NITROX for any and all dives?

[txgoose]

What's great about my proposed challenge is that you can define "feeling better and "less tired" or "less fatigued" any way you want!

Just pick which of the two tanks is more beneficial in regard to those factors, however you care to define them and report back.

I can't run the test on myself, because I know there's no difference. I can tell you in advance the results will be 50/50.

You cannot disprove a negative, you might as well tell me to go find proof of no Santa Claus.

Finally, it probably doesn't matter why Nitrox makes divers feel better, it's just a way of helping to settle the debate as to whether there's a real physiological factor or if it's all just psychological. Nothing more.

My thought on a modification would be to have the third/outside person change the mix for the entire day. All bottles have the same gas mixture. Record the feeling at end of day (scale of 1 to 10). Then after 10 dive days, compare felt results against the mixtures of gas? If there is a benefit, mixing gases in a single day might dilute the affect?

Not saying that there is or is not a benefit. But I do like trying to get to the essence of the test.

 

[MXGratefulDiver]

25 min on air, 30 min on nitrox. Problem is there is not enough gas either way to stay down that long without running out of air. Your limit is a factor of gas in the tank, not what is in it.

Too general a statement ... depends entirely on tank size and consumption rate ...

... Bob (Grateful Diver)

 

[MaxBottomtime]

Why make double blind studies when we have Scubaboard instead? I've learned a lot here that is not taught in any nitrox course. The miracle of Enriched Air is the greatest thing since sliced bread. Nitrox not only makes you feel better, less tired or less fatigued, it decreases your gas consumption, turns 80 cu ft tanks into 100s, relieves dry mouth, cures cancer, eliminates DCS and improves your looks. We need to find a way to increase oxygen output from plankton and trees so our atmosphere will improve. I've gone my entire life breathing air. It's time to fix that so we can all be better looking.

 

[Bob DBF]

I'd expect if there was any positive benefit to Nitrox when it comes to fatigue and "feeling better" then the majority of time the Nitrox tank would be chosen but I'll bet that the results are close to 50/50.

Measurement of Fatigue following 18 msw Open Water Dives Breathing Air or EAN36.

Earlier in the thread, study found no difference in fatigue, however noticed that a significant difference in the Nitrox divers feeling better after the dives. Since the study was about fatigue, not feeling better, they could only draw a conclusion on fatigue.


Bob

 

[BRT]

To say there is no advantage to nitrox is to say that it does not matter how close we come to NDL's. If it really does not matter how close we come to NDL's why not dive a liberal computer and ride the 1 minute mark all the way up? I don't think anybody believes that DCS is a light switch, full on or full off, do they? If I need to I will push NDL's, but I avoid it if I can. Nitrox changes dives that are close to NDL's into dives that are not close at all. Why is it so hard to believe that the body might feel better without that stress?

 

[tursiops]

My thought on a modification would be to have the third/outside person change the mix for the entire day. All bottles have the same gas mixture. Record the feeling at end of day (scale of 1 to 10). Then after 10 dive days, compare felt results against the mixtures of gas? If there is a benefit, mixing gases in a single day might dilute the affect?

Not saying that there is or is not a benefit. But I do like trying to get to the essence of the test.

The assumption of his test is that changing gas in the tanks is not noticeable. But the concept is flawed: it is diving several times a day, for several days, where the effect is typically felt. If I dive one tank of air, no big deal. I can't do a liveaboard on air, but no problem on Nitrox. He needs to design a test that does not violate the information already available. The proposed test is not testing the observed facts. If the reasons for the "benefit" is indeed subclinical DCS, then the proper tests would also involve measurement of sub-clinical DCS (e.g., microbubbles), in those who feel "benefit' and those who do not.

 

[decompression]

This is likely backwards. Originally, plain old air fills had a certain amount of filtration, which removed some moisture. Then Nitrox came along and more filtration was desirable to avoid any chance of petroleum products in the tank; that extra filtration mean even less moisture in the Nitrox, so you got "dry mouth." Now, pretty much all the air fills are double-filtered as well as the Nitrox, so there should not be any difference. That is, dry mouth from both.

However, more filtration doesn’t necessarily mean less moisture as it’s the particle size of the media that will or will not allow the water molecules to pass. But yes, bottom line it’s highly unlikely that nitrox contains more moisture than air after the compression process.

 

[boulderjohn]

For easy math, let's assume a 0.5 SAC rate and a tank a usable capacity of 60 cubic feet in your tank. We will use PADI tables to make it equally easy.

First dive to 99 feet

Time limit based on gas: 2 cubic feet per minute, so maximum time = 30 minutes.
Air Diver NDL = 20 minutes
Nitrox 32 NDL = 30 minutes
Both divers continue to their NDL, so the Nitrox 32 diver gets 10 more minutes (50% more time)
​

Second dive to 66 feet after a one hour surface interval

Time limit based on gas: 1.5 cubic feet per minute, so maximum time = 40 minutes
Air Diver NDL = 25 minutes
Nitrox 32 NDL = 39 minutes
The Nitrox diver can continue to NDL (39 minutes), giving that diver 14 more minutes of bottom time than the air diver.​

Total dive times for the two dives:

Air: 45 minutes
Nitrox 32: 69 minutes. That is 24 more minutes--a 53% increase in bottom time.
​

We can continue through dives #3 and #4, as on a liveaboard trip, if you like to see how the difference mounts throughout the day.

Note: The nitrox diver on the the 2-tank dive above could have switched to Nitrox 36 for the second dive. That would have given him or her a NDL of 52 minutes. With enough gas capacity, that diver's bottom time for the two dives would have been nearly double the air diver's bottom time. Note also that the extra tank capacity would not have helped the air diver, who would be limited by NDLs on each dive.

As for me, that last sequence--Nitrox 32 on the deep dive and Nitrox 36 on the shallower dive--is what I do on most two tank recreational dives in Florida, and I have the tank volume to reach NDLs on each dive. I usually surface on the second dive earlier to accommodate the preferences of the dive operation.

 

[northernone]

To say there is no advantage to nitrox is to say that it does not matter how close we come to NDL's. If it really does not matter how close we come to NDL's why not dive a liberal computer and ride the 1 minute mark all the way up? I don't think anybody believes that DCS is a light switch, full on or full off, do they? If I need to I will push NDL's, but I avoid it if I can. Nitrox changes dives that are close to NDL's into dives that are not close at all. Why is it so hard to believe that the body might feel better without that stress?

I too suspect this might be the factor.

Is it agreed an "almost bent" diver anecdotally feels worse than one with adequate decompression?

I can't feel the difference between a series of dives with leaner nitrox mixes compared to richer but the few times I've cut deco close it sure tires me out.

With this in mind, would extending a safety stop to 5 minutes instead of 3 result in the same feelings as diving nitrox?

Or are people claiming it's the hyperbaric oxygen dose increase that is helping them feel better? If so, do you feel less tired after deeper dives?

Cameron

 

[tursiops]

Note: The nitrox diver on the the 2-tank dive above could have switched to Nitrox 36 for the second dive.

Yes, this is my preferred strategy too. But not on a liveaboard, where just one (membrane-determined) mix is available.