Fast ascend

[PoolDiver]

Today I was having a normall dive. After 28minutes and well within my non decompression limits and at a depth of 9-10metres I suddenly started ascending quickly. My computer (Mosquito) indicated SLOW and then STOP but I couldn't. I couldn't hold it down so I simply let myself go while blowing. I guess that the cause of this rapid ascent was a mixture of an almost empty tank, a very thick wet suit 8mm and low on leads (I had trouble going down).
Now, the Mosquito didn't go on Error so I guess it was not that bad, it even allowed for a consecutive dive only after 15mins, even without the safety stop.

Question: Does decompresion sicknes occur due to a rapid ascent or is it mainly caused by exceeding non decompression times and not respecting the mandatory safety stops?
I had no simptons and my instructor said it was no problem, just in case I decided not to di my second dive.
Thanks for your oppinions.

 

[Gombessa]

How fast was the ascent (was it like a "normal" controlled emergency ascent)?

I'm sure those with more experience will chime in, but IIRC, at 25-30ft, though OW training usually calls for a "mandatory safety stop," it's technically optional, which means you should be OK.

 

[Gary D.]

Could be both and Safety Stops are not mandatory, just a recomended good idea.

Gary D.

 

[spectrum]

Anything that brings you to the surface has the potential to produce gas bubbles. The faster you rise the more likely. The longer and deeper you have been down the more gas is in solution to cause problems. The the whole thing is a sliding scale.

By doing a good "go and blow" from a modest depth you avoided serious trouble. If you feel uncommonly fatigued some sub clinical DCS is a possibility.

It sounds like you recognize your configuration shortfalls for next time.

Pete

 

[DandyDon]

PoolDiver, it would help with discussions if you completed your profile. I take it that you are in OW class, somewhere cold...?

Just how low were you on air pressure? If under 500 psi, you were already in a threatening situtation. Yeah, use that last 500# if needed, but if so - a problem exists there already.

Anytime you have a problem descending, you may well have a bigger problem just like this one at the end. An 8 mil jumpsuit would mean at least 30# of lead for me in saltwater, more for a 2 piece suit. Sinking with proper weight should be easy if you don't tense up and hold your lung full as newbies do sometimes.

There were a couple of articles in the DAN magazine this month about newbies getting bent on rapid ascents from shallow dives within NDLs. Are you a member yet, get the magazine?

How many hours ago was this? You are probly not hurt, but just in case - if you are, you really do not want to ignore symptoms that would probly show up within a couple of hours - but, if a diver does show symptoms, immediate care is indicated - both EMS and DAN consultion. Too many hits are complicated with denial and lack of action.

I don't know where you are so cannot give you contact info for Free consultation with DAN medics and doctors, but you can obtain those numbers at www.DAN.com. Again, I understand that you are probly not injured, but if you have any symptoms, I want you to have access to those numbers. Put a few of them in your cell phone for later on.

 

[String]

DCS is more likely to be caused by a rapid ascent than anything else. Deco stops are simply a way of slowing the ascent to an acceptable rate (given that very very precise slow varying ascent rates are in the real world impossible so instead of that you go up a bit, stop, go up a bit more, stop).

No-stop limits are only valid if ascent rates are valid, you can be inside a NDL but a rapid ascent can still incude DCS. ie NDLs are in part valid only for specific ascent rates.


*HOWEVER* in your case from that depth i wouldnt worry about it just be aware that DCS is all to do with ascent rate and not whether you stayed inside NDLs or not.

 

[DandyDon]

*HOWEVER* in your case from that depth i wouldnt worry about it just be aware that DCS is all to do with ascent rate and not whether you stayed inside NDLs or not.

I would have agreed had it not been for those DAN articles. I don't guess you get the magazine.

NDLs and Ascent rates both can be involved with DCS. I do not know why you used the word "not" in this dicussion, as it is not really appropriate as used. Typos happen, of course - to us all.

 

[String]

Cant see the error?

Rephrased.. Someone staying inside the NDLs but violating the tables prescribed ascent rate is "no longer" in the realms of that table so could be at a greater risk of DCS.

Staying inside the NDLs and ascending rapidly puts you at a greater risk than straying slightly outside them and ascending normally.

 

[DandyDon]

Well the UK and the US are seperated by a common language. :lol2: Some of the wordings y'all use throw me at times. I often have to stop my Scottish friend for explanations.

I read "...that DCS is all to do with ascent rate and not whether you stayed inside NDLs or not" as suggesting that exceeding an NDL would not lead to DCS - but it could. Either exceeding NDL or Rapid Ascent or worse both can.

 

[String]

OK interpretation problem - it still reas fine to me

Rephrase should help.