O2 and Cypriot airliner crash

In accounts of the crash of the Cypriot airliner in Greece, all I've
read say that loss of cabin pressure could not, by itself, incapacitate
the pilot. Yet, I was once told by an ATP that at 40k feet (admittedly
this plane was at 35k) O2 supply by itself will not suffice to keep you
conscious and that the drop down masks only give a false sense of
security. He said that the ambient pressure is so low that even 100% O2
does not provide enough to keep you conscious without a pressure
breathing mask. If he's right, that could explain the crash, especially
given that all it would take is 20 seconds of distraction (i.e., not
donning the mask) to knock out the pilot as indicated in the table
below. On the other hand, I checked and a standard atmosphere at 35k
feet is 7.0 in of Hg, which is more than the partial pressure of O2 at
sea level (6 in = 20% of 30 inches), which would seem to contradict the
info given by the ATP. Any thoughts or corrections to my reasoning?


Tlme of useful
consciousness
Altitude (ft) without oxygen

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds
28,000 1 minute
26,000 2 minutes
24,000 3 minutes
22,000 6 minutes
20,000 10 minutes
15.000 Indefinite

wrote:
40,000 15 seconds
35.000 20 seconds
30,000 30 seconds

I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

"Bucky" wrote in message
oups.com...
I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

When they do that, they are using up a small reserve of oxygen-filled air
contained in their lungs. Exhale as much air from your lungs as you can,
and THEN see how long you can hold your breath.

Peter Duniho wrote:

When they do that, they are using up a small reserve of oxygen-filled air
contained in their lungs. Exhale as much air from your lungs as you can,
and THEN see how long you can hold your breath.

Even then, there's still a lot of oxygen in the lungs, the human lung is
pretty inefficient. What happens at altitude is that you don't feel the
absence of oxygen, hence just continue to breath normally. This empties
your oxygen reserves rather quickly.

On airliners, though, there are instruments which alarm the pilot of
pressure loss and drop the mask immediately. So there must have been
another problem.

Stefan

"Peter Duniho" wrote in message
"Bucky" wrote in message
oups.com...
I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

When they do that, they are using up a small reserve of oxygen-filled air
contained in their lungs. Exhale as much air from your lungs as you can,
and THEN see how long you can hold your breath.

Partially crap. Learn how lungs work.

moo

Happy Dog wrote:

Partially crap. Learn how lungs work.

Your post is complete crapp. Why don't you spend five seconds and tell us
all you know in the subject?


Jack

"Jack" wrote in message
Partially crap. Learn how lungs work.

Your post is complete crapp. Why don't you spend five seconds and tell us
all you know in the subject?

Adorable. In five seconds. Below a minimal partial pressure of O2, (40mm
Hg is the typical partial pressure in tissue / 100mm is pO2 in the lungs) an
exchange won't occur in the lungs. Period. Exhaling to the best of one's
ability, as the previous poster suggested, isn't analogous. Lungs work just
fine in reverse.

For more, Google +oxygen +"partial pressure" +respiration 39,500 hits.

moo

Totally crap. Teach someone how lungs work.

Peter Duniho wrote:
"Bucky" wrote in message
oups.com...

I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.


When they do that, they are using up a small reserve of oxygen-filled air
contained in their lungs. Exhale as much air from your lungs as you can,
and THEN see how long you can hold your breath.

At high altitude you breath out the oxygen bound to the hemoglobin in
your blood. Your blood gives up its O2 to the air. Hold your breath or
just stop breathing and you may last longer (never done the experiment
though ;-) ).

Shawn

Bucky wrote:

wrote:

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds


I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

If the drop in pressure is rapid, can a person hold in the air? Or
perhaps it is expelled because the pressure in the lungs is double the
cabin pressure?


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Eric Greenwell
Washington State
USA