Value of TDI-Extended Range course

[TrimixToo]

Absolutely, there were many things that should have kept them from doing that dive. However, what killed them was the inability to maintain reasonable cognitive function at depth because they were narc'd out of their gourds. The accident slope that they headed down because of that was just way too steep. Any of the other factors present are pretty immaterial comparatively.

Had they been of sound mind, they would have been more readily able to deal with the entanglement in the wreck, they would have been able to get to their deco gas without issue, and they would have been able to do their planned decompression, or at least would have been able to attempt that ascent. Now could the swell have drowned them? Sure. Could the current have blown them off? Absolutely. But neither of those were a factor in their inability to deal with the problems presented at depth because they couldn't think straight in the first place.

Could that dive have still ended in tragedy? Of course. Could the dive have still ended successfully with only some poopy exposure protection? Yeah, it very well could have Unfortunately they're all moot points. A circulatory system full of foam was the consequence of being unable to deal with the issues they had. And a significant part of their inability to deal with issues was their inability to think straight because they were suffering from severe nitrogen narcosis. Because helium costs money....

I'm with Johnny C. on this one. Not only were they likely impaired by narcosis, but probably also by CO2 retention with a gas density of 9.9g/l (!), caused by the exertion required to free Chrissy from the compartment where he got stuck. That would have exacerbated the narcosis considerably. To quote Simon Mitchell, "Unfortunately, CO2 retention is synergistic with nitrogen narcosis. There is enough evidence to believe that there is a synergy between the two; that is they are actually worse than the sum of their parts. CO2 retention is bad for narcosis. CO2 is a very narcotic gas."

 

[Nasser]

I'm with Johnny C. on this one. Not only were they likely impaired by narcosis, but probably also by CO2 retention with a gas density of 9.9g/l (!), caused by the exertion required to free Chrissy from the compartment where he got stuck. That would have exacerbated the narcosis considerably. To quote Simon Mitchell, "Unfortunately, CO2 retention is synergistic with nitrogen narcosis. There is enough evidence to believe that there is a synergy between the two; that is they are actually worse than the sum of their parts. CO2 retention is bad for narcosis. CO2 is a very narcotic gas."

I think you may be missing my point. The issue is not C02 retention or being impaired under those very adverse conditions and at those depths... of course that will happen! It's the decision making process in of itself prior to diving that was flawed and they should never have been making those dives... even diving mix it was too dangerous on that day.

Moreover and more to the point of this thread, the Rouse's dive that JohnnyC cited is not a good example because at 73m (240ft) they were clearly in the hypoxic range. Those dives do not reflect the current training standard of the TDI ER course which maxes out at 55m. So the Rouses's dive is somewhat irrelevant in this context... and frankly I think we've exhausted the whole Rouse's dive issue anyway.

Now if you choose not to dive more than 30m on air regardless of the dive conditions that is clearly your individual choice and the ER course is not for you.

 

[TrimixToo]

I think you may be missing my point. The issue is not C02 retention or being impaired under those very adverse conditions and at those depths... of course that will happen! It's the decision making process in of itself prior to diving that was flawed and they should never have been making those dives... even diving mix it was too dangerous on that day.

Moreover and more to the point of this thread, the Rouse's dive that JohnnyC cited is not a good example because at 73m (240ft) they were clearly in the hypoxic range. Those dives do not reflect the current training standard of the TDI ER course which maxes out at 55m. So the Rouses's dive is somewhat irrelevant in this context... and frankly I think we've exhausted the whole Rouse's dive issue anyway.

Now if you choose not to dive more than 30m on air regardless of the dive conditions that is clearly your individual choice and the ER course is not for you.

We do agree that the pre-dive decision-making process was fatally flawed, but I need to point out that some of us are not claustrophobic, are equipped for cold water, and accustomed to working in zero viz. The captains didn't call the dive, so they apparently thought it was safe enough. Indeed, the crew recovered both divers from the water, which is much harder than climbing the ladder would have been when it's rough.

One could likewise argue that planning for a 180' dive on air is unsafe, with gas density at 7.7g/l, well above Simon's recommendation of 6g/l, maximum. Interestingly, the density of air at 130' happens to be 5.9g/l. I have sipped the Kool-Aid here, but not gulped it, and will likely continue to plan for a maximum of 145' or so on air (6.5g/l).

I believe I have an ER card, somewhere, and I've done 180' on air, though it was unplanned. Thought it was going to be a bounce dive to 150' or so, with the single task of tying a knot in a rope. When it was deeper, I mentally shrugged, knowing it was within that 180' on air limit. Knowing what I know now, I'd call the dive and go back another day with mix. (For one thing, I wound up retying that "knot" on mix another day anyway.)

Was the course beneficial? Sure. I learned some stuff. But, it was mostly repeated in the two subsequent trimix courses. Given the state of knowledge we have today, it's not entirely clear to me that it should continue to exist as-is.

 

[Nasser]

We do agree that the pre-dive decision-making process was fatally flawed, but I need to point out that some of us are not claustrophobic, are equipped for cold water, and accustomed to working in zero viz. The captains didn't call the dive, so they apparently thought it was safe enough. Indeed, the crew recovered both divers from the water, which is much harder than climbing the ladder would have been when it's rough.

One could likewise argue that planning for a 180' dive on air is unsafe, with gas density at 7.7g/l, well above Simon's recommendation of 6g/l, maximum. Interestingly, the density of air at 130' happens to be 5.9g/l. I have sipped the Kool-Aid here, but not gulped it, and will likely continue to plan for a maximum of 145' or so on air (6.5g/l).

I believe I have an ER card, somewhere, and I've done 180' on air, though it was unplanned. Thought it was going to be a bounce dive to 150' or so, with the single task of tying a knot in a rope. When it was deeper, I mentally shrugged, knowing it was within that 180' on air limit. Knowing what I know now, I'd call the dive and go back another day with mix. (For one thing, I wound up retying that "knot" on mix another day anyway.)

Was the course beneficial? Sure. I learned some stuff. But, it was mostly repeated in the two subsequent trimix courses. Given the state of knowledge we have today, it's not entirely clear to me that it should continue to exist as-is.

You make some good points, especially about being equipped to dive in cold, zero vis conditions, but conversely let me ask you... if you were in warm water with no current and 40m vis in a country or area where Trimix was not available, and you had a chance to dive to say 50m to see a classic WWII wreck or amazing geological site, would you make the dive if you had training and experience in ER diving?

(barring owning your own rebreather which is not always feasible or desirable for some).

For me the answer is yes and very much reflects the conditions and circumstances I may find myself in when no Trimix is available. This is why I find the ER course very beneficial. If the answer for you is no regardless of where you're diving then this is where we may differ in opinion.

 

[TrimixToo]

You make some good points, especially about being equipped to dive in cold, zero vis conditions, but conversely let me ask you... if you were in warm water with no current and 40m vis in a country or area where Trimix was not available, and you had a chance to dive to say 50m to see a classic WWII wreck or amazing geological site, would you make the dive if you had training and experience in ER diving?

For me the answer is yes and very much reflects the favorable conditions and circumstances I may find myself in when no Trimix is available. If the answer for you is no regardless of where you're diving and if mix is unavailable then this is where we may differ in opinion.

My personal hard limit for planning a dive on air has long been 165', so this is really an edge case. But the more I learn and the more I do this stuff, the more conservative I get, and these days I am very reluctant to go deeper than about 150' or so on air, and never below 140' if the dive will be complex (going well inside a wreck, for example). There would have to be a very strong reason for me to go to 165' on air these days, and a lack of other attractive destinations that did not have this restriction. There's plenty of cool stuff to see on air that's shallower. I'd sure want to try to solve the availability problem first, but I'm a trimix gas blender so that might be a bit easier for me than for some.

All that said, everyone chooses what diving contracts to sign with themselves, based on available information, skills, known personal characteristics, experience, and opinion. You choose your risks, I'll choose mine, and we'll both be happy with our choices. At least, I certainly hope so.

 

[Nasser]

All that said, everyone chooses what diving contracts to sign with themselves, based on available information, skills, known personal characteristics, experience, and opinion. You choose your risks, I'll choose mine, and we'll both be happy with our choices. At least, I certainly hope so.

Exactly my point.

 

[rjack321]

For many years the Rouse's dive was highlighted as THE example of people working up to it, having tons of experience, thinking they were "adapted" to narcosis and fine on deep air... Until they had a bad day, the dive plan went to hell, and they fell so far down the incident pit there was no recovery.

It's in the distant past now (they died Oct 12,1992), and not part of people's consciousness unless you're seeing their memorial in Ginnie Springs. Deep air really has killed people who were considered very good divers at the time.

 

[wedivebc]

So nowadays adding 30ft onto your 150ft AN/DP card is all you get

I seem to recall that extended range used to be a 200ft/60m card - 10-15yrs ago.

I've been a TDI instructor for about 18 years and I don't recall an Ext Range program going beyond 180ft, you're likely thinking of PSAI.
I have never taught an ER class as I don't see the value in it but I can see in places like Truuk, Bikini, etc where He is scarce it would have value.

 

[rjack321]

I've been a TDI instructor for about 18 years and I don't recall an Ext Range program going beyond 180ft, you're likely thinking of PSAI.
I have never taught an ER class as I don't see the value in it but I can see in places like Truuk, Bikini, etc where He is scarce it would have value.

It was even further back, 1999-2002ish (a little before my time, I have no idea why this factoid stuck in my head)

@Blue Quaker explained when the MOD rose from 218 to 200 to 180
Value of TDI-Extended Range course

 

[wedivebc]

It was even further back, 1999-2002ish (a little before my time, I have no idea why this factoid stuck in my head)

@Blue Quaker explained when the MOD rose from 218 to 200 to 180
Value of TDI-Extended Range course

Yeah I saw that post. It looks like I joined TDI just after the change. Intrestingly I crossed over from ANDI who did have a 200ft XR class back then although the training director I worked with at the time did not think it was a good idea but I wasn't completely certain until way later in my instructor progression.