The 2014 flying season is starting up with the opening of Sun ‘n Fun which means it is time to think about what makes our flying safer.
Hypoxia (low oxygen levels) continues to be a problem for pilots even at altitudes below the 12,500 foot MSL FAA requirement. Many pilots, especially those with any underlying heart or pulmonary disease, who are obese, and even those who have had LASIK surgery, need oxygen below FAA mandated altitudes and there are simple ways to prove this to yourself.
My favorite example is to fly at night at 8,000 feet MSL or so for 30 minutes. Look at the lights around you. Then turn on some oxygen. Two liters per minutes should do. You will see the lights become brighter just like they were on a rheostat!
The same is true for our brains. After a long flight, even in a pressurized aircraft, our brains do not function as well be subjected to “relative hypoxia.” That is hypoxia that would not be clinically significant in a hospital setting but might make our thinking process or our reflexes not as good as they could be. Unfortunately, increased age tends to make this effect more pronounced.
Have you had LASIK surgery? Have you ever noticed that after a long flight, your vision does not seem to be quite 20/20? This is due to the hypoxic effect directly on the cornea. Unfortunately, this will not be improved with oxygen unless the mask covers your eyes as well.
Those big stomachs also get in the way of our breathing, especially when we are in a sitting position. Thus, hypoventilation or not taking a deep breath can increase our susceptibility to hypoxia at lower altitudes. Obviously, anyone with a history of heart or lung disease will have a lower tolerance to low ambient oxygen levels as well.
Oxygen is cheap and usually readily obtainable. Portable tanks can be filled at most gas or medical supply houses. (I will provide a free prescription if some yahoo requires it to fill a tank. Just email me at Aeromedix.com.) Unfortunately, only an A&P is supposed to fill a built in aircraft oxygen system but many choose to ignore this.
Also, oxygen is oxygen. It all comes from liquid sources now and there is absolutely no difference between medical oxygen and aviator’s oxygen. Without getting into a long explanation of why, just believe me on this. Oxygen is oxygen and it is all the same from an inhalation point of view so buy where ever you can find it.
The best way to know for sure what your oxygen level is by using a pulse oximeter. These inexpensive fingertip devices show the percentage of oxygen in your blood stream. The normal range for people who live at or near sea level is 95-100%. For people who live at 6,000’ MSL, it is 90 to 95%. My general recommendation for oxygen use is a person “should” use oxygen when their saturation drops by 5% from their home airport saturation and they “must” use oxygen if it drops by 10 percentage points. When starting the oxygen, the pilot should titrate the flow of oxygen to raise their saturation back to their home airport baseline saturation.
Dr. Brent Blue is a Senior Aviation Medical Examiner based in Jackson Hole, Wyoming. He can be reached at firstname.lastname@example.org.