BlankThanks, Bill - actually I was recently involved in a study at USAFA (I am a 1960 graduate) in which it was shown that jumpers could wear cannulae up to their highest jump altitude of 18,000 using "regular" nasal cannulae at flow reates of around 2.5. and not saturate at under 90%. Prior to this they had to wear a mask, and you can imagine the hassle of getting out of a mask with all the jump gear all over the place. They are awaiting approval from HQ but it seems like this will be approved. Just how low the flow could get and stil saturate at over 90% unfortunately was not part of the protocol.

I did try to contact the Army Flight Surgeons at Fort Carson but didn't get any replies to my phone messages. Shortly after this I departed for six months in New Zealand so didn't follow it up.

This summer there is going to be a series of studies starting at AFA level and going up to Pikes Peak where the Army has a facility. Unfortunately this will not involve oxygen delivery systems asit has to do moreso with exercise physiology, but I will get a chance to meet the Army docs out of their facility at Natick, Mass who will be coming to Colorado. So thanks for the thought - I'm onto this one, thought.

Any other thoughts for getting data? Have any ides as to whether anyone has done objective medical research on nasal cannulae and pulsed systems, or even masks and pulsed systems over 18,000?

Dave Reed M.D., Boulder CO.

"Bill Daniels" wrote in message news:MsAqc.4202$zw.1832@attbi_s01...
You didn't mention if you had contacted the US military. They have an interest in seeing to it that their expensively trained personnel operating even more expensive equipment are performing at an optimum level. They also spend a lot of money on aeromedicine. I would expect that the Pentagon has public access records on their research. Start with the Virtual Naval Hospital. ( www.vnh.org search keyword "oxygen")

It's possibly worth noting that no military oxygen system uses a cannula. Constant flow oxygen systems were discarded early in WWII when they were found inadequate above 18,000 feet. If you need oxygen as a military pilot today you will use a well fitted and sealed full-face mask connected to a pressure demand regulator. Anything less is inadequate. My reading of the literature indicates that pressure demand systems have been extensively tested at cabin altitudes up to 45,000 and found safe for healthy personnel.

I have used both a cannula and a pressure demand system with a pulse oxymeter on wave flights. I found that the constant flow cannula system could not maintain a steady SpO2 with fluctuations above and below 90% but the pressure demand system delivered a rock solid 98% - 99% SpO2 readings at all altitudes. I'd like to see all wave flights use pressure demand O2 systems.

Bill Daniels


"Neptune" wrote in message ...
Thanks to all who have replied to my previous messages. I admit I may not have
been clear in why I am asking for feedback/information on flight testing of oxygen
delivery systems. Apologies. Let me explain and ask for HELPFUL feedback.

My concern is with the lack of scientifically-valid information available on
the performance of light aircraft/glider oxygen systems. As an anesthesia doc (and former USAF
fighter jock) I feel have some background in this area. In addition I have done significant medical literature research, been to CAMI to speak with the honchos there, had contact with the Brits, in-person chats with several New Zealanders at Omarama, etc.

When I started to fly gliders out of Boulder several years ago I was
surprised at the masks that pilots were taking up into the wave. Having had
a cardiac bypass operation myself perhaps I was unusually concerned. I began
to do National Library of Medicine research and found no published studies
that dealt with the use of nasal cannulae or masks performance at altitude.

I then got access (with permission from the CEO as long as I didn't mention the
name) to company data that had to do with a flight to 18,000 during which 6
subjects using an A4 had pulse-ox readings taken at FAA-mandated flow rates.
In the process the Oxymizer was compared with the "regular" cannula. At each
altitude from 13,000 to 18,000 at least one subject was hypoxic with one subject,
at 18,000, saturating at 78% on an Oxymizer at the FAA rate of 1.46. All six were
supposedly all fit and healthy people. One had a bypass operation, but he was never
one of the hypoxic ones. No physician had been involved.

I then discovered that FAA mandates oxygen flow rates only - not oxygen
saturations. The mandates, so I discovered, are at least 40 years out of
date and relate to tracheal oxygen measurements - two levels of medical
monitoring sophistication out of date (arterial blood gases, pulse
oximetry). Of course the modern "pulse" systems are not mentioned.

I then discovered that there are no FAA mandates requiring an oxygen
delivery system to meet any specific performance requirements as long as it
is "portable".

I noticed that manufacturers were making remarkable claims for the
oxygen-saving abilities of their systems but - as I discussed above - not
based on any form of objective peer-reviewed published study. It seemed to
me that I could show that the A4 at FAA rates probably produced some
hypoxia, and the Oxymizer probably did not have the characteristics claimed
for it, but how about "pulsed" systems and mask performance over 18,000?

Please note - I am not saying they are wrong - but before trusting my pink body
and those of my passengers to a strange-looking system I'd like some objective
and verifiable proof.

I use a D1 and I think the modern pulse systems are magnificent - probably -
at least as far as their use up to 18,000 with cannulae are concerned (but I
cannot prove this - no releasable data). They have been in use for many years with no
apparent untoward events. I am more concerned, however, at how the pulsed
systems perform with mask systems above 18,000. Several of the mask systems
I have seen in use appear to me to be dangerous regardless of the system
used to deliver the oxygen. Again - no data.

It doesn't make sense to me that a pulsed system should work with the sorts of
reservoir-style masks that should be used at altitude. But I may be wrong, that is
why I am asking if anyone out there has any information/data (preferable data)
that could answer these questions. I have asked several other companies but they
(rightly) regard what they have done (or possibly not done)as proprietary information.
So - no objective information.

I agree - pulse oximetry should solve the problem, IF one doesn't consider
the realities of what pilots are ACTUALLY liable to do as far as non-use. Will every
pilot who might go over 14,000 buy a pulse ox just in case? Probably not. Is it
realistic for an FBO to rent out a pulse ox? Probably not. It seems more sensible
to me to make sure the claims manufacturers make are objectively valid, then use
the pulse-ox (if you have one, didn't leave it at home, didn't realize how good the
thermals/wave were so didn't bring it along, its battery is OK, the ambient temp
isn't frigid, you have a glove over your finger, etc., etc.) to make sure.

In summary - In my opinion FAA mandates are way, way out of date and should
be brought up to modern standards reflecting pulse oximetry. Studies need to
be done in an open published manner documenting that manufactured equipment
will produce non-hypoxic saturation levels in every day use for "most"
pilots. In my opinion it isn't enough for a manufacturer to say "yep, we
haven't flight-tested the gadget because we don't have to, but trust me - it is OK".

Please let me know what you think in a helpful manner - after all I am only trying
to make flying safer for all of us and I have no hidden agendas.

David Reed M.D, Boulder CO