What's the deal with the "Advanced Nitrox" certification?

[ianr33]

Helium reduces CO2 production? CO2 "retention" is from shallow breathing (or failure to fully expire, and rebreathe your exhaled breath from dead spaces within your regulator's second stage), and failure to fully expire the CO2 produced from your breath. Deeper dives require more force to fully expire your breath, and can result in increased CO2 levels. How does Helium offset this?

Helium mixtures are less dense than air/nitrox,therefore they will flow more easily.(The atoms are moving more quickly) That leads to better gas exchange in the lungs. Also the work of breathing from the reg will be less.

 

[HowardE]

Can you post a link to an actual study that backs this data?

 

[ianr33]

Some quick Googling brought up this to do with WOB
Helium-oxygen reduces work of breathing in mechani...[Intensive Care Med. 2003] - PubMed Result

Something that mentions gas exchange www.chem.yorku.ca/hall_of_fame/essays00/helium.htm
<<In medicine, it is used to relieve sufferers of respiratory difficulties because it promotes oxygen intake and carbon dioxide removal>>

I'm sure there are much better references to this. The physics seems pretty clear cut to me.Helium diffuses very quickly,so will help in getting CO2 out of the lungs.

Helium really is your friend for deep dives.

 

[HowardE]

has anyone corrolated this to diving?

 

[nereas]

Well, I hate to actually discuss the original question, but out of respect to the OP...

Originally, the question was which course would be more useful: Advanced Nitrox or Recreational Trimix? Which led inexorably to what kinds of mixes would be practical and affordable in the depths and durations I plan to dive.

I honestly don't know: is CO2 a problem for short dives in the 100' to 140' range? I imagine "recreational trimix" being interesting for a dive like the Forest City: it lies on a slope with the bow at about 70' to 150' if you visit the rudder under the stern.

The railing is about 135', you can visit it, shine your light on the rudder, then make your way up to the bow slowly, visiting the boilers on the way. You'll probably pass a couple of thermoclines on the way down and back up, you you have a few incentives for not spending too much time at the stern.

I realize that the "bottom time" of a no deco dive is quite short, but you still spend significant time deeper than 80', so I'm quite interested in lowering the END on a dive like this.

Is lowering CO2 a significant factor for a dive like this? I honestly don't know. It certainly can't hurt. That being said, I imagine that the first order of business for being a safe deep diver is breathing correctly, and only then working on the gas mixture.

As Howard has said, I also see no use in "recreational trimix."

I presume by "recreational trimix" is meant TMX 30/30. I find that this mix works better for deco in the range of 140 to 70 ft than as a back-gas mix. I don't know why some recent agencies advocate using this as a back-gas, unless it is specifically for diving in the range of 100 to 140 ft. I see no benefit in it for dives shallower than 100 ft. I know that anecdotal benefits are broadcast, however the cast of characters who subscribe to these kind of agencies will believe anything they are told to believe from the top of the agency, unfortunately.

This kind of person makes a very poor diving buddy because (1) they often cannot resist criticizing everything you do and (2) they further cannot explain why they are doing what they themselves do.

So, back to Advanced Nitrox, then.

Various tech agencies spead the tech curriculum over several stages. Some do this by depth. Others by gas mixture.

Tech instructors are the supermen/women within their agencies, so they have a license to customize their courses to the needs and abilities of their students, as they see fit. [Not true in all agencies, just some.]

Advanced Nitrox is normally the first tech course in any sequence. It is the class where the instructor gets to meet the new students and work on their weighting, trim, buoyancy control, sculling, finning, and what not. So normally ordinary 100 ft dives are done with EAN 50 used as a "clean up" mix in simulated decompression.

Some instructors combine the Advanced Nitrox with the Stage Deco. This however defeats the purpose of going through a simulation phase alone, although the first dive of the 4 to 6 dive combined course then is normally simulated deco.

Advanced Nitrox is just a stepping stone in the continuum of tech training, up to full advanced hypoxic trimix.

It all depends on the instructor that you choose.

 

[nereas]

Well I guess that depends on the model you are using and depth.

Dive one with air RT 79.

Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 180ft (3) Air 60ft/min descent.
Level 180ft 27:00 (30) Air 1.32 ppO2, 179ft ead
Asc to 110ft (32) Air -30ft/min ascent.
Stop at 110ft 0:40 (33) Air 0.89 ppO2, 109ft ead
Stop at 100ft 1:00 (34) Air 0.82 ppO2, 99ft ead
Stop at 90ft 2:00 (36) Air 0.76 ppO2, 89ft ead
Stop at 80ft 2:00 (38) Air 0.70 ppO2, 79ft ead
Stop at 70ft 2:00 (40) Nitrox 50 1.52 ppO2, 31ft ead
Stop at 60ft 3:00 (43) Nitrox 50 1.37 ppO2, 25ft ead
Stop at 50ft 4:00 (47) Nitrox 50 1.23 ppO2, 19ft ead
Stop at 40ft 6:00 (53) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 7:00 (60) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 7:00 (67) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 12:00 (79) Oxygen 1.27 ppO2, 0ft ead
Surface (79) Oxygen -30ft/min ascent.

Off gassing starts at 132.4ft

OTU's this dive: 106
CNS Total: 43.0%

127.0 cu ft Air
25.0 cu ft Nitrox 50
13.1 cu ft Oxygen
165 cu ft TOTAL


DIVE PLAN COMPLETE

Dive 2 with mix RT 72 min.


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 180ft (3) Triox 21/35 60ft/min descent.
Level 180ft 27:00 (30) Triox 21/35 1.32 ppO2, 85ft ead, 105ft end
Asc to 110ft (32) Triox 21/35 -30ft/min ascent.
Stop at 110ft 0:40 (33) Triox 21/35 0.89 ppO2, 46ft ead, 59ft end
Stop at 100ft 1:00 (34) Triox 21/35 0.82 ppO2, 40ft ead, 53ft end
Stop at 90ft 1:00 (35) Triox 21/35 0.76 ppO2, 35ft ead, 46ft end
Stop at 80ft 2:00 (37) Triox 21/35 0.70 ppO2, 29ft ead, 40ft end
Stop at 70ft 2:00 (39) Nitrox 50 1.52 ppO2, 31ft ead
Stop at 60ft 2:00 (41) Nitrox 50 1.37 ppO2, 25ft ead
Stop at 50ft 2:00 (43) Nitrox 50 1.23 ppO2, 19ft ead
Stop at 40ft 4:00 (47) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 6:00 (53) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 7:00 (60) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 12:00 (72) Oxygen 1.27 ppO2, 0ft ead
Surface (72) Oxygen -30ft/min ascent.

Off gassing starts at 130.8ft

OTU's this dive: 98
CNS Total: 40.1%

125.2 cu ft Triox 21/35
18.0 cu ft Nitrox 50
13.1 cu ft Oxygen
156.3 cu ft TOTAL


DIVE PLAN COMPLETE

Run your same comparison using TMX 30/30 versus EAN 30. That would be more relevant.

 

[nereas]

I've dived to 143' on air twice in gorgeous, sunlit, warm water (Reino Magico at Isla Juventud, Cuba) and to 135' in gorgeous, cold water on the Forest City in Tobermory, Ontario. And a few others deeper than 100', some cold, some warm.

Right now, I am not consumed with a desire to go deeper for its own sake, and up here in Ontario there is plenty to explore at shallower depths. That being said, I am quite aware I got narc'd and I am not particularly enamoured of the idea of dealing with an emergency when my judgement is impaired.

So, my goal is to become a better diver on "recreational" dives, thus my interest in some form of Intro to Tech training (like DIR-F) where there will be an emphasis on trim and bouyancy control and executing basic procedures correctly. I see learning more about gas mixes as an add-on to such training, but not an end in itself.

A Recreational Helium course could be useful for improving my dives in the depths I am already diving, thus my interest in it. Advanced Nitrox doesn't seem that useful unless you are taking it as a stepping stone to technical diving, but I will probably take it eventually. Accelerated deco on 100% O2 might be useful one day for contingencies, and someone pointed out that having a cylinder of 100% O2 is useful if you also take an O2 provider course.

The kind of dives you are speaking of are also called "normoxic trimix" dives. Some agencies now teach these before the decompression stage, although I don't believe that is smart to do.

I therefore recommend the more normal progression:

Advanced Nitrox
Stage Decompression
Normoxic Basic Trimix.

IANTD invented this approach, and TDI and NAUI have followed it for quite some time.

 

[texdiveguy]

The kind of dives you are speaking of are also called "normoxic trimix" dives. Some agencies now teach these before the decompression stage, although I don't believe that is smart to do.

I therefore recommend the more normal progression:

Advanced Nitrox
Stage Decompression
Normoxic Basic Trimix.

IANTD invented this approach, and TDI and NAUI have followed it for quite some time.

The proper term for 30/30 is hyperoxic trimix, (any trimix were the % O2 is greater than 21%).

Tech. only trimix with 21% O2 is normoxic,,,, a blend containing less then 21% O2 is hypoxic by def..

 

[BlueDreamDivers]

"has anyone corrolated this to diving?"

"There is work supporting that CO2 retention is minimal or non-existent when the breathing medium is a HeO2 mixture and Trimix..."
Technnical Diver Encyclopedia- Carbon Dioxide Retention -Tom Mount
Dr.Ed Lanphier, M.D. EH 1955. Nitrogen-Oxygen Mixture Physiology, Phases 1 and 2. Washington:Navy Experimental Diving Unit
Lanphier.EH.June 1958.Nitrogen-Oxygen Mixture Physiology, Phases 4 and 6. Washington:Navy Experimental Diving Unit

 

[HowardE]

thanks Marcos for the interesting reading.