Deep Air - Here we go again....

[DCBC]

I don't have access to the full article, just the abstract. From that, it seems that they were trying to determine if nitrox blends decrease narcosis. The conclusion seems to be: no. "It thus seems that substituting O2 for some of the N2 does not ameliorate the mild narcosis. Within the limitations of the experimental design our results suggest that O2 contributes to the narcosis of hyperbaric air."

It's not clearly known how in a mixture of gases each gas interacts with the other to increase narcosis. For argument sake, lets say that O2 in-itself is non-narcotic. If however a higher PPO2 exists, it causes the current narcotic affect of Nitrogen to increase. It thereby acts as a trigger for the nitrogen in the same way as CO2 is believed to, as opposed to oxygen being narcotic itself.

When referring to Dr. Hamilton's research (which has been referenced by the "other side") Dr. Sawatsky mentions that Dr. Hamilton stated that: "a difference in narcosis could not be detected when they switched between a high and low oxygen in an oxygen-enriched air mix." Obviously this does not indicate that oxygen is narcotic, as the resulting narcosis wasn't increased or decreased. Dr Sawatsky goes on to state: "There are many problems with the research that has been done trying to determine if oxygen is narcotic or if it increases the narcotic effects of other gases." He believes that there has been no evidence to-date to indicate the former.

Another way of looking at this is by eliminating nitrogen from the breathing mixture all-together, such as Heliox. If oxygen was narcotic, wouldn't there be some evidence that oxygen produces narcosis? It hasn't. Now I'm not saying that it doesn't but believe that the diver would OxTox long before any narcotic effects were evident.

Now to put it in perspective, does oxygen play a role in nitrogen narcosis? Possibly, CO2 definitely does. Is a recreational technical diver wise to work in END into their calculations? Absolutely. It must be kept in-mind however, that this is not really understood. END has no firm scientific proof and remains a "theory of practice" as far as the hyperbaric community is concerned. It does however place the diver on the correct side of safety for recreational purposes.

 

[DCBC]

I wish you would pick a position...

It's pretty clear actually. I posted a study into the deaths of almost 1000 divers. Suffice it to say that narcosis wasn't even listed as a contributing factor in one death.

 

[DCBC]

...we have absolutely no way of knowing how more or less Narc'ed someone was.

Exactly. So posting a list of individuals who died with hypothetical ENDs >100' on a public forum solves nothing and is in bad taste. Consider the families of the victims.

 

[LiteHedded]

It's not clearly known how in a mixture of gases each gas interacts with the other to increase narcosis. For argument sake, lets say that O2 in-itself is non-narcotic. If however a higher PPO2 exists, it causes the current narcotic affect of Nitrogen to increase. It thereby acts as a trigger for the nitrogen in the same way as CO2 is believed to, as opposed to oxygen being narcotic itself.

When referring to Dr. Hamilton's research (which has been referenced by the "other side") Dr. Sawatsky mentions that Dr. Hamilton stated that: "a difference in narcosis could not be detected when they switched between a high and low oxygen in an oxygen-enriched air mix." Obviously this does not indicate that oxygen is narcotic, as the resulting narcosis wasn't increased or decreased. Dr Sawatsky goes on to state: "There are many problems with the research that has been done trying to determine if oxygen is narcotic or if it increases the narcotic effects of other gases." He believes that there has been no evidence to-date to indicate the former.

Another way of looking at this is by eliminating nitrogen from the breathing mixture all-together, such as Heliox. If oxygen was narcotic, wouldn't there be some evidence that oxygen produces narcosis? It hasn't. Now I'm not saying that it doesn't but believe that the diver would OxTox long before any narcotic effects were evident.

Now to put it in perspective, does oxygen play a role in nitrogen narcosis? Possibly, CO2 definitely does. Is a recreational technical diver wise to work in END into their calculations? Absolutely. It must be kept in-mind however, that this is not really understood. END has no firm scientific proof and remains a "theory of practice" as far as the hyperbaric community is concerned. It does however place the diver on the correct side of safety for recreational purposes.

also increased co2 retention.

 

[Blackwood]

Another way of looking at this is by eliminating nitrogen from the breathing mixture all-together, such as Heliox. If oxygen was narcotic, wouldn't there be some evidence that oxygen produces narcosis? It hasn't.

In the study I cited, they introduced the subjects to pure hyperbaric (1.7ATM) oxygen and noted a decrease in cognitive performance.

"The oxygen effect on arithmetic skill consisted of decrements in both speed and accuracy of performance. Thus the number of problems attempted decreased by approximately 10%, and the number of problems solved correctly dropped from about 90% at 1.3 ATA air to 89% at 1.7 ATA O2."

The 1% drop in correctly solved problems is a "who cares" kind of conclusion to me, but a 10% drop in problems attempted is a bit scary.

Now I'm not saying that it doesn't but believe that the diver would OxTox long before any narcotic effects were evident.

Sure, that's always the most stringent concern in selecting a breathing gas.

 

[DCBC]

In the study I cited, they introduced the subjects to pure hyperbaric (1.7ATM) oxygen and noted a decrease in cognitive performance.

Although human performance decrease doesn't necessarily have to be attributable to narcosis, I'm not in any position to dispute the findings of this study. But it's worthwhile to keep in-mind that the results were only based on 8 participants; which isn't something that would necessarily swing the current accepted position of the hyperbaric community.

It also doesn't support the personal experience of thousands of divers. Even back in WWII, oxygen re-breathers were used at PPO2s of 2 ATM without any indication of narcosis. The commercial diving community possesses the greatest experience of divers breathing mixed-gas mixtures at various partial pressures. Again, oxygen narcosis has never been a consideration.

With the science largely unknown, no one can categorically say the way it is. To-date however, it would seem that no one has been able to provide the hyperbaric community with a convincing argument that oxygen narcosis exists.

 

[PfcAJ]

It's pretty clear actually. I posted a study into the deaths of almost 1000 divers. Suffice it to say that narcosis wasn't even listed as a contributing factor in one death.

So what? If a diver is narc'd, it would stand to reason that they are more likely to run out of gas or get entangled, etc.

The ONLY reason people are diving deep air is to save a buck, and people keep getting injured or killed that just 'happen' to be diving deep air/ high END's. Hmm... It doesn't take a PhD to figure this stuff out.

Recreational (NOT COMMERCIAL) diving is supposed to be a fun activity. Why not stack the odds in your favor by maintaining a relatively shallow END?

 

[ucfdiver]

Hmm... It doesn't take a PhD to figure this stuff out.

Would you trust a PhD researcher over a commercial deep air diver? :shocked2:

 

[DCBC]

The ONLY reason people are diving deep air is to save a buck, and people keep getting injured or killed that just 'happen' to be diving deep air/ high END's.

You really don't get it do you? You live in Orlando and have the luxury of having a disposable income and everything your heart may desire available to you. Helium is not available everywhere. What about that don't you understand?

 

[DCBC]

Would you trust a PhD researcher over a commercial deep air diver? :shocked2:

I would chose the worldwide experience of 60 years of diving over 1 researcher who can't make a convincing argument to the hyperbaric medical community. Wouldn't you?