Topic: psychosomatic hypoxia (Pilots)

[SkeptiKiwi]

EDIT: I just want to comment that this is what I love about this forum. Where else can you have a discussion about hypoxia, rebreathers, f22's, oximetry and spectroscopy?

Absolutely!

 

[Citizen Skeptic]

Yes, good points. I've been using SpO2, which you probably know, but others may not, is O2 saturation in the blood and not to be confused with PPO2 or FO2.

I know a little about oximetry and capnometry but I am not an expert. I worked for the company that commercialized pulse oximetry for a while and ran the group that developed and manufactured the stuff.

[SkeptiKiwi]

I know feck all about oximetry but I am beginning to understand more and more about capnometry as accurate end tidal CO2 measurement would be an enormous leap in safety with rebreathers. Easy to do for anesthesia but try and get it in a small power conservative package that can handle hugely varying gas densities, exotic mixes, very high humidity, salt water and abuse and well....  Some prototypes are being trialled but they're not going be commercially available anytime soon.

[Citizen Skeptic]

Easy to do for anesthesia

You sound like my old boss. LOL

[SkeptiKiwi]

Anything that isn't my problem is easy..

 

[khendar]

Out of curiosity, someone mentioned that they pressurise some fighter cockpits to 8000ft. What then happens when they are at (say) 25000ft and have to eject ? Even with an oxygen mask, that decompression has to be hell on the body.

[SkeptiKiwi]

I think barotrauma (sinus and aural) can be common injuries following ejection.

I don't know if the pressure drop is enough to cause blackout.

[Plastique]

I dive using a Rebreather and when diving deep use a hypoxic gas mix to keep the ppO2 below a safe level at depth.

For recreation?

[Belgarath]

I think barotrauma (sinus and aural) can be common injuries following ejection.

I don't know if the pressure drop is enough to cause blackout.

Depending on the altitude, it is.  But if the choice is eject and live, or stay and die, I'll take the eject.

ETA:  the flight envelope for a safe ejection is much smaller than the flight envelope for the airplane.

[Belgarath]

I cannot imagine how a mask could be producing CO. They can cause retained CO2. It is my understanding that CO is only present as a product of incomplete combustion.

I have used Denitrogenation systems and they required a compressor to force the air (at about 300psi) through the molecular sieve or membrane that removes some of the N, the system I used only produced enriched gas at up to 40% O2.

If the compressor was poorly maintained or the wrong type of oil used then you could get CO produced but inline detectors are not rare in such systems. I'd be amazed if they did not have them in flight systems.

This system takes Bleed air from the compressors on the Jet and passes it through the system.  Compression ratios on these reach as high as 44:1.  Even at very high altitudes, this should provide sufficient compression to run these O2 concentration systems adequately, again provided they don't fail.

Regarding CO production.  I was only speculating.  I do not know the technical details of how these 'molecular sieve's' operate.

[Citizen Skeptic]

I cannot imagine how a mask could be producing CO. They can cause retained CO2. It is my understanding that CO is only present as a product of incomplete combustion.

I have used Denitrogenation systems and they required a compressor to force the air (at about 300psi) through the molecular sieve or membrane that removes some of the N, the system I used only produced enriched gas at up to 40% O2.

If the compressor was poorly maintained or the wrong type of oil used then you could get CO produced but inline detectors are not rare in such systems. I'd be amazed if they did not have them in flight systems.

This system takes Bleed air from the compressors on the Jet and passes it through the system.  Compression ratios on these reach as high as 44:1.  Even at very high altitudes, this should provide sufficient compression to run these O2 concentration systems adequately, again provided they don't fail.

Regarding CO production.  I was only speculating.  I do not know the technical details of how these 'molecular sieve's' operate.

Aha - it has to be the lubricants in the air compressors.

j/k, but it reminded me of the care you have to take with diving equipment not to use the wrong o-ring lubricants, for example.

[Belgarath]

I cannot imagine how a mask could be producing CO. They can cause retained CO2. It is my understanding that CO is only present as a product of incomplete combustion.

I have used Denitrogenation systems and they required a compressor to force the air (at about 300psi) through the molecular sieve or membrane that removes some of the N, the system I used only produced enriched gas at up to 40% O2.

If the compressor was poorly maintained or the wrong type of oil used then you could get CO produced but inline detectors are not rare in such systems. I'd be amazed if they did not have them in flight systems.

This system takes Bleed air from the compressors on the Jet and passes it through the system.  Compression ratios on these reach as high as 44:1.  Even at very high altitudes, this should provide sufficient compression to run these O2 concentration systems adequately, again provided they don't fail.

Regarding CO production.  I was only speculating.  I do not know the technical details of how these 'molecular sieve's' operate.

Aha - it has to be the lubricants in the air compressors.

j/k, but it reminded me of the care you have to take with diving equipment not to use the wrong o-ring lubricants, for example.

Well, to be honest, when I say compressors, Realize I'm talking about the spinning blades at the front of the engine.  There is no lubrication at the point where the air is 'bled' off.



In the above illustration, the 'bleed air' comes from somewhere in the blue area on the left.  The closer you are to the combustion chamber, the greater the pressure and thus the greater the bleed pressure.  There's no lubrication involved, all of that is either in the center sealed off, or further aft where it couldn't possibly affect bleed air.

[Citizen Skeptic]

Now that's a compressor!

[Belgarath]

Now that's a compressor!

Yea, I don't think you'd be able to fit it on your diving backpack thingie.  (That's a technical term in aviation meaning a device with a proper name which I don't know at the present time)

[SkeptiKiwi]

I dive using a Rebreather and when diving deep use a hypoxic gas mix to keep the ppO2 below a safe level at depth.

For recreation?

Yeah for recreation. It would take the fun out of it to be paid for it.