What to do if you ascend too quickly?

[DCBC]

For the record, it wasn't I who rapidly ascended from 90fsw then continued to dive. This story was a follow-up to another post made by another diver. I have never (knock wood) had any issues with rapid ascents... though I may be eating my words when I start using a dry suit.
I think the OP (and myself) were just asking general "what if" questions in order to further our edukayshun. It's always good to ask questions of those with more experience.

Yes Sir and you have your answers.

 

[The Chairman]

Dang NetDoc, you are a Gator - "Ameliorate". I must have missed that day.

Improve the outcome. "Reading my posts might ameliorate the paucity of your vocabulary". This is probably the product of having a polyglot mother who taught remedial English.

The point is, blood and neural tissues have a half time of 2:30-3:00. 6 intervals at depth (15:00-18:00) results in those tissues having attained 98% saturation. DAN has noted that while still quite low, recreational divers who get DCS almost always get type II (neural). Getting back down to a half stop for 3:00 will take out a large portion of the N2 and an additional 5 minutes at 20 FSW will bring you to less than 20% of what you started with.

But then, I do this for every dive deeper than 60 FSW. I certainly don't see it as IWR if it is indeed a safety stop.

 

[Scott L]

I'm a new diver - 1 year, 51 dives. I just read another post titled uncontrolled ascent in which the diver overinflated the bc at 90', couldn't dump air, and shot to the surface. Once surfaced, the diver dumped the air in the bc and went back down to 90' to meet buddies and then ascend under control and with safety stops.

I would have thought this a very big deal, and the diver should have gone straight to the boat or shore for 100% oxygen/medical attention. The last thing i would have thought the diver should do is go back down. But, I didn't hear this from many of the responses on the thread. Some even said the diver did the right thing by going back down.

Can you help me understand this? What should the diver have done? If you ascend too quickly, does diving back down and ascending properly helpful?

This would not have been an option here in SE as the Gulfstream's current involves surface current being stronger than the bottom or vice versa. Had he not meet up with his dive buddies and repeated the process he probaly would have utilizied his Dan insurance. The key here as mentioned in an earlier post was how long had he been at depth (nitrogen loading) before the fiasco. What's really the down side if we were to assume he would have taken a DCS hit? It's not like CNS whereas one could convulse. No? Thoughts?

 

[The Chairman]

What's really the down side if we were to assume he would have taken a DCS hit? It's not like CNS whereas one could convulse. No? Thoughts?

DCS Type II???

• Vomiting
• Paralysis
• Disorientation
• Tingling in extremities
• Unconsciousness
• Incontinence
• Extreme tiredness

I think the list can go on. DCS is nothing to sneeze at and type II is especially so since it deals with neural issues.

 

[Bubbletrubble]

If there is enough gas, and I was feeling no symptoms, I would be back down to do my SAFETY stop. This is not the same as IWR. If the diver was 20 minutes at that depth, then neural and blood tissues would be essentially saturated. Type II DCS is a much greater risk, and doing the missed SAFETY stops (3 deep & 5 shallow) will ameliorate that possibillity.

First off all, we might want to consider changing the title of this thread to: "What to do if you have an uncontrolled ascent and miss your safety stop?"

There appears to be some dissent as to what should be done in the case of an uncontrolled ascent from 90 fsw with no deco obligation. Some advocate re-descending to do the safety stops, whereas others recommend remaining on the surface.

The US Navy Diving Manual provides some impressive contingency planning for missed safety and deco stops. Here's a link to a downloadable PDF version of the US Navy Diving Manual. In Chapter 21 entitled "Recompression Therapy," Table 21-3 (Management of Asymptomatic Omitted Decompression" and section 21-3.6 recommend observation for 1 hour in the case of an asymptomatic diver who experienced an uncontrolled ascent from a depth greater than 20 fsw. Keep in mind that the Chapter 21 guidelines are designed for dives conducted according to USN tables and standards (set forth in Chapter 9).

Hope you guys find this info interesting...

 

[Nailer99]

Wait- we're talking about recreational diving here, right? No decompression obligation? diving within the NDLs on air or nitrox, right?

So, why are we even having this conversation? One should be able to do a CESA at any point during such a dive, right? Not that it's recommended, but, still- we're talking about bubble formation and In Water Recompression in a thread about no deco recreational diving. You cork, you get back on the boat, or swim to shore, and you monitor for DCS symptoms.......right?

 

[Bubbletrubble]

Wait- we're talking about recreational diving here, right? No decompression obligation? diving within the NDLs on air or nitrox, right?

So, why are we even having this conversation? One should be able to do a CESA at any point during such a dive, right? Not that it's recommended, but, still- we're talking about bubble formation and In Water Recompression in a thread about no deco recreational diving. You cork, you get back on the boat, or swim to shore, and you monitor for DCS symptoms.......right?

Uh. Yep. The thread got a little side-tracked once the concept of IWR was introduced. Of course, IWR is only a viable course of action when a diver skips out on a decompression obligation. Someone also mentioned that commercial divers will surface, take a shower, and then recompress in a chamber. Although this is accurate for commercial diving ops conducting decompression dives, in my mind it is very different from a recreational diver re-descending to carry out a missed safety stop.

I've been a little surprised by some of the posts, too. I think people are a little confused about the scenario in question.

There's also the issue of distinguishing arterial gas embolism from Type II DCS...but that's a subtlety that probably bears explanation outside of the "Basic Scuba Discussions" forum.

 

[Big Toes]

If i may: ex-navy diver, current commercial diver.

US Navy dive manual:

IWR should never be performed if there is a chamber available within 12 hours. the operative word here being 'recompression'. by this they're assuming a symptomatic diver; asymptomatic has a completely different set of rules.

if it's a no d dive and the diver is on the surface and asymptomatic, put on o2 and observe.

if it's a deco dive and the diver can get down to the depth of the last stop in less than one minute, return to the stop and add a minute to the stop time. finish deco.

greater than one minute but less than 5, return to depth of last missed stop, multiply stop times by 1.5 and finish out deco.

those are some basic rules for shallow deco stops and the most basic of stops that we'd encounter. stops deeper than about 30' (i think? check the manual...) require a more involved process...

commercial diving:

sometimes we'll do very long, deep dives in which we'll do just a bit of the deco in the water. the diver is then brought to the surface and placed in a recompression chamber where the bulk of the deco is performed. he's basically got :05 to get from the depth of his last stop until he gets to the depth of his first stop in the chamber. he'll finish these stops in the tube breathing straight o2 with air breaks and no, nobody's taking showers during this time...

so these are just some basics, but hope they help!

erik

 

[Cave Diver]

Wait- we're talking about recreational diving here, right? No decompression obligation? diving within the NDLs on air or nitrox, right?

So, why are we even having this conversation? One should be able to do a CESA at any point during such a dive, right? Not that it's recommended, but, still- we're talking about bubble formation and In Water Recompression in a thread about no deco recreational diving. You cork, you get back on the boat, or swim to shore, and you monitor for DCS symptoms.......right?

The question was about whether returning to depth and re-ascending was an alternative.

If you ascend too quickly, does diving back down and ascending properly helpful?

Every dive is a deco dive. We just accept that dives we classify as being "within NDL" have an acceptably low enough risk to allow a direct ascent to the surface.

I mentioned IWR, because in my opinion this is what is being done when a diver returns to depth and attempts to rectify a rapid ascent. I also mentioned that this *should* be unnecessary in normal NDL diving and in my first post, I recommended a different course of action.

 

[I Dive]

What's really the down side if we were to assume he would have taken a DCS hit? It's not like CNS whereas one could convulse. No? Thoughts?

Paralysis and Death come to mind as two potential downsides...