Diving Nitrox to increase safety AND bottom time!

[fjpatrum]

My version of the implication was that he seemed have more time to talk about it then I. Since I teach, run a dive shop and manufacture scuba diving components and really didn't have time to keep talking about the effects of EANx at the moment- or simply tired of talking about it. I figured no matter what I said the end result would be the same. I will only argue or debate to a point ~fjpatrum seems to do a lot more talking then diving. I merely pointed that out in my own way. Call it what you want, but I wasn't thumping my chest, its to hard and I wouldn't want to hurt my hands lol. That was a joke... Posting numbers have no relevance to dive experience which could also be implied by what I said. Its all in how you turn text to context, and starts more arguments then needed. My apologies if any actual offense was taken.

I believe statements like what I bolded are where people tend to take offense. I personally didn't take much offense but it's easily interpreted as "he doesn't dive a lot so his opinion has no value" whether that's what you intended or not. For those of us who Love diving but don't happen to live in Palm Beach FL, talking is often the only diving venue we have. We can't all live in paradise. We can't all dive every day, and even those of use who can don't always choose to do so. That doesn't make our experiences and/or opinions about diving any less valuable than those of us who can and do dive all the time.

For what it's worth, I think people should have a thicker skin when posting in forums like this but there's nothing wrong with pointing out where people can pose a response more politely. Vladimir tends to do both... have a thick skin (and understanding of humor) and also politely point out when people might be construed as rude whether or not they intended to be rude.

 

[Zen Diving Inc.]

I believe statements like what I bolded are where people tend to take offense. I personally didn't take much offense but it's easily interpreted as "he doesn't dive a lot so his opinion has no value" whether that's what you intended or not. For those of us who Love diving but don't happen to live in Palm Beach FL, talking is often the only diving venue we have. We can't all live in paradise. We can't all dive every day, and even those of use who can don't always choose to do so. That doesn't make our experiences and/or opinions about diving any less valuable than those of us who can and do dive all the time.

For what it's worth, I think people should have a thicker skin when posting in forums like this but there's nothing wrong with pointing out where people can pose a response more politely. Vladimir tends to do both... have a thick skin (and understanding of humor) and also politely point out when people might be construed as rude whether or not they intended to be rude.

HAHAHAHA. LOL. How can argue with someone who's avatar matches mine so closely (look closely) my zen friend. Your point is taken, I didn't mean to be rude. Trust me S. Florida is no paradise unless your viewing if from the boat!

 

[Tortuga68]

If nitrox is only useful to extend bottom time then it would have no value to a diver with a higher SAC who's bottom time is dictated by their cylinder volume - would you tell such a student to avoid using nitrox since it would provide no benefit to them?

I would tell them it's a waste of time to do a nitrox course, yes

 

[MaxBottomtime]

See this is what I'm not getting. Different people have told me they have better outcomes when diving with nitrox ie. no headaches, less tired, more alert etc... So regardless of how it 'feels' at the time is it not beneficial to try it to see what effects (if any) it has on you as an individual rather than just studying it in the classroom?

Try slower ascents. The headaches and fatigue will go away. I've been nitrox certified for a dozen years and have never felt a difference. I'm usually refreshed after every dive! As far as safety goes, the incedent rate of DCS is so low now that any reduction using nitrox would be miniscule. There are two reasons to dive nitrox. All the "feel good" reasons are placebos but some people insist on believing anything they hear.

 

[Wolfie]

SDI COMPUTER NITROX COURSE: Traditionally, becoming a Nitrox Diver required long hours in the classroom, learning how to work obscure formulas and use complex dive tables. No more. Through SDI's on-line training program, you can complete most of the required academic study in the comfort and convenience of your home or office. And, as with all SDI programs, you'll learn to dive Nitrox the modern way, using Nitrox-programmable dive computers instead of arcane formulas and complicated tables.

I went to my LSD for our I think 2 hour course and he didn't even mention tables. The he asked if we had any questions..... Uh yah, how do you use the tables? He spent another half hour with all of us to go through it but I was pretty floored that it wasn't covered in class. That's when I looked deeply into the Above course description.. Should've skipped it althogether and gone straight to advanced nitrox. I'm sure that would break some rules of not paying for all the classes! Arcane formulas and complicated tables? Really? Just shove them off the gunnel with a $200 computer..... They'll be fine.....

 

[lamont]

See this is what I'm not getting. Different people have told me they have better outcomes when diving with nitrox ie. no headaches, less tired, more alert etc... So regardless of how it 'feels' at the time is it not beneficial to try it to see what effects (if any) it has on you as an individual rather than just studying it in the classroom?

There's no medical reason why that would happen.

Consider also that as people become nitrox trained and use it more they're also becoming more experienced divers, and are probably more relaxed. And we know that hypercapnia from skip breathing or over exertion under water will give you nasty headaches. So does the lowered ppN2 and higher O2 have something to do with that? Or does it just go with becoming a better diver and becoming more calm in the water?

And I'm *positive* that the latter approach is going to be more effective if you turn the question on its head and ask "how do I get rid of these headaches I'm having after dives?" The best answer to that is going to be to fix your breathing and get calm and comfortable in the water.

I tend to *believe* that 32% is a better gas for 100 foot recreational dives and it lessens fatigue after a dive compared to air, but concretely I have no medical evidence and I'll also admit that doing an extended shore-profile safety stop of 15 mins or so from 30 to the surface is going to be an order of magnitude more important than the precise mix that you're breathing.

The reason to dive 32% is really because you're nudging up against NDLs on deeper dives around 100 feet and you're getting more aggressive in your diving. You should already be safe, and comfortable, and be calm, and not be getting hypercapnic headaches, etc. The answers to all of those questions are elsewhere, not primarily with diving nitrox.

While at the same time, as long as you're not going deeper than 110 feet (which you really shouldn't be doing as a recreational diver for several reasons), 32% makes a better mix than air and I fill my tanks with it nearly exclusively. But that isn't because its magic gas, its just because its the mix that makes the most sense for recreational diving.

---------- Post Merged at 06:02 PM ---------- Previous Post was at 05:56 PM ----------

While it may provide a buffer in the sense that if you dive nitrox while using air tables and blow past your NDL inadvertently, you would still be within non-deco range, I am not aware of research that shows a lower rate of undeserved hits in this situation. Of course, the problem is that undeserved hits are rare, so to really draw a scientific conclusion about that, you would need to accumulate profiles on huge numbers of dives in order to get enough of these events to see if they were less common with EAN than with air. Making such a study even harder to do is the fact that you would need to match cases with controls - you would have to find divers with similar profiles but different mixes who had a UDH.

You are right that the incidence of those hits is so low that doing miniscule fine tuning to the incidence isn't going to result in much of a different outcome.

I suspect that the effect on DCS is going to be washed out by the incidence of divers losing buoyancy control on walls and toxing at depth after exceeding their MOD (or just of divers being cavalier about MOD and it biting them in the ass some day).

Nitrox is almost certainly more dangerous overall.

---------- Post Merged at 06:12 PM ---------- Previous Post was at 05:56 PM ----------

Having recently completed an EAN course, I have the book, I have the DVD, I spent time with an instructor going over the fundamentals and the use of a computer and tables for planning a dive, testing tanks with 3 different analyzers and at least 2 hours of discussion. It was about 2 weeks from completion of the course until I got a chance to dive breathing Nitrox (EAN32). My experience is that using nitrox is not a 1 dive thing, Nitrox to me appears to help with fatigue but isn't noticed after 1 dive but a series of dives. Does that mean the certification should require multiple dives? I see where others say it doesn't change anything for them. I am of the opinion that having to complete a dive after having taken the course has no practical value and would only add to the cost of the course.

Everyone does that kind of tea-leaf-reading of their "symptomology" after they've been nitrox certified. I fondly recall writing stuff exactly like you just wrote. If I had a penny for every minute I've spend arguing over nitrox's effects on narcosis or fatigue or whatever in the past decade I'd be rich. There's just no way to eliminate placebo effect or simply random chance. To take an example, I've done back-to-back dives at the same site over two days, under the same conditions (light, silt, current, cold, etc) and one dive got completely hammered by narcosis and one dive had no issues at all -- both dives on 32%. And to top it off my dive buddy had the reverse experience, she was narc'd out of her mind on the dive I was clear on, and vice versa. You throw random variables like that at this problem and whatever pattern you think you found in the first few dives you've done on nitrox is likely very wrong.

You could do a controlled study with a 100 dives per diver under identical circumstances using 32% and 21% and measure narcosis and symptomology using more objective measures and then get yourself some bell curves and see if the mean of the distributions shift in any kind of statistically significant way. I doubt they would. And it wouldn't be much of an effect.

Wanna feel better after dives? Do more *deco* and treat those dives like lightweight decompression dives.
Wanna eliminate headaches after dives? Work on breathing (mostly exhaling consistently and not holding your breath) and comfort and stillness and buoyancy.
Wanna eliminate narcosis? Dive helium.

 

[dmoore19]

Everyone does that kind of tea-leaf-reading of their "symptomology" after they've been nitrox certified. I fondly recall writing stuff exactly like you just wrote. If I had a penny for every minute I've spend arguing over nitrox's effects on narcosis or fatigue or whatever in the past decade I'd be rich. There's just no way to eliminate placebo effect or simply random chance. To take an example, I've done back-to-back dives at the same site over two days, under the same conditions (light, silt, current, cold, etc) and one dive got completely hammered by narcosis and one dive had no issues at all -- both dives on 32%. And to top it off my dive buddy had the reverse experience, she was narc'd out of her mind on the dive I was clear on, and vice versa. You throw random variables like that at this problem and whatever pattern you think you found in the first few dives you've done on nitrox is likely very wrong.

You could do a controlled study with a 100 dives per diver under identical circumstances using 32% and 21% and measure narcosis and symptomology using more objective measures and then get yourself some bell curves and see if the mean of the distributions shift in any kind of statistically significant way. I doubt they would. And it wouldn't be much of an effect.

Wanna feel better after dives? Do more *deco* and treat those dives like lightweight decompression dives.
Wanna eliminate headaches after dives? Work on breathing (mostly exhaling consistently and not holding your breath) and comfort and stillness and buoyancy.
Wanna eliminate narcosis? Dive helium.

Cool, except I don't have headaches and don't have any of the symptoms that others have mentioned. I didn't notice any difference after 1 day of diving nor 2 days of diving 3 or 4 a day. It was later in the week that it seemed to make a difference. I felt less fatigued in the evenings than on previous trips. If this is a placebo effect, I am good with it, it works for me.

My post was more related to the idea that diving a tank of nitrox after taking the class didn't seem to make much sense to me and would only serve to increase the price of the class. It might not be that big of a deal to those who live where places to dive are close and convenient, I don't live where that is the case.

 

[DaleC]

Actually, the decision not to teach the commonly held assumption that nitrox reduces the rate of undeserved hits is not based on whimsy, but rather a reluctance to present a reasonable but unproven theory as fact.



I agree




I do not agree.

While it may provide a buffer in the sense that if you dive nitrox while using air tables and blow past your NDL inadvertently, you would still be within non-deco range, I am not aware of research that shows a lower rate of undeserved hits in this situation. Of course, the problem is that undeserved hits are rare, so to really draw a scientific conclusion about that, you would need to accumulate profiles on huge numbers of dives in order to get enough of these events to see if they were less common with EAN than with air. Making such a study even harder to do is the fact that you would need to match cases with controls - you would have to find divers with similar profiles but different mixes who had a UDH.

This is one of the reasons why it's hard to do good science in the realm of diving physiology. To find strong evidence that a drug works in humans, the gold standard is to do a prospective, double blind study where you randomized similar patients to two groups, and assess outcomes without knowing which group got which treatment. The more uncommon the outcome that you are looking for, the bigger the group you need to achieve statistical significance, even if you are doing a lesser study (like the retrospective case series that you would do in studying DCS).

Why do you need an additional study? The science has already been done. All the work that went into the creation of the dive tables is directly based on this hypothesis.

Your argument that most recreational dives within the NDL's are already so safe that the additional buffer of EAN would be negligible is correct, but this is like trying to describe an elephant by only knowing its trunk. Move the dive profile outward until DCS becomes a notable probability and the safety factor of EAN becomes more tangible. I don't need a study to understand or accept that.

That agencies would try to discourage that behavior I also understand because they have a vested interest in promoting diving as a safe pastime and (thus) maintaining the status quo. They would prefer one not extend the risk of DCS outward and would prefer one increase safety by extending SI's, reducing the amount and nature of repetitive dives, increasing PG's for altitude diving and having extended no fly intervals (all of which are designed to increase safety) but that still doesn't change basic gas physiology.

The litmus test for me is that I don't know any educated diver who, having performed a dive wherein (for whatever reason) DCS were predictably imminent, would reach for air instead of an appropriately MOD'd EAN mix.

 

[doctormike]

Why do you need an additional study? The science has already been done. All the work that went into the creation of the dive tables is directly based on this hypothesis.

Your argument that most recreational dives within the NDL's are already so safe that the additional buffer of EAN would be negligible is correct, but this is like trying to describe an elephant by only knowing its trunk. Move the dive profile outward until DCS becomes a notable probability and the safety factor of EAN becomes more tangible. I don't need a study to understand or accept that.

That agencies would try to discourage that behavior I also understand because they have a vested interest in promoting diving as a safe pastime and (thus) maintaining the status quo. They would prefer one not extend the risk of DCS outward and would prefer one increase safety by extending SI's, reducing the amount and nature of repetitive dives, increasing PG's for altitude diving and having extended no fly intervals (all of which are designed to increase safety) but that still doesn't change basic gas physiology.

I'm a little confused about your objections to what I wrote.... I was talking about undeserved hits. Period. When someone recommends breathing nitrox but diving air tables, they are attempting to increase safety by making an undeserved hit less likely, right? All I was saying was that there isn't any evidence that it does this. But if you feel that it is worth the cost, oxtox issues, equipment issues, and any other potential risks for an unproven benefit in preventing a very rare occurrence, then that's OK....

Don't get me wrong, I'm not nitrox bashing - I dive it all the time... so that I can extend my bottom time.

The litmus test for me is that I don't know any educated diver who, having performed a dive wherein (for whatever reason) DCS were predictably imminent, would reach for air instead of an appropriately MOD'd EAN mix.

I don't understand this - are you saying that if you had performed a dive that put you at risk for DCS you would then choose EAN? After the dive? Or are you saying that you should plan a dive so that you are as far from NDL as possible by using the richest mix possible for a given depth..? I guess that's an argument for using a CCR...

 

[DaleC]

No, I'm saying that anyone who argues that EAN does not provide safety against DCS has to explain why one would breath it should they fear an impending hit. What's the protocol for a rapid ascent or missed deco stop? Amongst other things, breath the richest mix possible - why? I say we do it because we hope EAN will provide more safety from DCS than just breathing air. It's not complicated. You can do it after the dive as an acute measure or or during the dive as a preventative measure.

Anyways, isn't saying one dives EAN to extend BT just a backwards way of saying it provides more safety? According to sport diving tables, doing 30 minutes at 100' on EAN is considered safer than doing 30 minutes at 100' on air, DCS wise - that's why people do it. There's no other factor at play other than the increased safety from DCS.

The occasions that I (currently) personally use EAN to offset DCS risk for is doing the occasional one day altitude dive trip which involves going over a pass on the return journey. I dive the richest mix I can to reduce the amount of N loading. Unlike some, I don't have the disposable income to purchase a CCR for those moments. If I were doing multi day, multi dives (like on a live a board) where the depths/times were such that the accumulated exposure might lead to a hit I would also dive EAN for the safety factor.

I also believe that some people are more disposed to DCS than others either genetically or lifestyle/age/health wise; we are not "one size fits all" in that regard. For those that show a predisposition and insist on continuing to dive, using EAN is one way that they could increase their safety.

Also, though I can not prove it, I believe that some cases of divers experiencing what we call the placebo effect from EAN may in fact be the reduction of sub clinical DCS symptoms - but that is a different discussion.

However, for the most part I dive air because my profiles and physiology do not put me at that sort of risk.

I believe true safety for the diver is not to become habituated to always trying to push the limits.