Recreational Trimix classes

[100days-a-year]

I don't claim to be smarter than the math wizards who wrote all the software I have but as a devil's advocate I have run tables with every conceivable mix and despite any claims to the contrary I have found that different conditions reward certain mixes and penalize others.FI..32/36 and 80/20 will sometimes get you out sooner,sometimes more He does beget more deco.What I also found was that the differences either way in dives I've done which are <250' and BTs less than 35min amount to less than 5 minutes in most cases.If people would back off those easily disproved claims(I used VPM,Voyager,GAP,ZPlan,MPlan)and concentrate on Rich' posts claims and goals there would be a lot more agreement.Standardization prevents a lot of problems from ever arising.Is it really so important that everyone dive exactly as you do? no, but getting out the info in a combative manner makes it seem that way.It is funny to see that cost is an issue in deco gases that have much less volume used versus back gas which can eat up more He than a deco cylinder can carry.Are the "benefits less important?200cuft of 30/30 equals 60 cuft of he and stages of al40 50o2/50he would have 20cuft and at 1/3 s it would be 40cuftHe used backgas and 13.6cuftHe seems to me.

 

[narcT]

detroit diver once bubbled...


Conventional thought is that ppo2 should be no higher than 1.4.

The advantages of higher helium is that you have less nitrogen to breathe.

Weeelllll I have had this debate before. My wife and I set our dive computers to 1.6 and dive it all the time.

EAN32 at 130 is the norm. Its a personal choice, we simply have chosen to dive this (EAN32 is all we can get on a lot of live aboards anyway).

The 1.4 is a good place for most people, but I don't know any tech divers where I live that dive 1.4 And in thousands of dives out here I have never seen anyone take a hit...even after 30 minutes at 1.6. Just doesn't happen were I live, maybe its because of all the BC's we burn to the DIR gods???

NOTE: I DO NOT RECOMMEND ANYONE DIVE PPO2'S OVER 1.4

Triox 30/30 for rec divers is a money making scam. Its a waste of money (and makes my nads hurt when I think of all that precious helium being wasted!!!). Dive nitrox or take a real trimix class, then dive the proper mix for the dive.

Hummmm tomorrow at 425 I'll use a mix of

Have you hugged a Troll today???<<--:boom:

 

[chrisch]

Hey guys I thought we were debating He/N2 here not PO2s!!

While I agree that 30/30 sounds wierd as the PO2 limits the depth and therefore makes the He content questionable I really was trying to get some feedback on the other (non-GUE) mixes. If a high PN2 has problems with red cell rigidity and CO2 retention then some He is helpful. Likewise narcosis can be combatted by some He in the mix.

Qustion is how much is needed at "recreational" depths - i.e. less than 150fsw/45m

What's the thing about 30% He?

Chris

BTW I've signed up for the damn thing now so too late...

 

[narcT]

Ask your instructor to explain this (decoplanner 2.0.49):

120ft for 30 minutes on 30/30 is 20 minute deco.
120ft for 30 minutes on 30/17 is 17 minute deco.
120ft for 30 minutes on EAN30 is 15 minute deco.

30/30 is just tooooo much darn helium at rec depths IMHO.

NOTE: FOR TROLLING PURPOSES ONLY, DO NOT USE FOR DIVING

 

[chrisch]

Mmmm...

Well that's software for you. Just run the same profiles on V Planner and the longest stop is the EAN30 with the 30/30 next then the 30/17.

Guess we could do this lots of times and get lots of answers. I also notice that you can speed things up by using a EAN deco gas or travel gas to "pull" the He out and then He mixes get way better.

However, my question still stands why should the fraction of gas (FHe30) be important? Surely its the PP (PPHe) that is important??

Dazed and confused..

Chris

 

[narcT]

The only reason He is important to me is because out here it costs $1.50 per cubic foot!

So if 30/17 works at 120ft or less, why pay for 30/30?

 

[cornfed]

chrisch once bubbled...
Mmmm...

Well that's software for you. Just run the same profiles on V Planner and the longest stop is the EAN30 with the 30/30 next then the 30/17.

I think it's pretty obvious that you can't draw any meaningful conclusions about helium use from these numbers.

But then again, what I think is obvious isn't always what others see as such.

 

[100days-a-year]

And could someone post a link to a study or even an MD that validates the red blood cell rigidity thingie.I have seached,googled and talked to DSOs and could get no validation.In the law buisness we call that hearsay. and it's not accepted as evidence.

 

[Delta_P]

Councillor: Much as I would like to believe that Diving Safety Officers are the font of all diving related knowledge, you're better off searching the medical literature:

www.pubmed.com

A search on Erythrocytes and Rigidity produces ~ 400 hits. I leave it to you to comb the abstracts. Lots of interesting stuff on changes in RBC membrane structure with exposure to hyperbaric oxygen and hydrogen, and some on hyperbaric nitrogen.

This paper from the 80's is a little old, but might be a good place to start:


"Alterations in red blood cell morphology during a 500 metre dive."

Paciorek JA, Onarheim J.

 

[flw]

I had a look in ovid this morning out of interest, and came accross lots of references to the mechanisms for hyperbaric O2 causing changes in membrane lipid order, and one for a 100m dive using heliox causing changes in osmostic resistance and decreases in Cl, K and Na - but nothing suggesting it was hyperbaric N2 as is commonly suggested.
Is it therefore a mechanism dependant purely on hydrostatic pressure, or a function of high PO2s rather than high pN2's