hit is to go back down. People have done that (in more drastic situations than you describe, of course) and passed out at depth.

 

[DandyDon]

OMG it happens to me all the time. I usually just stop ascending and hold that depth for about as long as I might have ascend too fast - then do a 1 min stop at 1/2 maximum depth and a 3 min around 15 ft.

[Also: would the answer depend on the depths involved? (i.e. is there a difference if you came up from 60' to 40' too fast, vs. from 100' to 60', etc.) or how "too fast" the ascent was??)]

If you're talking about the same ascent rate, yes. My Oceanic computers are happy at 1 ft/second below 60 ft, 1 ft/2 second above 60 ft.

 

[Atticus]

On a recreational NDL dive I stop my ascent and start 1 minute stops every 10'. If it was really bad I'll drop down to half my max depth and do one minute stops every 10'.

This doesn't differ much from my normal recreational ascent.

 

[vjongene]

The official CMAS procedure is that once you have regained control of your ascent you stay at current depth for the length of time it would have taken you to get there with a normal ascent (10 m/min). Then you proceed to your safety stop (assuming that you are within NDL).
However, if you reach the surface after an uncontrolled ascent (a more common problem), the procedure is to go back down to half of you maximum depth, spend five minutes at that depth, and then proceed to the surface and do your deco stops (if any) as if you had spent the entire time necessary for the procedure at your maximum depth (i.e. actual bottom time plus at least five minutes).

 

[miked]

Thanks to all for the replies.

BTW, my answer to my friend, was:

"Stay where you are for a few minutes, continue to the safety stop at a proper rate, then make a longer than normal SS."

To which my non diver friend asked " why not go back down, and come up at the correct speed?"
Prompting my question to you.

Thanks again for the input.

Take care,

Mike

 

[Vayu]

Because in water re-decompression can be dangerous. Imagine your body is a coke can and on ascent you just shook it up and popped the top. You can't close the can again and hope to repressurize the contents.

Of course your body is not a coke can however by the time you notice the fluke it is likely that your tissues have been offgassing and equalizing to the ambient pressure. Going back to your max depth and starting from scratch is only going to make your tissues load on more nitrogen. On top of this if you have DCI as a result you need to be getting out of the water and hopping on a bottle of 02.

Don't miss your decompression and if you do then it is likely you won't be able to stop in the shallows. 30' ascent per minute is preferred by most agencies, but a 60' per minute ascent can be done relatively safely if needed. Try taking it at a 10' per minute rate once you hit 40' or so and it is unlikely that you will miss your stops due to lack of awareness or control.

(i.e. is there a difference if you came up from 60' to 40' too fast, vs. from 100' to 60', etc.) or how "too fast" the ascent was??)

The worst place to come up too fast is between 34' and the surface. This area is a danger zone because the absolute pressure is doubled within a relatively small area.

-V

 

[jagfish]

To which my non diver friend asked " why not go back down, and come up at the correct speed?"

I heard an answer to this in some recent training...

If bubbles had been formed on your rapid ascent, they would be confined to the "pulmonary" side of your heart and will hopefully be released through the alveoli in the lungs, allowing the diver to remain asymptomatic.

If one descends again, the bubbles will reduce in size, and may be able to pass by the lungs and into the side of the heart that pumps to the brain. At this time, the diver would have micro bubbles in the total circulation system, including neural tissue.

If the diver now ascends before these micro bubbles are completely purged from the blood, one or more of them could expand in neural tissue upon final final ascent.

For this reason, I was advised to never re-descend in this kind of situation.

This is also apparently the mechanism of danger in bounce dives.

 

[Atticus]

If you're not yet symptomatic and are willing to spend at least several minutes at depth then descending can be a very reasonable alternative to surfacing and getting on precautionary O2, especially if you are carrying O2 on your dive (I know, this is joe recreational diver, but I typically carry O2 during a dive for deco).

The NAUI technical diving program teaches a relatively common missed stop procedure which includes doing just this *if you are not yet symptomatic*.

If you are symptomatic (ie: already bent) then it gets more controversial. Many divers have been treated successfully with in water recompression (Richard Pyle comes to mind). I'm sure others have perished in the attempt. The agencies by and large say "don't".

In response to the previous post - if you are going to descend again, be prepared to spend several minutes at depth. Doing a hard dive followed by a quick bounce dive (or diving and then freediving) is problematic. The rumor mill suggests that several WKPP support divers were bent doing equipment retrieval bounce dives (source: GI's web page).