Why Nitrox

[espenskogen]

I have read them, and I do understand your belief that fatigue is caused by subclinical DCS. I once thought that might be a logical explanation as well. It would explain the differences in how some people feel depending on their gas and also why I feel no difference. The problem with that concept is the lack of evidence that subclinical DCS actually causes fatigue.

I think we can all agree we'd like to see more double blind studies to answer additional questions on this topic.

I see your point. Personally, I've had a DCS hit that was quite serious, and in my case I was certainly knocked out for a while - Felt like death.

It is difficult to do a do accurate observations on this however, as not many want to bend themselves on purpose.

Either way - We agree that microbubbles or subclinical dcs should be avoided, and that Nitrox might assist in avoiding that.

Whether the symptoms include fatigue is probably less relevant.

 

[Pyrofish]

I don't believe that would explain it. At a PPO2 of .21 bar (ie O2 Exposure on the surface) the haemaglobine is typically saturated 99% with O2. Increasing the partial pressure would account for a very small increase in O2 saturation in the blood plasma itself (Which is mainly water), but because O2 doesn't dissolve in water very easily, the increased oxygen uptake in the body is relatively insignificant.

The increase in PPO2 is mainly to reduce the PPN2, by replacing nitrogen with a gas which we metabolise hence during off-gassing it doesn't cause bubble trouble.

E

Something similar occurs to athletes who live at high altitudes and train in lower, more oxygen rich altitudes. They can work longer and more efficiently. This has always, I believe, been attributed to higher O2 concentrations at sea level.

I know that the higher O2 concentrations are their for reduction of nitrogen exposure, however, there are side effects to most everything we do.

This is terribly unscientific of me, because the hypothesis came first, and then I looked for a way to prove it, which is obviously not the way it's supposed to work, but then this whole thread has been that way , but this site:
http://www.cdli.ca/~dpower/resp/exchange.htm#Cellular
If I'm reading it correctly, says that haemoglobine releases more of the oxygen it's carrying in the presence of higher concentrations of O2. There are also more than a few studies that show increased endurance and general health when the participants have exercised in higher PPO2.

Just throwing it out there, I could very easily by wrong

 

[Pyrofish]

Define average size. I'm about 180 lbs and 49 years old. I feel no difference.

Average size is relative. 180lbs is average for someone, oh I don't know, 5'-9". You know if you're average or big. 180lbs wouldn't be average for someone 5'-3". I'm 6'-1" and 300lbs, I'm not average My buddy is 5'-11" and 250lbs, not average either. It's just an informal survey though.

Put yourself in one category or the other, and say yes or no as to whether you feel better after diving nitrox.

Bigger and/or older: yes or no
Younger and/or average: yes or no

If you're still a very active person at 49, you probably wouldn't consider yourself older. Another buddy of mine is 52, smokes, and drinks alot, but is of average size. He would consider himself older. He's never dove nitrox though, so I can't count him

 

[espenskogen]

Something similar occurs to athletes who live at high altitudes and train in lower, more oxygen rich altitudes. They can work longer and more efficiently. This has always, I believe, been attributed to higher O2 concentrations at sea level.

I know that the higher O2 concentrations are their for reduction of nitrogen exposure, however, there are side effects to most everything we do.

This is terribly unscientific of me, because the hypothesis came first, and then I looked for a way to prove it, which is obviously not the way it's supposed to work, but then this whole thread has been that way , but this site:
http://www.cdli.ca/~dpower/resp/exchange.htm#Cellular
If I'm reading it correctly, says that haemoglobine releases more of the oxygen it's carrying in the presence of higher concentrations of O2. There are also more than a few studies that show increased endurance and general health when the participants have exercised in higher PPO2.

Just throwing it out there, I could very easily by wrong

Yes, but I think the reason behind the altitude training is that the body learns to deal with lower O2 saturation. If you have a chat to a paramedic, they have a device in the ambulances which measures the blood oxygen saturation. If you stick that on your finger whilst sitting at the surface, I think it will read between 95 - 99 % saturation. The haemoglobine can't carry more than it can carry, and that's the reason you don't get any added 'energy boost' by exposing yourself to high O2 concentrations. I have a feeling altitude training makes the body produce more haemoglobine, so that even if each proteine can only get 50 % saturated (for example), it's enough of them to supply all organs with sufficient O2.

As for the link you provided - I think you're reading it wrong. What it says is that if you expose plasma to a PPO2 of 100 mm HG (Which means Mercury millimetres - It's a term for pressure used by meterologists primarily) it will only be saturated with a very small amount of O2. This is because O2 does not dissolve easily in water - And plasma is predominately water. If you add haemoglobine to the mix however, the haemoglobine will bind easily with the O2, and that's what causes our blood flow to work. This is also why increasing the PPO2 has no added benefit, because the increased PPO2 would increase saturation in the plasma - but not in the haemoglobine, as the proteine binding isn't controlled by partial pressure. And since the O2 doesn't dissolve easily in plasma, the increase in blood oxygen would be very low, regardless of partial pressure.

E

 

[Pyrofish]

Yes, but I think the reason behind the altitude training is that the body learns to deal with lower O2 saturation. If you have a chat to a paramedic, they have a device in the ambulances which measures the blood oxygen saturation. If you stick that on your finger whilst sitting at the surface, I think it will read between 95 - 99 % saturation. The haemoglobine can't carry more than it can carry, and that's the reason you don't get any added 'energy boost' by exposing yourself to high O2 concentrations. I have a feeling altitude training makes the body produce more haemoglobine, so that even if each proteine can only get 50 % saturated (for example), it's enough of them to supply all organs with sufficient O2.

Actually the high altitude training increases red blood cells, well EPO which increases red blood cell production in bone marrow, and a checmical 2.3DPG. DPG which aids in the delivery of oxygen to the muscles. Preface this with, this is what I read somewhere. May or may not be true

As for the link you provided - I think you're reading it wrong. What it says is that if you expose plasma to a PPO2 of 100 mm HG (Which means Mercury millimetres - It's a term for pressure used by meterologists primarily) it will only be saturated with a very small amount of O2. This is because O2 does not dissolve easily in water - And plasma is predominately water. If you add haemoglobine to the mix however, the haemoglobine will bind easily with the O2, and that's what causes our blood flow to work. This is also why increasing the PPO2 has no added benefit, because the increased PPO2 would increase saturation in the plasma - but not in the haemoglobine, as the proteine binding isn't controlled by partial pressure. And since the O2 doesn't dissolve easily in plasma, the increase in blood oxygen would be very low, regardless of partial pressure.
E

I think you're ref. to the paragraph on Gas Transport which deals in pressure (mm HG). The next paragraph, Oxygen transport deals with O2 concentrations. Specifically:

Over the range of oxygen concentrations where the curve has a steep slope, the slightest change in concentration will cause haemoglobin to load or unload a substantial amount of oxygen. Notice that the steep part of the curve corresponds to the range of oxygen concentrations found in the tissues. When the cells in a particular location begin to work harder, e.g. during exercise, oxygen concentration dips in that location, as the oxygen is used in cellular respiration. Because of the cooperation between the haem groups, this slight change in concentration is enough to cause a large increase in the amount of oxygen unloaded.

Now that I think about it, aren't we breathing air at higher pressure when we're down anyway? Wouldn't the mmHG affect us also?

Of course, this is internet information, and we all know how reliable that can be Worse yet, it's Canadian I believe, and you can't trust those sneaky Canadians!

 

[espenskogen]

Actually the high altitude training increases red blood cells, well EPO which increases red blood cell production in bone marrow, and a checmical 2.3DPG. DPG which aids in the delivery of oxygen to the muscles. Preface this with, this is what I read somewhere. May or may not be true



I think you're ref. to the paragraph on Gas Transport which deals in pressure (mm HG). The next paragraph, Oxygen transport deals with O2 concentrations. Specifically:

Over the range of oxygen concentrations where the curve has a steep slope, the slightest change in concentration will cause haemoglobin to load or unload a substantial amount of oxygen. Notice that the steep part of the curve corresponds to the range of oxygen concentrations found in the tissues. When the cells in a particular location begin to work harder, e.g. during exercise, oxygen concentration dips in that location, as the oxygen is used in cellular respiration. Because of the cooperation between the haem groups, this slight change in concentration is enough to cause a large increase in the amount of oxygen unloaded.

Now that I think about it, aren't we breathing air at higher pressure when we're down anyway? Wouldn't the mmHG affect us also?

Of course, this is internet information, and we all know how reliable that can be Worse yet, it's Canadian I believe, and you can't trust those sneaky Canadians!

Yes, get what you are referring to. Red blood cells are the haemoglobin part of the blood, so this confirms what I said above. When it comes to the oxygen loading and unloading of the haemoglobin, this is actually ruled by Daltons Law of Partial Pressures - (http://www.science.uwaterloo.ca/~cchieh/cact/c120/abcdgas.html) - When we exercise, the body metabolizes oxygen and produces CO2. When the blood is arriving in the lungs, the partial pressure of O2 in the lungs is higher than the partial pressure of O2 in the blood, and the partial pressure of CO2 in the blood is higher than the partial pressure of CO2 in the lungs. This makes the CO2 rush from the blood to the lungs, and the O2 in the lungs rush to the blood. This is the effect the article is referring to. (Incidentially, it's the same effect, but with N2 that causes decompression illness - It's all interlinked, you see..)

This would not be affected in any way by having a O2 partial pressure higher than 21 millibar. The article here deals with changes in PPO2 in the red blood cells as a result of organs metabolizing O2 and producing CO2.

The higher pressure at depth would affect us to a degree, but because of the poor solubility of Oxygen in plasma, it doesn't affect us in any noticable way - The PPO2 will need to be much higher than what we can survive to actually make an impact on plasma saturation.

 

[SharkRider]

After spending some time searching for information I can't seem to find a simple thread explaining the benefits/disadvantages to diving with Nitrox. I can't beleive that this hasn't been discussed so can some post a link or discuss them here?

Thanks

Why Nitrox? That is a great question.

The answer is that LDS's make more money selling it to you... so they espouse the benefits... which are insignificant for recreational divers.

The benefits:
Longer bottom times are possible for "mid range" diving... this is assuming you have enough air in your tank (your consumption rate is good enough) to allow you to take advantage of the increased bottom times. Most recreational divers and especially newer divers suck air so fast that they need to surface (low on air) before the additional bottom times could be taken advantage of.

You feel better... this is something some Nitrox divers swear by. They say that the extra 02 in the mix gives them more pep in their step when the diving day is over. I say hogwash. Theoritically higher 02 levels will invigorate the body... but at the typical 32 percent Nitrox mix... a human would not be capable of noticing a difference. It's all in their mind. Which I suppose could mean just thinking it makes them feel better - does actually make them feel better. Breathing a significantly increased partial 02 such as 70, 80 or even 100% will definately make you feel better. I've had 100% after a dive and I felt great. The problem is you can not dive with these mixes because of oxygen toxicity... so ...

Save your money for now... at least until you have excellent air consumption. Then if you want to waste your money... go ahead. I have dove with both 02 and Nitrox and I decided the Nitrox was not worth the money. While I'm Nitrox Certified and an Instructor, I tell all my students to forget the Nitrox crap.

If you want to get into technical diving such as deeper, wreck penetration, cave diving etc... then learn more about Nitrox and TriMix. While these gases can not be safely dove at depth due to the aforementioned 02 Tox... they are used at varying points during ascents.

Happy Diving

 

[DiveGolfSki]

He's actually entirely correct.
Now, O2 is mildly narcotic, but the effect of O2 narcosis only comes into effect at high partial pressures. So you might experience it a bit at a PP02 of 1.6 or higher, but it is far less narcotic than Nitrogen - Probably more on par with Helium, in fact.
For a detailed reference on this read: http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10849687&dopt=Citation

In an earlier thread on the merits of nitrox, this was discussed. Here's a response to the issue from String:

Most science would disagree with that:

http://www.techdiver.ws/trimix_narcosis.shtml

http://www.divefortyoung.com/whatisnitrox.html



Dont believe that? Try IANTD:

http://www.iantd.co.uk/IANTD/pages/TA Kev Gurr.htm

PADI do(did?) teach oxygen was to be considered as narcotic as oxygen in their enriched air manual.

Given the latest thoughts about mechanisms for narcosis oxygen indeed should be as or more narcotic than nitrogen as well.

 

[espenskogen]

In an earlier thread on the merits of nitrox, this was discussed. Here's a response to the issue from String:

This was copied out of the IANTD article:

Problems with Oxygen Oxygen would appear to be the answer to all our problems, the more the better. Hmmm perhaps not. Oxygen is toxic, narcotic, can cause temporary bends and is a vasoconstrictor. What does this mean to us as divers? Oxygen is potentially twice as narcotic than Nitrogen. The upside being that at the partial pressures of oxygen within which we normally operate (0.21 to 1.6), oxygen narcosis is not a relevant issue.


It seems you are right - Oxygen is narcotic to a degree. However, as it is the PPO2 that dictates narcosis (And before we reach narcotic O2 pressures, we have other worries with O2), it can be controlled by using appropriate gasses for the depths you're diving to. By reducing PPN2 by increasing PPO2, you can reduce the overall narcosis, by avoiding the PPg to reach narcotic levels.

Research has indicated that the narcosis effect of O2 could not be proven in clinical studies. This is not to say that it is nonexistent - But that it is not conclusive. Either way, O2 is required , and during deep dives it's a tradeoff between deco times and the theoretical narcosis of Oxygen and Helium.

We know Nitrogen is narcotic at high PPN2. (Most notably seen at PPN2 around 3.5 bar and higher). I expect Oxygen might prove to be narcotic around the same PPO2 (3.5 bar or higher) but it is irrelevant, as we would be toxed at that kind of PPO2 anyway.

There are theories that Helium is also narcotic under high PPhe, but it is infinately less so than the other gasses we could use. (Maybe with the exception of Hydrogen or Xenon, but Hydrogen is explosive, and Xenon is very rare, and hence very expensive.)

When you calculate Equivalent Air Depths with trimix, you can choose to take into account O2 narcosis and He Narcosis as well - This will give different EAD's - But at the end of the day, it's just a tradeoff between different degrees of narcosis. If you go really deep (As in record depth deep) I expect you would experience narcosis regardless of the gas mix - But we probably ought to ask Nuno Gomes or Mark Elliyat about that.

It is however beyond doubt that high PPO2 within the NOAA tables are far less narcotic than Nitrogen at depth - We can prove that easily by breathing 100% O2 at 6 meters and see if we feel narked. At that depth, we would have as high PPO2 as ever, so if we don't notice narcosis from O2 there, then I don't think we need to account for O2 Narcosis at depth, when PPO2 at no point exceeds 1.6 bar.

Edit: Bit of a typo there - I wrote Xenon instead of Neon. Xenon is not useful as a breathing gas - It is rather narcotic. Neon on the other hand is useful in terms of narcosis and in that it doesn't distort speach at depth, but it carries a rather heavy decompression obligation, and treatment of dcs caused by Neon is an absolute nightmare.

 

[gt3073b]

There are theories that Helium is also narcotic under high PPhe, but it is infinately less so than the other gasses we could use. (Maybe with the exception of Hydrogen or Xenon, but Hydrogen is explosive, and Xenon is very rare, and hence very expensive.)

According to this page (and others) He is only 23% narcotic relative to N2.
http://www.techdiver.ws/exotic_gases.shtml#2

At depth, helium causes problems other than narcosis.

http://en.wikipedia.org/wiki/High_pressure_nervous_syndrome

According to the Meyer-Overton Hypothesis the mechanism for narcosis is believed to be tied to fat solubility of the various gasses and interference with the lipids in nerves. Its not a coincidence that nitrous oxide is equally good in whipped cream and anesthesia.

Bryan.