Aeromedix has developed a miniature aviation-grade personal oxygen system that slips easily into in your flight bag, briefcase or tote-bag, and provides up to 113 liters of breathing oxygen that you can have with you wherever you go. Active pilot and aviation medicine expert Dr. Brent Blue (president of Aeromedix) thinks this little $200 system is a terrific option for GA pilots who don't do enough high-altitude flying to justify spending $600 to $900 for a full-blown portable oxygen system. And in an emergency, it could be a lifesaver.
February 2, 2003
genesis of E-Ox occurred several years ago when I stopped by the White
Mountain Products Group booth at AOPA Expo in Atlantic City to look at a
miniature emergency oxygen system they'd introduced. To be honest, my first
reaction was skepticism. To begin with, I was a little put off by the
melodramatic name they'd given to the product: "Breath of Life."
More important, I had a tough time believing that the little 12-ounce
palm-sized disposable oxygen cylinders it used -- reminiscent of the
disposable carbon dioxide cartridges used in some beverage dispensers and wine
bottle cork removers -- could hold enough aviator's breathing oxygen to be
Original 18-liter "Breath
of Life" system
(about $150) is no longer available.
A four-outlet portable oxygen system
New E-Ox system (about $200)
comes in 36 and 113-liter models.
Yet I was intrigued with White Mountain's concept. As a physician and
aviation medical examiner, I have long had an intense interest in pilot
hypoxia. After decades of flying and working with other pilots, I've gradually
become convinced that hypoxic impairment is a factor in a lot more aviation
accidents than the FAA or NTSB is willing to acknowledge. My
experiments using pulse oximetry to measure the precise oxygen needs of
the body at altitude have shown me that the FAA's requirement for pilots to
use supplemental oxygen when flying unpressurized above 14,000 feet -- or
above 12,500 feet for more than 30 minutes -- is completely inadequate to
prevent sensory and cognitive impairment, not to mention serious fatigue. That
goes double when flying at night. (For a superb discussion of high-altitude
physiology and hypoxia, see Linda Pendleton's article "When
Humans Fly High.")
In short, I've come to believe that pilots should be using O2 a
lot more often than they do.
Turbocharged and pressurized aircraft typically have factory-installed
oxygen systems, but the vast majority of GA aircraft are not so equipped.
Portable oxygen systems are available from a number of companies, such as Aerox,
SkyOx and Nelson,
and most of them are excellent. But at $600 to $900, these systems cost more
than most pilots are willing to shell out unless they do a lot of
The bottom line is that the majority of GA pilots who fly
normally-aspirated piston airplanes do so without any supplemental oxygen
whatsoever. When they fly at altitudes above 5,000 to 10,000 feet (depending
on the individual), they do so with some significant degree of hypoxic
impairment. They can't think or see as clearly or make decisions as well as
they should, and they get tired more quickly than they should. On those
occasions where weather and/or terrain force them up above 12,500 feet, they
also may be violating the FARs ... but frankly that's not my concern because
I'm a doc, not a cop.
As a doc, I wish all airplanes (not just turbocharged and pressurized ones)
had built-in oxygen systems. I wish oxygen refills were so cheap and easy to
obtain that pilots could top off their oxygen as easily as their fuel tanks. I
wish pilots felt as comfortable and casual about using supplemental oxygen in
flight when they get tired or headachy as they do about sipping a Coke or a
cup of coffee. I wish they'd stop believing that O2 is unnecessary
at or below 12,500 feet just because the FAA doesn't mandate its use.
"Breath of Life"
All these thoughts were going through my mind as I returned to the White
Mountain Products booth the next day to take another look at their
"Breath of Life" (BoL) emergency oxygen system. Priced around $150,
small enough to carry around in any flight bag or briefcase, and using little
pre-filled disposable oxygen cylinders that eliminate the bother of oxygen
refills, I wondered whether BoL could fill the bill for GA pilots who fly
aircraft without built-in oxygen systems and can't justify the expense or
hassle of a portable oxygen system. Might this be the answer to making
supplemental oxygen use so simple and painless that pilots would use it when
appropriate without hesitation? The concept was starting to intrigue me.
But I kept returning to the threshold question: Can a pocket-sized 12-ounce
cylinder hold enough oxygen to be worthwhile?
At first glance, the answer seemed to be no. According to White Mountain,
each disposable Breath of Life cylinder contained 18 liters of aviator's
breathing oxygen. From my medical training, I knew that a normal adult male
typically takes 12 breaths a minute with a volume of about one-half liter per
breath. That's a total of six liters per minute, which suggested that a Breath
of Life cylinder would be empty in just three minutes.
Then I realized that this calculation was based on two unreasonable
assumptions: that the pilot would be breathing normally (i.e., rapid, shallow
breaths), and that the pilot would be breathing 100% oxygen. I say
unreasonable because normal breathing is extremely wasteful of oxygen (see
Mike Busch's article "Respiration:
What Pilots Need To Know"), and because breathing 100% oxygen is
extreme overkill at altitudes below FL250 or so.
Taking a fresh look at the matter, I considered that the normal flow rate
of built-in altitude-compensated oxygen systems is about one liter/minute per
10,000 feet of altitude. Using this figure, it seemed to me that a single BoL
cylinder ought to last about 18 minutes at 10,000 feet, or 9 minutes at 20,000
feet. That was reasonably consistent with White Mountain's claim that each
cylinder provides an 8- to 12-minute supply.
On the other hand, I knew that even those flow rates for built-in oxygen
systems were predicated on the immensely inefficient use of oxygen provided by
a constant-flow rebreather-mask system, and that they could be reduced by
approximately two-thirds by using a conserving nasal cannula instead of a
mask. The conserving cannula accomplishes this magic in two ways: It stops the
flow of oxygen during exhalation, and it concentrates the oxygen flow at the
very beginning of the inhalation cycle where it does the most good. (As Mike
Busch's article explains, the last part of each inhaled breath never
reaches the lungs, so oxygenating it is a total waste.)
Since the BoL oxygen flow is controlled by a trigger-operated valve, it
seemed to me that it should be possible to achieve these same kinds of
efficiencies by releasing the trigger prior to the end of each inspiration,
and to leave the flow shut off during each expiration. Additional efficiencies
could be achieved by breathing more deeply and less frequently than normal,
just as divers and mountain climbers are taught to do. Using these methods, it
seemed to me that it should be possible to make an 18-liter Breath of Life
cylinder last a good hour or so at 10,000 feet, and perhaps half that at
20,000 feet. Maybe longer.
My in-flight tests
While these mental exercises were interesting, I knew that the only really
meaningful data would come from testing the Breath of Life system in actual
flight conditions, while using a pulse oximeter to determine exactly how much
oxygen is enough to keep the pilot in the safety zone. I spent several hours
doing exactly that, experimenting with different ways of breathing while using
the system. The results were fascinating, and some were a little surprising.
|NOTE: In case you've never used a pulse
oximeter in flight, a few words may be in order here. By
allowing you to monitor your blood oxygen saturation (%SpO2),
the pulse oximeter enables you to administer precisely the
amount of supplemental oxygen you need (and no more), often
allowing you to stretch your oxygen supply considerably.
Ideally, the use of supplemental oxygen should bring oxygen
saturation up to the saturation level you normally have at your
home elevation. However, this would require a substantial oxygen
flow rate and shorten the duration of your oxygen system
considerably. Therefore, here are my recommendations for using
supplemental oxygen in-flight by reference to a pulse oximeter:
- If your saturation level drops to 5 percentage points
below your normal home saturation level, you should
use supplemental oxygen to keep it from dropping further.
- If your oxygen saturation drops to 10 percentage points
below your normal home saturation level, you must use
supplemental oxygen to raise your saturation to within 5
points of your normal home saturation level.
Flying at 12,500 feet without supplemental oxygen and breathing normally,
my blood oxygen saturation dropped into the mid-80s, compared to a normal 98%
reading on the ground. That's definitely well into the impairment zone. I
found that by consciously slowing and deepening my breathing (still without
supplemental oxygen), I could bring the pulse oximeter reading up to 88% to
90%, which is back in the safety zone (just barely). On the other hand,
breathing like that required total concentration. The moment I had to talk to
ATC, look at a chart, or change heading or altitude, my breathing reverted
back to its normal rapid/shallow pattern, and the oximeter reading dropped
back into the red.
I experimented with the BoL, trying various methods of using it: continuous,
intermittent, mask, cannula, etc. Not surprisingly, the most convenient method
was to hook the BoL to a cannula and adjust the oxygen flow to the minimum
required to maintain a pulse oximeter reading of 90% or so ... but this
continuous-flow method was definitely not the most efficient way to stretch
the oxygen supply.
The best way to do that, it turned out, was to use the BoL with its nasal
mask to take one or two deep breaths of pure O2, holding it in like a pot
smoker to provide time for as much blood as possible to be oxygenated. (Humor
me ... I'm a child of the 60s!) Within about 15 seconds after doing so, the
pulse oximeter reading would shoot up to 98% or more, then gradually ebb back
toward 90% over a period of minutes, at which point it was time to take
another "hit" from the BoL cylinder and start the cycle over again.
Using this intermittent deep breathing technique together with oximeter
monitoring, I found it possible to keep my "O2 sat" in the safety
range with remarkably little oxygen consumption, stretching the endurance of
that little 12-ounce oxygen cylinder to several hours.
AOPA's test results
As I was doing these experiments, I was unaware that Peter A. Bedell,
technical editor of AOPA Pilot magazine, was conducting his own
evaluation of the BoL system. Peter published his results in the January 2000
issue of the magazine (page 127), and his conclusions were strikingly similar
to mine. Here in part is what Peter wrote:
brought the pulse oximeter and emergency oxygen kit along on a 4.5-hour
nonstop cross-country flight at a VFR cruising altitude of 9,500 feet. On
the ground, our tester registered a 99-percent saturation level with a pulse
of 64. More than an hour into the en route portion of the trip at 9,500 feet
msl on this relaxing VFR night flight, our subject scored an 88- to
90-percent saturation level with a pulse of 100. After a deep breath from
the Breath of Life oxygen bottle, the saturation level quickly returned to
99 percent. After 3.5 to 5 minutes, the saturation level would trickle back
down to 90 percent, where he would take another hit to keep saturation
levels above 90 percent. For the next three hours, we repeated this cycle
until the canister ran out a few minutes before the planned descent into the
destination airport. Our subject was a 29-year-old male in good physical
condition. Those who are elderly, overweight, smokers, or are in generally
poor health could expect worse results, but as always it depends on the
As a result of these tests, I became enthusiastic about the idea of an
inexpensive, miniature, personal, take-with-you-anywhere emergency oxygen
system like BoL. I contacted White Mountain Products and signed Aeromedix up
as a distributor for BoL. But it didn't take long to discover that there was a
serious fundamental problem with the BoL concept: The U.S. government didn't
exactly share my enthusiasm.
out that oxygen is classified as a Class 2 Hazardous Material, and federal
hazmat regulations prohibit the shipment of filled oxygen cylinders by air --
even if they're tiny palm-sized 18-liter cylinders. Since the essence of the
BoL system was its pre-filled, disposable cylinders -- and since the
cylinders could not be refilled in the field -- these hazmat regs presented a
huge problem. Shipment of BoL systems and refills had to be done strictly via
ground transportation, which essentially ruled out all international sales and
severely limited domestic sales. If you needed some refills and wanted them
via FedEx or UPS Blue, you were out of luck. In fact, even if you were willing
to wait for them to be delivered via truck, UPS slapped on a $20 hazmat fee to
the normal shipping charges. Not a good situation.
After a few "interesting" meetings with federal hazmat
investigators, Aeromedix decided to drop the BoL product from its catalog. Not
long after that, White Mountain Products turned off its Web site, disconnected
its phone, and vanished.
Available in 36- and 113-liter capacities. The smaller
system weighs less than two pounds; the larger one less than three.
Built-in gauge monitors how much oxygen remains.
Regulator provides flow rate of 2.0 liters/minute.
Standard CGA-540 filler valve allows the E-Ox to be
refilled anywhere oxygen is sold.
...and hello E-Ox
Despite the BoL hazmat debacle, I remained intrigued with the potential for
a small, low-cost personal emergency oxygen system. So I challenged my staff
at Aeromedix to see if we could put together such a system ourselves. I
explained to them that what we needed was a miniature personal emergency
oxygen system similar to the BoL system, but that it had to be easily
field-refillable, which meant it had to have an industry-standard CGA-540
filler valve and an oxygen pressure gauge. It also had to be built from
top-quality medical-grade components that would stand up to long use and
numerous refillings. And it had to comply with federal regulations, and
preferably be FDA-approved so that it could be used for medical as well as
aviation use. Could something like this be developed to sell at a reasonably
inexpensive price -- say $200? A year, many phone calls, and several
prototypes later, the E-Ox system was born.
The system is a marvel of miniaturization and quality. It's available in
two sizes: an extremely compact 36-liter model that weighs less than two
pounds and is only nine inches tall (small enough to fit in a woman's
pocketbook), and also a higher-duration 113-liter model. Each features an
FDA-approved 2,000-PSI oxygen cylinder, a fixed-flow regulator that delivers
2.0 liters per minute, a shutoff valve, a calibrated oxygen pressure gauge,
and a standard CGA-540 filler valve that enables the E-Ox to be easily
refilled anywhere oxygen is sold (FBOs, welding and industrial gas suppliers,
medical suppliers, etc.) Each system also comes with a clear plastic oxygen
mask (with strap and nose clip), a length of tubing to connect the mask to the
cylinder/regulator, and optionally an "Oxymizer" conserving cannula
that can stretch the duration of the system by up to four times. (See table
below.) Extra tanks, extra masks, standard and conserving cannulas are
available as optional accessories.
The E-Ox system is normally supplied empty in order to avoid running afoul
of hazmat regulations. You can also order it pre-filled with aviator's
breathing oxygen, but pre-filled systems may be shipped only via truck, only
within the continental U.S. (48 states), and involve an additional $20 hazmat
charge levied by United Parcel Service. For all these reasons, we generally
recommend that you order the system empty and get it filled locally.
Here are the specs for the two E-Ox models:
|E-Ox System 36
|E-Ox System 113
|Note 1: Overall height, including
valve and regulator.
Note 2: Continuous flow duration based on maximum flow rate of
Note 3: Intermittent flow duration based on one 500 ml. bolus
delivered every 4 minutes.
Emergency and non-aviation uses
Although my initial interest in this system was as a source of supplemental
oxygen while flying at altitude, this is by no means its only use. In fact,
one of the niftiest things about the E-Ox system is its versatility. It's
perfect for dealing with in-flight emergencies such as smoke in the cockpit,
loss of pressurization or ditching, where it can provide the precious minutes
you need to remain conscious while you make your way to safety. In the event
of an underwater escape situation, the E-Ox supply tube can be disconnected
from the mask and placed in the mouth to provide an underwater oxygen supply.
Since the Learjet accident that killed golfer Payne Stewart, an increasing
number of executives who travel on corporate bizjets have taken to carrying
these units in their briefcases. Note, however, that current Transportation
Security Administration regulations forbid passengers from carrying oxygen on
board a commercial airliner unless it is furnished by the airline -- empty
E-Ox cylinders may be carried in checked baggage, but not full ones. Generally
speaking, there's no such obstacle with private or corporate aircraft.
Uses of personal oxygen systems are by no means limited to aviation. If you
ski, climb, hike, or otherwise exert yourself at altitude, supplemental oxygen
is the best remedy for fatigue. For example, a number of ski instructors have
started recommending the system to students who find themselves easily winded
on the slopes. A small personal oxygen system makes it easy to have an oxygen
supply with you anywhere and anytime. If you suffer symptoms of altitude
sickness (and almost everyone who lives near sea level does from time to time
when at higher elevations), having a supply of oxygen at hand can eliminate
As you might imagine, supplemental oxygen can be invaluable for dealing
with a wide range of exigencies: a fire, a boating accident, a medical crisis,
etc. Think about it ... when the victim of an accident, heart attack or stroke
first gets to a paramedic or emergency room physician, what's the first thing
they do? That's right -- they put the patient on supplemental oxygen!
Our E-Ox system is FDA approved for medical use by prescription only. No
prescription is required if you buy the system for aviation or emergency use.
But all oxygen is the same nowadays -- aviator's breathing oxygen, medical
oxygen and welding oxygen all come from the same liquid oxygen source. How you
choose to use your personal oxygen system is strictly up to you ... and in an
emergency, oxygen is oxygen. I can tell you from my point of view as a
physician that if the closest oxygen tank was the one on a welding rig, I
would use it in a New York minute!
What it is ... and what it's not
my opinion, the E-Ox system provides an excellent a source of short-duration
supplemental oxygen for occasional use when you need to climb to "oxygen
altitudes" to avoid high terrain or weather, or when you need to
"sharpen up" at night before shooting an approach. Oxygen also can
be a lifesaver in a variety of emergency situations, and is useful in lots of
non-aviation situations as well.
However, it is not a substitute for a built-in or portable oxygen
system. If you regularly fly for long hours at high altitudes in an
unpressurized aircraft that doesn't have a built-in oxygen system, and
especially if you carry passengers who also need supplemental oxygen, you
really ought to consider buying a good portable system, preferably one with
conserving cannulas and vernier flowmeters like the ones available from Aerox,
SkyOx and Nelson.
Bottom line: If you're an "oxygen power-user" who does lots of
flight-level flying (particularly with passengers), E-Ox is probably not your
answer (except perhaps as an emergency backup). On the other hand, I think
it's an excellent solution for the tens of thousands of GA pilots, both
aircraft owners and renters, who really ought to have access to supplemental
oxygen from time to time, but just don't do enough high-altitude flying to
justify the expense and hassle of buying, carrying and refilling a
full-fledged portable oxygen system. It's also perfect for those who want a
personal take-anywhere oxygen supply for emergencies and various other
non-aviation uses. I frequently take my E-Ox system with me in the car and
during outdoor activities just to have it available for emergencies.
E-Ox system is distributed exclusively on my pilot products Web site Aeromedix.com.