Why do you use nitrox ?

[MXGratefulDiver]

You forgot "spare air"

nitrox ... of course ...

 

[Rick Murchison]

I'm only saying it changes something for me, I dove air for about 15 years before trying nitrox. I was stunned by the difference in myself after doing a familiar dive on a different gas. I don't think I've ever met anyone who has had the same result. I did a dive to 135 on nitrox and was so fuzzy headed I couldn't even tell when I needed to clear my ears or add air to my wing. I took my cue from my buddy, when he did it I did it. I would be interested in trying trimix on the same dive to see if there is a noticeable difference on a deep dive.
Ber :lilbunny:

I have not noticed any difference in narcosis susceptibility between nitrox and air.

Must be a woman/man thingie. The Lovely Young Kat swears that compared to air, she feels better and sharper diving Nitrox, and better after a Nitrox dive, while I can't tell any difference at all.
She says it's 'cause I'm "just another insensitive man."
I reckon she may be onto something...
Rick

 

[SkimFisher]

You forgot "spare air"

I was going to throw it in there, but figured I'd stop at "snorkels"

 

[Blackwood]

nitrox ... of course ...

Naturally. You wouldn't want to worry about decompression after all.

 

[muddiver]

Must be a woman/man thingie. The Lovely Young Kat swears that compared to air, she feels better and sharper diving Nitrox, and better after a Nitrox dive, while I can't tell any difference at all.
She says it's 'cause I'm "just another insensitive man."
I reckon she may be onto something...
Rick

Could it be from all the beer typically consumed immedeately after the last dive by most male divers vs. female divers typical choice to discuss the dive?

 

[Blackwood]

Could it be from all the beer typically consumed immedeately after the last dive by most male divers vs. female divers typical choice to discuss the dive?

My general excuse is that I was distracted by the mermaids.

 

[Firefyter]

I started using nitrox after my dives became NDL limited rather than gas limited. I only use it on vacation to extend my bottom times.

 

[RTee]

1)...extend my bottom time
2)...minimize surface intervals while doing multi dives during same day
3)...started doing it on local dives; and
4)... might be doing it on vacation in places like Bonaire

 

[Puffer Fish]

Well Rick already gave the answer I was about to give.

Have you actually checked out any trimix training material?
You'll find that practically all of it uses the (100% - He) rule.

NOAA Diving Manual, Diving for Science and Technology. 4th. National Oceanic and Atmospheric Administration. 2002. "[16.3.1.2.4] ... since oxygen has some narcotic properties, it is appropriate to include the oxygen in the END calculation when using trimixes (Lambersten et al. 1977,1978). The non-helium portion (i.e., the sum of the oxygen and the nitrogen) is to be regarded as having the same narcotic potency as an equivalent partial pressure of nitrogen in air, regardless of the proportions of oxygen and nitrogen."

Some years ago the rule was to consider only the N2 as narcotic but AFAIK current thinking is based on the fact that although oxygen has greater lipid solubility than nitrogen and therefore should be more narcotic (Meyer-Overton correlation), it is likely that some of the oxygen is metabolized, thus reducing its effect to a level similar to that of nitrogen.

You can also check out
Rubicon Research Repository: Item 123456789/2810

"Title: Roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis

Abstract: In an attempt to determine the roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis, the effects on performance (mental function and manual dexterity) of adding CO2 in various concentrations to the inspired gas under three different conditions were studied in eight healthy male volunteers. The three conditions were: (1) air breathing at 1.3 ATA; (2) oxygen breathing at 1.7 ATA; and (3) air breathing at 8.0 ATA (same inspired O2 pressure as in (2)). By relating performance to the changes induced in end-tidal (alveolar) gas pressures, and comparing the data from the three conditions, we arrived at the following results and conclusions. A rise in O2 pressure to 1.65 ATA, or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a significant decrement of 10percent in mental function but no consistent effect on psychomotor function. A rise in end-tidal PCO2 of 10 mmHg caused an impairment of approximately 10percent in both mental and psychomotor functions. The results suggest that, at raised partial pressures, all three gases have narcotic properties,....."

I'm really curious where the 300 FSW figure that you quoted comes from.

Thanks for posting that link... nice paper.

There must be more to this story though.

Their conclusions are:

1. Of the three gasses, Nitrogen is the least narcotic, and only effect is mental fuction.

2. Oxygen is around 2.6 times more narcotic (at the pressures they were testing) and also only effects mental function.

3. CO2 is hundreds of time more narcotic and effect both mental and motor fuction.

Given the date, if that was the whole story, then we should be talking about CO2/O2 narcosis... but we don't.

Is it possible the effects of O2 are not linear? They were, after all, testing O2 at a level that is not recommended today.

8 atms is a fairly deep dive, but if using nitrox to 1.7 causes the same effect (a bit less, but in the ball park), why would that not be discussed and avoided.

I'm guessing these were military divers, who would have been selected for their resistance to being narced in the first place. Is it possible the effects are somewhat different in the general population?

Either there is a lot more to this story, or everyone has been ignoring reality. Wonder which it is?

 

[njedrn]

I have heard more than plenty of people say that the "feeling better after diving nitrox" is just anecdotal, and I haven't seen any research, but I have experienced this when doing multiple dives a day for 2-3 days.

Weekend one - 3 dives a day for 3 days. Diving air. Absolutely exhausted.
Following weekend - 3 dives a day for 3 days, diving nitrox. Tired but not nearly as exhausted.
Conditions were just about the same, ocean boat dives, with mild current, 1-2ft chop.

There may be other factors involved, but since then I dive almost exclusively nitrox.