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Reprise - Oxygen concerns
BlankThanks 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 The mandates, so I discovered, are at least 40 years out of date and relate to tracheal oxygen measurements - two levels of medical monitoring sophistication out of date (arterial blood gases, pulse oximetry).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 |
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