NITROX for any and all dives?

[Neilwood]

The study was also flawed in that the dives compared were such simple short, shallow dives that no one would feel any fatigue regardless of what was breathed.

What you need to do is put people on a liveaboard for a week and see what happens.

Two dives of 20 mins @18m with an hour SI -as you say, hardly suprising the divers weren't fatigued.

A blind trial of Nitrox vs air for a week liveaboard with 3/4 dives per day with similar dive profiles and times (cylinders sized appropriately to make sure the dives were near air NDL limited) would probably be the best way to do it.

 

[BRT]

I use nitrox for any and all dives unless I'm somewhere that I just can't get nitrox. Given the cost of diving, it's dirt cheap. I'm also one of those that believes he feels better after diving with nitrox than I do after diving on regular air. I know it's supposed to be placebo effect, but I don't care. I have done a few dives in the keys where the bottom was less than 20 feet from the surface. On those dives, I thought I might as well have used air but I had nitrox in my tanks and used it anyway.

If I recall, the studies about nitrox making you feel less tired were very limited in scope. I didn't think they were the be all and end all of that topic. For now, I've decided just to use statements like "I know it's supposed to be placebo effect, but I don't care."

At home, nitrox costs me $2-$5 more than air fills. Some other locations it costs more, but it's still always quite affordable. "Local" diving for me is at least an hour drive away, usually more like 5. Boat dives cost $50-100 per two-tank trip.. nitrox is a mere drop in the buckt cost wise. Unless you're doing a blue/black water dive with an unreachable ocean floor, I see very few drawbacks to nitrox and potentially several benefits.

Also, I usually dive "best mix" so I can get as much 02 in the tank as the dive will allow up to 40%. If you're gonna go, go all out. I wish I had my own membrane system so I could extend that higher than 40%.

Hard to get too far beyond 40% with a membrane I think.

 

[Lorenzoid]

It's awfully hard to measure fatigue, "less tired," etc., with any kind of scientific accuracy.

 

[mi000ke]

As an older diver, and at an added cost of only $6/tank for locals here, I figure why not use nitrox. Most of the ops here on GC do a deep wall dive (100') followed by a shallow reef dive (50-60', although there is usually an opportunity to go deeper, as we're never too far from the deep wall) , usually with a SI of about 45 minutes. I have a fairly low SAC rate and have bumped up against NDL a couple of times on both first and second dives when on air. So rather than potentially having to shallow out or shorten the dive by a few minutes, I use nitrox.

I take most of our non-diver visitors (and we get lots of those) on 2-tank discovery/resort dives, and I will use just air, as the dives are limited to 40' or so.

I had dinner last year with the doctor who runs the bari chamber on CG, and he believed that the best approach was always to dive nitrox but using air tables. I don't do that but have never experienced anything close to DCS. Of course he sees it all the time.

BTW, he was pretty sure that using nitrox did not make me better looking.

 

[Bob DBF]

I guess the chamber study you mean is this one of 2003: Measurement of fatigue following 18 msw dry chamber dives breathing air or enriched air nitrox. - PubMed - NCBI
and the later one of 2008 is: Measurement of Fatigue following 18 msw Open Water Dives Breathing Air or EAN36.
Both don't support Nitrox having an influence on fatigue. In the second study, the divers' DHS survey responses were a little better for Nitrox than for Air.

Yes those would be the ones.

The subjects felt better on Nitrox, but it was not scientifically "fatigue", and it was significant enough for the researchers to note it and say it might be due to reduced decompression stress. It would be nice to have a definitive answer, but I dont see that in the near future. May be a go fund me study will pop up.

As I've said before, I stick with air for most dives, but when doing multi day multi dives I use Nitrox because I feel better than the same dives with Air. Whether it is fatigue or reduced decompression stress or Nitrox faeries tickling me, it makes no difference to me as long as I feel better when the day is done.


Bob

 

[Storker]

BTW, he was pretty sure that using nitrox did not make me better looking.

Dang!

 

[kmarks]

That's the flawed study I was talking about earlier. Here's the first big flaw:

The people being studied were not exercising at all, exactly the opposite of what you have on a recreational scuba dive. Although it may be somewhat similar to what a very experienced cave diver with a Sheck Exley award does a recreational dive.

That's not a flaw, that controlling for variables. If you put everybody on a liveaboard and tell them to go dive, some people are going to bounce up and down from 60 to 40 feet the whole dive, some are going to kick, some are going to float, and your data will be meaningless. When doing a scientific study, you can only get meaningful data when you change one variable at a time. By having a large sample population, evenly distributed between sex, age, physical fitness level, race, etc., you would get the best data, but you would want to make sure they are all experiencing the same dive, which means sitting in a chamber as it pressurizes to 60 feet.

Well, nitrox is NOT for putting in your tires. Oxygen and rubber do not go well together.

100% nitrogen is commonly used for tires because it doesn't leak or heat up as much.

I had dinner last year with the doctor who runs the bari chamber on CG, and he believed that the best approach was always to dive nitrox but using air tables. I don't do that but have never experienced anything close to DCS. Of course he sees it all the time.

My wife was told to do this because of an injury that could make her more likely to have problems off-gassing absorbed nitrogen from scar tissue. You just have to be sure you are diving air tables while considering the MOD of your EAN#

 

[Storker]

You just have to be sure you are diving air tables while considering the MOD of your EAN#

Who the heck dives tables these days (don't bother chiming in; it was a rhetorical question, somewhat exaggerated for effect)?

Although I love my tables and frequently consult them for a quick sanity check on planning for depth and run time, I follow my computer and my spg under water. Now, what's interesting is that with my current tank size (10L 300 bar, or roughly 100 cf steels) and my current RMV, my NDL and my min gas time are pretty darned close if I'm breathing air. Some times my bottom time is gas limited, some times it's NDL limited. So if I try to get the most out of my tank, I'm pretty close to the NDL, AKA riding my NDL. When I'm on EAN, it's always min gas that limits my bottom time. Which means that when I'm on EAN, I'm further away from my NDL than I am when I'm on air.

YMMV. You are probably using a different tank size than I'm using, or you might have a different RMV than I have, or both.

 

[jodylynn007]

As many have said already, I as well dive nitrox all the time, unless it is not available.

My tanks at home are steel HP100's and dive sites are all at least an hour and 15 minute drive from home. Sites themselves vary considerably but more often than not can dip as low as you'd like to go (whether by shore or boat) and I find the sweet spot to be around 80 ft. So to do two dives with as much bottom time at my preferred depth, which can vary depending on what I see (I am good with not going deeper usually than around 110 ft), I definitely always pre-fill my tanks with nitrox not even knowing what my dives will bring as I am going to hit my NDL possibly on the 1st dive but most certainly on the 2nd. On occasions when I've had to dive air, I have noticed the difference immediately when I have had to ascend earlier than I would have liked and wasn't too happy about it.

Perfect example was a couple of weekends ago I had fills on the onboard compressor on a boat I was on (air) and had filled the tank with air to start and there was quite a chill on the ocean surface. Once you hit about 50 ft., it was unbearably cold. However, down at 65 ft and below, it was quite lovely. 1st dive was great... stayed at the depths I like and only froze my butt off (about 42F) for the safety stop, which I couldn't avoid coming up shallow for. 2nd dive... another story, had to cut it short before the air on my tank ran low (which is usually how I prefer to end the dive) because I was frozen and my NDL wouldn't allow for me to stay in the warmer part of the ocean anymore!!! ARGH.

So yeah.... nitrox, all the time as much of the time if possible.

 

[ystrout]

I never dive without it. Here's an anecdotal story for those interested.

I ran a liveaboard dive boat for 20 years. When we started, we ran 25-30 trips a year, averaging 8 dives per trip (we were a weekend boat), with 34 divers on a boat. That's about 6000 dives a year rounded.

We averaged 8 cases of bends per year, which meant the boat came home early 8 times a year. The Coast Guard was furious.

in 1998, we installed a Membrane nitrox system. It was a Nitrox Technologies system, made great 32%. We sold nitrox for $10 a fill or $60 for the trip.

We averaged 8 cases of bends per year, because the people most likely to get bent are the same people least likely to pay $60 for gas. Remember, this is in Texas. None of the divers bent were on nitrox. I noticed this.

In 2009 we moved the boat to Florida, cut 10 passengers from the boat, made nitrox inclusive, and upped the price to cover it. Now, 99% are diving nitrox. We offered a "discover nitrox" class for free. The class lasted for the duration of the trip. We rarely dove (dived?) where you could go deeper than 130 feet, so 32% was the right mix. From 2009 to 2016 when I sold the boat, we never had a case of bends again. The average depth in the Dry Tortugas is slightly shallower than the Flower Gardens, but I don't believe that is the only reason. I'm a believer in Nitrox.

Can't argue with those results. I'm sure not having to return early and give people partial refunds more than paid for the training and oxygen costs you absorbed.

I'm also surprised to hear that boats return early, rather than order a helicopter (low flying) or coastguard rescue to come pick them up. Ordered through the customer's insurance so they deal with the bill.