Any value sucking on your EAN tank during ride back to the dock?

[TMHeimer]

I think I read that too about using it if you ran out of O2 but can't remember where. You remember where that was from?

My Rescue manual (took it in 2006). Probably in the DM manual too.

 

[Eric Sedletzky]

Just make sure to inform the crew beforehand so they have a fresh stock
of rotten vegetables to throw at you whilst you are doing all that sucking

I don’t understand the joke but it sounded funny.

 

[hsinhai]

1.4 metres ABOVE surface [...] would breathing EAN32 after the dive benefit you in terms of on off gassing? Yes, but it would be very, very insignificant

So what your saying is staying in an upper floor at the resort prior to flight home has more benefit

 

[Blackfrogfeet]

So what your saying is staying in an upper floor at the resort prior to flight home has more benefit

You know what I made a mistake on my calculation on my last post. Breathing EAN32 at the surface gives an EAD being at 0.86 ATA, but that is not 1.4m above sea level. I don't know what altitude that would be, any ways, the point remains, the difference in off gassing would be negligible.

 

[beester]

You know what I made a mistake on my calculation on my last post. Breathing EAN32 at the surface gives an EAD being at 0.86 ATA, but that is not 1.4m above sea level. I don't know what altitude that would be, any ways, the point remains, the difference in off gassing would be negligible.

Increasing altitude by 1000m will drop the airpressure about 0.1bar (rule of thumb, 1013kPa at sealevel 898kPa at 1000m). But I'm not sure that calculating a "reverse" EAD will give you a solid view on the exact difference in off gassing between breathing air on the surface or Nx32. There are 2 many variables involved. The speed of offgassing is helped by breathing a mix of higher % O² (ideally pure O²), but it also depends on the inert gas loading in your body (the dive you made). Offgassing N² at the surface continues for hours (sometimes even days after the dive), and (micro)bubble creation peaks even shorthly after you have surfaced. In that regard I believe making sure your slowing down the last few meters of ascend (from 6 to the surface) is more important than breathing a mix with a slightly higher O² % (nitrox 32).

All of the above just as a theoretical discussion on the Op's question "is there value in breathing a higher O² gas going back to dock"!

If we are talking about using a higher O² mix to shorten your surface interval before a 2nd dive I would say definitely NO, not that it would work but you have no idea what your NDL will be or how much to shorten the interval. You are just making assumptions.

If we are talking about using a higher O² mix after a DCS accident. Also different. in this case the O² not only helps with off gassing and bubble reduction, but also aids with the oxygenation of the damages areas in your body, possibly reducing further damage. If no O² is available or you run out (bad!) take the next best thing (the breathing gas with the highest content of O²), everything will be better than nothing.

Someone was saying "don't give O² because it might hide symptoms"... well that is total bollocks! DCS diagnosis is in any case very difficult, so better safe than sorry... if I'm feeling slightly queasy, if anything feels off, I'll inform my buddies and will go on the O², and will start sipping water. Doesn't mean it's immediately DEFCON1, coast guard being called and the decompression chamber being readied. I keep on the O² for 15, 20 min, if situation improves I go off the O² and check if any slight symptoms or queasiness returns... if I inform the buddies we do a quick physical and neurological check... etc etc. Of course if someone comes up and has immediate neurological symptoms, it's DEFCON 1 ;-)

Also in my diving context, nobody is going to look strange... it's almost standard operating procedure.
My 2 cents

 

[UCFKnightDiver]

Could make a small positive difference. Rate of off gassing is linked to the differential between the nitrogen in the gas mix you're breathing and the nitrogen in your tissues. The greater the differential the more efficient/quick the off gassing, so if you have a rich mix, it definitely can't hurt and it might help a bit. Likely not going to make a huge difference though.

 

[kelemvor]

I've heard of captains, DM etc giving a nitrox tank to someone with sea sickness.

Works well if they've been in the back of the boat breathing diesel exhaust fumes while they chum the water... heck even if it's just a tank of air it will be beneficial.

 

[EFX]

It looks like the difference is very slight. I ran two profiles using my dive Excel spreadsheet. You can download the spreadsheet here.

The two profiles have this common data: salt water, first dive of the day, Buhlmann ZHL-16C using a GF (gradient factor) of 95/95, Nx32, 90 ft. for 25 min, 60 fpm descent rate, 30 fpm ascent rate, safety stop at 15 ft for 3 min, total SI of 12 hr, immediate flight to 8k ft taking 15 minutes to get to altitude.

Profile 1: air for the entire SI. Upon reaching the surface GF = 57. After SI of 12 hr GF = 8. After reaching altitude of 8K ft GF = 31.

Profile 2: Nx32 for 1 hr, air for 11 hr. Upon reaching surface GF = 57. After SI on Nx32 GF = 53. After SI on air GF = 7. After reaching altitude of 8k ft GF = 31.

The only benefit is after completing the SI (GF of 8 vs. 7) and that benefit is so minor as to be completely insignificant. Reducing the total SI to 4 hours reduced GF by 2 on Nx32 at the end of the SI and increased the 8k ft GF from 31 to 33.

 

[MaxTorque]

Surely the issue is that any slow tissues with a high PPN2 are going to take time to off-gas, and breathing the remains of your EAN tank for, what, perhaps 20 to 25 minutes, with an increase the gradient of say 0.1 bar (ish) really isn't going to do a lot is it?. I guess if you were (stupidly) planning on traveling to altitude (flight or climbing a mountain) soon after your dive, and effectively increasing the gradient of the fast tissues as well, then yes, perhaps a 0.1bar increase might help, but you wouldn't do that would you? (well if you would i'd suggest 100% o2 for a start!)

 

[EFX]

It looks like the difference is very slight. I ran two profiles using my dive Excel spreadsheet. You can download the spreadsheet here.

The link in the above quote points to the GoFile server. I deleted the file there because they automatically delete the file if there has been no downloads in a few days. Geesh! What a pain. So, I put the file on Filehosting.org's site. You can go to the "Dive Calculation Spreadsheet" thread in this forum to get it.