O2 and Cypriot airliner crash

wrote:

Any thoughts or corrections to my reasoning?

The ATP is correct. While people do vary greatly, and some people have been able
to perform adequately without oxygen at 20,000' or more, most people can't go
much higher than 10,000' without suffering some ill effects. Because of this,
the FAA requires that a pilot use oxygen if they spend over 30 minutes above
12,500'.

In general, people can use a cranula or similar device to provide oxygen up to
about 20,000' (the FAA limits use of these to 18,000'). These simply bleed
oxygen into the air you breathe. Above that, you need a low-pressure mask. These
ensure that all you are breathing is oxygen and are good up to about 25,000'.
Above that, you need a pressure mask. Those increase the pressure of the oxygen
and work well up to about 35,000'. Above that, you need a pressure suit or a
pressurized aircraft.

The emergency drop-down masks for airline passengers are low-pressure. They
won't keep you conscious at 35,000', but they may keep you alive.

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.

"pbc76049" wrote in message
...
Most passenger O2 systems use chemically generated O2.
There are no bottles to check. There are cabin walk around bottles
and the flight deck is bottled O2, but passengers are not. Remember
the Valujet crash. The initiating event was a cargo bay/cabin fire casued
by
improperly shipped O2 generators igniting in flight.


Even if the passengers have chemically generated O2, the pilots have O2 from
a bottle. Pilots are required (and most do) check their O2 before take-off.
The chemically generated O2 units cannot be turned off once in use and then
must be replaced. Therefore pilot positions have bottled O2.

Duane

On Mon, 15 Aug 2005 18:36:13 UTC, T o d d P a t t i s t
wrote:

: "Ian Johnston" wrote:
:
: Oxygen is only part of it. The breathing reflex is triggered by the
: carbon dioxide partial pressure in your lungs: when atmospheric
: pressure falls below that you never get the trigger and your lungs
: just stop working. This is a Bad Thing.
:
: Your lungs work OK, but there's not enough O2 to keep you
: conscious. ...

Thanks.

: Of course, at high altitudes, if the PP of CO2 is so low
: that your body fails to breathe, then that can cause of
: death, even if the PP of O2 would be high enough to keep you
: alive.

That's what I ws thinking of. Doesn't that effect kick in about thirty
something thousand feet?

Ian

"Ian Johnston" wrote in message
wrote:
: Of course, at high altitudes, if the PP of CO2 is so low
: that your body fails to breathe, then that can cause of
: death, even if the PP of O2 would be high enough to keep you
: alive.

That's what I ws thinking of. Doesn't that effect kick in about thirty
something thousand feet?

It starts at about 14,000 feet. People sleeping above this altitude can
suffer a condition called "Periodic Breathing". This is a cycle of
breathing until CO2 levels drop (the body enters a state of alkalosis), then
breathing stops, CO2 levels rise, the body responds by gasping and
hyperventilating and then stops breathing again. As altitude goes up, the
effect becomes nastier. And a bunch of other bad things become a looming
possibility.

le m

"T o d d P a t t i s t" wrote in message
"Ian Johnston" wrote:

: Of course, at high altitudes, if the PP of CO2 is so low
: that your body fails to breathe, then that can cause of
: death, even if the PP of O2 would be high enough to keep you
: alive.

That's what I ws thinking of. Doesn't that effect kick in about thirty
something thousand feet?

It's no lower than that, and is typically higher. I'm not
sure of the actual point.

That the breathing response is diminished? It starts much lower. But the
rest of your post indicates that you agree with that.
I've been through the
FAA/military oxygen training 3 times and I've flown to 30K'
in a glider on 100% diluter demand O2. I was breathing
deeply and carefully under conscious control, not relying on
my breathing reflex.

That's a real feat. Without acclimatisation training, which, among other
things, increases hemoglobin counts, it's hard to stay usefully awake after
a rapid ascent to that altitude. If you used an oximeter, I'd be interested
in the readings. Did you notice any of the usual effects of hypoxia?

moo

George Patterson wrote:


In general, people can use a cranula or similar device to provide oxygen
up to about 20,000' (the FAA limits use of these to 18,000'). These
simply bleed oxygen into the air you breathe. Above that, you need a
low-pressure mask. These ensure that all you are breathing is oxygen and
are good up to about 25,000'.

My understanding is cannulas are still effective to at least 25,000',
and the FAA mask requirement is only to guard against pilots that might
inadvertently breathe through their mouth instead of their nose. The
masks I've used all allow ambient air into the mask; i.e., they are not
intended to supply only oxygen. They used staged valves for constant
flow systems, or just small holes in the sides of the mask for
pulse-delivery devices like Mountain High's EDS controller.



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

On Mon, 15 Aug 2005 18:54:18 GMT, George Patterson wrote:

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 apparently there was enough time to write a short message on the cell
phone and send it - if one can trust the news (*doh*).

#m


--
The most likely way for the world to be destroyed,
most experts agree, is by accident. That's where we
come in; we're computer professionals. We cause accidents.
-- Nathaniel Borenstein

In article , Martin Hotze wrote:
On Mon, 15 Aug 2005 18:54:18 GMT, George Patterson wrote:

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 apparently there was enough time to write a short message on the cell
phone and send it - if one can trust the news (*doh*).

They arrested the person whom reported it a short time ago, it
apparently being a disgusting and cruel hoax.

-Dan

On Mon, 15 Aug 2005 21:08:03 +0000 (UTC), Dan Foster wrote:

but apparently there was enough time to write a short message on the cell
phone and send it - if one can trust the news (*doh*).

They arrested the person whom reported it a short time ago, it
apparently being a disgusting and cruel hoax.

thanks for the info. I have to check that.

-Dan

#m

--
The most likely way for the world to be destroyed,
most experts agree, is by accident. That's where we
come in; we're computer professionals. We cause accidents.
-- Nathaniel Borenstein

CO2 is generated by cellular respiration. This is essentially
independent of oxygen, as a matter of fact, anaerobic respiration can
occur in the absense of adequate oxygen, but it is VERY inefficient, and
makes LOTS of waste products.

Arterial CO2 concentration, having left the lungs, is around 35-45 torr
(mmHg). In mixed venous blood, returning to the lungs, it is around 50
torr/mmhg or so.

At sea level, atmospheric CO2 is in the high 20's/low 30's mmhg. The
body's buffer system in a healthy individual will RAPIDLY move the CO2
level back towards normal if it vary's too much from those values. So,
even at altitude, your venous blood gas values are pretty much normal
after one pass around the body. You hold your breath, and this blood
with "venous" levels of CO2 will make a second pass, and when it hits
the chemo and baro receptors in in your carotid (artery) bodies you will
start getting that URGE to breath.

All of this is independent of how oxygen is handled by the blood. Each
gas's function in the body is more or less independent of each other.
Even though your body uses oxygen to make CO2 as a waste product, your
body will continue to make CO2 for a short time without adequate oxygen.
As an example: the burn in your muscles after a sprint - lactic acid
generated along with CO2 when the oxygen requirement of the muscles
outstrips the oxygen supply.

To say "the lungs stop working" is at best, technically inaccurate. You
are just too hypoxic to make the muscles responsible for gas exchange to
work properly.

Dave