Gue Vs Tdi

[jonnythan]

I've always thought of the oxygen window as a theary. How does this window follow Dalton's law (laws of partial pressure)? Beacuse it seems odd that the human body, saturated with N2, can change the physics of Daltons law , by changeing to 100% O2, for an oxygen window and not bend the diver. I.E A N2 saturated diver changes gas to 100% O2 , this releaves the N2 partial pressure and can bend a diver at 20 feet. Just a thought?

It doesn't quite work like that. What matters for bubble formation is the saturation level of the tissue in relation to the ambient pressure, no matter what the partial pressures are. I'm not really sure what Dalton's law has to do with it. Breathing 100% O2 vs 50% at 20 ft will mean that in the lungs, there is greater diffusion of N2 into the lungs because of a higher gradient. However, since the ambient pressure is the same neither is more likely to cause gas to actually come out of solution.

 

[nova]

It doesn't quite work like that. What matters for bubble formation is the saturation level of the tissue in relation to the ambient pressure, no matter what the partial pressures are. I'm not really sure what Dalton's law has to do with it. Breathing 100% O2 vs 50% at 20 ft will mean that in the lungs, there is greater diffusion of N2 into the lungs because of a higher gradient. However, since the ambient pressure is the same neither is more likely to cause gas to actually come out of solution.

sound like your confusing Boyles law with Daltons law.but with either, the rapid pressure change can, and does, cause the formation of bubbles.

that was the point that was driven home in my TDI course. Avoid rapid pressure changes! Both ata and partial pressure.

maybe I had a good instructor. Do you feel your tech instructor has a firm grasp on dive science?

 

[jonnythan]

sound like your confusing Boyles law with Daltons law.but with either, the rapid pressure change can, and does, cause the formation of bubbles.

that was the point that was driven home in my TDI course. Avoid rapid pressure changes! Both ata and partial pressure.

maybe I had a good instructor. Do you feel your tech instructor has a firm grasp on dive science?

I'm not going to belabor the point, but you are right when you say that rapid pressure change can cause the formation of bubbles. The thing you're missing is that there's no pressure change going from, say, EAN32 to O2.

 

[cornfed]

sound like your confusing Boyles law with Daltons law.but with either, the rapid pressure change can, and does, cause the formation of bubbles.

Both of those are -gas- laws. They apply to gas mixtures not dissolved gases.

 

[WarmWaterDiver]

sound like your confusing Boyles law with Daltons law.but with either, the rapid pressure change can, and does, cause the formation of bubbles.

that was the point that was driven home in my TDI course. Avoid rapid pressure changes! Both ata and partial pressure.

maybe I had a good instructor. Do you feel your tech instructor has a firm grasp on dive science?

For the gradient / gas transfer, diffusion and / or effusion are involved, for gas transfer to and from the tissues and bloodstream through the alveoli. If I remeber my physical chemistry / mass transfer anywhere close to correctly, it would be Graham's laws that would be most applicable to the point of the discussion. Take a look and see. If you didn't receive that from your instructor, then my judgement is that instructor didn't have a good grip on the science involved.

http://www.molecularsoft.com/data/help/Gas_Laws-Effusion_Diffusion.htm

http://chemed.chem.purdue.edu/demos/main_pages/4.19.html

http://chemed.chem.purdue.edu/demos/moviesheets/4.17.html

 

[true]

Very well stated. . .
Just a passing comment/question, wondering how all this will apply to the forthcoming GUE Recreational Diving Course . . .
Will GUE split into two divisions a la TDI/SDI?
(Good & Safe Diving All --My Clock is countin' down & I'm outta here! )

Kevrumbo, the short answer is no. Here's the longer answer: The openwater course will be very true to the spirit of the founding of GUE-- the return to the sort of rigorous sort of dive training that one might have expected in an academic course at a university (or the way that courses were taught before dive training became a somewhat big business). It isn't going to attract someone with a casual flirtation with diving-- the person who wants to take a Saturday afternoon to get a c-card so they can do one dive in Cancun on their honeymoon will still be looking for a $50 course offered by one of the larger agencies. That said, one of the biggest problems with the dive industry is that so many people come out of the quickie cert courses unsure of their skills and uncomfortable with diving on their own; the industry has a dizzying turnover rate of people who certify, dive a few times on vacation, and then never dive again. The goal of the GUE openwater course will be to create an independently thinking diver who is comfortable enough with their skills to want to continue diving. The instructors that I've talked to are very excited because it is the sort of course that they (as technical and cave dive instructors) would teach their family and friends if they were to design the "perfect" openwater course.

That said, most people on the boards loose sight of the fact that teaching is only one component of GUE. The (small) staff is still focused on larger issues of education-- the Quest journal is one of the few dive publications run as if it were an academic publication, there's a very interesting DVD on the history and theory of decompression on the near horizon, and GUE is hosting its first conference in the fall. Most of the instructors are involved in exploration and research-- there's work being done with the Florida Geologic Survey on the Floridan aquifer, work with the Italian government agency responsible for preservation of antiquities to survey Roman wrecks, and exploration in the Baltic. The organization, by design, will never have aspirations to manage hundreds (let alone thousands or tens of thousands) of instructors. Instead, I imagine we'll see what we've already seen with DIR so far-- the larger agencies will recognize the impact and begin to incorporate what GUE started into their own courses. Although it's more than a little frustrating to see the message diluted and used for other ends, I have to be pragmatic enough to amazed that its had an impact on the industry and the sport as a whole. I think most people would be shocked to learn how small of an organization GUE is; give its short history and limited resources, the influence is already disproportionate to its size. It is a testament to the power of a good idea.

Best,

anthony
true(at)gue

 

[nova]

For the gradient / gas transfer, diffusion and / or effusion are involved, for gas transfer to and from the tissues and bloodstream through the alveoli. If I remeber my physical chemistry / mass transfer anywhere close to correctly, it would be Graham's laws that would be most applicable to the point of the discussion. Take a look and see. If you didn't receive that from your instructor, then my judgement is that instructor didn't have a good grip on the science involved.

http://www.molecularsoft.com/data/help/Gas_Laws-Effusion_Diffusion.htm

http://chemed.chem.purdue.edu/demos/main_pages/4.19.html

http://chemed.chem.purdue.edu/demos/moviesheets/4.17.html

and this relates to the oxygen window?and please explain gradient pressures that are involved?

 

[nova]

Both of those are -gas- laws. They apply to gas mixtures not dissolved gases.

they apply to dissolved gasses under pressure. everything about diving revolves around pressure

 

[jonnythan]

and this relates to the oxygen window?and please explain gradient presures that are involved?

I would respectfully suggest you seek a qualified instructor to teach you the difference between gas diffusion in liquids and bubble formation. The internet may not be the best place to learn/

 

[nova]

I would respectfully suggest you seek a qualified instructor to teach you the difference between gas diffusion in liquids and bubble formation. The internet may not be the best place to learn/

It was a retorical question jonnythan, I didn't expect an answer. That's one of the nice things about knowing what I'm talking about, not everyone gets it, that's just the way life is

and Graham's law of effussion deals with gasses that are of the same PRESSURE, I'm sure your not going to tell me the PARTIAL PRESSURE of O2 and the PARTIAL PRESSURE of N2 are the same in the human body at depth?