Reprise - Oxygen concerns

"Raphael Warshaw" wrote in message
m...

There's no doubt that pressure-demand systems using fitted masks are
the way to go for flights to high altitude(18,000 feet). My concern
is with what happens down low (between 5,000 and 18,000 feet). My
suspicion and concern is that more than a few pilots are, at
relatively low altitudes, desaturated sufficient to experience
measurable performance decrements.

Raphael Warshaw
Claremont, CA

I encountered an example of low altitude desaturation on my last flight out
of Boulder Colorado. (Elevation 5200')

I had struggled to push the ballasted Nimbus onto the runway while wearing a
parachute. Then I rushed to remove the tail dolly before struggling into
the cockpit and straps. I felt a little out of breath. (I've GOT to spend
less time at this computer and more in the gym.) I slipped the little
oxymeter cuff onto my finger as soon as I was strapped in and the SpO2 was
88%. Yikes!

I selected 100% emergency O2 and took a couple of deep breaths and my SpO2
jumped up to 99%. I have always saved a shot of straight O2 for the
landing.

I wonder how many takeoff accidents are the result of a desaturated pilot
who is out of breath from the rush to get ready. Two deep breaths of pure
O2 are now on my pre-takeoff checklist.

Bill Daniels

BlankDo Drager still manufacture their diluter demand system for aircraft?

I used one of these sets in an ASW20 some 20 years ago. It was a very good set, I understand the design was originally military for the German air force in the 1930s. It was proper aviation equipment for use in unpressurised and unheated aircraft.

It had several safety features.

1./ You could turn on the bottle on the ground, when you wanted oxygen you simply put the mask on and breathe, nothing else to do or adjust.

2./ There was a blinker, and the demand valve made a distinctive noise. In diluter mode if you breathe with the mask on, with the oxygen turned off, then no blink and no noise.

3./ When set to 100% oxygen, if the oxygen is turned off or fails then the mask immediately collapses and you cannot breath - instant warning.

I notice that Mountain High are advertising a mask by Drager for their EDS system, it looks similar to the one I used
http://www.mhoxygen.com/index.phtml?...product_id=406 .

I suspect that the Drager system was as good as any of the ex-military systems up to the altitude where pressure breathing becomes necessary.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.
"Bill Daniels" wrote in message news:hMusc.111328$xw3.6407916@attbi_s04...

Dave, keep your eye open for a surplus source of 0 - 2000 PSI panel mounted regulators like the MD-2, CRU-72/A, 29255-6B1 or 29255-6B-A1. These regulators are proving very hard to find. The masks that work with them are very easy to find though.

Bill Daniels
"Neptune" wrote in message ...
Thanks, 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

Blank
"W.J. (Bill) Dean (U.K.)." wrote in message ...
Do Drager still manufacture their diluter demand system for aircraft?

I used one of these sets in an ASW20 some 20 years ago. It was a very good set, I understand the design was originally military for the German air force in the 1930s. It was proper aviation equipment for use in unpressurised and unheated aircraft.

It had several safety features.

1./ You could turn on the bottle on the ground, when you wanted oxygen you simply put the mask on and breathe, nothing else to do or adjust.

2./ There was a blinker, and the demand valve made a distinctive noise. In diluter mode if you breathe with the mask on, with the oxygen turned off, then no blink and no noise.

3./ When set to 100% oxygen, if the oxygen is turned off or fails then the mask immediately collapses and you cannot breath - instant warning.

I notice that Mountain High are advertising a mask by Drager for their EDS system, it looks similar to the one I used
http://www.mhoxygen.com/index.phtml?...product_id=406 .

I suspect that the Drager system was as good as any of the ex-military systems up to the altitude where pressure breathing becomes necessary.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.
This is exactly how the diluter demand systems work. The aneroid altimeter in the regulator adjusts the dilution by cockpit air so as to deliver the proper O2 partial pressure to the mask.

Pressure demand systems work like diluter demand systems until some preset altitude such as 37,000 feet above which they automatically begin to deliver O2 under slight pressure . In the pressure demand mode, the pilot must consciously shift his breathing to force air out of the lungs and relax to let the O2 system force oxygen in. This is tiring and it's a big relief to descend below the pressure breathing level.

Masks for the pressure demand systems have an exhaust valve that requires an air pressure of 1 or 2 mm of Hg to open. This makes a pressure demand system and mask a bit harder to breath through below about 15,000 feet. The exhaust valve is slightly more susceptible to icing than a diluter demand mask.

You can use a diluter demand mask with a pressure demand regulator as long as you stay below the altitude at which the regulator shifts to pressure demand. Then the O2 will just be lost overboard as the exhaust valve in the diluter demand mask won't hold the pressure.

The complaint that the military systems are "very uncomfortable to use" comes from civilians unknowingly using pressure demand masks not understanding that the mask exhaust valve is restrictive below 20,000 feet.

The advantage of the latest military regulators is that they use long life components unlike the A-14 that uses natural rubber elastomers that are attacked by O2 and so requires rebuilding every 3 years or so. Also, the pressures are balanced so breathing is effortless at all altitudes.

Bill Daniels

Eric:

Sorry, I didn't mean post to the whole group using technical terms.

Dead-space is the volume of the conducting airways through which we
breath. In order to ventilate the alveoli where gas exchange with the
blood takes place, it's neccessary to breath more than this volume so
that gases are exchanged, not just rebreathed. A shallow breath, as
you correctly surmise, may not clear the dead-space. End-tidal is
fancy talk for the end-expiratory portion of a resting breath.

My EDS system did indeed come with a mask. Since I'm not flying above
18,000 feet, I don't use it.

My point on demand systems using masks is that they supply a full
breath of 100% O2, not just a pulse. The one I've used didn't supply
oxygen under pressure. I'm not, BTW, suggesting that such systems are
needed below 18,000 feet.

Raphael Warshaw
Claremont, CA

Eric Greenwell wrote in message ...
Raphael Warshaw wrote:

Raphael Warshaw wrote:
Eric:

Sorry, I didn't mean post to the whole group using technical terms.

Dead-space is the volume of the conducting airways through which we
breath. In order to ventilate the alveoli where gas exchange with the
blood takes place, it's neccessary to breath more than this volume so
that gases are exchanged, not just rebreathed. A shallow breath, as
you correctly surmise, may not clear the dead-space. End-tidal is
fancy talk for the end-expiratory portion of a resting breath.

My EDS system did indeed come with a mask. Since I'm not flying above
18,000 feet, I don't use it.

My point on demand systems using masks is that they supply a full
breath of 100% O2, not just a pulse. The one I've used didn't supply
oxygen under pressure. I'm not, BTW, suggesting that such systems are
needed below 18,000 feet.

Perhaps I don't know what you mean by a "demand" system. The EDS seems
like a "demand" system to me even though only supplies a pulse with
mask. About 30 years ago, I had a Puritan "diluter demand" system that
mixed oxygen and ambient air, based on ambient pressure. It would supply
100% oxygen only if you selected that function. Does "demand" no longer
encompass the "diluter demand" type?



--
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Eric Greenwell
Washington State
USA

W.J. (Bill) Dean (U.K.). wrote:

Do Drager still manufacture their diluter demand system for aircraft?

I used one of these sets in an ASW20 some 20 years ago. It was a very
good set, I understand the design was originally military for the German
air force in the 1930s. It was proper aviation equipment for use in
unpressurised and unheated aircraft.

It

Hi Bill

I am not sure whether you can purchase a new Diluter system from Drager, but hey
do still manufacture the parts.

Recently had the experience where the testing company mashed the valve on my
cylinder. This caused me a moment's panic as the unit was installed as original
equipment in the glider in 1970.

I was amazed that Drager were able to supply the correct part in less than a
week - in South Africa. They are based in Kiel in Germany, although they are
concentrating on Medical gasses. I believe and have sold the Aviation systems
(selected for the A380 I believe) to a UK concern - BAE Cobham PLC.

If anyone is interested it is a bit heavy, and a bit bulky (rough conditions
give me a Drager shaped bruise on my right arm). The mask is not particularly
comfortable, but it does ensure you are getting the oxygen. Overall it works
very well. The telltale flasher is a potential life saver. The said test was
because one of the bits developed a leak and I suddenly got no "click-flash"
when I breathed. OK , I was only at 16,500" - but I wonder what your useful
consciousness is even at this relatively low altitude. How long do you have to
work out you are not getting oxygen.

Eric:

A demand system delivers gas in response to inspiratory effort. By
this definition, the EDS is a demand system. The EDS attempts to
deliver it's pulse of oxygen after the dead-space has been cleared.

Ray Warshaw


Eric Greenwell wrote in message ...
Raphael Warshaw wrote:
Eric:

Sorry, I didn't mean post to the whole group using technical terms.

Dead-space is the volume of the conducting airways through which we
breath. In order to ventilate the alveoli where gas exchange with the
blood takes place, it's neccessary to breath more than this volume so
that gases are exchanged, not just rebreathed. A shallow breath, as
you correctly surmise, may not clear the dead-space. End-tidal is
fancy talk for the end-expiratory portion of a resting breath.

My EDS system did indeed come with a mask. Since I'm not flying above
18,000 feet, I don't use it.

My point on demand systems using masks is that they supply a full
breath of 100% O2, not just a pulse. The one I've used didn't supply
oxygen under pressure. I'm not, BTW, suggesting that such systems are
needed below 18,000 feet.

Perhaps I don't know what you mean by a "demand" system. The EDS seems
like a "demand" system to me even though only supplies a pulse with
mask. About 30 years ago, I had a Puritan "diluter demand" system that
mixed oxygen and ambient air, based on ambient pressure. It would supply
100% oxygen only if you selected that function. Does "demand" no longer
encompass the "diluter demand" type?

Raphael Warshaw wrote:
Eric:

A demand system delivers gas in response to inspiratory effort. By
this definition, the EDS is a demand system.

That's what I thought, also, but I was confused by your remark that
"demand systems using masks is that they supply a full breath of 100%
O2, not just a pulse".

The EDS attempts to
deliver it's pulse of oxygen after the dead-space has been cleared.

According to my EDS manual (original model EDS), it delivers a pulse the
instant the start of inhalation is detected. This is a key part of their
claim for effectiveness, because this adds the 100% oxygen pulse to
first part of the air intake, which is the part that will go the deepest
into the lungs. Delivering it later might mean it ended up in the
dead-space, wouldn't it?


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Eric Greenwell
Washington State
USA

Eric:

Right you are. I'll blame jet lag. It's at the beginning for just that
reason.

Ray Warshaw


"Eric Greenwell" wrote in message
...
Raphael Warshaw wrote:
Eric:

A demand system delivers gas in response to inspiratory effort. By
this definition, the EDS is a demand system.

That's what I thought, also, but I was confused by your remark that
"demand systems using masks is that they supply a full breath of 100%
O2, not just a pulse".

The EDS attempts to
deliver it's pulse of oxygen after the dead-space has been cleared.

According to my EDS manual (original model EDS), it delivers a pulse the
instant the start of inhalation is detected. This is a key part of their
claim for effectiveness, because this adds the 100% oxygen pulse to
first part of the air intake, which is the part that will go the deepest
into the lungs. Delivering it later might mean it ended up in the
dead-space, wouldn't it?


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

"Raphael Warshaw" wrote in message
...
Eric:

Right you are. I'll blame jet lag.

Or perhaps a lack of oxygen?