Dry Hypoxia Training for Rebreather Divers

[Dave Sutton]

^^^ to the above, I reject the agrument. Really... and I say this with a smile.. it's nonsense.

Hypoxia in rebreather use is caused by technical failure (IE: a freeflowing ADV with hypoxic diluent near the surface), or human error (IE: not turning on 02), but not by any deliberate act.

Divers do not "Push" towards low PP02... there is no positive value to it. Low PP02 is an error state, not a concious decision that is actively made. Normal Target PP02s are a full order of magnitude above that which causes hypoxia for reasons of narcosis and decompression.

I think that rational analysis shows this argument to be a non-player. In the same rhetorical way the same exact argument would be considred a non-player in aerospace (where pilots can *also* choose the cabin altitude of pressurized aircraft). By that same argument, pilots should not be taking high altitude training because they might "push the pressurization system".

It's just not a rational argument. It is, in fact, a rationalization of a decision not to obtain a holistic and complete set of training targets, knowing that every tiny bit of knowlage that you obtain increases your survival potential. I mean... "I refuse to learn because after I learn I might mis-use the information" is not a sensible thing when the sport you participate in weeds out the weak by killing them.

Best quality training pays attention to both proactive and reactive responses. One hopes that the former precudes need to use the latter, but does not ignore the possibility.


Dave

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[silentbob]

It's just not a rational argument. It is, in fact, a rationalization of a decision not to obtain a holistic and complete set of training targets, knowing that every tiny bit of knowlage that you obtain increases your survival potential. I mean... "I refuse to learn because after I learn I might mis-use the information" is not a sensible thing when the sport you participate in weeds out the weak by killing them.
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Please don't misrepresent my argument Dave. I do not refuse to learn because I might misuse information. I refuse to ignore evidence that we are highly fallible primates that become overly confident in our abilities.

A near miss is often cited as a salutary experience precisely because it pulls us out of our complacency and familiar comforts of heuristic behavior. Till the shock wears off and we get complacent again.

I ask you how it is that you know that "every tiny bit of knowlage (sic) that you obtain increases your survival potential." I would call that (in anyone) overly optimistic. There is a long list of dead "gurus".

Can there be be a straight forward comparison between flying hypoxia and diving hypoxia? Fatigue, in water cognitive impairment, CO2 retention, narcosis and alternobaric vertigo (to name but a few) are all phenomena that could confuse an ability to recognize hypoxia. How many phenomena are present in flying that could confound a self awareness of hypoxia? I can think of fatigue and high Gs but I guess there could well be more, I am not a pilot.

 

[PeterN]

Dave your continued assertion that those who question the validity of the aviation model to diving borders on the ad hominen. It is more than a little patronizing to suggest that anyone who disagrees with you is anti training. Especialy with this crowd.

My level two avalanche instructor, one of Canada's most acomplished climbers, went out and got himself killed a few weeks after my course. The details were tragic as conditions were appaling and no one should have been out in them.

All that of course proves little, exept that training has many unintended concequences.

I take Silent Bob's point that human behavior is much more complicated than simple stimulus and responce.

I feel that the whole muscle responce theory of dive training is over rated. Don't get me wrong, practice is a critical component of high performance. It is just that sometimes one just needs to know what is going on.

This has been an instructive thread. If nothing else it illustrates just how much work remains to be done in the field of re breather training.

Thanks for taking the initiative.

Peter

 

[silentbob]

I take Silent Bob's point that human behavior is much more complicated than simple stimulus and responce.

Very succinctly put Peter.

If anyone hasn't read "Thinking Fast and Slow" by Daniel Kahneman (Daniel Kahneman - Wikipedia, the free encyclopedia) I urge you to.

It is a humbling read that makes it clear why checklists and formal risk assessments are essential if we want to reliably decrease risk.

 

[silentbob]

Double up

 

[silentbob]

^^^ to the above, I reject the agrument. Really... and I say this with a smile.. it's nonsense.

Are you trying to be condescending?

Hypoxia in rebreather use is caused by technical failure (IE: a freeflowing ADV with hypoxic diluent near the surface), or human error (IE: not turning on 02), but not by any deliberate act.

Divers do not "Push" towards low PP02... there is no positive value to it. Low PP02 is an error state, not a concious decision that is actively made. Normal Target PP02s are a full order of magnitude above that which causes hypoxia for reasons of narcosis and decompression.

I think that rational analysis shows this argument to be a non-player. In the same rhetorical way the same exact argument would be considred a non-player in aerospace (where pilots can *also* choose the cabin altitude of pressurized aircraft). By that same argument, pilots should not be taking high altitude training because they might "push the pressurization system".

It's just not a rational argument. It is, in fact, a rationalization of a decision not to obtain a holistic and complete set of training targets, knowing that every tiny bit of knowlage that you obtain increases your survival potential. I mean... "I refuse to learn because after I learn I might mis-use the information" is not a sensible thing when the sport you participate in weeds out the weak by killing them.

Best quality training pays attention to both proactive and reactive responses. One hopes that the former precudes need to use the latter, but does not ignore the possibility.


Dave

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Dawkins Law of the Conservation of Difficulty states: "Obscurantism in an academic subject expands to fill the vacuum of its intrinsic simplicity"

There, we're even..

 

[anarchista]

Best quality training pays attention to both proactive and reactive responses. One hopes that the former precudes need to use the latter, but does not ignore the possibility.

The third element is the hardware that precedes, informed about upcoming issues.

greet rc

 

[PeteG]

Dawkins Law of the Conservation of Difficulty states: "Obscurantism in an academic subject expands to fill the vacuum of its intrinsic simplicity"

What has Obscurantism got to do with this? Dave is actually suggesting the opposite; to arm the diver with all the knowledge he can gather so he has more to base the decision to jump into the water with this life support machine on his/her back or not!

I also do not think that the human response to hypoxia and the individual decision of each diver to weight the pros and cons if they should (or want to) undertake dry hypoxia training with trained personnel in a professional environment, should be referred to as "intrinsic simplicity".

You are indeed correct that there will be those individuals that will, if they undertook this training, become more complacent about their PPO2 thinking they can rely on 'signs' or hypoxia.

However, I think this would be a minority and if the training material was to be developed, I would like to see it clearly put that the 'signs' can not be 100% relied on, 100% of the time. I'm sure Dave could clarify if this is the case in the aviation industry.

If of course your quote was not to do with the OP question of if dry hypoxia is something people want, then disregard the above!

Can there be be a straight forward comparison between flying hypoxia and diving hypoxia?

Good question, one I would like to know as well. I would assume there would have to be more research into if the differences Silentbob described and then one or more training agencies would have to fund the time and money to find out if it's worth going down the path in the first place.

I feel that the whole muscle responce theory of dive training is over rated. Don't get me wrong, practice is a critical component of high performance. It is just that sometimes one just needs to know what is going on.

If this is in regards to the tread; if dry hypoxia training is a good thing or not, then doesn't having that training arm you with more knowledge so you have more a chance of identifying whats going on before the time of useful consciousness has past?

This has been an instructive thread. If nothing else it illustrates just how much work remains to be done in the field of re breather training.

Thanks for taking the initiative.

100% agree! Thank you to all for giving me more 'food for thought' so to speak.

 

[silentbob]

What has Obscurantism got to do with this?
If of course your quote was not to do with the OP question of if dry hypoxia is something people want, then disregard the above!

Yes the quote has nothing whatsoever to do with the OP. It was a playful/reciprocal dig at Daves' rebuttal.

 

[anarchista]

I breathed pure nitrogen in the OC. (I have already dived on my closed-circuit oxygen.)
I did not notice a large or small signs, of that breathing nitrogen.
The body reacted share increased depth of breathing, it was late a few breaths in relation to the stimulus (there is no delay when the action of breathing control and there ppCO2 but at high levels of respiratory stimulus is turned off).
It was still nice.
There is no comparison to the high levels of CO2.

Therefore I personally do not see the usefulness of training, in which the only symptom is numbness in the fingers, three days earlier.

Firefighters and rescuers mining have ppO2 detectors, as is the low level, the use of open circuit, closed-circuit with compressed oxygen, closed circuit oxygen chemically accumulated.
Equipment is more reliable.

rc greet

 

[matt]

Hypoxia in rebreather use is caused by technical failure (IE: a freeflowing ADV with hypoxic diluent near the surface), or human error (IE: not turning on 02), but not by any deliberate act.

...coupled with gross absence of monitoring.

 

[anarchista]

Then I estimated about.
Reasons: Many CCR and SCR structures are not safe.
Allow for life-threatening conditions. mCCR generate such states in a wide range. Other designs also, it's still fledgling technology.

Enhancing safety training is always valuable. But one must be able to defend its position substantive and documented arguments.
Therefore, the assessment is not high.

rc greet

 

[Dave Sutton]

...coupled with gross absence of monitoring.

I'm not so sure about that... Jury is out on this part. I can't see anyone not monitoring within the time base needed to drop a loop from 1.3 to 0.08-0.05 or so, which is where TUC and real time begin to merge to produce an unconcious diver. Maybe I am giving diver-kind more of a benefit of the doubt than I should.

Ever do a dry "breathe-down" drill to be able to tell me what sort of time base we are talking about?

In any event, anyone who is so grossly negligent is in exactly the right sport to become a nominee for the Darwin Award, and nothing that we can do will help. I can't base training suggestions on that lowest common denominator.



Dave


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[Dave Sutton]

Are you trying to be condescending?

Dawkins Law of the Conservation of Difficulty states: "Obscurantism in an academic subject expands to fill the vacuum of its intrinsic simplicity"

There, we're even..

Excellent, well said, and well taken. :kiss:

I continue to reject the argument however. Then again... I can only view the world thru the looking glasss of my own nature and experience. I could never believe that "less is more" when if comes to my education in any subject and have a hard time believing that it's true for anyone. Perhaps I give the human animal more credit than I ought.


Best,

Dave


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[matt]

I think I lost the plot. Humour me. Can you outline the scenario that this training is mitigating risk for?

Matt.

I'm not so sure about that... Jury is out on this part. I can't see anyone not monitoring within the time base needed to drop a loop from 1.3 to 0.08-0.05 or so, which is where TUC and real time begin to merge to produce an unconcious diver. Maybe I am giving diver-kind more of a benefit of the doubt than I should.

Ever do a dry "breathe-down" drill to be able to tell me what sort of time base we are talking about?

In any event, anyone who is so grossly negligent is in exactly the right sport to become a nominee for the Darwin Award, and nothing that we can do will help. I can't base training suggestions on that lowest common denominator.



Dave


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[Dave Sutton]

I'm just curious if you (not you particularly, the readership in general) has an accurate idea of how long you have after your solenoid sticks shut (or for you rEvo and KISS divers, after your orifice get clogged with a bit of crud) before your PP02 drops from 1.3 to where you would be unconcious. That's just a framework for good situational awareness. It speaks to KNOWING how often you need to monitor.. not guessing. I teach divers that it is ESSENTIAL to monitor each time period that would result in a PP02 drop of 0.1 from setpoint.



For both a 0.1 Delta-PP02 (normal monitoring period requirement) and for a 1.2 to 0.2 Delta-PP02 (time to drop loop to where you are in immediate peril should you ascend, and very close to unconciousness if you do not soon take action):

Is it:

30 seconds?

3 minutes?

10 minutes?

30 minutes?


Might make a no-display SCC cave exit strategy a bit easier to figure out.

The lesson can be learned either dry or wet. You have probably done it already if you were trained well.


Didn't you do a drill in MOD-1, where your 02 was turned off and you were made to sit with a slate and write down the PP02 each minute for a drop from 1.0 to 0.5 to learn some basics on the timing for PP02 decay? Did your instructor then not make you do a basic plot on a rough X/Y graph to show you what the time delay would be to a PP02 which would ensure "lights out" for you? This is basic pool training stuff for MOD 1. And "Yes", your instructor should have been sitting with you staring at your displays with you continuously. One student at a time, please...


Dave

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[matt]

Didn't we do this crude calculation several posts ago?

Loop volume was omitted as was ascents, both of which cock-up any preconceived idea about how long the loop may last without o2 being added. I'd go for between 3 and 10 minutes - let's call it 6.

Post up the chart, I'd be interested to see it?

Matt.

 

[anarchista]

For both a 0.1 Delta-PP02 (normal monitoring period requirement) and for a 1.2 to 0.2 Delta-PP02 (time to drop loop to where you are in immediate peril should you ascend, and very close to unconciousness if you do not soon take action):

Is it:

30 seconds?

3 minutes?

10 minutes?

30 minutes?


Might make a no-display SCC cave exit strategy a bit easier to figure out.

The lesson can be learned either dry or wet. You have probably done it already if you were trained well.

As I wrote a similar task, I gave metabolic rate O2 l / min and the total volume of closed circut
Let's say, my English is poor and I did not find this information, in your post.

If it is not, You rated himself.

greet rc (SCR SMS designer)

 

[matt]

This one cheats as it add diluent:

Dead in 7 Minutes - The importance of a constant flow oxygen orifice - ADVANCED DIVER MAGAZINE - By Curt Bowen

Matt.

 

[Packhorse]

My take on this is you dont have to stick your head in a tigers mouth to know its dangerous.

But I also question if while in the water and you suffer hypoxia if you would actually recognize it as such from a dry experiment some time earlier.

I quite often suffer from alternobaric vertigo (a term I had not previously hear of, thanks Spongebob) and every time it happens I question myself if it may be something else.

A little math.

30 meter dive air dil 1.3 set point. PPN= 2.7 gives us a air equivalent depth of 24 meters
PPO drops to 0.2 and PPN rises to 3.8 or air equivalent depth of 38 meters.

Now while I accept O2 is narcotic, is it as narcotic as Nitrogen? Would this drop in PPO from 1.3 to 0.2 have an effect on narcosis? And if so would this mask any signs you may get of hypoxia?