A.G.E. Questions and answers

[Cave Diver]

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.

Yes, I almost always take aspirin pre-dive.

Cold temps cause blood vessels to restrict, reducing blood flow and off gassing efficiency. It's much more desirable to be warm during the dive, or at least deco.
Commening on the PH levels etc. is beyond my knowledge on the subject.

 

[scubapolly]

Ok, just trying to make sure I follow everything:

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.

I agree with you as far as this is what happens, but don't think the pressure of the surrounding tissue has anything to do with why the bubbles stick together.

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).

The bubbles are formed when the ambient pressure decreases and thus decreases the amount of gas which can be dissolved in the tissues (henry's law). So I am still following you.

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.

Do you mean Nitrogen? The bubbles should not have much oxygen in them. They are composed primarily of Nitrogen. Addition of oxygen in the breathing gases would increase the partial pressure of oxygen in the blood, thus decreasing the partial pressure of the nitrogen (dalton's law). Therefore the partial pressure of nitrogen in the bubble would be greater than the partial pressure of nitrogen 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.

Here I am not following you at all. Could you explain that part?

Using a gas with a lower partial pressure such as helium can also increase the rate that it diffuses out of the bubble.

So what you are saying is introducing any new gas would accomplish this so long as the partial pressure of the gas in the mix you are breathing is lower than the partial pressure of that gas in the bubble? obviously we are limited by the gases which we can safely breathe.

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.

 

[scubapolly]

every time I pop an aspirin before a dive, I wonder if the acidity effects my blood ph.....probably not.

I don't think there would be an overall change in blood pH with taking an aspirin. You are talking such a huge volume of blood, and such a small quantity of asprin. I think you would have a greater change in pH caused by drinking a glass of lemonade before a dive. Your blood is buffered to prevent such changes.

 

[Diver0001]

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.

John, can you run us through your thinking on this again? What you're saying sounds to me like it contradicts the gas laws.

The way I see it, the O2, like all the gasses in your body will just go where ever it can according to the gas laws. Some of it will get into the bubbles, i guess, but it's poorly soluble in water and it's unlikely (read - I think it's impossible) for the O2 to be getting into the bubbles in huge concentrations and dissolving them.

From what I know about offgassing, the bubble is dissolving because no more inert gas is being inspired and offgassing is occurring in the lungs thereby constantly diminishing the partial pressure of inert gasses throughout the system, including outside of bubbles or tissues where the gas is present in either gaseous or dissolved form.... Dalton's law & Henry's law (diffusion of gasses in partial pressures) governs the distribution of gasses in the system. In other words, the O2 doesn't do anything except act as a placeholder so you can stop inhaling inert gas.

The way I'm reading you, you appear to be saying that the O2 is working like little nano-bots, getting into bubbles at higher pressures than the gas laws will allow and forcing them to disintegrate. Maybe I'm confused about what you wrote but if that's the case, then I'm not the only one.

R..

 

[Cave Diver]

Ok, just trying to make sure I follow everything:

I agree with you as far as this is what happens, but don't think the pressure of the surrounding tissue has anything to do with why the bubbles stick together.

Note that I said "held together" not "stick together." The implication is that the surface tension is what keeps the bubbles from "popping", not that it keeps them in close proximity to each other. Sorry if that terminology caused any confusion.

Regarding the confusion on the other part, let me see if I can find references that explain it better than I did. While I understand a lot of the concepts, explaining it is not my forte and I'm obviously not making myself clear.

 

[lamont]

O2 actually diffuses into acqueous tissue and bubbles in blood faster than N2 which is actually faster than He.

That means that if you go onto 100% there will be an isobaric counter-diffusion effect where the bubble initially grows in size. If you go onto 50/50 O2/He then the slower ongassing helium (yeah, you read that correctly) will prevent that initial bubble growth. O2 is still going to be better in the long run though since it washes out all of the inert gases.

Flipping that around, I'd expect that if you form large bubbles of He in the blood, particularly early in the deco, you've got a serious problem.

 

[TheRedHead]

Lamont, conventional wisdom says that He ongasses faster than N2. What's the story behind this assertion?

 

[lamont]

Lamont, conventional wisdom says that He ongasses faster than N2. What's the story behind this assertion?

differences in the oil-gas partition coefficient and blood-gas partition coefficient for those gases.

 

[Cacia]

Note that I said "held together" not "stick together." The implication is that the surface tension is what keeps the bubbles from "popping", not that it keeps them in close proximity to each other. Sorry if that terminology caused any confusion.

Regarding the confusion on the other part, let me see if I can find references that explain it better than I did. While I understand a lot of the concepts, explaining it is not my forte and I'm obviously not making myself clear.

Hey-- I get a lot from all of it.. Explaining things is really putting yourself out there, which is why so few around here attempt it. (Lamont and Rob being exceptions, of course) I learn a lot through the discussions even about the terminology. I remember surface tension, surfactants and that stuff from Chem....vaguely. Water, has a high ST I think, because of the strong_____bonds. Okay...that is the total of my knowledge. So gear those explanations towards ME okay? Doc V will be in here in a second to tell me I need to take the class again. (TRUE)

 

[stardiver]

Hey-- I get a lot from all of it.. Explaining things is really putting yourself out there, which is why so few around here attempt it. (Lamont and Rob being exceptions, of course) I learn a lot through the discussions even about the terminology. I remember surface tension, surfactants and that stuff from Chem....vaguely. Water, has a high ST I think, because of the strong_____bonds. Okay...that is the total of my knowledge. So gear those explanations towards ME okay? Doc V will be in here in a second to tell me I need to take the class again. (TRUE)

Hydrogen bonds.

Covalent bonds hold the H's to the O to make H2O. Hydrogen bonds are the attraction of the positively charged H on one molecule to the high electron density around the very electronegative O of another molecule. These bonds cause many of the unique properties of water, including surface tension.

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