Sold On Nitrox

[MaxBottomtime]

Really? Let's state your thesis another way. Nitrogen load at surface makes no difference at all in how you feel post-dive. Presumably you are excepting cases of clinical DCS.

Or another way to look at it. Let's assume identical dive profiles in terms of depth and time. Dive A is on air and rides the NDL for the full dive, except for a 3 minute safety stop. SurfGF at the end of the safety stop is 90. Dive B is on the max Nitrox for the depth and does the 3 minute safety stop on 100% O2. SurfGF at the end of the safety stop is 20.

Do you really believe the diver will feel exactly the same in terms of fatigue after these dives?

Yes. Until science can accurately test for fatigue caused by nitrogen, it's all theory.

 

[inquis]

It seems that the aviation industry has known that ascent speed is correlated with DCS for 30 years or more.

I don't think the dive industry is ignorant of this. Something made them switch to 30 fpm vs the old 60 fpm guideline. Also, everyone knows that volume changes (per unit depth change) more rapidly near the surface, so it's not a real stretch to realize you have to slow down at 10 ft to get the same rate of bubble expansion that you were comfortable with at 30 ft. Thus, the common admonition of an even slower ascent rates from the safety stop.

 

[Nemrod]

Really? Let's state your thesis another way. Nitrogen load at surface makes no difference at all in how you feel post-dive. Presumably you are excepting cases of clinical DCS.

Or another way to look at it. Let's assume identical dive profiles in terms of depth and time. Dive A is on air and rides the NDL for the full dive, except for a 3 minute safety stop. SurfGF at the end of the safety stop is 90. Dive B is on the max Nitrox for the depth and does the 3 minute safety stop on 100% O2. SurfGF at the end of the safety stop is 20.

Do you really believe the diver will feel exactly the same in terms of fatigue after these dives?

For a given SurfGF there would be no difference. The advantage of Nitrox is that at moderate depths bottom time is increased usefully over air for the (same) acceptable SurfGF. If pushing air to the limit and surfacing without using the additional time Nitrox affored, then, yes, I guess I would agree. But that is not what people are doing with Nitrox, largely they are using it to extend bottom time vs air. If you surface with either with the same SurfGF then there is no difference except the Nitrox diver got more BT for that same SurfGF and paid more $$ for the Nitrox for that additional time.

I know this is not what is being inferred, I find the whole idea of cheating computers and dialing in safety factors by leaving a computer in air mode and then diving Nitrox to be potentially dangerous especially if switching back and forth between mixes without resetting to the actual gas. Then you have no idea of what your real SurfGF is. In the end, it is the resulting actual nitrogen load, the SurfGF that matters?

 

[Duke Dive Medicine]

For a given SurfGF there would be no difference. The advantage of Nitrox is that at moderate depths bottom time is increased usefully over air for the (same) acceptable SurfGF. If pushing air to the limit and surfacing without using the additional time Nitrox affored, then, yes, I guess I would agree. But that is not what people are doing with Nitrox, largely they are using it to extend bottom time vs air. If you surface with either with the same SurfGF then there is no difference except the Nitrox diver got more BT for that same SurfGF and paid more $$ for the Nitrox for that additional time.

This is a good callout. Put another way, if you dive either gas to the edge of the no-stop limit, there's little benefit to Nitrox save for the mild decompression benefit with the decreased pN2. The benefit comes if the diver exhausts the gas supply well before the no-stop time, in which case, assuming equal tank volumes, he/she would on-gas less N2 with Nitrox.

Best regards,
DDM

 

[Jafo19D]

For those that say that part of this effect is due to perhaps being a better diver and being more efficient I gotta say that this weekend’s dives were more strenuous than normal dives. The first day was boat dives (2) but the next 2 days were 5 dives and all of them involved long surface swims plus it was a pain getting to the entry and exit points. I definitely got more of a workout than normal and I felt great.

 

[Micko1974]

I do 12 - 14 day dive vacations where I dive 3 or 4 dives a day doing 36 - 45 dives per two week dive trip.

21% or 32% I feel no difference.

I certainly feel the difference after dives. I guess it is an individual experience as we are all different.

 

[Blackcrusader]

I certainly feel the difference after dives. I guess it is an individual experience as we are all different.

I do tend to eat and sleep well. Asleep by 10pm at latest often 9pm and wake up at 7am have a healthy hot breakfast and dive at 8:30am to 9am. A lot of people do go night clubbing on dive vacations till 4am then turn up complaining about being tired on dives lol.

My dive times are generally 75 mins per dive max 90 more or less.