I cut and pasted it-use google to find your postings.


I apologize for starting this thread again - it somehow
vanished...

To those of you who left helpful messages - thanks.

My interest in this are is not limited to soaring flight
- the powered boys
have (in my opinion) the same potential problem and
perhaps moreso in that
they can carry more passengers.

I apologize for being listed as 'Neptune' - something
I must have set this
up way back when and don't remember how to change it.
I am - in real life -
David Reed M.D. from Boulder, CO

My concerns with oxygen utilization are as follows:

1. Presently the FAA mandates for oxygen flow rates
at altitude are found
in 14CFR23.1443. They are based on tracheal oxygen
saturation measurements -
a technique that has been superseded by arterial blood
gas measurements and
now pulse oximetry. These same mandates date back to
the old (at least 40
year-old!) CAA mandates.

2. There appear to be no peer-reviewed published studies
- either in flight
or an altitude chamber - that validate these flow rates.

3. I do have some flight data from the one company
that was willing to
release the data as long as I did not mention the company
name. 6-subject
in-flight with an A-4. A 'regular' nasal cannula was
tested, then repeated
with an Oxymizer at each nominated altitude. Results:

13M - FAA flow rate 0.86LPM - saturations of 87-97%
14M - 0.98
88-98%
15M - 1.10
87-97%
16M - 1.22
85-97%
17M - 1.34
86-95%
18M - 1.46
78-94%

There was no significant difference in use of the
Oxymizer.

As most of us physicians will agree - at around
90% saturation we begin
to get concerned. The above data indicate to me that
at the FAA flow rates
that were extrapolated from the 1443 graph some individuals
were clinically
hypoxic - a condition not changed by using the Oxymizer.
Am I coming up with
a solution without a problem as someone has suggested?
Not if a pilot can
saturate at 78%...

3. 1443 mandates flow rates for continuous flow systems.
Newer systems
utilize 'pulsed' flows. Manufacturers claim greatly
reduced oxygen
utilization using these systems, and even lesser use
when these 'pulsed'
systems are used with an Oxymizer type of cannula.
As far as I can tell
these claims have never been objectively and openly
verified by any
peer-reviewed research.

4. There does not appear to be any FAA requirement
that oxygen delivery
systems claims such as those above be independently
verified.

I am not at all saying that these performance claims
are wrong. All I would
like to see is some FAA mandate that oxygen delivery
systems should be
objectively tested for compliance with pulse-oximetry
values of over 90% at
all altitudes at which they will be used. At this point
all I can say as I
put on my system is that is SHOULD be OK - and if I
have (and use) a pulse
ox I SHOULD be OK.

I agree - a pulse ox should solve the problem - but
how many of us have/use
one? Sure we should - but out in the 'real world'?
Not very likely. In a
four-place 210 at FL240 are all people including passengers
going to be
using a pulse ox? My friend in the back seat? Will
I own two pulse ox - one
for me and one for the for the guy in back?

So - it would be nice to know that a system one uses
will keep a pilot (or
passenger) from getting hypoxic even if a pulse ox
isn't used. It appears
that, company claims to the contrary, the A4 does not
do this. This (in my
opinion) is not the fault of the A4 - it simply was
manufactured IAW 40
year-old obsolete 1443 flow rates. The new 'pulsed'
systems have no mandates
at all - at least as far as I can tell. I may be wrong
- if so please let me
know.

The research should not be hard to do. Perhaps someone
out there has some
data that could be of interest. The FAA has no funds
for this so I am trying
to find a university/altitude chamber that would be
interested in some
studies.

Any comments (at least any helpful and non-sarcastic
ones) would be
appreciated.

David Reed M.D., Boulder, CO (presently living in New
Zealand until end
May).








At 22:06 17 May 2004, Neptune wrote:
BlankI hate to sound paranoid, but I had put on a posting
asking for
information on oxygen systems. It disappeared after
several days. I
reposted - same thing - was gone several days later.
I then posted what I
thought was a nice bit of information and suggested
preflight for the D1 -
same thing - gone after several days.

Frankly I was unaware that anyone could - either technically
or ethically -
erase someone else's post. Maybe this isn't what is
happening, if so -
anyone have any idea what is? The messages were in
HTML - should this make
any difference?

David Reed M.D., Boulder CO