What's minimum safe O2 level?

I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level
breathing.

"PaulH" wrote in message
om...
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime?

It all depends on the individual, but 90% saturation is considered about the
safe minimum.

The effects ARE cumulative over time, hence the 30 minutes granted for
operations without oxygen between 12,500' and 14,000'. However, IMHO at a
safe saturation level the main effects of extended time without supplemental
O2 have to do with fatigue, leading to secondary impairment, rather than
impairment due directly to hypoxia.

All that said, the bottom line is that even at 10,000' anyone can benefit
from supplemental oxygen. If nothing else, you'll feel better after a long
flight, and you may find that mental tasks are actually easier.

Pete

On mountaineering trips we would often have O2 saturation levels in the 80s
(some people low 80s) upon reaching a new altitude. After a day (or three
sometimes) it would recover to the low 90s. Then we could go up another
thousand meters. This went on for weeks. I don't think that it is
cumulative.

Mike
MU-2


"PaulH" wrote in message
om...
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level
breathing.

On 6 Nov 2004 19:20:43 -0800, (PaulH) wrote:

I took my Arrow up to 10,500 today

I have been skiing at Ajax (Aspen Mountain) on a regular basis for
nearly forty years and have never noticed any effect on mental acuity
at 11,000 feet. Of course it may be that skiers are mentally inacute
to begin with.

all the best -- Dan Ford
email: (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net

On Sun, 07 Nov 2004 06:20:01 -0500, Cub Driver
wrote:

I have been skiing at Ajax (Aspen Mountain) on a regular basis for
nearly forty years and have never noticed any effect on mental acuity
at 11,000 feet. Of course it may be that skiers are mentally inacute
to begin with.

Relying on yourself to "notice" a change has been shown to be an
exceedingly UNreliable assessment method. There have been numerous
experiments in altitude chambers demonstrating that. The subjects were not
aware of their errors in, for example, performing simple mathematical
computations, until they were returned to sea level pressure and could view
what they had written.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

On Sun, 07 Nov 2004 06:54:42 -0500, Ron Rosenfeld
wrote:

until they were returned to sea level pressure and could view
what they had written.

Of course, returning to standard pressure at Aspen means 8,000 feet.
Perhaps we are off the wall the whole time?

Still, I've never had a waiter complain that I was miscalculating the
tip. Perhaps I've been overtipping? It seems unlikely: my wife has
never complained.

Seriously, 11,000 feet is not a problem unless you have medical
problems. People get altitude *sickness* while skiing at high
altitudes; they might be insomniac; they get dehydrated, especially if
they booze it up; and sometimes they hyperventilate. (One of the ski
patrol tricks with ailing turkeys is to have them breath into a paper
bag, to *cut down* on their oxygen intake.)

Loveland Pass, west of Denver, was higher than 10,000 feet, and
carried all traffic before the I-70 tunnel was built.


all the best -- Dan Ford
email: (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net

Cub Driver wrote:

they booze it up; and sometimes they hyperventilate. (One of the ski
patrol tricks with ailing turkeys is to have them breath into a paper
bag, to *cut down* on their oxygen intake.)

Wrong again. The idea of this trick is to keep the CO2 level up.

Stefan

Cub Driver wrote:
(One of the ski
patrol tricks with ailing turkeys is to have them breath into a paper
bag, to *cut down* on their oxygen intake.)

ABSOLUTELY WRONG.... hyperventilation is treated by increasing the CO2
content..The paper bag's therapeutic effect is acheived by allowing CO2
to be rebreathed, and hindering its passage from the body. Hypocapnia is
not treated by inducing hypoxia.

Dave

Cub Driver wrote:
On 6 Nov 2004 19:20:43 -0800, (PaulH) wrote:

I took my Arrow up to 10,500 today

I have been skiing at Ajax (Aspen Mountain) on a regular basis for
nearly forty years and have never noticed any effect on mental acuity
at 11,000 feet. Of course it may be that skiers are mentally inacute
to begin with.

But Dan, we *start* at 5K+ MSL! I ski Loveland (10-11K) all the
time with no problems. But remember, we're up and down within
15-30 min (depending on the lift lines and being amazed at where
we live). Flying is something else -- we stay up there for long
periods of time.

My body prefers O2 any time I've over 8K MSL for more than an
hour.

Well, what's about all the "high-landers" who often live at ore above
8K? ;-) (I live above 7K year round for example)
I would guess that goes with Mike's obervation. One adapts to high
altitudes but it takes a day or two (or three). For short trips up one
may end up hypoxic.
What I still have to find out (in an pressure chamber) where my limits
would be.

Chris
PP-ASEL, Glider
New Mexico

Blanche wrote:
Cub Driver wrote:

On 6 Nov 2004 19:20:43 -0800, (PaulH) wrote:


I took my Arrow up to 10,500 today

I have been skiing at Ajax (Aspen Mountain) on a regular basis for
nearly forty years and have never noticed any effect on mental acuity
at 11,000 feet. Of course it may be that skiers are mentally inacute
to begin with.


But Dan, we *start* at 5K+ MSL! I ski Loveland (10-11K) all the
time with no problems. But remember, we're up and down within
15-30 min (depending on the lift lines and being amazed at where
we live). Flying is something else -- we stay up there for long
periods of time.

My body prefers O2 any time I've over 8K MSL for more than an
hour.