air embolism possible from < 10' deep?

[suprasteve]

I was surfing the 'net and came across this site: Autopsy Protocol Dr. Raymond Sawchuk
The quotation below was from that site:
"We know air embolism can occur in water depths of as little as 6 to 8 feet in experiments with animals. It has been shown transpulmonic pressure differential of 80 mm of mercury is enough to rupture the wall of the alveoli or air sacs forcing air into the pulmonary vasculature. This pressure gradient corresponds to a change in water depth or pressure of approximately 4 to 6 feet."
This got me thinking about decompression depths, mainly the fact that our stops are in intervals of 10 feet (stop at 30', stop at 20', stop at 10', etc). According to that article an ascent from a decompression stop at 10 feet, assuming you were fully saturated at that depth, could result in an embolism. I'm sure the tests the article is referring to are extreme examples, but being fully saturated at 10' isn't hard to do. I have never heard of deco stops at, say 5' or anything shallower than 10', and I'm sure it isn't common to suffer an embolism when following a proper deco schedule, but it sounds a little scary. Am I missing something here?

 

[TSandM]

Air embolism is completely independent of nitrogen saturation. It's simply the expansion of the gas in the lungs, whatever that gas is. You can embolize from shallow depths in a swimming pool, and as I recall, a young student died of that last year.

Decompression stops can pose particular hazards, though, especially if executed in current where you have to stabilize yourself on a surging upline. David Swift's painful account of Denton Byers' death on the Deco Stop is a beautiful example of this.

 

[Blackwood]

I'm not quite clear on what your concern is, steve.

It seems that you are supposing that lung tissues which are saturated and introduced to a pressure gradient of >88mmHg will embolize, but that's not how it works. Inert gas loading doesn't cause the lungs to expand.

 

[suprasteve]

So I'm confusing saturation with an embolism then? I.E. if you filled your lungs at, say, 10' off your regulator and swam to the surface without exhaling, that's when you could potentially have an embolism. That makes a lot more sense, I was thinking the saturated nitrogen in the bloodstream could form large enough bubbles in those 10 feet to cause problems regardless of decompression. I figured I was missing something , thanks!

 

[DCBC]

Air embolism has to do with holding your breath on ascent and can occur in 4 feet of water, as previously stated. Gas absorption is something entirely different. I suggest that you review your gas laws and understand them before going diving.

 

[LiteHedded]

i'd think it would be worse shallow

 

[DCBC]

i'd think it would be worse shallow

Shallower than 4 feet?

 

[DaleC]

Steve,

I understand (I think) what you are thinking about.

I noticed early on that I would be very conscientious about my stop at 10-20' then I would rise rapidly the last 10' or so to the surface. During that time I also noticed that I would often have fuzzy ears and fatigue after diving. As I learned more about sub clinical DCS I realized that a lot of gas expansion was occuring in those last 15' or so. I don't know why I didn't twig to this earlier as it is quite apparent even when diving in a swimming pool (compression causing pain in ears).
I began taking the last few feet quite slowly and those symptoms I described went away.
I have no idea if they were in fact symptoms of SCDCS but now, I am far more concerned with rapid ascent from the shallows than from depth.

But, you say fully saturated at the 10' deco stop. I know that some old school divers used to do their full deco stops at shallow depths but wouldn't being fully saturated at 10' be a no no now (having blown all your deeper stops)? Adding to that wouldn't ascent being fully saturated just be called getting bent?

Wayne, when commercial divers surface with a deco obligation and quickly transfer to a ship board chamber do they risk an AGE? I know they try to do it fast so they can recompress. Most recreation oriented boats don't have chambers so I wonder if that is one reason why doing all the deco shallow has grown out of favour.

 

[LiteHedded]

Shallower than 4 feet?

nah
just shallow as opposed to deep

 

[suprasteve]

I suggest that you review your gas laws and understand them before going diving.

thanks for the tip, wouldn't want to break any laws...

As I had stated in my second post, I confused embolism with saturated gases. My thanks to those who pointed this out without devolving to the 'I'm a gooder diver cuz I'm more smarter than you' attitude, I did learn something and for that I am appreciative. But who knew that ascending slowly and breathing continuously was less effective in preventing embolisms than the proper usage of technical terminology! Guess I'd better brush up on the dictionary of scuba before I get wet again or I might forget that bubbles go up :classic: