Oxygen above 20,000 feet

[O. Sami Saydjari]

I seem to recall that my portable 02 system said something about not
being about to go above 20,000 feet with it. This does not present a
problem with my Turbo Arrow since that represents its service ceiling.
Now, I am contemplating a Cessna Turbo 310 R and I am wondering whether
the 02 will be the limiting factor on how high I fly?

-Sami

[O. Sami Saydjari]

Yes, I think so. So if I use a mask, then is there some upper limit?
This seems counter-intuitive. It seems like nasal canulas deliver
oxygen more directly into the lungs (assuming you are a nose
breather)...especially if you use a pusher (a little device that detects
when you breath and pushes O2 to you...and then shuts it off when you
are not breathing). What am I misunderstanding here?

-Sami


Aaron Coolidge wrote:

> O. Sami Saydjari > wrote:
> : I seem to recall that my portable 02 system said something about not
> : being about to go above 20,000 feet with it. This does not present a
> : problem with my Turbo Arrow since that represents its service ceiling.
> : Now, I am contemplating a Cessna Turbo 310 R and I am wondering whether
> : the 02 will be the limiting factor on how high I fly?
>
> : -Sami
>
> For some reason, the nasal "cannula" oxygen systems state they should not
> be used over 18000 feet. Perhaps this is the limit you're thinking of?

[Mike W.]

"O. Sami Saydjari" > wrote in message
...
> Yes, I think so. So if I use a mask, then is there some upper limit?
> This seems counter-intuitive. It seems like nasal canulas deliver
> oxygen more directly into the lungs (assuming you are a nose
> breather)...especially if you use a pusher (a little device that detects
> when you breath and pushes O2 to you...and then shuts it off when you
> are not breathing). What am I misunderstanding here?
>
> -Sami
>

A mask is more of a sealed system, whereas a canula allows a leak out of
your nose. With the air that thin, I would think the oxygen coming out would
migrate towards the atmosphere a lot faster than into you.
Another thing to ponder might be the physical strength of the O2 bottle, it
may not be safe at the reduced atmospheric pressure at higher altitudes.

[BTIZ]

most "standard" masks are not sealed.. but have rebeather bags.. and are not
suited about 25,000ft

above 25,000 unpressurized you should have a military aviators style mask
with pressure regulator

BT

"Mike W." > wrote in message
...
>
> "O. Sami Saydjari" > wrote in message
> ...
>> Yes, I think so. So if I use a mask, then is there some upper limit?
>> This seems counter-intuitive. It seems like nasal canulas deliver
>> oxygen more directly into the lungs (assuming you are a nose
>> breather)...especially if you use a pusher (a little device that detects
>> when you breath and pushes O2 to you...and then shuts it off when you
>> are not breathing). What am I misunderstanding here?
>>
>> -Sami
>>
>
> A mask is more of a sealed system, whereas a canula allows a leak out of
> your nose. With the air that thin, I would think the oxygen coming out
> would
> migrate towards the atmosphere a lot faster than into you.
> Another thing to ponder might be the physical strength of the O2 bottle,
> it
> may not be safe at the reduced atmospheric pressure at higher altitudes.
>
>

[Ben Hallert]

I think the other posters have it right. The specific concept behind
it, if I remember my science fiction books correctly, is 'partial
pressure'. With the open cycle (the one that hooks to your nose),
there's an open path direct to the low pressure area through your
mouth. The oxygen enters your lungs through osmosis, and if the
pressure on the inside of the hemoglobin in your pulmonary capillary is
greater then the pressure of the O2 against it, it just won't enter.

Another part of the problem may be that at high enough altitudes, CO2
may no longer be effective at triggering the breathing impulse.

I think the partial pressure issue is probably more relevant.

If someone here is a doctor or actually KNOWS the answer, feel free to
tell me where I pooched it up. My education comes from the likes of
Del Rey Publishing and Baen Books, not John Hopkins.

Ben Hallert
PP-ASEL

[Viperdoc]

The oxygen tank will be safe at altitude. Normally they contain a pressure
of 1200 to 2000 PSI, while sea level atmospheric pressure is 14.7 PSI. Even
in a vacuum the pressure differential between the atmosphere and inside the
tank is miniscule.

[john smith]

Very good answer Ben!
The partial pressure of O2 at FL180 is 50% that of sea level.
As you go higher, the rate of partial pressure change decreases more
rapidly, so that by FL270 it is into single digits.
A pressurized mask is necessary to force the air into your lungs and
into your blood.

Ben Hallert wrote:
> I think the other posters have it right. The specific concept behind
> it, if I remember my science fiction books correctly, is 'partial
> pressure'. With the open cycle (the one that hooks to your nose),
> there's an open path direct to the low pressure area through your
> mouth. The oxygen enters your lungs through osmosis, and if the
> pressure on the inside of the hemoglobin in your pulmonary capillary is
> greater then the pressure of the O2 against it, it just won't enter.
> Another part of the problem may be that at high enough altitudes, CO2
> may no longer be effective at triggering the breathing impulse.
> I think the partial pressure issue is probably more relevant.

[Juan Jimenez]

"Mike W." > wrote in message
...
>
> Another thing to ponder might be the physical strength of the O2 bottle,
> it
> may not be safe at the reduced atmospheric pressure at higher altitudes.

That's a myth, the bottles will certainly not have a problem handling the
minimal changes in pressure at altitude.

Juan

[BTIZ]

> Another thing to ponder might be the physical strength of the O2 bottle,
> it
> may not be safe at the reduced atmospheric pressure at higher altitudes.

They why carry it? O2 tanks are pressure tested every 5 years.. a standard
O2 tank should be able to go to 50,000ft.. but you'll need a pressure
regulator and fitted sealed mask for pressure breathing

BT

[O. Sami Saydjari]

OK, very helpful answers. But, how does one get a "pressurized mask"?
Is this a matter of buying a pressurized mask and hooking it to a
built-in O2 system (such as might be found on a Cessna Turbo 310), or is
there something special about the 02 system itself that is needed. It
sounds like one needs a special pressure regulator like one might find
in Scuba equipment. I ask this because I want to know what to ask for
when I am looking at Turbo Cessna 310s in terms of an adequate O2 system
to make it up to its 28,000 ft service ceiling.

-Sami


john smith wrote:

> Very good answer Ben!
> The partial pressure of O2 at FL180 is 50% that of sea level.
> As you go higher, the rate of partial pressure change decreases more
> rapidly, so that by FL270 it is into single digits.
> A pressurized mask is necessary to force the air into your lungs and
> into your blood.
>
> Ben Hallert wrote:
>
>> I think the other posters have it right. The specific concept behind
>> it, if I remember my science fiction books correctly, is 'partial
>> pressure'. With the open cycle (the one that hooks to your nose),
>> there's an open path direct to the low pressure area through your
>> mouth. The oxygen enters your lungs through osmosis, and if the
>> pressure on the inside of the hemoglobin in your pulmonary capillary is
>> greater then the pressure of the O2 against it, it just won't enter.
>> Another part of the problem may be that at high enough altitudes, CO2
>> may no longer be effective at triggering the breathing impulse.
>> I think the partial pressure issue is probably more relevant.

[Viperdoc]

If you're thinking about going from an Arrow to a T-310, I hope you've also
thought about burning 30 gallons an hour and the need for recurrent
multiengine training as well as the management of turbocharged engines.

A T-310 may cost $300 an hour (at least compared to my Baron), and there
have been some expensive ADs on the twin Cessnas regarding the exhaust
systems (as I recall).

You should also strongly consider a ride in an altitude chamber to be able
to recognize the signs and symptoms of hypoxia, which can be insidious.

The transition from an Arrow to a T-310 is a pretty big jump in cost and
complexity.

[George Patterson]

O. Sami Saydjari wrote:
> Yes, I think so. So if I use a mask, then is there some upper limit?
> What am I misunderstanding here?

As the ambient air pressure decreases, you need to increase the percentage of
oxygen in the air you breath to get the same amount of oxygen into your blood.
The nasal canulae will do this up to a point.

Once you get up to about 20,000', the ambient air pressure is so low that the
canula just can't do the job. You need to go with a full mask. Even there, the
less expensive low pressure masks are only good for something like another
8,000'. Then you need a high pressure mask (such as the military used in WWII).
Those will work up to about 35,000'. Above that, you need either a pressure suit
or a pressurized cabin.

George Patterson
"Naked" means you ain't got no clothes on; "nekkid" means you ain't got
no clothes on - and are up to somethin'.

[George Patterson]

O. Sami Saydjari wrote:
> OK, very helpful answers. But, how does one get a "pressurized mask"?

Here's a low pressure model.
http://www.mhoxygen.com/index.phtml?nav_id=28&product_id=373

Here's this retailer's entire offering.
http://www.mhoxygen.com/index.phtml?nav_id=34&prd_group_id=9

George Patterson
"Naked" means you ain't got no clothes on; "nekkid" means you ain't got
no clothes on - and are up to somethin'.

[[email protected]]

On 26-May-2005, john smith > wrote:

> The partial pressure of O2 at FL180 is 50% that of sea level.
> As you go higher, the rate of partial pressure change decreases more
> rapidly, so that by FL270 it is into single digits.
> A pressurized mask is necessary to force the air into your lungs and
> into your blood.

Actually, you nailed the main issue -- oxygen partial pressure -- but missed
the precise reason for the pressure mask.

As altitude increases, partial pressure of O2 decreases, as you correctly
state. The O2 PP at sea level is way more than we need, and healthy
individuals can tolerate the air at up to about 14000 ft without much loss
of mental capacity (physical capacity, including visual acuity, is another
matter.) Above that (actually, above 12500 ft), in an unpressurized
airplane, we increase the PP of the O2 we breath by adding supplemental
oxygen. The cannulas and/or masks typically used in light aircraft mix pure
O2 from the bottle with atmospheric air at a ratio that can be somewhat
adjusted (by the flow adjustment) to result in roughly the desired O2 PP.
But these systems are not designed to deliver anything close to pure O2 to
the user. The maximum O2 concentration they CAN deliver will provide
sufficient O2 PP at about 18000 ft for cannulas and about 26000 ft (if I
recall correctly) for masks. Above that, you need a system that can deliver
higher O2 concentrations, up to and including pure O2, which is where the
pressure mask comes in. What it does is provide O2 at slight positive
pressure relative to the outside air to prevent uncontrolled mixing in the
mask. Such masks also cover both nose and mouth to prevent leakage/mixing
that way. It doesn't really "force" the O2 into the user's lungs, nor does
it need to.

Above about 35000 ft even pure O2 will not have sufficient PP for adequate
breathing, so unpressurized aircraft cannot safely operate at anything close
to that level (unless the occupants are equipped with pressure suits).

This also explains why cabin depressurization above 30000 feet is an
emergency requiring (a) the immediate donning by the pilot(s) of a pressure
mask and (b) emergency descent to an altitude where the conventional
emergency masks used by passengers will be sufficient.

--
-Elliott Drucker

[Mike Rapoport]

You don't normally use a pressure O2 system in anything except jets (for
emergencies) and some high altitude gliders and you don't want to anyway.
Pressure O2 systems are very uncomfortable.

Mike
MU-2

"O. Sami Saydjari" > wrote in message
...
> OK, very helpful answers. But, how does one get a "pressurized mask"? Is
> this a matter of buying a pressurized mask and hooking it to a built-in O2
> system (such as might be found on a Cessna Turbo 310), or is there
> something special about the 02 system itself that is needed. It sounds
> like one needs a special pressure regulator like one might find in Scuba
> equipment. I ask this because I want to know what to ask for when I am
> looking at Turbo Cessna 310s in terms of an adequate O2 system to make it
> up to its 28,000 ft service ceiling.
>
> -Sami
>
>
> john smith wrote:
>
>> Very good answer Ben!
>> The partial pressure of O2 at FL180 is 50% that of sea level.
>> As you go higher, the rate of partial pressure change decreases more
>> rapidly, so that by FL270 it is into single digits.
>> A pressurized mask is necessary to force the air into your lungs and into
>> your blood.
>>
>> Ben Hallert wrote:
>>
>>> I think the other posters have it right. The specific concept behind
>>> it, if I remember my science fiction books correctly, is 'partial
>>> pressure'. With the open cycle (the one that hooks to your nose),
>>> there's an open path direct to the low pressure area through your
>>> mouth. The oxygen enters your lungs through osmosis, and if the
>>> pressure on the inside of the hemoglobin in your pulmonary capillary is
>>> greater then the pressure of the O2 against it, it just won't enter.
>>> Another part of the problem may be that at high enough altitudes, CO2
>>> may no longer be effective at triggering the breathing impulse.
>>> I think the partial pressure issue is probably more relevant.

[Matt Barrow]

"O. Sami Saydjari" > wrote in message
...
> OK, very helpful answers. But, how does one get a "pressurized mask"?
> Is this a matter of buying a pressurized mask and hooking it to a
> built-in O2 system (such as might be found on a Cessna Turbo 310), or is
> there something special about the 02 system itself that is needed. It
> sounds like one needs a special pressure regulator like one might find
> in Scuba equipment. I ask this because I want to know what to ask for
> when I am looking at Turbo Cessna 310s in terms of an adequate O2 system
> to make it up to its 28,000 ft service ceiling.
>
> -Sami

Some information!

http://www.mhoxygen.com/index.phtml?nav_id=20&prd_group_id=4

http://www.aerox.com/Pages/masks.html

[Dave S]

Ben Hallert wrote:
> I think the other posters have it right. The specific concept behind
> it, if I remember my science fiction books correctly, is 'partial
> pressure'. With the open cycle (the one that hooks to your nose),
> there's an open path direct to the low pressure area through your
> mouth. The oxygen enters your lungs through osmosis, and if the
> pressure on the inside of the hemoglobin in your pulmonary capillary is
> greater then the pressure of the O2 against it, it just won't enter.

Partial pressures of the gas in question DO define how oxygentation and
ventilation work, BUT the term you are looking for is "pressure
gradient", the difference between the partial pressures in question.
>
> Another part of the problem may be that at high enough altitudes, CO2
> may no longer be effective at triggering the breathing impulse.

Not hardly. In the body, arterial blood leaving the lungs has a partial
pressure of CO in the 35-45 mmHG range. In a "mixed venous sample" which
is in the blood returning to the lungs, this value is even higher. The
majority of healthy individuals use CO2 as the determining factor in
their breathing depth and rate, and this does not vary with altitude.
>
> I think the partial pressure issue is probably more relevant.
>
> If someone here is a doctor or actually KNOWS the answer, feel free to
> tell me where I pooched it up. My education comes from the likes of
> Del Rey Publishing and Baen Books, not John Hopkins.
>
> Ben Hallert
> PP-ASEL
>

I'm not a doc, just an ICU and ER nurse, Paramedic, and former
firefighter. I didn't go to John's Hopkins either.

Other posts elsewhere in the thread raised other questions I wanted to
address:

With a cannula, the limitation is due to the volume of oxygen that is
useable. In a cannula, once your "nose" is filled with free flowing
oxygen, the excess spills over into the mouth, and also out into the
environment. Increasing the flow rate past the point where the "nose"
fills between breaths only increases the waste.

A pulsed regulator (someone called it a "pusher") is helpful in this
regard because the regulator gives HIGH flow, but only during a breath,
so its OFF when not inhaling. Cuts waste WAY down. May give you a little
extra altitude as well. These devices were originally developed for home
health care type patients to extend their supply of oxygen on their
transport bottles, allowing them to get out of the house longer.

A mask gets its effect from having a larger area being filled with
oxygen between breaths (the entire mouth, and then the area under the
mask). For aviation use, a reservoir mask allows you to get an even
larger charge of oxygen per breath.

Those of you who are talking about "pressure breathing" need to
understand that the pressures involved are VERY miniscule. The pressures
that these "pressure breathing" regulators use is measured in
CENTIMETERS of water, which corresponds to a SMALL fraction of a single
PSI. Anything more than that would cause the lung to pop (barotrauma).
The pressures involved contribute LITTLE to the pressure differential.

What is different about the pressure breathing setup is that NORMALLY,
you WORK to breathe in, and relax to exhale. With this setup, your
inhalation is assisted (slightly, its called "pressure support" in the
medical community) and you have to WORK to exhale.

The tanks in question carry in the neighborhood of 1800-2000 psi. They
are routinely filled to 10% over (2000-2200 psi), and when they are
tested I believe the value is 150%. Adding 15 psi by taking the tank
into outer space (yea.. REALLY at altitude) is a miniscule thing in this
pressure equation. The altitude restrictions are a function of the
delivery device, not the storage tank.

Dave

[Roy Smith]

wrote:
> This also explains why cabin depressurization above 30000 feet is an
> emergency requiring (a) the immediate donning by the pilot(s) of a pressure
> mask and (b) emergency descent to an altitude where the conventional
> emergency masks used by passengers will be sufficient.

I believe that emergency descent capability is one of the factors that
limits allowable operating ceilings. Some aircraft could get higher than
their certified ceilings, but are not allowed to do so because getting down
to breathable air before the pax suffocated would involve tearing the wings
off (or some other overspeed disaster).

[Montblack]

("Roy Smith" wrote)
[snip]
> I believe that emergency descent capability is one of the factors that
> limits allowable operating ceilings. Some aircraft could get higher than
> their certified ceilings, but are not allowed to do so because getting
> down
> to breathable air before the pax suffocated would involve tearing the
> wings
> off (or some other overspeed disaster).


What is the time limit - 3 minutes? Tell me it's not 4 minutes.

What are planes/jets doing (ft/min) in emergency descents - and how low must
they go to get to "breathable air?" What's the reg for breathable air out of
an emergency descent - 18,000 ft?


Montblack

[Mike Rapoport]

Most jets can do 10,000fpm+. It is going to take a couple of minutes in any
case, that is why it is required for either one pilot to be wearing a mask
or to have quick donning masks immediatly available.

Mike
MU-2

"Montblack" > wrote in message
...
> ("Roy Smith" wrote)
> [snip]
>> I believe that emergency descent capability is one of the factors that
>> limits allowable operating ceilings. Some aircraft could get higher than
>> their certified ceilings, but are not allowed to do so because getting
>> down
>> to breathable air before the pax suffocated would involve tearing the
>> wings
>> off (or some other overspeed disaster).
>
>
> What is the time limit - 3 minutes? Tell me it's not 4 minutes.
>
> What are planes/jets doing (ft/min) in emergency descents - and how low
> must they go to get to "breathable air?" What's the reg for breathable air
> out of an emergency descent - 18,000 ft?
>
>
> Montblack

[[email protected]]

Most people I know seldom go very high in their turbo airplanes -- 02
is just too big a hassle.
Try to buy it on Sunday. Many places require a mechanic to fill.

So, with you experts on board here, I want to investigate this cannula
business a bit.

Using a mountain high pulse system, with a rebreather cannula at 18,000
feet, I easily get measured
low 90s saturation and it is still using only brief pulses on each
inhalation.
BTW, this thing really saves O2 & you feel good.

So the simple question is: So long as I climb higher and still
maintain the measured 02 saturation,
what's the harm in using the cannula? Why not at 210?

What else don't we know?

Bill Hale

[Scott Skylane]

Montblack wrote:


>
>
> What is the time limit - 3 minutes? Tell me it's not 4 minutes.
>
> What are planes/jets doing (ft/min) in emergency descents - and how low
> must they go to get to "breathable air?" What's the reg for breathable
> air out of an emergency descent - 18,000 ft?
>
>
> Montblack

I believe the reg states "4 minutes to get to 14000 ft."

Happy Flying!
Scott Skylane

[[email protected]]

Mike Rapoport wrote:
> Most jets can do 10,000fpm+. It is going to take a couple of minutes in any
> case, that is why it is required for either one pilot to be wearing a mask
> or to have quick donning masks immediatly available.
>

It's pretty impressive. Many years ago I was meandering over eastern
AZ at 12.5K ft. when a TWA DC-9 variant lost cabin pressure overhead
(we were on the same Center freq.). That guy was down to my altitude
in just a few minutes. The deck angle of his decent looked downright
scary.

John Galban=====>N4BQ (PA28-180)

[Matt Barrow]

> wrote in message
oups.com...
> Most people I know seldom go very high in their turbo airplanes -- 02
> is just too big a hassle.
> Try to buy it on Sunday. Many places require a mechanic to fill.

http://www.avweb.com/news/columns/182079-1.html

-------------------------------------------------------------------------
January 24, 1999

Pelican's Perch #13:
Getting High on Welder's Oxygen

Having problems finding Aviator's Breathing Oxygen to refill your bottle?
Upset about the rip-off prices some FBOs charge for an O2 fill? Don't put up
with it, says AVweb's John Deakin, who explains why it's perfectly safe -
and perfectly legal - to use cheap welder's oxygen, and tells you exactly
what you need to know to buy it in bulk and do your own refills

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

I have the MH 4ip pulse system, and it makes filling my own hardly worth the
effort. In going any direction from here, it's pretty assured I will need to
go to 15,000 or 16,000 feet or more. I live at nearly 6000 feet and don't
smoke cigarettes.
I have masks, but only use them three or fiur times a year.

>
> So, with you experts on board here, I want to investigate this cannula
> business a bit.
>
> Using a mountain high pulse system, with a rebreather cannula at 18,000
> feet, I easily get measured
> low 90s saturation and it is still using only brief pulses on each
> inhalation.
> BTW, this thing really saves O2 & you feel good.

Yes, thhey are a good deal in eliminating waste and also in automatically
adjusting for altitude and night/day.

> So the simple question is: So long as I climb higher and still
> maintain the measured 02 saturation,
> what's the harm in using the cannula? Why not at 210?

Have you tested this theory of yours? As someone pointed out, you'll lose
more oxygen outside the cannula the higher you go.

> What else don't we know?

A persons physiology and other health considerations. Would a sea level
resident who is in poor shape and smokes need a mask at a much lower
altitude than someone else?


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[john smith]

Time of useful consciousness at FL250 is 10-15 seconds without
supplemental O2.

wrote:
[snip]
> But these systems are not designed to deliver anything close to pure O2 to
> the user. The maximum O2 concentration they CAN deliver will provide
> sufficient O2 PP at about 18000 ft for cannulas and about 26000 ft (if I
> recall correctly) for masks.
[snip]

[Matt Barrow]

"john smith" > wrote in message
...
> Time of useful consciousness at FL250 is 10-15 seconds without
> supplemental O2.

He's talking about using cannulas versus a full face mask.

>
> wrote:
> [snip]
> > But these systems are not designed to deliver anything close to pure O2
to
> > the user. The maximum O2 concentration they CAN deliver will provide
> > sufficient O2 PP at about 18000 ft for cannulas and about 26000 ft (if I
> > recall correctly) for masks.
> [snip]
>

[[email protected]]

I've been at 23000 feet hanging on to a bar out side of the airplane
with 300 of my best friends without oxygen. We used supplemental o2
(mostly cannulas) on the climb to alt but when it was time to climb out
of the aircraft we were without o2 during the 30-45 seconds waiting to
exit.
We didn't carry o2 on us, but were in more dense air in short order.
We learned to conserve our energy so we didn't burn the o2 we had stored
in our bodies.
There have been climbers that have reached the top of everest without o2.
keeping calm is the secret to most high altitude operations.






Matt Barrow wrote:
> "john smith" > wrote in message
> ...
>
>>Time of useful consciousness at FL250 is 10-15 seconds without
>>supplemental O2.
>
>
> He's talking about using cannulas versus a full face mask.
>
>
wrote:
>>[snip]
>>
>>>But these systems are not designed to deliver anything close to pure O2
>
> to
>
>>>the user. The maximum O2 concentration they CAN deliver will provide
>>>sufficient O2 PP at about 18000 ft for cannulas and about 26000 ft (if I
>>>recall correctly) for masks.
>>
>>[snip]
>>
>
>
>

[Matt Barrow]

> wrote in message ...
> I've been at 23000 feet hanging on to a bar out side of the airplane
> with 300 of my best friends without oxygen. We used supplemental o2
> (mostly cannulas) on the climb to alt but when it was time to climb out
> of the aircraft we were without o2 during the 30-45 seconds waiting to
> exit.
> We didn't carry o2 on us, but were in more dense air in short order.
> We learned to conserve our energy so we didn't burn the o2 we had stored
> in our bodies.

IN which case you have ONE and only ONE decision to make during that lfight
:~)


> There have been climbers that have reached the top of everest without o2.
> keeping calm is the secret to most high altitude operations.

And acclimation.

Oxygen for flights over 5000 feet at night? I live at 5800 feet and the
cannula gets in the way when having sex.


>
>
>
> Matt Barrow wrote:
> > "john smith" > wrote in message
> > ...
> >
> >>Time of useful consciousness at FL250 is 10-15 seconds without
> >>supplemental O2.
> >
> >
> > He's talking about using cannulas versus a full face mask.
> >
> >
> wrote:
> >>[snip]
> >>
> >>>But these systems are not designed to deliver anything close to pure O2
> >
> > to
> >
> >>>the user. The maximum O2 concentration they CAN deliver will provide
> >>>sufficient O2 PP at about 18000 ft for cannulas and about 26000 ft (if
I
> >>>recall correctly) for masks.
> >>
> >>[snip]
> >>
> >
> >
> >
>

[Dave S]

wrote:

> We learned to conserve our energy so we didn't burn the o2 we had stored
> in our bodies.

Thats nice.. unfortunately, the body doesn't store oxygen. It either
uses it or it doesnt. That is a medical fact, regardless of what type of
old wives tales you apply to it.

Dave

[[email protected]]

Hey dave,
Ever swam under water?
Ever hypervent your self before taking that last breath so you can stay
down longer?
What would you call that?


Dave S wrote:

>
>
> wrote:
>
>> We learned to conserve our energy so we didn't burn the o2 we had
>> stored in our bodies.
>
>
> Thats nice.. unfortunately, the body doesn't store oxygen. It either
> uses it or it doesnt. That is a medical fact, regardless of what type of
> old wives tales you apply to it.
>
> Dave
>

[Dave S]

wrote:

> Hey dave,
> Ever swam under water?
> Ever hypervent your self before taking that last breath so you can stay
> down longer?
> What would you call that?


You are eliminating the Carbon Dioxide in your body to VERY low levels,
which helps forestall the URGE to breath until they build back up to
higher levels.

Hyperventilation does not increase oxygen capacity over and above what
normal breathing does. It simply clears out waste products. All of this
is again a function of the partial pressures and pressure gradients that
were discussed elsewhere in this thread.

On room air, your pO2 in arterial blood is in the area of 80-100 mmhg.
Your pC02 is in the neighborhood of 40 mmhg. Oxygen Saturation is in the
90-100% range.

Mixed venous blood gases (which are sampled from the pulmonary artery,
in patients with the proper monitoring equipment) on room air tends to
be in the 40-50 mmHg range. This corresponds with about ONE of the FOUR
oxygen molecules on each hemoglobin molecule being extracted, and a
saturation in the 60-75% range. Without a fresh supply of oxygen in the
lungs to extract from, this "desaturated" blood makes a second trip
around, and because of the laws of nature, it is even more difficult for
the remaining oxygen to be extracted. For practical purposes, its
essentially NOT going to release more than two of the four
hemoglobin-bound oxygen molecules. Your arterial oxygen saturation gets
too low and you will end up getting confused, euphoric, or just unconscious.

Hyperventilation in an otherwise healthy individual will not increase
the p02, but can/will drive the pCO2 in arterial blood down to the 20's.
Prolonged hyperventilation will cause vasoconstriction in the brain
(as well as everywhere else), resulting in lightheadedness, dizziness,
cramping in the fingers/toes, and chest pain. I deal with persons on
breathing machines EVERY DAY for a living. If their oxygen level is low,
we dont turn up the rate or volume, we turn up the oxygen concentration.
If their CO2 level is high, THEN we turn up rate/volume to increase
the amount of VENTILATION. Ventilation is the removal of waste products.
Oxygenation is the delivery of oxygen. They are TWO completely different
functions, and not very related to each other, despite the fact they are
happening in the same place at the same time.

It is still possible to pass out from Hypoxia without building up CO2
levels back to the amount needed to trigger the chemoreceptors to tell
your brain "I GOTTA BREATHE". It has been the cause of more than one
drowning/diving accident. If you want further reference on this, a
knowledgeable professional diver, an aerospace medicine MD or a
hyperbaric technician should be able to validate this information.

Dave

[Juan Jimenez]

Once in a while you get these little gems that are worth filing in the ol'
grey matter. The rest of the time, I run the usenet shredder almost
continuously. :)

"Dave S" > wrote in message
k.net...
>
>
> wrote:
>
>> Hey dave,
>> Ever swam under water?
>> Ever hypervent your self before taking that last breath so you can stay
>> down longer?
>> What would you call that?
>
>
> You are eliminating the Carbon Dioxide in your body to VERY low levels,
> which helps forestall the URGE to breath until they build back up to
> higher levels.
>
> Hyperventilation does not increase oxygen capacity over and above what
> normal breathing does. It simply clears out waste products. All of this is
> again a function of the partial pressures and pressure gradients that were
> discussed elsewhere in this thread.
>
> On room air, your pO2 in arterial blood is in the area of 80-100 mmhg.
> Your pC02 is in the neighborhood of 40 mmhg. Oxygen Saturation is in the
> 90-100% range.
>
> Mixed venous blood gases (which are sampled from the pulmonary artery, in
> patients with the proper monitoring equipment) on room air tends to be in
> the 40-50 mmHg range. This corresponds with about ONE of the FOUR oxygen
> molecules on each hemoglobin molecule being extracted, and a saturation in
> the 60-75% range. Without a fresh supply of oxygen in the lungs to extract
> from, this "desaturated" blood makes a second trip around, and because of
> the laws of nature, it is even more difficult for the remaining oxygen to
> be extracted. For practical purposes, its essentially NOT going to release
> more than two of the four hemoglobin-bound oxygen molecules. Your arterial
> oxygen saturation gets too low and you will end up getting confused,
> euphoric, or just unconscious.
>
> Hyperventilation in an otherwise healthy individual will not increase the
> p02, but can/will drive the pCO2 in arterial blood down to the 20's.
> Prolonged hyperventilation will cause vasoconstriction in the brain (as
> well as everywhere else), resulting in lightheadedness, dizziness,
> cramping in the fingers/toes, and chest pain. I deal with persons on
> breathing machines EVERY DAY for a living. If their oxygen level is low,
> we dont turn up the rate or volume, we turn up the oxygen concentration.
> If their CO2 level is high, THEN we turn up rate/volume to increase the
> amount of VENTILATION. Ventilation is the removal of waste products.
> Oxygenation is the delivery of oxygen. They are TWO completely different
> functions, and not very related to each other, despite the fact they are
> happening in the same place at the same time.
>
> It is still possible to pass out from Hypoxia without building up CO2
> levels back to the amount needed to trigger the chemoreceptors to tell
> your brain "I GOTTA BREATHE". It has been the cause of more than one
> drowning/diving accident. If you want further reference on this, a
> knowledgeable professional diver, an aerospace medicine MD or a hyperbaric
> technician should be able to validate this information.
>
> Dave
>

[David Lesher]

Roy Smith > writes:

wrote:
>> This also explains why cabin depressurization above 30000 feet is an
>> emergency requiring (a) the immediate donning by the pilot(s) of a pressure
>> mask and (b) emergency descent to an altitude where the conventional
>> emergency masks used by passengers will be sufficient.

>I believe that emergency descent capability is one of the factors that
>limits allowable operating ceilings. Some aircraft could get higher than
>their certified ceilings, but are not allowed to do so because getting down
>to breathable air before the pax suffocated would involve tearing the wings
>off (or some other overspeed disaster).

After that golfer bizjet case; I mentally speculated about an
autopilot altitude un-hold. When the cabin pressure failed, the
autopilot would decend to $FEET, that being a level humans would
revive at.

Of course, you COULD run into Mount Whatever, but you're surely
dead at altitude...

It's not clear to me what the survival time is those altitudes; I
thought it was several minutes...


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[Mike W.]

"David Lesher" > wrote in message
...

> It's not clear to me what the survival time is those altitudes; I
> thought it was several minutes...
>
Survival time may be 2-3 minutes, time to totally lose consciousness is more
like 15-30 seconds. The oxygen just 'bleeds' out of your body.

[jmk]

> It is still possible to pass out from Hypoxia without building up CO2
> levels back to the amount needed to trigger the chemoreceptors to tell
> your brain "I GOTTA BREATHE". It has been the cause of more than one
> drowning/diving accident.

Some years back I saw a GREAT film on this. They take several guys,
just sitting on a couch, and hook them up to full face masks, bypassing
a CO2 scrubber, and an auxilliary air cannister. So they can just sit
there and breathe normally.

Then they shut off the fresh air, so they are breathing the same air
over and over. After a couple of minutes they start breathing hard,
and finally start grabbing for their masks and gasping for air. The "I
can't stand it any longer and I have to breathe" response.

Then, after they have recovered and are back on the original system,
they shut off the fresh air and ADD the CO2 scrubber. The guys just
sit there on the couch for a few minutes, and slowly, calmly, one by
one, pass out!

jmk

[Ron Natalie]

jmk wrote:
>>It is still possible to pass out from Hypoxia without building up CO2
>>levels back to the amount needed to trigger the chemoreceptors to tell
>>your brain "I GOTTA BREATHE". It has been the cause of more than one
>>drowning/diving accident.
>
>
> Some years back I saw a GREAT film on this. They take several guys,
> just sitting on a couch, and hook them up to full face masks, bypassing
> a CO2 scrubber, and an auxilliary air cannister. So they can just sit
> there and breathe normally.

Normally, it is the CO2 levels that tell you to breath. How ever those
with chronic obstructive disease (emphasema, long term bronchitis,
etc...) have so much CO2 in their system on a regular basis, that their
body switches to using the O2 levels (hypoxic drive) to control their
breathing. These folks you can put into respiratory arrest giving them
100% oxygen.

[Don Hammer]

>After that golfer bizjet case; I mentally speculated about an
>autopilot altitude un-hold. When the cabin pressure failed, the
>autopilot would decend to $FEET, that being a level humans would
>revive at.
I'm sure there are others, but the Citation X will automatically turn
and descend at max speed and level at 14K