Neptune
May 9th 04, 10:48 AM
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a technique that has been superseded by arterial blood gas measurements and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).
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).