PADI Trimix

[roakey]

Originally posted by neil
I just want to ask at what point does a statistical sample become large enough to be counted

This is one of those cases where no number of dives constitutes a statistical sample such that a valid conclusion of “deep air is safe” can be drawn. The reason is that a cognitive deficit can be shown among divers at, say, 150 feet. The intoxicated driver analogy works here, too. For every DUI accident or “bust” they’re literally hundreds of others out there that don’t get caught or have accidents. No matter how much “accident free” diving can be shown among intoxicated drivers, it’s not safe.

The reason it’s not safe is that though you can function with a cognitive deficit, the problem is when a emergency comes up, like someone stepping out in front of you in traffic or your buddy running out of air. Note: these are mere examples, please, no one come back with “I’ve solved an OOA at 200 feet!” it’s anecdotal, drunk drivers have avoided pedestrians, too.

If no problems occur, almost anyone can go to 180 and come back so-called “safely” (been there, done that, feel pretty stupid). It’s when you have to problem solve, and I’m not talking about calmly multiplying numbers on a slate, I’m talking about solving an entanglement hazard while swimming against a stiff current and your bottom time’s up.

Another nasty problem with nitrogen narcosis is you don’t know how it’s going to effect you day to day. I can pretty well predict how I’m going to feel and act after two Adios Muthus (Greenstreets bar in San Luis Obispo, California, late 70s ) but I don’t know how wacked I’m going to be at 150 feet, or more sinister, how AWARE I’m going to be of being wacked at 150 feet from day to day.

In my opinion, there are two kinds of air divers at 150 feet, those who know they’re diving under the influence and those that don’t. And it’s the second batch, the “I’ve been at 180 and felt just fine” crowd that scares the bejeebies out of me.

Roak

 

[Uncle Pug]

Originally posted by MikeFerrara
I had a student claim he was noticably narced at 100ft. Maybe we should use a max END of 80ft. Are we getting carried away?

I think that with a little *cognitive awareness* you could discern the effects of narcosis at 80....

It is a simple psyiological fact that you are effected....
It is just that narcosis is by nature insidious....
Most divers are unaware of it....

I am surprise that your student was so in tune to what was happening....

Good for him!

 

[Lost Yooper]

I've done more than my fair share of deep air diving going while in and out of shipwrecks and following a computer for deco. I never had one single problem with narcosis, but I freely admit that doing that stuff was stupid. I've also done my fair share of DUI and, again, never had a problem. Narcosis is a fact, and it affects everybody. It cannot be dealt with "reliably" and anyone who thinks they can are only fooling themselves. By continuing to dive deep on air, you are setting yourself up for a meeting with Murphy.

You can't cheat physiology.

Mike

 

[Matt]

One thing I will comment on about Padi is the fact that they've always had the Best course outline's, and best materials. To mock the Tec Rec course which some of you have classed "Deep Air" isn't accurate either.

The course if you look at the outline (how many of you have actually done this?? Be HONEST!) is quite well done. The book is a little repetitious, but there are some good things in the course. I especially like all the unbungeed OMS wings, and Scubapro regs!
You DIR guys will most likely agree w/alot of the gear suggestions as well.

But seriously, The amount of dives you require to pass the course is also good.

Things I don't agree w/about tec rec. Padi's continuing attitude to jump on the bandwagon, that everyone can do it, and the amount of slates needed as an instructor is excessive as well.

Padi Trimix. If they do the materials like tec rec, and get some good instructors the course should be good.

The course will boil down to instructor. As long as Padi's tough on who becomes an instructor (like they have for tec rec), the course should be as good as any of the other agencies courses.

Don't knock it till ya see it!

:mean:

 

[Drew Sailbum]

Originally posted by roakey:
This is one of those cases where no number of dives constitutes a statistical sample such that a valid conclusion of “deep air is safe” can be drawn.

Heck, diving isn't safe! The question is really whether the risk is acceptable.

Using the drinking and driving analogy, the law sets a maximum limit of alcohol use above which impairment may be presumed in most states, just don't ask about SC :anon:. Usually that is a set blood alcohol level, and there is a lot of arguing over what that level should be - 0.10% and 0.08% are common legal limits in the U.S.

Since it is not practical to run blood tests (or other truly objective tests) underwater to gauge nitrogen narcosis, recommended equivalent nitrogen depth limits are usually discussed. So what should it be? 80ft END? 100ft END? 130ft END? 165ft END? After all, doesn't nitrogen loading start in less than 1fsw?

So what is the objective rationale for setting any particular limit? There is none. It is a best guess at a level at which most people will be able to manage despite any narcosis effect.

 

[VTWarrenG]

Matt,

I disagree whole-heartedly with the concept of "Rec Tec." It's an oxymoron. Technical diving is antithetical to recreational diving in almost every way -- training, fitness, equipment, attitude, skill. I don't believe PADI has the calibre of instructors or the curriculum necessary to safely teach any kind of technical diving. A significant number of PADI instructors aren't really even competent to teach OW, IMO.

- Warren

 

[VTWarrenG]

Drew,

So what is the objective rationale for setting any particular limit? There is none. It is a best guess at a level at which most people will be able to manage despite any narcosis effect.

Exactly. You answered your own question. The rationale for setting 100 fsw as the rule of thumb for max END is precisely because most people will experience only very mild narcosis there. Certainly, some people could go much deeper without symptoms, while some can't even go to 100 fsw.

The gov't sets limits on blood alcohol content the same way -- experiments and experience suggest that the vast majority of people can safely drive a vehicle with a BAC of 0.08% or less. Some people, of course, can function well above that limit, and some cannot function at all even well below it.

We're talking statistics here -- we'd like to keep ENDs shallow enough that severe narcosis symptoms are only anecdotal, and don't occur commonly enough to be significant. Just as 0.08% seems reasonable for BAC, 100 fsw seems reasonable for END.

- Warren

 

[Uncle Pug]

But the advantages are harder to detect shallower that 80 fsw....
And since it is a tad bit more expensive....
We can live with the END <100 but if we can we'll add the good stuff from 80' on down.

 

[Drew Sailbum]

Warren,

With regard to the qualifications of PADI Instructors to teach a tec course; to each his own opinion. To be fully aware, "PADI's" TecRec and Gas Blender courses were released as a DSAT courses. All indications are that Trimix will be a DSAT course as well.

Before you ever go past 130ft as a student you must meet the prerequisites for the DSAT Tec Deep Diver Course:

• Be certified as a PADI Advanced Open Water Diver or equivalent.
• Be certified as a PADI Rescue Diver or equivalent.
• Be certified as a PADI Enriched Air Diver or equivalent.
• Be certified as a PADI Deep Diver or equivalent.
• Have a minimum of 100 logged dives of which 20 must be enriched air dives, 25 dives must be deeper than 18 metres/60 feet and at least 15 dives must be deeper than 30 metres/100 feet.

Qualifying to teach the current TecRec courses requires more documented diving experience than a Course Director. To teach these courses, you must:

• Be a renewed PADI Master Scuba Diver Trainer or PADI Instructor with a higher rating.
• Be a PADI Enriched Air Instructor.
• Be a PADI Deep Diver Specialty Instructor.
• Be certified as a DSAT Tec Deep Diver (or equivalent). (This may be part of the Tec Deep Instructor training course).
• Have assisted with at least two DSAT Tec Deep Diver courses or one Apprentice Tec Diver course and one Tec Deep Diver course. (Completing the DSAT Tec Deep Instructor training course credits you as having assisted with an Apprentice Tec Diver course.)
• Have a minimum of 270 dives logged, with at least 25 stage decompression dives that had a maximum depth deeper than 40 metres/130 feet.
• Have certified a total of ten or more PADI Deep Divers and/or PADI Enriched Air Divers. Any combination that totals ten in acceptable.
• Have successfully completed the Tec Deep Instructor Standards Exam and the Tec Deep Instructor Theory and Practical Application Exam. (This is usually part of the Tec Deep Instructor training course).
• Meet the peer review waterskill requirements listed on the DSAT Tec Deep Instructor Application through the attesting signature of a DSAT Tec Deep Instructor or a PADI Instructor with an equivalent rating. (This is usually handled by the instructor trainer during the Tec Deep Instructor training course).

From the DSAT Gas Blender:
"DSAT is a corporate affiliate of PADI. The DSAT TecRec Program is distributed by International PADI, Inc."

 

[BIGJC]

I read an article about a US navy study of narcosis (an old one from the 70's I think) and it said that below 100 feet 100% of the programs participants were effected by narcosis, much like alcohol that "feeling of well being" is clouding your ability to evaluate yourself..... on the other hand I have been deep on air and so have most of you guys.... we're all still here! I have also driven a car when I have had to many as well... dont care to repeat that one.. know what I mean???