Can Someone Provide Me Alittle Help/Info?

Yankee Rebel

i understand that different peoples physiology results in different effects.. but ive been trying to locate information on the absorption rate of N2 into the body.
can anyone help me out?

what exactly im after is is there a ball park rate at wich the average human body will absorb N2 out of the loop at depth?

yes this question probly reflects clearly my level of training.... but i was wondering all the same.

if this post is inappropriate please remove it.

thankyou for your time
Yankee Rebel

nigelh

The way you've phrased the question sound like you're asking for a quick précis of decompression theory but I suspect you're interested in quantities.

When I first thought about deco theory I wondered how much gas is actually involved and search as I might I could not find anybody quoting it. However a dig in the usual sources (The old Rubber book) turned up the molar fraction solubility for nitrogen in water and lipids that leads me believe that at 0.79bar ppN2 (on the surface) we have about 0.72 grams of dissolved nitrogen in a 70Kg person. So a good exposure to breathing air at 25 meters will give us 2.5gms of nitrogen which is 3.2 surface litres.

I can't put time/rate to it on the stuff I have to hand, although I'd expect most of it to be in the first ten minutes, but is that what you are after?

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nigelh

Yankee Rebel

hi Nigel!!!
i think what im looking for is a time rate of absorption. like some sort of a baseline..
for example if the human body absorbed "X" liters of N2 per "Y" amount of time per atmosphere depth.
i appreciate your initial responce alot though as it has taught me something as well.

Yankee Rebel

tibby

I'm no decompression expert or anything of the sort so you can ignore my comment if you wish.
I belive you can have a very large range of nitrogen absorbtion rate due to variables such as multiple tissue densities found in the body, physical work rate, breathing rate, water temperature, body hydration...so it may not be a constant or measurable on a realistic scale if considering the entire human body. Buhlmann came up with 16 tissue compartments in order to make some sense of these variables but I doubt it's a true representation of all tissue densities and gas diffusion rates. It is probably better than the earlier haldanian model though.
I also belive that we start on gassing nitrogen as soon as the breathing gas pressure increases (start descending as opposed to below 30ft as the Navy tables suggest) even in the first few feet but initially it takes place in the "fast" (or soft, highly vascularized) tissues which in turn are as fast off gassing as soon as the gas pressure is reduced so it's of minor consequence. With longer exposure the slower tissues start on gassing and so forth until saturation. I guess if you would pick a particular type of tissue there may be data out there supporting a time/pressure absorbtion rate but how would that help? I got skin bends and shoulder joint bends at the same time so does that mean I can ignore my muscles or other organs? Probably not.
This is probably stuff you already know, if not, I hope it helps.
Tibby

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Does the voice of reason change when you add helium to the mix?...hmm

mountain diver

you could try this web site, it has a good pdf file to down load.
but, you will have to sign in first. hope this helps.
http://jap.physiology.org/cgi/reprint/20/5/927.pdf

all the best.