Tissue stress associated with bubble formation; potential benefits of diving enriched air

[boulderjohn]

so you have to either dive on NITROX or cut bottom time. At least, this is my understanding of the article I found.

This is a common and absolutely silly statement made in many places. It is featured regularly in Dive Training Magazine, where Alex Bryskie is adamant about it. The theory is that you can either use nitrox to extend bottom times, or you can dive nitrox on an air table and this get a little level of increased safety. That's it. You have only two choices--nothing in between. That false dilemma assumes that once you enter the water, you have no choice but to stay for the full duration of NDLs. If the table says you can stay for 150 minutes at 50 feet, then, dammit, you have to stay for 150 minutes, no matter how much you want to surface earlier. Better bring a lot of gas.

I have done comparisons of this kind a number of times. Here we go again.

Diver A is diving on air, using the PADI tables. He does the first dive to 80 feet for the maximum time of 30 minutes. He is in pressure group R. He has a one hour surface interval, putting him in pressure group F, and then he does a 50 foot dive to the maximum time of 56 minutes. This puts him in pressure group X.

Diver B is diving on EANx 36, using the PADI tables. He does the first dive to 80 feet for 40 minutes. He is in pressure group P. He has a one hour surface interval, putting him in pressure group E, and then he does a 50 foot dive for 70 minutes. This puts him in pressure group R.

Diver A had a total of 86 minutes of bottom time. He stayed to the end of his NDL's on each dive. He ended in pressure group X.

Diver B had a total of 110 minutes, He was 15 minutes short of NDLs on the first dive and a whopping 117 minutes short of NDLs on the second dive. He ended up in Pressure group R.

It sure looks to me like Diver B had more bottom time and less decompression stress.

 

[packrat12]

Whoa, you require a peer reviewed paper from me but give me this BS about "tissue stress" w/o any reference whatsoever? As far as I know, tissue stress is nothing but a theory. I do know, however, what oxidative stress is. Here is a peer reviewed paper on simulated diving with air and NITROX. They show that FMD response was significantly reduced in EAN divers only. This is a sign of oxidative stress. I do not know how bad this actually is but I do not want it because it is still bad.

As for the NDL, no question that NITROX is beneficial here but for me this benefit is obvious only in, say, Bonaire where I can dive myself off to the limit. There diving on NITROX pays off.

Took a look at the abstract you quoted. Specifically "Significantly higher bubbling was found after all air dives as compared to nitrox dives" - Seems to support what I stated about tissue stress regarding bubble formation. I may have used the term sloppily but what my statement meant "the maximum value of inert gas pressure that a hypothetical 'tissue' compartment can 'tolerate' without presenting overt symptoms of decompression sickness" as quoted from Understanding M-Values by Erik Baker. But notice how I said it "Nitrox reduces tissue stress for divers. This is a benefit. It further buffers us from the NDL limits regardless of depths."

Here is a good research article about it.

Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

We would love to see peer reviewed publications regarding O2 cellular and DNA damage due to O2 at the quantities and level used by scuba divers.

 

[RyanT]

You either dive nitrox for added conservatism or for added safety, not both. This ridiculous concept is like herpes, it just keeps coming back. Thanks again @boulderjohn for illustrating how divers can gain both benefits from nitrox.

 

[flyboy08]

This is an amusing thread

Thanks Boulderjohn.....your my hero!

 

[tarponchik]

This is a common and absolutely silly statement made in many places. It is featured regularly in Dive Training Magazine, where Alex Bryskie is adamant about it. The theory is that you can either use nitrox to extend bottom times, or you can dive nitrox on an air table and this get a little level of increased safety. That's it. You have only two choices--nothing in between. That false dilemma assumes that once you enter the water, you have no choice but to stay for the full duration of NDLs. If the table says you can stay for 150 minutes at 50 feet, then, dammit, you have to stay for 150 minutes, no matter how much you want to surface earlier. Better bring a lot of gas.

I have done comparisons of this kind a number of times. Here we go again.

Diver A is diving on air, using the PADI tables. He does the first dive to 80 feet for the maximum time of 30 minutes. He is in pressure group R. He has a one hour surface interval, putting him in pressure group F, and then he does a 50 foot dive to the maximum time of 56 minutes. This puts him in pressure group X.

Diver B is diving on EANx 36, using the PADI tables. He does the first dive to 80 feet for 40 minutes. He is in pressure group P. He has a one hour surface interval, putting him in pressure group E, and then he does a 50 foot dive for 70 minutes. This puts him in pressure group R.

Diver A had a total of 86 minutes of bottom time. He stayed to the end of his NDL's on each dive. He ended in pressure group X.

Diver B had a total of 110 minutes, He was 15 minutes short of NDLs on the first dive and a whopping 117 minutes short of NDLs on the second dive. He ended up in Pressure group R.

It sure looks to me like Diver B had more bottom time and less decompression stress.

Your comment is entirely off topic and has no relation to our discussion with @uncfnp.

 

[tarponchik]

Took a look at the abstract you quoted. Specifically "Significantly higher bubbling was found after all air dives as compared to nitrox dives" - Seems to support what I stated about tissue stress regarding bubble formation. I may have used the term sloppily but what my statement meant "the maximum value of inert gas pressure that a hypothetical 'tissue' compartment can 'tolerate' without presenting overt symptoms of decompression sickness" as quoted from Understanding M-Values by Erik Baker. But notice how I said it "Nitrox reduces tissue stress for divers. This is a benefit. It further buffers us from the NDL limits regardless of depths."

Here is a good research article about it.

Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

We would love to see peer reviewed publications regarding O2 cellular and DNA damage due to O2 at the quantities and level used by scuba divers.

I never argued against NITROX making less bubbles in our blood, tissue etc; this is quite obvious. What I have a problem with is the concept that bubble formation somehow "stresses" tissue. Unlike O2, N2 is truly inert, so N2 bubbles form and dissolve later w/o any chemical reactions. Unless you get too many bubbles and develop DCS, who cares.

 

[Storker]

What I have a problem with is the concept that bubble formation somehow "stresses" tissue.

In that case, I'd recommend that you read up on the science. You could start with a pretty good review: Venous gas embolism as a predictive tool for improving CNS decompression safety

And your claim that @boulderjohn 's direct reply to one of your claims should be off topic and irrelevant is nothing but disingenuous hand-waving.

 

[tursiops]

This discussion has been about the benefits of Nitrox during the on-gassing phase of a dive. You take on less nitrogen per breath because there is less nitrogen IN each breath, compared to air. But there are clear benefits to Nitrox during the off-gassing phases of a dive: multi-levels, ascent, safety stop. During these phases you are trying to get rid of the nitrogen you on-gassed earlier. If the gas you are breathing has less nitrogen in it, i.e. Nitrox, then the off-gassing is more efficient. It is exactly the reason 80 or 100% O2 is used by technical divers during their deco stops.....each breath they exhale has more nitrogen removed from it than if they were using air, or even Nitrox, for that matter. It is easiest to think about this if you think of Nitrox NOT as oxygen-enriched air, but rather as "nitrogen-deriched" air. This is the principle of "accelerated decompression" used by technical divers and taught in the Advanced Nitrox classes. In our NDL recreational diving, we are not trying to hurry past a virtual ceiling caused by being in deco, but we are trying to get rid of the nigrogen in our boddies using the same principles.

So, Yes, there is perfectly good and straightforward reason to think that Nitrox can help with feeling better after a dive, since feeling bad after a dive is commonly due to poor washout of the nitrogen in our system.

 

[MaxBottomtime]

So, Yes, there is perfectly good and straightforward reason to think that Nitrox can help with feeling better after a dive, since feeling bad after a dive is commonly due to poor washout of the nitrogen in our system.

Did you just make this up or are you just repeating what you read on Scubaboard? How exactly does "poor washout" cause you to feel bad?
I've been nitrox certified for many years and have yet to see any difference. A slow ascent following a relaxing dive makes me feel pretty good no matter what gas I breathe.

 

[Jerome O'Neil]

OK, so I totally get the whole benefit of using nitrox, to increase your NDL. When diving on regular air at 20 feet, you'll run out of air before you run out of time.

When diving 20ft on Nitrox, you'll still run out of sir before you run out of time. So, my question is, why would someone still choose to dive nitrox at 20ft?

I've been on a few beach and shallow spring dives over the summer and have seen this. Just asking!

Because that isn't the only dive they're doing that day. One dive on mixed gas at that depth? Sure. But what if they're getting out of the water, getting on a boat, and going somewhere else for the rest of the day? It doesn't just extend your NDLs for the dive you're on, it extends your NDLs for every dive you're going to do that day.