A.G.E. Questions and answers

[Cave Diver]

Are there "undeserved" occurences of a CAGE? Does choice of breathing gas play a factor (helium vs. nitrox or air). The latest accident has worried me more than any other diving accident I've read about.

To answer this accurately, I'd probably have to go back to notes I took at a DEMA conference with Dr. Wienke and some discussion we had after the class, but I'm not sure how long it will take me to find them.

Until then, I think the best way that I can summarize it, is that there is a pressure differential in the surface tensions between helium and nitrogen bubbles and your goal is to minimize the differential as much as possible, otherwise you can create "bubble nuclei" which encourages the formation of smaller bubbles.

A lot of people are shifting towards the use of helium in deco mixes as well, as this reduces the chance of spiking your deco curve when switching to a different mix.

I'll leave any further discussion of that to those that are more qualified to speak on specifics than I am.

Can you do everything right and embolize?

I believe Steve Lewis said something once along the lines of decompression profiles being a mathematic attempt to model a biological occurence, with the problem being that mathematics are a poor way to model biology.

So the short answer to your question would probably be "yes." Although if you did everything correctly, the chances are greatly reduced.

 

[Cacia]

otherwise you can create "bubble nuclei" which encourages the formation of smaller bubbles.

Thanks for that explanation. I am curious about the trend of thinking on this. I also keep wondering if medications will effect off-gassing.

The hit Kimber took has me paranoid. I was thinking about it yesterday while diving and ascending slower than ever.

 

[Cave Diver]

Thanks for that explanation. I am curious about the trend of thinking on this. I also keep wondering if medications will effect off-gassing.

The hit Kimber took has me paranoid. I was thinking about it yesterday while diving and ascending slower than ever.

Okay, I'll try to give you ans answer on this as cleary as possible based on my understanding of it. Remember, I'm not a Dr. and I don't play one on SB, so take this info for what you think it's worth and keep in mind that I'm offering it for free...

 

[Cacia]

yes I am able to discern that!
Look, as far as we know, the hit was a mystery. That always has people soul searching for answers, prevention, etc. I won't mail the check then.

 

[Cave Diver]

As you ascend, imagine the bubbles forming. Bubbles are held together because the surface tension of the bubble is higher than pressure in surrounding tissue. The gas inside the bubble will be similar the to the composition of the gasses that are diffused into the tissue surrounding the area the bubble is in, which in most cases will be an inert gas (nitrogen or helium).

In order to remove the inert gas from the bubble, you have to lower the pressure gradient outside of the bubble. One way to do this is the introduction of oxygen. Bubbles exist at ambient pressure and the partial pressure of oxygen inside the bubble is greater than the partial pressure of oxygen in the arterial blood.

As the partial pressure of oxygen inside the bubble goes up, it increases the speed of the transfer of nitrogen from the bubble and causes the bubble to decrease in size. Using a gas with a lower partial pressure such as helium can also increase the rate that it diffuses out of the bubble.

If you end up with a bunch of small bubbles, that increases the odds that one could travel somewhere you don't want it to be and then grow to a size that it could be dangerous.

The idea is to minimize the number of bubbles that form and then reduce the size of those bubbles as quickly as possible.

Medicines can most assuredly have an effect on the way that the body handles this.

 

[Cacia]

well, thank you. So, is this diffusion gradient driven, then? and the pp difference might make helium form microbubbles faster. I am curious what makes them "form bigger bubbles" but that would seem to be a surface tension function too; it seems bigger bubbles would cause a more deadly emboli. (block blood supply, etc) Do they do most of the damage by causing hypoxia to the surrounding tissue?

Also, would you mind telling me if you are an aspirin beleiver? I take it because I assume it cannot hurt. Do you hear much discussion ever, about this at the current meetings you attend? I remember BJD PM'd me once to say he beleived in it, as a concept enough to take it. I am just wondering if there is a downside I am missing.
CVA...etc.

Very nice explanation.

 

[pickens_46929]

I've also been taught by several instructors, that at the end of the dive to hang out and float on the surface for at least two minutes before climbing onto the boat or shore. This allows time for your blood to circulate one complete time and reduce the risk of any of those bubbles growing or causing problems because of the extra exertion.

Yes, I was too... by both my technical instructors. Also recently on a dive boat we had a tired diver situation, I was on the boat but still geared up. Offered to go in with the tag line to get the other diver. Captain basically said "sit your *** down" politely and added "don't want you to embolize on me and have 2 divers in distress"... he was also a technical dive instructor as well.

So post dive exercise, especially after deeper or mutiple dives, is not a good thing. I don't want DCS or to experience an AGE...

http://www.awoosh.com/Doc%20Vikingo's%20Resource%20Page/Exercise%20&%20DCS.htm

http://www.diversalertnetwork.org/medical/faq/faq.asp?faqid=166

However they say pre-dive exercise *24 hours before* is good...

http://jp.physoc.org/cgi/content/abstract/555/3/637

http://diveubc.6.forumer.com/a/dive-fitness-book_post11.html

 

[pickens_46929]

I am just wondering if there is a downside I am missing.
CVA...etc.

Only conditions I know that low dose preventative aspirin isn't good are if you have trouble clotting, have an ulcer (like I did) or are on non-steriod anti-inflammatories (NSAIDs) (which I have also been on)... if it's a really big deal because of family history, my doctor said we would have looked at alternatives to the NSAIDs and kept taking the asprin.

Ultimately I've stopped due to stomach sensativity... the aspirin combined with stress resulted in the ulcer... only alternative was to take asprin plus prilosec or something like that...

Oh... one benefit of the once a day 75mg of aspirin... is helps prevents DVT... deep vein thrombosis... that stuff you get on long airplane flights...

Doctor said if I don't want to do aspirin... keep up on the garlic and olive oil... more seafood... (I'm a midwesterner... seafood isn't something I grew up with...)

 

[lamont]

keep up on the garlic and olive oil...

if garlic and olive oil prevents DCS i'm never getting bent...

i like it when i eat enough garlic that i can smell it on my skin...

 

[Cacia]

So, being hypothermic could favor a hit too, right?

I am always wondering about suble PH changes because in Chemistry they influence the rate of equations pretty profoundly, can't they?

I always wonder about lactic acid, slight acidosis, etc and how maybe anything that pushes your Blood ph from one side of 7.4 could change solubility of gases, etc.

Maybe the hungover person is more acidic, not just dehydrated. I guess I am reaching, but every time I pop an aspirin before a dive, I wonder if the acidity effects my blood ph.....probably not.