Effects Due to Altitude.
As the total
atmospheric pressure decreases with altitude, the
available oxygen pressure decreases in proportion, thus
necessitating supplemental oxygen. A lack of sufficient
oxygen will bring on hypoxia. Symptoms of hypoxia may
begin as low as 5,000 feet with decreased night vision.
The retina of the eye is affected by even extremely mild
hypoxia. At 8,000 feet, forced concentration, fatigue and
headache may occur. At 14,000 feet, forgetfulness,
incompetence and indifference makes flying without the
proper supplemental oxygen quite hazardous. At 17,000
feet, serious handicap and collapse may occur. These
effects do not necessarily occur in the same sequence nor
to the same extent in all individuals.
People Living at High Altitudes.
A normal healthy person who lives at higher altitudes has somewhat adapted to the effects of high altitude. However that person still must have supplemental oxygen above 12,500 feet. The effects of hypoxia may be lesser for that person at 12,500 feet, but the problems are still there. Above 15,000 feet it doesn't make any difference what altitude you live at.
Requirement of More Oxygen for Passengers.
We have many pilots
tell us women passengers need oxygen much sooner than
they do. We are not talking high altitude either.
Typically the problem seems to occur around 9,000 to
10,000 feet. The symptoms for the women passengers are
sleepiness and headaches. Several doctors have told us
the reason for women to be effected by the beginning
symptoms of Hypoxia is caused by a difference in their
hemoglobin content in their blood. Of interest, women
also experience different conditions in breathing
requirements while scuba diving. We have received several
orders for oxygen equipment mainly for women passenger
use at these low oxygen altitudes. A good rule of thumb
is that women normally need oxygen about 2,000 feet
sooner than men. Of course there are exceptions.
Use of Oxygen in Pressurized Cabins.
Under normal conditions there is no need for supplemental oxygen in an aircraft equipped with a pressurized cockpit. However, there are conditions that can require additional oxygen. Many pressurized aircraft only bring the cabin altitude down to 10,000 feet. We have found that many people have trouble at 10,000 foot altitudes, in this case the equivalent altitude of 10,000 feet. There is a strong possibility that a heavy smoker could have problems with a lack of oxygen when in a pressurized cabin. We have a few customers who have purchased portable systems to provide the additional need for oxygen. Recently we have a customer with a Cessna 340 (pressurized cabin twin) that has been complaining about fatigue while flying at 25,000 feet. To solve his problem he is using the built in emergency constant flow system. The normal duration is not sufficient, but with the Nelson A-3 flow meter and oxygen conserving Oxymizer breathing device, he now has several hours of supplemental oxygen available to assist with his breathing needs.
Safety Considerations Dealing With High Pressure Cylinders.
The use of oxygen in
general aviation is quite safe. The use of it is done on
a regular basis throughout the world. Reading the
manufactures instructions and going by them, as well as
the use of common sense, make oxygen use practical. The
use of oxygen, no different than the use of the aircraft
itself, does have some potential problems. In that light,
the following information is important and should be
remembered when dealing with oxygen.