O2 and Cypriot airliner crash

Bucky wrote:

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 aircraft loses pressure at 35,000', you cannot hold your breath. The
pressure difference will force you to exhale. Nothing you can do about it.

But that's not the biggest deal. The biggest problem is the fact that the
ambient pressure at that altitude is too low to keep oxygen in your bloodstream.
All the oxygen immediately begins to flow out of your bloodstream into your
lungs and out into the surrounding air. It doesn't matter whether you breathe
or not.

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

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 you try to hold your breath your lungs will explode when the outside
pressure drops. That's why in altitude chambers they never tell you when
they're going to give the explosive decompression. When it happens the air
in your lungs automatically expels from your body since it is at a much
higher pressure than the ambient air. Pressure breathing through an oxygen
mask is difficult since your must manually forcibly exhale and just relax to
inhale.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

The chart is for time of USEFUL consciousness. The part where the pilot
starts thinking "I feel really great. Look how beautiful the scenery is.
The cold is my friend...." isn't useful consciousness.
"Bucky" wrote in message
oups.com...
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.

The "partial pressure of O2" has nothing to do with it.

Your premise is wrong. Loss of cabin pressure IS what incapacitates
pilots. The lungs need atmospheric pressure to exchange gasses with
hemoglobin in the alveoli. It doesn't matter what gas it is - without
the pressure, respiration stops happening. As altitude increases and
pressure decreases, respiration becomes less effective. Below a
certain pressure, you can suffocate on 100% oxygen.

Brien K. Meehan opined

The "partial pressure of O2" has nothing to do with it.

Your premise is wrong. Loss of cabin pressure IS what incapacitates
pilots. The lungs need atmospheric pressure to exchange gasses with
hemoglobin in the alveoli. It doesn't matter what gas it is - without
the pressure, respiration stops happening. As altitude increases and
pressure decreases, respiration becomes less effective. Below a
certain pressure, you can suffocate on 100% oxygen.

Seems to me that astronauts use 3psi of pure O2 during EVAs.


-ash
Cthulhu in 2005!
Why wait for nature?

Ash Wyllie wrote:

Seems to me that astronauts use 3psi of pure O2 during EVAs.


-ash
Cthulhu in 2005!
Why wait for nature?


Correct and 3psi of pure O2 is about the same as the ppO2 in Air at Sea
Level.
--
--------------------
Scott F. Migaldi
CP-ASEL-IA
N8116B

PADI MI-150972
Join the PADI Instructor Yahoo Group
http://groups.yahoo.com/group/PADI-Instructors/

--------------------

In article .com,
wrote:

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.

I personally know glider pilots here in New Zealand who have flown to
betweeen 35,000 and 37,000 ft with only an ordinary oxygen mask, not a
pressure system.

The glider world record of 49,000 ft used a pressure system.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

"Bruce Hoult" wrote in message news:bruce-566936.
wrote:

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.

I personally know glider pilots here in New Zealand who have flown to
betweeen 35,000 and 37,000 ft with only an ordinary oxygen mask, not a
pressure system.

It's OK at 34,000 ft and above 38,000 ft. And all other altitudes,
partialy. You were asleep or missed this class, right?

moo

Bruce Hoult wrote:

I personally know glider pilots here in New Zealand who have flown to
betweeen 35,000 and 37,000 ft with only an ordinary oxygen mask, not a
pressure system.

The glider world record of 49,000 ft used a pressure system.

Thanks for getting back on topic for this NG.


Jack

Tlme of useful
consciousness
Altitude (ft) without oxygen

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds
28,000 1 minute


How, then, can someone like Ed Viesturs repeatedly climb the tallest
mountain peaks in the world without supplemental oxygen? Is it because of
the slower ascent and the time spent acclimating to the higher altitudes?

John K.