Ascending faster than 60ft/minute

[Fish_Whisperer]

LOL! I'll probably be doing Nitrox next week, as a matter of fact. I already have the manual.

 

[Azotino]

You really need to do your basic Nitrox! It really helps when you are slinging a bottle of rum and coke. :laughing:

CubaLibreMix SPECIALTY ............

 

[Fish_Whisperer]

Can I get a cert card and a chevron with that $125 specialty class? LMAO!

 

[aboalreem]

If you have enough air in your tank, go as slow as possible even 15 feet a minute...why not...

 

[TSandM]

Thalassamania, in fact, you are right; if one maintains a closed glottis through a given amount of pressure (and therefore volume) change, the effect on the lung structure is likely to be the same. However, one is highly unlikely to maintain a closed glottis through sixty feet of depth change if that depth change takes at least two minutes . . .

All this discussion of gas laws reminds me of why I hate eponyms so much (strange, for a doctor, huh?) PV=nRT combines them all, is easy to memorize, and "Ideal Gas Law" is a name which at least has something to do with the subject matter!

 

[TSandM]

aboalreem, there is actually a good reason not to go as slowly as your air supply will permit . . . and that's why decompression diving is more complicated than just going slow. If you go TOO slowly, particularly at depth, you will continue to ongas in certain compartments. One of the things the decompression algorithms do is to compute at what point each compartment begins to offgas, and what the gradients are across that compartment at each point. Ascents are generally more rapid at depth, and gradually slow. If you want to read something very good on this topic, look for the threads on the Deco Stop written by Doppler and entitled, "The shape of the curve".

 

[Thalassamania]

Thalassamania, in fact, you are right; if one maintains a closed glottis through a given amount of pressure (and therefore volume) change, the effect on the lung structure is likely to be the same. However, one is highly unlikely to maintain a closed glottis through sixty feet of depth change if that depth change takes at least two minutes . . .

The reason it is so hard to make anything foolproof is that the damn fools are so ingenious. I've learned, by trial and error to never say it can’t be done; some damn fool will always do it or die trying.

All this discussion of gas laws reminds me of why I hate eponyms so much (strange, for a doctor, huh?) PV=nRT combines them all, is easy to memorize, and "Ideal Gas Law" is a name which at least has something to do with the subject matter!

I go with the ideal gas law myself, but then there's trying to remember avocado's<G> number and the proper value of K for the units used, etc.

Human dissection was much easier (Oh, Oh, Oh, To, Touch, And, Fondle, A, ...) For the gas laws there's Boyles, Daltons and Henry's (alphabetical, no?) and there's Volume, Partial Pressure and Dissolved (reverse alphabetical). That's poor, but the best I can do.

 

[Ishie]

Thanks for all the replies!

If I make a controlled emergency swimming ascent from 30 feet for 30 minutes, am I definitely going to get the bends? While I get DCS half the time? Same question for ascending at, say 80ft/min.

You're rarely going to "definitely get the bends". There are a few exceptions but they are usually extreme (read about a guy that had his drysuit autoinflate and rocketed him up over 100 feet with about a significant amount of deco left and he was still only in his deep stops, so yeah). There's no set numbers because everyone's system is different. I've seen one person show symptoms of DCS, they'd been diving for 15 years, and their profile was more conservative than my own, and mine was within the limits of my Pat-Buchanan-voting computer. There was no real "should I?" period with her because she staggered to our room presenting with numb hands, vertigo, dizziness, and confusion, all of which improved with O2. Oops. I've also talked to a guy that did a bit of a fast ascent from 150', was in bends denial, but did end up needing chamber treatment (he's fine).

Personally, I've done an ascent WELL over 60 ft/min from 60' (probably hit the surface in less than 10 seconds) when I had a borrowed BC with apparently an excellent lift capacity autoinflate, and I couldn't disconnect the hose in time. My main concern with an ascent that fast was keeping my airway open so I wouldn't get a lung overexpansion injury, and despite rolling and flaring, I still breached the surface like a dolphin. Aside from being shaken and incredibly pissed off, I was fine. This is hardly the recommended action, but no bends, and I don't think I 'beat the odds' (I don't think my chances of DCS were anywhere near, say 50/50). Given that, anyone would agree that calling this an 'acceptable' ascent is totally bogus. What if I'd been down longer? What if I'd been deeper? Both would increase my chances depending on changing factors. If that had happened after being at 130 for 20 minutes, my chances of being bent would have increased drastically.

From 30'? Unlikely. But I wouldn't make a habit of it.

And an unrelated question: reading the boards it sounds like it is possible to have a mild case of DCS and simply not notice (ie, mild joint soreness and fatigue are pretty vague symptoms). If this is the case, is medical treatment required or will things resolve spontaneously over time?

I believe it is possible to not notice, and there seems to be a high incidence of "bends denial" in which someone is feeling symptoms (like nausea, tingling, and numbness) and won't acknowledge that it's DCS.

I don't know the medical histories. My mom dived back in the 70s and got skin bends (very minor symptoms and a rash), didn't get treatment (fewer chambers back then), and had no long term difficulties, but with the availability of help now, personally, I wouldn't take my chances. That's what DAN insurance is for.

I'm a little worried that I will accidentally ascend at 70ft/min, have a sore shoulder from lugging scuba gear around the beach and not know if I need to run off to a recompression chamber "just in case".

Only you can determine what feels normal to your body. Personally, I'd say, that if you accidentally ascend at 70 ft/min, and ONLY your shoulders (from lugging scuba gear) are sore, you have no other joint pains, no tingling, no numbness, no nausea, and no dizziness, *I* certainly wouldn't go chamber on it. Another key is if you're experiencing symptoms, you should be on O2 anyway, and if the symptoms subside with O2, get to a chamber.

 

[Fireman Ken]

NWGrateful Diver says:

Most technical divers will ascend in a manner that they call “shaping the curve” … which, to simplify, means that the closer to the surface they get, the slower they will ascend.


BINGO!!

 

[Azotino]

NWGrateful Diver says:

Most technical divers will ascend in a manner that they call “shaping the curve” … which, to simplify, means that the closer to the surface they get, the slower they will ascend.


BINGO!!

Are we talking about rek or tek diver??????????
If you are a rek diver you don't need to change your speed.......tek are different.