matt
Well-Known Member
So 1.3 to 0.1 is 12x2=24 minutes or 12x0.66=8 minutes. Seems plenty of time to monitor your handset to me.
What depth have you assumed for that calculation - 60m?
How do you account for addition of diluent?
Matt.
Dry Hypoxia Training for Rebreather Divers
- Thread starter Dave Sutton
- Start date
So 1.3 to 0.1 is 12x2=24 minutes or 12x0.66=8 minutes. Seems plenty of time to monitor your handset to me.
What depth have you assumed for that calculation - 60m?
How do you account for addition of diluent?
Matt.
Megangel1
Member
Possibly.
My assumption is that divers think they can recognise and deal with hypoxia anyway.
and
Such a hypoxic drill would not cause more divers to make this assumption when presented with the direct evidence of their own behaviour during such a drill but that it might cause them to change their held beliefs.
Is your position:-
That generally divers think they can not recognise or deal with hypoxia.
and
That when confronted with video evidence of themselves being unable to so do (re-enforcing their already held belief) that they now believe they can recognise and deal with this event?
Likewise, where's the data for the opposed view?
matt
Well-Known Member
Possibly.
My assumption is that divers think they can recognise and deal with hypoxia anyway.
and
Such a hypoxic drill would not cause more divers to make this assumption when presented with the direct evidence of their own behaviour during such a drill but that it might cause them to change their held beliefs.
Is your position:-
That generally divers think they can not recognise or deal with hypoxia.
and
That when confronted with video evidence of themselves being unable to so do (re-enforcing their already held belief) that they now believe they can recognise and deal with this event?
Likewise, where's the data for the opposed view?
AFAIK there is no data either way for scuba-divers.
My thinking is that the experiment gives the diver some confidence that they can recognise hypoxic symptoms and that this leads to monitoring complacency.
It stems from this comment in post #1:
dave said:
Matt.
erikradstrom
Deep Pursuit 001
What if you ascent then Matt?
The PO2 will drop and the ADV will not fire.
All dives are not on a line or a wreck. Many people do wall dives there they ascend during a longer period of the dive.
Bottomline is that practicing things never can be bad. A medically trained person has commented in the thread that the risks are minimal and still people here say that the risks are big. What training do you guys saying that have?
matt
Well-Known Member
Ascending makes things worse not better and means more observation not less.
Practice what?
I don't think there is any risk for the experiment - providing you don't use the gag-strap.
Megangel1
Member
But
1. Faced with video evidence of themselves, how can any sane person refute that they can not?
2. We don't think this way about nitrogen narcosis and chamber dives.
anarchista
New Member
PpO2 drop from 1.3 to 0.1 is quite long, but the safe limit is 0.2 not safe 0.17.
Depth just does not matter, it's physiological knowledge base.
For smaller gaps in knowledge, I meant red.
The diver may be overloaded tasks.
A diver is subjected to the influence ppN2.
Diver does not feel the reduction in respiratory medium density.
I breathed pure nitrogen in the OC, is nice. Even after starting the physiological systems that respond to low oxygen levels.
That's why it's very dangerous situation for the diver, hypoxia with a well-absorber
greet rc
anarchista
New Member
What is reperfusion injury?
Is blood after cardiac arrest, it is better to provide pure oxygen or air?
greet rc
matt
Well-Known Member
I'm not buying the narcosis thing. The effect is pronounced and the threat to life minimal - I don't personally know anyone who died from nitrogen-narcosis. There is also no way to sense it on the handset.
I could go with an argument around CO2 though. That's also (currently) not measured and outside of temp-sticks and stop-watches all there is left to do is the couch test.
Matt.
matt
Well-Known Member
No idea.
matt
Well-Known Member
Dave Sutton
Banned
I am reminded of the movie "Flatliners"
Just because Mr Sutton feels qualified to monitor a diver's descent into near unconsciousness and back does not mean this should be attempted by us mere mortal average Joe CCR instructors.
I assume that the testing performed by FAA is conducted under the supervision of a fully trained and qualified medical person and not just someone who read about this on the internet.[/UOTE]
Hey Dave, glad you've come to the party. Glad to see another of the old gang here.
I don't trust the "average" diving instructor to be able to teach mask clearing...
This however is a training area that is done routinely by lay technicians in the aviation industry. I ought to know... I was doing it as a trainer for years at my day job teaching corporate pilots. I even put photos up on burger world several years back. So to say "because a TDI instructor cannot do it nobody can do it" is disingenuous.
It's interesting to note the reactions here. In aviation the answer to the question about training is "Of course I went thru it.. Doesn't everyone?" While the answers here range from skeptical to violently disagreeing. That alone tells me that the rebreather training community is doing a pretty poor job of ACTALLY teaching divers about the reality of hypoxia. We tell divers it exists. But we don't teach any of the subtle clues that you might be experiencing it. It's NOT a binary "on/off" paradigm in your brain. Go read up on TUC (times of useful consciousness). During that time period you can self assist. There is a period after TUC when you can still see and hear... But are just a detached observer. Get there underwater and you are dead. Funny, I got that way on Monday when a student in the fighter pulled 6 G without telling me.. No anti G straining in advance and I was done. Watched vision close in and tunnel, then was lost... Then came back. Typical day in a fighter.
One thing the diving community has taught is that loss of consciousnesses due to hypoxia will kill you. Really? Drowning kills you. Go hypoxic in the water and you drown. Stand up too rapidly and faint and you fall down. No different at all. I remember on Monday thinking "this sucks.. I hope he finishes the loop before I pass out completely and smack my face on the stick like the last time this happened". Then he relaxed the G and I was back in the fight. No biggie.
One thing to note: taking a student to unconsciousness is NOT the excercise. If the is done, the student gets ZERO benefit, as he will not remember anything and as a result the training opportunity is lost. Hypoxia often takes many minutes to progress from normal to unable to assist own rescue (which happens before loss of consciousness). Depending on the RATE of onset, detection of own symptoms and correction of the problem is a VERY real possibility. This is EXACTLY why the subject is taught to aircrew.
How about putting an introduction on the intro page so we can welcome you to the forum? And BTW, call me "Dave". Mr. Sutton was my Dad. ;-)
Dave
.
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anarchista
New Member
Especially as we begin the ascent, RIGHT?
Oxygen mass decreases due to: the ascent and wear. The partial pressure of oxygen decreases, because the total pressure decreases. we do not have proofreaders ppO2 systems, which are known SCR SMS constant ppO2 (there are such solutions provide a safe mixture to the surface, even at rapid ascent)
rc greet
Megangel1
Member
You missed the point I was making. Your point appears to be that because divers experienced something in a controlled environment, that they (some) (automatically) then believe that they can recognise that same physiological response in another environment; and because of this belief, experiencing hypoxia in the controlled environment would lead the diver to believe that they could recognise the effect in the dive environment and hence would be complacent in ppo2 monitoring. Further, due to this, the drill should not be performed.
I use the narcosis example not for a comparison against hypoxia risk or monitoring, but as an alternate example where we generally accept that exposing people to the effect in a controlled environment has no detrimental effect on their belief that they could or could not recognise such in the dive environment.
matt
Well-Known Member
I thought the point of the thread was to examine if the effects of hypoxia can be recognised through trial and test at the individual level. Is that not so (your brackets lead me to think it is not)?
But otherwise yes, that's my point with the exception of your futher - I never intended to say or imply that it should not be done - each to their own - but not for me, thanks.
I got that, but I'm not sure it's the same as hypoxia - narcosis is also quite pleasant but you don't normally die of it.
I'm not passionate either way on the point. I trust Dave, as an aviation professional, that when he says that this is a good idea for aviators then this is fact. I just don't see the point (for me) in recreational scuba diving and I'd be quite alarmed if my instructor though it a good idea to get me to "have a go on his couch".
Matt.
anarchista
New Member
In the closed circuit at a constant depth is not necessary amount of inert gas filling.
From elementary physics, know that the V(Pi) = P(Vi)
Where the total pressure P, Pi, and the partial pressure of the i component.
Similarly, the total volume V, Vi, and the volume occupied by the i component.
With this property quickly calculate, many of the balance of gases in closed circuits.
rc greet
"Fast counting partial pressures.
Known method partial pressure component count is count the fraction of the mixture, and this, according to the pressure component.
It is a faster method to some calculations, according to another awarding of the ideal gas equation. PV = const
but P = Pa + Pb and V = Va + Vb and where one of the components b second, Pa partial pressure of component a and component b Vb volume, similar to the others.
PV = P (Va + Vb) = (Pa + Pb) V, hence the resulting equations for the components PVa = PaV, PVb = PbV
Example of calculation which is the partial pressure of component ai 20l 90l component b, 10l tank.
2 at pressure of component a and 9 at the component b, the total pressure 11at.
exactly the same as calculated by the gas mole fractions (fractions)
Ryszard Czarnecki greet"
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PeterN
Active Member
I may not be following this properly, so forgive me if I digress.
Back in the early 90's my dive partner and I had a cave project in a remote location that was tight and trending deep. Well, deep for air. We "trained" for this by repeatedly diving to 170 to 200 feet on air. When I found myself at the sharp end, alone, at a mere 150 odd feet deep but 400 meters in, I blew my thirds just trying to tie a knot in the line!
I must have been narced out of my gourd. But I suposedly was "trained up" for this. I had no idea. Ten min. at 170, doing nothing, is not at all the same as being tasked and frightened and at the sharp end.
I accept that this type of hypoxic training can be done safely. I am not so sure that it has been demonstrated to be benificial to divers.
Peter
Dave Sutton
Banned
.
No demonstration for a large population of divers, because a large population of divers has not taken the training.
Chicken or Egg then?
Aviation: As per the USAF study previously cited: When exposed to real-world loss of cabin pressurization, less than 4% of those trained to recognize and respond to their own first symptoms have failed to sucessfully self-assist. More than 95% of untrained aircrews loose conciousness before they recogize their first symptoms.
This is pretty solid evidence that the training has significant impact on the ability of people to recognize incipient symptoms while there's still time to do something about it.
Put another way: What's the *downside* to getting more training? I've never found that more knowlage was ever a bad thing. Does anyone really prefer ignorance over knowlage?
Interesting tidbit: My own first symptom of hypoxia, a VERY early symptom in fact, is a perception of sun-glare or light-glare. It's as if I cannot see well bcause I am looking towards the sun. I get this at a PP02 of about 0.10, and can detect it on the surface if I take a few breaths of 10/50. It happens LONG before any other symptom FOR ME. It's a result of the fact that your retinas are likely the most 02 sensitive tissue in your body, and as I begin to lose the first bit of vision I sense this as sun glare. Know why this information is completely useless to others? It's because everyone has their OWN personal set of first symptoms. There is no way to gain experience in this area without learning it firsthand. I can tell you this... at the first sign of glare underwater I'll bail out first and check PP02 second... while someone else who might have the same personal symptoms might be wasting time looking at a PP02 monitor... and looking.... and looking... puzzled why they cannot read it.............. trying harder to see it...... but unconcerned now..... happy....... <bingo, they are unconcious and drowning>.
I lost a good friend on a Mark-15 years back: He was walking to the water from his truck with the rig on his back pre-breathing it. Rig was turned off (common then with only one setpoint which was usually 1.2, so the 'lekkies were only turned on at 6 meters, before that you added 02 manually and watched the old analog secondary to keep the PP02 up). As he walked he lost track of adding 02, walked into 3 feet of water to put on his fins, fell over and drowned.
I often wonder if he was seeing any sun glare as he walked to the water........
Think about it.
Dave
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silentbob
Member
.
Not bad does not equal good.
Training divers in hypoxia recognition could do little more than increase many divers willingness to push the envelope (or slacken the attentiveness) a little further once armed with the comforting "knowledge" of how they might respond to an hypoxic event. I think the extra effort would be better spent on reinforcing PO2 monitoring as it is proactive behavior rather than reactive.
The link below is a download of a paper on Heuristic traps (Heuristic - Wikipedia, the free encyclopedia). The focus is avalanche hazard but for some of the examples substituting the word hypoxia works equally well.
http://www.google.co.nz/url?sa=t&rc...i9KEEeTWKnqxoPpbA&sig2=QA8ennrtzc9lQ41ogxthdQ
And this one is an article about the same.
http://avtrainingadmin.org/pubs/McCammonHTraps.pdf
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