Review: TDI Normoxic Trimix with John Chatterton, November 2019

[NothingClever]

Great notes....very helpful.

I like the idea of using my SMB for the initial ascent and it gives me something new (to me) to add to my training portfolio.

 

[Diving Dubai]

I very much enjoy @tmassey write up's. They need to be read in detail, but with contemplation can be thought provoking as well as a damn good read.

I like the idea of using my SMB for the initial ascent and it gives me something new (to me) to add to my training portfolio

It's something we do fairly regularly, but for different reasons

If we get blown off a pinnacle with current, then it's imperative we get the dsmb on the surface ASAP. The chase boat will be primarily watching for dsmbs popping up off the site and reacting to them with some urgency, and you don't want to delay your time underwater because of the distance you may drift, and because the chase boat is with you, its not with someone else who might need assistance

My weapon of choice for a dynamic deployment (i.e. on the move) is the AP Valves crack bottle dsmb. In this case there's no faff inflating just a firm twist on the valve and off she flies. Obv no riding it up because that would be a real elevator ride

This frees up bandwidth to manage a max rate ascent etc and be able to react to the currents - and because we're likely to be blown off into the split, then there all likelihood of the possibility of down currents

I can see where inflating a normal dsmb could cause you to slow down while your dealing with whatever inflation method your using until of course you get practiced and add to the task loading

 

[CAPTAIN SINBAD]

Thanks for offering such a detailed perspective This thread has answered a lot of questions that were lingering in my mind.

Would you ask your GUE instructor if you had to wear your deco-bottles on one side or are they open to wearing them on both sides? No: it's an affront to the class *and* the instructor. I feel the same way about the reverse.

Not sure if I agree with the part that using a configuration different from the instructor is some kind of an offense to them. TDI Trimix manual explains both configurations in its text without pushing one over the other. Some TDI instructors insist that their students dive in the exact same configuration while others let them determine their own configuration.

GUE is a different animal because you are paying to achieve a very high level of proficiency in a very specific system. While GUE instructors are open to a conversation about why you should have both bottles on the right. they do not have the individual ability to change that.

I would be interested to know if you guys talked about Gas densities and work of breathing. Those are the two factors that led Dr. Simon Mitchell to publish his recommendations on the use of Helium for dives below the 100 ft mark. Since John Chatterton is apparently teaching in opposition to these recommendations, I was wondering if these concepts were part of his course and if yes what was his take on them?

Once again, many thanks for the detailed review.

 

[tmassey]

I would be interested to know if you guys talked about Gas densities and work of breathing. Those are the two factors that led Dr. Simon Mitchell to publish his recommendations on the use of Helium for dives below the 100 ft mark. Since John Chatterton is apparently teaching in opposition to these recommendations, I was wondering if these concepts were part of his course and if yes what was his take on them?

Very much so. There are extensive materials in advance of the class, including entire presentations from Dr. Mitchell and Dr. Doolittle and several peer-reviewed papers. The dates of several of these items was 2019...

As I mentioned in my Advanced Wreck review, Mr. Chatterton has been beating the CO2 drum for a long time — which has dovetailed with modern research.

As for ‘teaching in opposition’: I don’t think that’s accurate. We did discuss the findings and recommendations. I think that it’s more accurate to say he’s not a believer in blanket rules. Just because someone is not tied to a simple rule doesn’t mean they’re in opposition to it. Comments like that are *far* less nuanced than the reality. You put the lessons of this class into a box at your peril.

 

[helodriver87]

So what's his rationale for using air at 150'+?

I read the whole bit about experiencing narcosis or it's a boogeyman, etc... But what's his gain? Other than saving a few bucks on fills, what's it do for him? Why would he choose to dive air when it's an objectively poor choice in any environment?

I don't really agree with narcing students at 165' in class, but I can at least understand the perspective value. It teaches awareness of symptoms. What I don't get is his promoting of using gasses that provide a lower safety margin for zero benefit other than a cheaper gas bill.

 

[ChuckP]

What causes narcosis? Does it effect everyone the same? Does it effect the same person the same everyday given similar conditions? Are all dive sites and methods the same? Do you dive every now and then to say 150' or do you often go 130' or deeper?

Helium is just a tool in the toolbox.

I'll tell you a tool I just threw away today - swivel adapters for regulators used on single tank recreational set ups........

 

[helodriver87]

Sure, but you know what's guaranteed to reduce narcosis regardless of other factors that may or may not be in your control? Helium. Narcosis can happen shallower, but it's increasingly likely to occur deeper than recreational depths.

I don't have a set of lower performing regs for dives I expect to be easy. I use good regs regardless. Treat gas the same.

I'm sure you didn't intend it, but your first paragraph is exactly why you should err on the side of unnecessary helium.

 

[wetb4igetinthewater]

What causes narcosis? Does it effect everyone the same? Does it effect the same person the same everyday given similar conditions? Are all dive sites and methods the same? Do you dive every now and then to say 150' or do you often go 130' or deeper?

Helium is just a tool in the toolbox.

I'll tell you a tool I just threw away today - swivel adapters for regulators used on single tank recreational set ups........

Narcosis varies from person to person, and for each person from time to time.

When it comes to technical diving where the distance to serious injury or death is shorter, why mess around? Given that I know a whole lot less about this subject than Dr. Simon Mitchell, I'll just follow his advice. Those that know better than him can disregard it.

 

[ScubaWithTurk]

I absolutely LOVE these reviews and the subsequent comments from the OP.

They are well prepared and thought-provoking.

I do not love the idea of riding a smb up to the first stop but I now have something to think about. Just one example of the many things I have to consider thanks to these posts.

 

[KenGordon]

Helium high horsing here I think.

The cost and logistics of helium for OC are such that really most dives in 30 to 45m are not using it. Is that ideal? No, is it going to change? Probably not.

Back to the OP, I think you talked about taking a stage of 21/35 on an air dive to demonstrate the difference back to back. I have thought about doing that but decided I had no idea what the risk might be, imagining a whole load of He rushing into tissues while the N2 only gradually left, so concerned about ICD. Was this risk discussed? Is there a convincing argument as to why it is ok?