Making up for a fast ascent.

[Thalassamania]

The only purpose for dropping back down would be to compress bubbles that had formed (in-water recompression). That's not what we are talking about here, and is considered a treatment modality.

I would not be particularity concerned with the profile you describe. Where it to happen to me I would stop as soon as possible and let my proper ascent rate clock catch up with me. Then I'd take and extra minute or so to be sure I had everything squared away and make my normal ascent, with perhaps a little extra time at my safety stop. As always watch for any signs and symptoms of DCS and remember, it never hurts to break out the oxygen, even when it probably is not needed, in fact is is good practice to exercise the gear and refill the flask.

 

[Doppler]

OK, let's step back a little.


The situation outlined by the OP is a non-aggressive depth, and a short, rapid ascent the top of which was around one bar less pressure than at depth. We can also assume this was a dive within the scope of a "no-stop diving."

There is no omitted decompression and no need to roll out the guidebook for an In-Water Recompression... the punter in question remained in the water and my guess is was barely above the off-gassing ceiling for his dive when he arrested his ascent. No harm and this is a simple situation with a very simple fix... The OP did a pretty good job of applying that fix in-situ.

Someplace in my blog, I have entries about Omitted Deco and IWRC and Bounce Dives... which may be of interest for someone who suddenly gets it into his mind to jump back in the water to "recompress."

But surely we can put our bottles of coke and Perrier away since they hardly seem to apply here.

 

[DA Aquamaster]

Steve,

There is absolutely no fun in pointing out that a 15' rapid ascent from 40' to 25' on a 60' no deco dive is not exactly a crisis (provided the OP did not hold his breath, embolize, etc.)

Of course the OP probably figured that out already....

The point was not to suggest it, but rather to show the general concepts involved and make the point that as "decompression" goes, he was pretty far to the left hand side of the scale.

 

[dumpsterDiver]

Dove last night. 60ft started going up. 40ft to 25ft zoomed up by mistake. Stupid on my part. Stayed at 25ft for like ten minutes to make up then took another 5 minutes to get to surface. Whats the rule here?

If you totally stopped at 25 feet and your quick ascent began at 40 feet, i doubt you were going all that fast. If it was a typical recereational, no-deco dive, this kind of error is not much to worry about. It it much more common to shoot from 25 to zero, where there is a much bigger change in pressure and heavens knows many thousands of people have survived that with no injuries.

Loosing control of ascent rate for a short period during the middle part of the ascent is not normally a big deal (unless you hold your breath)

 

[rhwestfall]

Question: If in fact bubbles are formed, and since there is no 02 (100%) to create an enhanced gradient to promote accelerated off-gassing, wouldn't it be a poorer decision to recompress the potential bubbles, which would then allow for them to bypass the filters (lungs)?

I would vote for pause, catch up with some more time at the current depth, and then proceed slowly (more slowly than normal) after the safety stop. Many of us are still around despite learning and practicing at 60'/min....

Please feel free to explain errors in my thinking.

 

[DevonDiver]

Keep in mind the between 66 and 33 feet you will see 33% increase in bubble size. Between 33 feet and the surface you you will get a 100% increase (2x) of any bubble. So stopping a rapid ascent as deep as possible is better.

Whilst Boyle's Law does apply, there are a variety of other factors which come into play when talking about bubbles forming inside the human anatomy. Both because of the human physiology and the nature of bubbles themselves. It is incorrect to assume a direct correlation between absolute pressure and volume of gas when thinking DCI.

But can you un-ring the bell of DCS at that point?

My thoughts:

1. Recompressing a bubble is not the same as dissolving a bubble.

2. Whilst a return to depth can shrink the bubble, a timescale and ascent is necessary to eliminate it.

3. Boyle's Law fails to predict the bubble mechanics by itself - the relationship between absolute pressure and volume is not direct.

4. Returning to a higher absolute pressure increases nitrogen absorption/saturation in the body.

5. Increasing nitrogen saturation, in contact with an existing (albeit shrunk) bubble can cause further nitrogen loading to the bubble.

6. The relationship between nitrogen addition and subtraction from a shrunk bubble at a given depth is not something most divers could calculate 'on the fly'.

7. A re-descent and controlled ascent is necessary for bubble elimination, as a gradient needs to exist.

8. A re-descent and stop at depth may cause more damage than it does good.

Why would there be a delay in bubble formation? How much of a delay does a shaken bottle of coke give in forming the bubbles when you releive the pressure of the cap (ascend)?

From what I've seen, military divers (bend and mend) set the stopwatch for 5 minutes. Again, there are a myriad of factors in play due to human physiology, that don't exist in a coke bottle....i.e. pressure exerted by tissues etc.

 

[copter53]

"Either way, the general concept is that you have to go substantially deeper than a missed 10' stop to reduce the size of any bubbles that have formed and then ascend very slowly from there to reflect the reduced off gas efficiency that would accompany any bubble formation that may have occurred."


So if you cant go back deeper but can at-least go back like 20ft into the water is that something to do? Is going even a foot deeper to re-compress always a little safer? Or should we just stay outta the water all together once a mistake is made?

 

[DA Aquamaster]

It's probably pretty common for divers to end up ascending at 60 fpm rather than 30 fpm - at 60 fpm it would take only 15 seconds to go from 40' to 25'. In that case, I'd just stop the ascent and stay there until you'd have ascended there anyway at the 30 fpm rate, then hang another minute, just because, and then continue the ascent.

In terms of decompression diving, and decompression "stops" that's essentially what is being done. Rather than try to make a very slow and precise continuous ascent, the profile inserts stops every 10' that the diver makes - in essence ascending way too fast to the next stop depth, then pausing until the theoretical ascent rate "catches up" with the diver.

In a too rapid recreational ascent, you'd be doing the same thing - just stopping to let the ascent catch back up to you.

On the other hand, if you had a totally uncontrolled ascent and shot all the way to the surface, provided you were asymptomatic and descended again immediately, I'd suggest re-descending to about 1/2 your max depth, as that's probably a ball park guestimate of where your off gassing started, and then doa slow ascent and longer than average safety stop.

 

[RonFrank]

We are not talking about decompression diving. Fast ascents with no safety stops are NOT recommended but still are generally safe in recreational diving. They happen daily all over the world. We are overly cautious here on SB. AGE is more of a danger and we do hear about that every so often.

I studied the Lobster divers in South America recently and there is a poor nation that dives well beyond every limit with many divers becoming permanently disabled for life. What surprised me was the number of divers who break all the rules (like every rule of safe diving) and are not bent. Many do so daily for the entire lobster season. In the USA rec divers rarely get DCS. The safety guidelines we follow, even if not done religiously, are very safe.