A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Military Aviation
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

hi alt oxygen



 
 
Thread Tools Display Modes
  #1  
Old March 10th 04, 04:53 AM
Arquebus257WeaMag
external usenet poster
 
Posts: n/a
Default hi alt oxygen

Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.
Ads
  #2  
Old March 10th 04, 05:16 AM
Tarver Engineering
external usenet poster
 
Posts: n/a
Default


"Arquebus257WeaMag" wrote in message
m...
Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.


http://www.batnet.com/mfwright/hypoxia.html
Hypoxia

Hypoxia is a state of oxygen deficiency in the body which is sufficient to
cause an impairment of function. Hypoxia is caused by the reduction in
partial pressure of oxygen, inadequate oxygen transport, or the inability of
the tissues to use oxygen.

In brief, being drunk is kind of the same as being exposed to high altitude.
In both cases, oxygen to your brain and muscles is reduced.


  #3  
Old March 10th 04, 05:46 PM
Leslie Swartz
external usenet poster
 
Posts: n/a
Default

You live off off something called the "partial pressure of oxygen" in the
medium you are breathing. As altitude increases, the partial pressure of
oxygen in air decreases. Therefore, you must "enrich" the breathing medium
with more oxygen in order to achieve the *same* partial pressure of oxygen
that exists at lower altitudes.

Two solutions: 1) increase the relative percentage of oxygen inht e
medium, or 2) pressurize hte medium. 1) is much less expensive than 2).

Steve Swartz

(The partial pressure of oxygen is what gets the O2 across your lung tissue
into your bloodstream. As total pressure decreases, the partial pressure of
oxygen decreases. Eventually, as ambient pressure goes down, you would need
to breathe pure *pressurized* [3.2 psi IIRC] oxygen in order to make up the
deficit.)

"Arquebus257WeaMag" wrote in message
m...
Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.



  #4  
Old March 10th 04, 11:29 PM
Cub Driver
external usenet poster
 
Posts: n/a
Default


Thank you for the information. Very interesting!

On Wed, 10 Mar 2004 11:46:52 -0500, "Leslie Swartz"
wrote:

You live off off something called the "partial pressure of oxygen" in the
medium you are breathing. As altitude increases, the partial pressure of
oxygen in air decreases. Therefore, you must "enrich" the breathing medium
with more oxygen in order to achieve the *same* partial pressure of oxygen
that exists at lower altitudes.

Two solutions: 1) increase the relative percentage of oxygen inht e
medium, or 2) pressurize hte medium. 1) is much less expensive than 2).

Steve Swartz

(The partial pressure of oxygen is what gets the O2 across your lung tissue
into your bloodstream. As total pressure decreases, the partial pressure of
oxygen decreases. Eventually, as ambient pressure goes down, you would need
to breathe pure *pressurized* [3.2 psi IIRC] oxygen in order to make up the
deficit.)

"Arquebus257WeaMag" wrote in message
om...
Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.



all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at
www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com
  #5  
Old March 11th 04, 06:12 AM
WaltBJ
external usenet poster
 
Posts: n/a
Default

Here's some quick and dirty info on oxygen - normally about 1/5 of
'air'. So the 'partial pressure' is 1/5 of 29.92 inches/760 mm Hg
equalling 152mm O2. The ambient air pressure drops by 1/2 every 18,000
feet (roughly). So at sea level you get 1/5 of 760mm; at 18,000 you
get 1/5 of 380mm. At about 34000 you get the equivalent of sea level
oxygen partial pressure breathing 100% oxygen. If you keep going on up
pretty soon you reach a dangerously low level of partial pressure -
that's at about 41,000. So modern diluter-demand O2 regulators start
feeding you oxygen under pressure. Easy to inhale - you have to work
to exhale. This gets worse as you keep going up. At 50,000 cabin
pressure it is physically demanding to exhale and the mask has to be
very tightly strapped on your face. Not to mention painful. Note that
so far we don't have any 'cabin pressure' - air bled from the
engine(s) to remedy the situation. Also as you keep climbing into
areas of lesser pressure water boils at progrssively lower
temperatures. At 63,000 ambient pressure water boils at 98.6F/37C -
body temp. That means your lungs are now filled with water vapor and
you can no longer absorb oxygen. Hence pressure cabins and pressure
suits over 50,000 feet. Breathing pure oxygen for extended periods of
time is a hassle. First, there is no water in Aviator's oxygen - can't
take the chance of water freezing in the lines. Therefore every breath
you're becoming more and more dehydrated. Second, oxygen can flood the
inner ears (through the eustachian tubes) and late at night in bed
that oxygen gets absorbed by the blood and you wake up with giant
earaches. Third, if you're breathing pure O2 and pulling lots of G -
the lower airsacs in your lungs tend to stick together because with
pure O2 you're not breathing as deeply. Back on the ground when you
take a deep breath it feels as if someone just knifed you. This is
termed 'atelactasis'.
Now, oxygen is used to keep pilots crew and passengers functioning at
more or less an efficient level. Rule of thumb - O2 over 10,000 feet.
There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes. But even the best can screw
up - read 'Into Thin Air'. FWIW I used to teach this stuff.
Walt BJ
  #6  
Old March 11th 04, 06:24 AM
ArtKramr
external usenet poster
 
Posts: n/a
Default

Subject: hi alt oxygen
From: (WaltBJ)
Date: 3/10/04 9:12 PM Pacific Standard Time
Message-id:

Here's some quick and dirty info on oxygen - normally about 1/5 of
'air'. So the 'partial pressure' is 1/5 of 29.92 inches/760 mm Hg
equalling 152mm O2. The ambient air pressure drops by 1/2 every 18,000
feet (roughly). So at sea level you get 1/5 of 760mm; at 18,000 you
get 1/5 of 380mm. At about 34000 you get the equivalent of sea level
oxygen partial pressure breathing 100% oxygen. If you keep going on up
pretty soon you reach a dangerously low level of partial pressure -
that's at about 41,000. So modern diluter-demand O2 regulators start
feeding you oxygen under pressure. Easy to inhale - you have to work
to exhale. This gets worse as you keep going up. At 50,000 cabin
pressure it is physically demanding to exhale and the mask has to be
very tightly strapped on your face. Not to mention painful. Note that
so far we don't have any 'cabin pressure' - air bled from the
engine(s) to remedy the situation. Also as you keep climbing into
areas of lesser pressure water boils at progrssively lower
temperatures. At 63,000 ambient pressure water boils at 98.6F/37C -
body temp. That means your lungs are now filled with water vapor and
you can no longer absorb oxygen. Hence pressure cabins and pressure
suits over 50,000 feet. Breathing pure oxygen for extended periods of
time is a hassle. First, there is no water in Aviator's oxygen - can't
take the chance of water freezing in the lines. Therefore every breath
you're becoming more and more dehydrated. Second, oxygen can flood the
inner ears (through the eustachian tubes) and late at night in bed
that oxygen gets absorbed by the blood and you wake up with giant
earaches. Third, if you're breathing pure O2 and pulling lots of G -
the lower airsacs in your lungs tend to stick together because with
pure O2 you're not breathing as deeply. Back on the ground when you
take a deep breath it feels as if someone just knifed you. This is
termed 'atelactasis'.
Now, oxygen is used to keep pilots crew and passengers functioning at
more or less an efficient level. Rule of thumb - O2 over 10,000 feet.
There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes. But even the best can screw
up - read 'Into Thin Air'. FWIW I used to teach this stuff.
Walt BJ



I was just glad to get rid of the high pressure system with the spitbag to the
low pressure demand mask. It doesn't take much to make me happy.


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

  #7  
Old March 11th 04, 07:32 AM
QDurham
external usenet poster
 
Posts: n/a
Default

There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes.


Pensacola. Low pressure tank. 30,000 feet pressure. Instructor asks for
volunteer. (I tend to do dumb things) I said OK. "Please take this pencil
and write your name on this clipboard." "How many times?" "Don't worry. I'll
tell you when to stop."

Off comes mask. I write and I write and at the 4th perfect signature I stop --
wondering why am I doing this. "Hell, I can do this for the rest of my life."
(30,00 feet. Yeah) Instructor slams mask back on. My vision instantly
changed from looking down a soda straw to wide open, COLOR!, side vision. Wow!
Last signature was a straight line. (Hmmmm. Looked OK at the time.)

At 30K, one has about 4 seconds of useful consciousness -- unless one holds
one's breath. That may net one a couple of seconds more. No pain. No strain.
Quite pleasant. Been there. Done that. Fast and almost fun.

Humans need a constant supply of oxygen and we store almost none. Lack of
oxygen doesn't hurt. What hurts and gives the feeling of strangulation is an
overabundance of carbon dioxide. Want to know what too much CO2 feels like?
Hold your breath for 3-4 minutes.

Throw in a little exhaust gas and the ceiling easily drops to 20K or lower.

Quent
  #8  
Old March 11th 04, 07:40 AM
rnf2
external usenet poster
 
Posts: n/a
Default

On Wed, 10 Mar 2004 11:46:52 -0500, "Leslie Swartz"
wrote:

You live off off something called the "partial pressure of oxygen" in the
medium you are breathing. As altitude increases, the partial pressure of
oxygen in air decreases. Therefore, you must "enrich" the breathing medium
with more oxygen in order to achieve the *same* partial pressure of oxygen
that exists at lower altitudes.

Two solutions: 1) increase the relative percentage of oxygen inht e
medium, or 2) pressurize hte medium. 1) is much less expensive than 2).

Steve Swartz

(The partial pressure of oxygen is what gets the O2 across your lung tissue
into your bloodstream. As total pressure decreases, the partial pressure of
oxygen decreases. Eventually, as ambient pressure goes down, you would need
to breathe pure *pressurized* [3.2 psi IIRC] oxygen in order to make up the
deficit.)

"Arquebus257WeaMag" wrote in message
om...
Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.


Same basic idea of the PPO2 is why SCUBA divers going down need to cut
the oxy levels of their breathing gas down to avoid PPO2 levels above
1.4 ATA... so you can find divers using as low as 5% oxy in a deep
dive Trimix (Oxy, Nitrogen, and Helium) bottom gas
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: Nelson 4-Place Oxygen Sportsmen System Mary Kroening Aviation Marketplace 0 June 18th 04 05:31 PM
FS: Nelson 4-Person Sportsman Oxygen System Mary Kroening Aviation Marketplace 0 June 4th 04 05:48 PM
Securing portable oxygen dutch Instrument Flight Rules 4 February 10th 04 06:30 AM
Meting with a Lancaster rear gunner Dave Eadsforth Military Aviation 12 November 22nd 03 09:08 AM
oxygen sensors for aircraft Air Methods Corporation Home Built 0 September 21st 03 07:16 PM


All times are GMT +1. The time now is 04:04 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Copyright 2004-2022 AviationBanter.
The comments are property of their posters.