Dry Hypoxia Training for Rebreather Divers

Have you ever done an intentional dry hypoxia exposure?

  • Yes, monitored by a professional in training.

    Votes: 7 8.0%
  • Yes, at home with a friend.

    Votes: 8 9.1%
  • Yes, but as a part of an aviation training course.

    Votes: 2 2.3%
  • No, but believe that it might be useful for rebreather divers.

    Votes: 51 58.0%
  • No way, you kidding me?

    Votes: 23 26.1%

  • Total voters
    88
Love to discuss this, let's start a thread if there is more hardware to discuss v/s the human pysiological training which is the focus of this thread.

I think what you're trying to do with this thread is pretty good. Another as you suggest could be interesting, too. Let's face it, hypoxia & RB diving is a subject of interest to us all.
 
I remain unconvinced.

This "logic" reminds me of the drinkers who think they can drive after a few. Or better yet, one of my stoner friends who thinks his pot smoking makes him a better deep diver.

Or, maybe more to the point, who here remembers the good old days when we used to do deep air dives to train up to resist being narked?

Perhaps my analogies are week, but for me I am a dedicated prebreathing, PO2 watching kinda guy. I will not be hurried at the onset of a dive and I am in love with my HUD.

Peter:drink:
 
When I was a commercial diver working for Santa Fe, Tom Angel, who is a god among men in the diving industry, was the president of the company. He had a sign above his desk that said:



"The more you know, the longer you will live".




I am a firm believer in that creed. I'm always surprised by people who are not interested in learning *everything*. You never know when that tiny bit of data might save you.

What you learn in hypoxia training is that you CANNOT reliably detect symptoms, and that it's fun to go to sleep... that alone scares the living crap out of most people, and doubles their PP02 checking. It's the difference between personally earned respect and second hand respect. Unlike the drunk who thinks he can drive and looses respect, this is a humbling experience and ought to engender fear, because it would be TOO EASY to die this way...



I'm afraid of heights... that's why I went skydiving to learn what it feels like to parachute before I ever might need to eject. Some seek.. others avoid.


<shrugs>



Dave


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Personally, I'm quite interested in how long I'd have on the surface breathing a 10/50 dil before a). I'm incapable of being able to give an emergency signal to the boat or b). actually being able to mentally realise that I'm really in the sticky stuff and that I need to signal the boat and NOT swim hard back to the ladder in the first place or c). just go night night Zzzzzzzz!

I know, I know we don't want to be in that position, but if I HAD to breath the 10/50 OC, how long could I expect to be able to float around waiting to be picked up. ( eg bailout tins removed ready to climb ladder / get into RHIB in rough seas and I break the loop on the ladder or something)
 
<snip>

I'm afraid of heights... that's why I went skydiving to learn what it feels like to parachute before I ever might need to eject. Some seek.. others avoid.

<snip>

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And you're a test pilot?


Aquaphobic too by any chance? :chuckle:

Sorry, been one of those weeks, just joking.
 
That Youtube scene looks familiar! :luke: What I would add is that the incipient "you were near death" is really over-played. A pilot or a rebreather diver will die because they fly into the ground, or drown. The risk of injury in the excercise is near nil, it takes rather a longer time for any permanent injury to occur, many orders of magnitude longer.


Who is the grinning idiot here sitting in front looking at the camera like a dumb ox? This was taken during a symposium I sponsored for pilots flying surplus military jets, at the hypobaric chamber complex at the old Williams AFB, now part of the University of Arizona. I was able to recover myself and then sat and enjoyed the hysterical performance of some of the others. This was about my 10th chamber ride.


Note the ages of the occupants of the chamber: Ranging from 16 to 60 in that run.



Dave


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And you're a test pilot?


Aquaphobic too by any chance? :chuckle:

Sorry, been one of those weeks, just joking.



Yup... just don't get me near the edge of a subway platform... or a roof.

Nobody read my story about the commercial diving job into the inside of a water tower? My gut churns just thinking about it... :eek: I kid you not...



<sigh>... give me a nice safe Russian ejection seat any day.




Dave


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The really scary thing after exposure to the event is how normal it all feels. That's the takeaway.... it's "pleasant". That and the fact that you CAN often (but not always) detect your symptoms in time to bail out if you have learned your own symptoms. In the aviation training, "bailing out" means putting your own mask on in the chamber before you need external assistance.


Dave

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Since so many pilots have been put thru the training it would be valuable to know if they have run any tests to verify that this training results in any benefits in a contolled study. Seems they could easily test this by putting pilots in a simulator and reducing the O2 without their knowledge and then determine if they take action before passing out or not.

Armed with those results we would know if it really is beneficial to have experienced the conditions in advance or not.
 
I'd suggest a study of the literature produced by the USAF (and other air forces as well), which budgets many millions of dollars a year to provide this as a universal training event for aviators. All high altutude Army parachutists go thru it, all Naval Aviators, SEALs, etc.. it's universally recognized as absolutely essential training.



Typical synopsis in the literature, interestingly enough from Australia. There are hundreds of papers on this topic:


Background: Hypoxia has long been recognized as a significant physiological threat at altitude. Aircrew have traditionally been trained to recognize the symptoms of hypoxia using hypobaric chamber training at simulated altitudes of 25,000 ft or more. The aim of this study was to analyze incidents of hypoxia reported to the Directorate of Flying Safety of the Australian Defence Force (DFS-ADF) for the period 1990-2001, as no previous analysis of these incidents has been undertaken. The data will be useful in planning future training strategies for aircrew in aviation physiology. Method: A search was requested of the DFS-ADF database, for all Aircraft Safety Occurrence Reports (ASOR) listing hypoxia as a factor. These cases were reviewed and the following data analyzed: aircraft type, number of persons on board (POB), number of hypoxic POB, any fatalities, whether the victims were trained or untrained as aircrew, if the symptoms were recognized as hypoxia, symptoms experienced, the altitude at which the incident occurred, and the likely cause. Results: During the period studied, 27 reports of hypoxia were filed, involving 29 aircrew. In only two cases was consciousness lost, and one of these resulted in a fatality. Most incidents (85.1%) occurred in fighter or training aircraft with aircrew who use oxygen equipment routinely. The majority of symptoms occurred between 10,000 and 19,000 ft. The most common cause of hypoxia (63%) in these aircraft was the failure of the mask or regulator, or a mask leak. Rapid accidental decompression did not feature as a cause of hypoxia. Symptoms were subtle and often involved cognitive impairment or light-headedness. The vast majority (75.8%) of these episodes were recognized by the aircrew themselves, reinforcing the importance and benefit of hypoxia training. Conclusion: This study confirms the importance and effectiveness of hypoxia training for aircrew. Hypoxia incidents occur most commonly at altitudes less than 19,000 ft. This should be emphasized to aircrew, whose expectation may be that it is only a problem of high altitude. Proper fitting of masks, leak checks, and equipment checks should be taught to all aircrew and reinforced regularly. Current hypobaric chamber training methods should be reviewed for relevance to the most at-risk aircrew population. Methods that can simulate subtle incapacitation while wearing oxygen equipment should be explored. Hypoxia in flight still remains a serious threat to aviators, and can result in fatalities.


Full paper here:

http://docserver.ingentaconnect.com...ser&checksum=7348DD908CC7689A782B717788BE4C33


That's without even really looking for papers.


I especially liked this conclusion, which brings us right back to ROBS systems:


"Current hypobaric training methods should be reviewed
for relevance to the most at-risk aircrew population.
Methods which can simulate subtle incapacitation
while wearing oxygen equipment, such as the use
of reduced oxygen breathing, should be explored.

These methods would be especially useful for aircrew
already familiar with their personal hypoxia symptoms
and who are undergoing refresher training"





Here's another little synopsis from the USAF:


Analysis of USAF hypoxia incidents January 1976 through March 1990
Island, Richard T | Fraley, Earl V
International Symposium on Aviation Psychology, 7th, Columbus, OH; UNITED STATES; 26-29 Apr. 1993. pp. 664-668. 1993

656 in-flight incidents of hypoxia were reported to the USAF Safety Center between January 1976 and March 1990. These cases were analyzed to determine the effectiveness of high-altitude physiological chamber training.

Of the 606 cases involving chamber-trained aircrew, only 3.8 percent experienced an in-flight loss of consciousness (LOC), while the untrained group of 50 had a LOC rate of 94 percent.

Of the 520 chamber-trained aircrew that recognized their symptoms, 136 (26.15 percent), made comments to the effect that the symptoms were 'just like the chamber experience' and only 5 (0.96 percent) stated that the symptoms were 'unlike' the symptoms experienced in the chamber. (Author)

Descriptors: HYPOXIA | FLIGHT CREWS | UNITED STATES | DECOMPRESSION SICKNESS





Dave

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Since so many pilots have been put thru the training it would be valuable to know if they have run any tests to verify that this training results in any benefits in a contolled study. Seems they could easily test this by putting pilots in a simulator and reducing the O2 without their knowledge and then determine if they take action before passing out or not.

Armed with those results we would know if it really is beneficial to have experienced the conditions in advance or not.

Well put! I also remain unconvinced that the instructors I have known could come up with a repeatable and safe version of the aviators protocal. I can't imagine that there is any money in any divers pocket for such a test, and the living room version seems iffy at best.

I am also not convinced it is harmless to pass out due to lack of O2. Those little grey cells are not all that robust.

Peter
 
Well put! I also remain unconvinced that the instructors I have known could come up with a repeatable and safe version of the aviators protocal. I can't imagine that there is any money in any divers pocket for such a test, and the living room version seems iffy at best.

I am also not convinced it is harmless to pass out due to lack of O2. Those little grey cells are not all that robust.

Peter



(1): I'll run courses for free if asked. I think it's essential training.

(2): The entire aviation physiology community disagrees with your brain cell theory.


(here's the best part though)


(3): If you get a student pilots license (which means taking a physical and that's it), you can apply thru the FAA to receive the training at the hands of the FAA, USAF, or USN on a space-available basis for FREE


Got that? Free. No money, zilch, zero, nada, free. It's your tax dollars at work.


Airman Education Programs

That's just one venue. They run these all over the USA.


Here's a link to a story written by a guy who went thru a USAF space-available class.. $50 for the day...

FAA High Altitude Training and Chamber Flight at Beale AFB (by Jeremy Zawodny)


What other excuses can we come up with?


We fear that which we do not know.
We make excuses for not knowing our fears.
We fear not that which we have faced and learned.
Make not excuses, but seek and learn. Defeat fear.



:cheers:


Got FREE?


Dave

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Ha ha. OK I get free!

Also I would do this with the USAF, the USN, the FAA, and for sure you. However as a foreign national I doubt that the offer applies to me.

I still have a hard time believing that this sort of a program can be done in a meaningfull way in a living room or back yard. There is probably a reason that the course cited costs $ 5000.

Peter
 
The course that I used to teach that cost $5K was conducted in a full motion flight simulator, which itself cost over $2000/hour to run. The actual ROBS portion of the simulation was a throwaway. The entire scenario was scripted to simulate a slow loss of pressurization in the middle of an oceanic crossing. The issue for a jet there is that you have two bad choices: Depressurize and go on 02 (and do you have enough 02 in the system to make it for the next three hours?) or descend, where you will double your fuel burn and probably need to ditch the jet into the water. That scenario takes at least two hours to run in the simulator, and leads crews to want to maintain altitude... 02 becomes interchangable with fuel. It was a complex training scenario, and only a fraction of it involved the ROBS system. One of the creative ways to survive is to let the co-pilot pass out: only one person is needed to fly the jet... call it "aviation triage". The Time of Useful Conciousness and the time to suffer permanent physiological damage to the central nervous system at the PP02's we are discussing are several orders of magnitude apart. Witness the survival of people climbing Mt. Everest... PP02 there is about, oh... 0.05. You are dying there.. just slowly.

The rebreather lecture and demonstration "in the living room" takes about an hour. The actual "couch dive" takes abiout 5 minutes. If you have someone with the knowlage, and a rebreather, you have all that it takes. The knowlage is already there, it's just distributed in aviation circles, not diving circles. I'm advocating to change that in rebreather course development. Cross-Pollination of communities, so to speak.

This is NOT an area for self-discovery though. DO NOT read this and attempt it at home.


Dave

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New to the board here, gonna be quite the first post, anyways i was reading through the meg section and stumbled upon this thread and i must say, what the hell are you even thinking? Sure this test sounds reasonable in the hands of properly trained medical personal (i.e doctors, in a controlled environment), not in the hands of a rebreather instructors living room, whom is not a doctor, is not aware of the students previous medical conditions (if the student is even aware of any)and is not properly monitored by qualified people. Sure someone is watching the student to make sure they do not pass out, etc, but there is not real monitoring going on of body functions, just a simple visual inspection which really shows nothing of what is really happening within the body. I've read(can't remember where) of this test being conducted previously, with the test pilot(rebreather diver) stopping breathing all together, and having to be revived on the boat with AR while conducting this exact experiment.

Let me ask the obvious here, is this even sanctioned by any of the following manufactures/training agencies and more importantly the insurance underwriters you get your insurance through for instructing? I seriously doubt it, going to guess and say if any of them knew this was being done on a course, that said instructor would have there instructor rating pulled/yanked, well I hope they would.

Anyways, feel free to keep conducting this training, odd though when i did my meg and revo courses, this was not covered or part of the standards(both highly experienced instructors), and if it was i would flat out refuse to participate. Frankly I am surprised people would even agree to this, perhaps the ones that do are a little short on the grey matter, so maybe this does not affect them in the long run.

Interesting theory though, i see no harm in this sort of test being conducted in a controlled environment as Peter mentioned. However as he also alluded to, we are recreational divers not funded or backed by government funding which would allow this training to be conducted in a safe/controlled environment mentioned previously by others and myself.

Carry on. I'm open for debate, and if you can peak my interest, perhaps I 'll come out to the Wisconsin area and we can further discuss over beers and dives.

Regards

Steve Aaen

Sent from my iPad using Tapatalk
 
To be clear: This has never been a part of any sanctioned diving training course I have taught. It's always "friends gathered for advanced training". I'm trying to assess applicability to a more general enviroment.
.

The rebreather lecture and demonstration "in the living room" takes about an hour. The actual "couch dive" takes abiout 5 minutes. If you have someone with the knowlage, and a rebreather, you have all that it takes. The knowlage is already there, it's just distributed in aviation circles, not diving circles. I'm advocating to change that in rebreather course development. Cross-Pollination of communities, so to speak.

The later explanation of this sounds more formal than just friends gathering around.

Personally, I prefer to follow course standards and teach within the scope of the course and my professional liability insurance policy. It is absolutely essential to understand the seriousness and effects of hypoxia. It is also absolutely essential to understand the seriousness and aftermath of drowning. Doesn't mean I drown my students to drive the point home. Oxygen toxicity is very serious as well, and a risk to divers of all levels right from Open Water. Are you implying I should give my Advanced Nitrox students a bottle of 100% O2 to breath at 40ft so they understand what an ox tox feels like? Being a "dry" dive does not make the hypoxia drill any safer or in any more of a controlled environment unless trained medical professionals are present to control the situation. Having done the drill however many times, still does not grant you the training and experience to fully secure the situation if your students stops breathing or suffers a heart attack.

However, I'm sure youtube offers many examples of others experiencing hypoxia, ox tox hits, CO2 hits and drowning which I can present to my students as a teaching aid to support the seriousness of the foregoing. It's effective and much safer for them. Let them learn from someone else's mistakes and if that's not good enough motivation for them to understand the importance of properly monitoring their PO2, packing their scrubber properly, or analyzing their gas mixes then well, I guess natural selection isn't going to be on E.I. forever. It's important to be able to learn from the mistakes of others, it makes less mess.

Furthermore, there are three branches of diving: scientific, recreational and commercial. Technical diving falls within the recreational diving category (despite how its participants tend to grandiose it), comparing it and subjecting its participants to the same sort of tests as a military pilot is comparing apples to oranges. If this were something on a commercial diving course, the participants would have passed mental and physical tests leading up to it and would be monitored at all times by qualified medical professions. Not just a teacher/examiner.
 
Comparing moderate hypoxia in a dry normoxic environment with outside monitoring to drowning students or doing ox tox drills at depth is just silly and does nothing for the debate. Medically this is a scenario with very, very low risk. Just getting in the water with a rebreather is likely more dangerous.

Whether or not the training would be useful in our setting is another thing entirely.
 
The long term suggestion is simply that the diving industry leverage the knowlage base already established by the aviation community to develop a synergy in training a suibject that is common to both and to come to some concensus standard by which it might be made available as a sanctioned training event.

The short term suggestion is that divers be made aware of the professional training that is available as an off the shelf course at moderate fee in many areas of the world. Any rebreather diver ought to be interested in this. It's no different than us going to the hyperbaric center as a dive club to do a 200 foot air chamber run to look at the realities of narcosis. That was fun too. These training events are available for those who seek it.


The aerospace physiology community has put millions and millions of dollars into this type of training, and all of the literature supports the fact that trained aircrew are FAR more likely to self-rescue than untrained aircrew.

To restate one synopsis:


Of the 606 cases involving chamber-trained aircrew, only 3.8 percent experienced an in-flight loss of consciousness (LOC), while the untrained group of 50 had a LOC rate of 94 percent


Guys: 3.8% versus 94% is a HUGE difference.


FOUR percent (to make it easy) versus NINETY FOUR percent. Even I can do that math.


With the majority of rebreather deaths attribute to drowning "probably" being caused by a hypoxic incident, the parallels seem obvious.

What I am advancing is dialog on how this might be done in a more mainstream way as a more normal training event for rebreather divers. I am not "literally" suggesting it be done on your couch by an instructor without the background and guidance to perform it safely.

The value of the excercise is without debate.


I remember when we needed to blend nitrox and trimix in our garages too, and then sneak into a dive store to have the cylinders topped off. Because NO dive agencies supported anything other than air. What was then surreptitious voodoo is now industry norm.


Or... "As soon as there's money in it, there will be a PADI specialty" :banana1:




Dave


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Interesting theory though, i see no harm in this sort of test being conducted in a controlled environment as Peter mentioned. However as he also alluded to, we are recreational divers not funded or backed by government funding which would allow this training to be conducted in a safe/controlled environment mentioned previously by others and myself.

Carry on. I'm open for debate, and if you can peak my interest, perhaps I 'll come out to the Wisconsin area and we can further discuss over beers and dives.


To the first, have you not read above that the training is available essentially for free and conducted by either the FAA or the USAF? Funding for small groups is not an issue. You paid income tax, now take some advantage of it!

The latter is not going to happen, doesn't anyone understand rhetorical debate?



Actually, what I might do is to set up a course at the high altitude chamber and get a roster of divers who want to sign up for the training. I am sure that this could be done for a group without too much difficulty. Anyone interested in this? Cost would likely be minimal, travel obviously required.


It's 'Pique" BTW... Peaks are reserved for mountains.


Dave


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While I'm chiming in a bit late, I would put that knowledge and experience are invaluable in life, including diving a rebreather.

Having once jumped into the water with my O2 tank off, I know the sensation a low PO2 (0.11 on my displays) give me. It's a sort of disorientating, 'whoa!' feeling. Fortunately, I stopped finning to the bow and looked at my displays. And froze. And opened my O2 cylinder. And O2 flushed. And waited a bit, just to be sure.

I was lucky. I'd prefer to be more than lucky...

cheers

Andy
 
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