Frequently Asked Questions
What is hypoxia and what can happen with prolonged hypoxia?
Hypoxia is the physical condition induced by an inadequate concentration of oxygen in the blood and the organs. The insidious danger of hypoxia is the subject's unawareness of his deteriorating faculties which may actually be perceived as a feeling of well-being or euphoria. Prolonged exposure to moderate to severe hypoxia could result in brain damage to the extent of total intellectual deficiency. Note: there is a wide variability in individual tolerance.
I fly cross country a lot just below class 'A' airspace with my EDS and recently got a portable pulse oxymeter. I’ve noticed that my saturation rate frequently falls below 90% at altitudes around 16K to 18K ft. However, if I breathe a few times deeper the saturation goes well over 90%. I had my system tested and it checked out okay. What is going on?
We have found that about 60~80% of pilots and passengers reduce their respiration effort while at high altitudes thus causing a compromise in the effectiveness of an oxygen system while at moderate to high altitudes.
The respiratory volume and rate is determined by the detection of carbon dioxide (CO2) in the blood, not the lack of oxygen (O2). CO2 is principally generated by spent energy yielding carbohydrates during muscular activity. However, while one is at high altitudes both the CO2 and O2 are at lower absolute levels where the lack of CO2 pressure causes your respiration system to decrease in volume and rate because there is very little CO2 to purge. This causes you to breathe shallowly at a time you need to breath normally or greater.
In an effort to increase the relative amount of oxygen with respect to the air at altitudes, portable oxygen systems were developed. All oxygen systems will have to cope with the physiological fact. Pressure-demand oxygen masks compensate by trying to keep the tracheal and lung pressures at some pressure higher than ambient. Quite uncomfortable to many. The EDS was developed with this fact in mind to help compensate this by increasing tracheal pressures during the pulse delivery where the oxygen is delivered at the most useful point of the inhalation phase.
The problem, however, still remains that the body is fooled into thinking that no CO2 needs to be purged and therefore, not enough oxygen is inhaled because you are breathing more shallowly than you normally would at a lower altitude. Until pulse oxymeters became used by many while in-flight, no one knew much about this fact.Q:
How does a standard aviator's oxygen mask work and why does it have a bag hanging at the bottom
The standard passenger constant-flow mask primarily has the bag so that the FAA requirement of flow indication can be satisfied. Additionally, the standard aviators oxygen mask that we know of today has evolved from a medical mask where knowing if a person is breathing and getting the prescribed amount of oxygen is indeed happening. The accumulator (sometimes mistaken as a re-breather) bag does all this. The accumulator bag also helps to keep oxygen contained and ready for each inhalation phase.
An aviator's full face oxygen mask may contains up to three valves to control the dilution of the breathing phases. The first valve opens to allow the oxygen to be inhaled from the accumulator bag; the second valve allows the discharge (exhaust) of exhaled air to the out side of the mask and not back into the bag.
If the check valves are not operating properly, you may re-breath too much of you own CO2 or not get the prescribed amount of oxygen for the altitude you are exposed to. Also if the bag has cracks or holes, you will not get the prescribed amount of oxygen.Q:
How come the Alps aviator's oxygen mask for the EDS does not have a bag hanging at the bottom
Because the standard passenger constant-flow mask primarily has the bag so that the FAA requirement of flow indication can be satisfied, it is not needed because the EDS provides a positive indication of oxygen being supplied as well as an additional alert to indicate otherwise
The EDS system is an SBA (Supplementary Breathing Apparatus) class Active Phase Dilution system. That is it actively supplements the proper amount of oxygen and air at the proper phase dilution at the various points in your breathing cycles without the need of extra check valves in the mask.Q:
What type of fitting do I need to fill my built-in oxygen system?
In the U.S. there are two (2) standard fittings used to fill oxygen systems. One is the SAE AS1046, a 9/16-18 coupling nut and nipple, sometimes know as the 'SCOTT' fitting. This may also be the ISO standard. Our TA-916-N & TA-916-S transfiller adapters connect the standard CGA-540 fittings to this fitting.
The other is the older, but most common type, a 3/8-24 threaded fitting sometime known as the "AN" type. Our TA-380-N & TA-380-S transfiller adapters connect the standard CGA-540 fittings to this fitting.
Oxygen is oxygen. That is to say that it has to be 99.99% dry in order for it to be pressurized in a cylinder, else it will corrode and rupture. Oxygen is pure by the very nature of how it is produced. Therefore, no mater what the intended use is, oxygen should be as pure as it was the day it was produced. However, no one can continue to guarantee this once bottles go out into the field. This is why the FAA and FDA has come up with a set of min. purity standards for testing oxygen. It is these testing standards that may be the reason many feel that there are different grades of oxygen.Q:
If my oxygen system has more than one oxygen cylinder and they share a common manifold what will the pressure read? Why does the pressure drop a little sometime after the fill.
Regardless of the size of, or number of oxygen bottles in your aircraft if they share the same manifold the system will always read what ever the final pressure is. During an oxygen transfill the tank being filled will heat up. This causes the gas to expand. Depending on the cylinder volume, after it cools back to ambient temperature it will reduce in net pressure about 2% to 5%.
Why does the EDS cost more as compared to something like an MP3 player or a cell-phone that seems to be just as, if not more, complicated than the EDS unit?
We don't have the benefit of marketing the EDS anywhere outside of the aviation market. The FDA, which treats any oxygen device as a medical device and oxygen for consumption as a drug, vigorously inhibits any such marketing unless it is registered as a medical device and strictly sold through pre-approved marketing and distribution methods. However, the FAA requires the use of oxygen in aviation, placing such equipment and AVO/ABO marked oxygen just barely outside the ospisios of the FDA. With the FDA on one side and the FAA on the other our market freedom is indeed severely restricted.
Much R&D, money and man-years of testing along with state-of-the-art micro-electronics and proprietary sensor technology went into the patented EDS system so that it could be the best oxygen delivery technology available to the aviator.
The R&D was a costly gamble, but became obviously worth it in the first year it was released (1993). Feedback shows that aviators all over the world and of all types appreciate and use the EDS every day.Q:
In simple terms, what happens during rapid decompression?
Air at sea level will expand to 5 times its volume at 40,000ft. Lung capacity is approximately 6 liters. Therefore, during rapid decompression, a continuous exhalation is experienced. Holding one's breath may result in bursting of the lungs. Persons suffering from asthma or partially blocked lung passage due to age may be adversely affected by a rapid decompression.
How is the oxygen saturation level in the body affected when altitude is increased?
At sea level, oxygen saturation in the blood is approximately 95%, which does not appreciably decrease up to pressure altitudes of 10,000 ft. at which point it decreases to about 90%. Above 10,000 ft, the saturation drops more rapidly and human faculties begin to be impaired. Above 14,000 ft, physiological symptoms begin to appear. For more detailed information, see The Pilot's Atmosphere and Hypoxia in this web-site.
I would like to replace my old steel oxygen cylinder in my type-certified aircraft with a new light-weight kevlar bottle. Can this be done?
Yes, this can be successfully done using our MH-1 adapter. However, it is extremely important that the proper procedures be taken in order to receive an FAA-337 for this task. See the following PDF file for more information on this topic.
Every once in a while, our service dept. will get an EDS unit sent to us from a customer who complains about the Apnea Alarm (Alert) going off almost every time a breath is requested through the unit.
We test the unit and find no problem, at which time we call the customer and ask for further information. What we usually find is that they have been experiencing the Flow-Fault Alert rather than the Apnea Alert.
The Flow-Fault alert goes off if at any point the delivery of oxygen (valve open) is depleted, it will then alert you to the fact that the supply has been interrupted and that the dosage may not be enough for the altitude you are. The Apnea Alert is simply a series of beeps to let you know that after ~35 seconds the unit is no longer detecting your breathing.
Additionally, the customer will let us know that this only happens at certain altitudes and certain times. This allows us to suspect that the inlet pressure (~20-25 psig. static) is sufficient for operation but the mean flow has become compromised. This can be because the regulator or the feed tubing has developed an obstruction. This will allow the flow-fault detection device in the unit to be satisfied with short bursts of oxygen, but then detect insufficient pressure drops with longer pulses at higher altitudes. We then ask that the regulator and the tubing be sent back as well for further investigation.
Once the equipment arrives, yet again, at our service department, we perform a complete examination. Once again, however, no problem can be found with the unit, regulator or tubing. Again we call upon the user for further information. It is now that the user describes that they do not use the regulator and tubing that came with the unit, rather they connected it directly to one of the fittings that came with the portable or built-in system or cylinder that they already have.
Here is what we usually find:
The oxygen fitting the user decided to connect the EDS unit to has a flow-restricting orifice calibrated for either a cannula or facemask that came with the user's constant-flow system. The EDS unit had no problem with the small amount of oxygen in the line at ground level or modest altitudes. However, at higher altitudes where the valve demanded more, the flow-restriction orifice in the fitting limited the flow to the point that the unit experienced a series of true flow-faults. The unit was letting the user know that there was indeed a problem. The fitting was not letting enough oxygen through the tubing to provide the higher demands.
The customer connects the originally supplied regulator directly to the cylinder, bypassing about 8 lbs of fittings and high pressure tubing, resulting in a unit that now operates to the original specifications and very well at all altitudes.
While we are discussing using our system with other regulators and/or through other connectors, we should mention that we also find many problems with too much inlet pressure.
Here is what we usually find:
The customer complains that the unit quits operation at higher altitudes and simply beeps with the apnea alert. After communicating with the customer, we gather more information where we find that the inlet pressure has been allowed to go over the maximum allowable inlet pressure of ~30 psig. This causes the valve to leak past the plunger.
However, because the fitting being used has a flow-restriction orifice limiting the flow to some smaller amount, it goes undetected by the user. The EDS unit will have a small amount of force present upon the sensor that requires a much more aggressive inhalation effort than normal. Additionally, at higher altitudes the force becomes greater to the point that almost no inhalation efforts will allow the unit to trigger where the apnea condition then ensues shortly thereafter.
The customer connects the originally supplied regulator directly to the cylinder so that it now operates very well at all altitudes.
If you are experiencing any anomalous operations with your system, please look over the manual for an explanation. Additionally, please do not hesitate to call upon us for any advise.