How to safely ascend with Spare Air

[jonnythan]

Actually I am not a real doctor, I just play one on TV. Don't you understand sarcasm once in a while?

Honestly - no one has answered my question yet:

If you obey the dive table and dive conservatively under the recommended maximum bottom time - can you still get DCS?

If you can't get DCS - then the injury here we are concerned about is air embolism - right...????

You absolutely, 100% can. Dive tables are a statistical comprimise. "Stay under for less than xx minutes to reduce your likelihood of DCS to 1 in 1,000,000" would be a guesstimate at the kind of numbers we are talking about. It's absolutely possible and happens a fair bit. They're generally referred to as "undeserved hits" but can be made more likely by things like fast ascents.

If embolism were the only thing to worry about, everyone would scream and kick up like mad whenever they got to the ascent line

 

[OE2X]

So as I understand, if you use those stupid tables, and find the category you are supposed to be in, etc. etc... and stay within your time limits.... you should not have accumulated enough nitrogen so you can safely have an emergency ascend without having DCS, is that correct????

So the only issue here is that you don't have to give a hoot about DCS if you obey the tables or the dive computer.

The tables are used so that you hopefully don't get DCS. If you stay within your NDL or make sure you make all your stops according to your dive plan then you should be fine and these tables won't be considered to be "stupid". Stupid is the person that does not pay attention to the tables and gets themselves bent.

Now with that said: which would you prefer - 1. A rapid ascent, exhaling all the way to the surface, not suffering an embolism, but requiring a ride in a chamber or 2. Making your stop, going completely OOA on your spare air, going unconcious and dieing before you reached the surface?

My training agrees with the Uncle Pug school of thought: Your spare air is carried on your buddies back in the form of at least an 80 cf tank. Since I don't solo dive I would like to believe that the above scenario won't apply to me or my buddies. If it ever does though, I would have to choose number one. I for one want to watch my kids grow old.

 

[jonnythan]

BTW, it amazes me that anyone who has ever taken a scuba class (or anyone who has any science training whatsoever) would think that the NDL is a magical, absolute line, and you're guaranteed to be safe under it.

 

[fisherdvm]

Thank you for the last 2 post. They really reaffirm my understanding. The tables are guidelines. It would be interesting to find out what % of people fall into the guideline or outside. So it seems to me is the greatest threat of an out of air situation is air embolism.

So my original question about the best place to breath your tank or spare air is irrelevant. The focus then in an ooa situation is to keep your airway opened and letting excess air escape from your lung....

I wish more folks would answer politely like the last few post. I am not polite so I am sorry....

 

[OE2X]

True. For me, my profiles are always far more conservative than NDL. I use them as the absolute and then work back from there. On a nice warm sunny day my SI takes far longer than the recommended amount.

 

[MSilvia]

So it seems to me is the greatest threat of an out of air situation is air embolism.

Maybe... if you discount the possibility of not having enough air to make it to the surface, as would be the case if (for example) you got hooked or entangled in monofilament line on your way to the mooring line, and ran out of air while still trying to extricate yourself. Then, an embolism might be the least of your worries.

 

[jonnythan]

Thank you for the last 2 post. They really reaffirm my understanding. The tables are guidelines. It would be interesting to find out what % of people fall into the guideline or outside. So it seems to me is the greatest threat of an out of air situation is air embolism.

You're not understanding something.

By bolting for the surface, you increase your chances of DCS astronomically. The tables are built with a nice controlled ascent in mind.

 

[OE2X]

T
So my original question about the best place to breath your tank or spare air is irrelevant. The focus then in an ooa situation is to keep your airway opened and letting excess air escape from your lung....

No the focus shouldn't be about keeping your airway open, but to develope sound buddy skills so that this doesn't happen. Sound buddy skills include doing ooa drills regularly. In all the hundreds of dives that I've done, I have yet to have an ooa situation. That doesn't mean that I'm complacent about practicing S drills though. It doesn't mean that I don't constantly stay close and in touch with my buddy. Buddy skills and awareness are basic tennants of safe diving. These are the factors to prevent a situation where you need to do an emergency ascent exhaling to the surface.

 

[jonnythan]

So my original question about the best place to breath your tank or spare air is irrelevant. The focus then in an ooa situation is to keep your airway opened and letting excess air escape from your lung....

The focus is to get air from your buddy if you can't supply your own. "Bolt for the surface" is only an option if you can get there immediately without restriction, and that isn't always the case.

 

[OE2X]

The focus is to get air from your buddy if you can't supply your own. "Bolt for the surface" is only an option if you can get there immediately without restriction, and that isn't always the case.

Hey guys maybe he's talking about solo diving. Anyone want to touch that? I have 40 cf stage bottle when I do that, but my depths are no more than 30' fsw.