When at or above 11,000 feet for any length of time without supplemental oxygen, the authors have experienced trouble with simple routine tasks such as switching frequencies and manipulating the GPS or other controls. Also, our ability to distinguish colors deteriorates. One measure of the impact of altitude-related hypoxia is the Time of Useful Consciousness (TUC). As time at altitude or one’s altitude itself increases, the risk of los- ing consciousness increases. As might be expected, the TUC at altitude rapidly decreases as we go higher. An individual might be able to stay awake and functional for 20-30 minutes at 18,000 feet. This can decrease to 15-20 SECONDS by 40,000 feet. Probably the most highly publicized case in recent history, where altitude killed a pilot and his passengers, was the October 1999 crash involving Payne Stewart, the professional golfer. Payne, along with two pilots and three other passengers was enroute to Love Field, Texas in a business jet. At 37,000 feet contact was lost with the aircraft. Military aircraft were scrambled and intercepted their jet. Many attempts at contacting the unresponsive crew were made. Unfortunately, history recounts that they were unsuccessful and the aircraft crashed in South Dakota after fuel starvation. It is believed that they lost cabin pressure, and were unable to utilize emergency oxygen before becoming unconscious. It is also believed they were dead before they crashed. How do we protect ourselves from this silent killer? The first step at a minimum is to be familiar with and fol- low the FAA regulations regarding oxygen use at altitude. After 30 minutes above 12,500 feet, the crew of the air- craft must use supplemental oxygen. Above 14,000 feet the crew must use continuous oxygen for the duration of the flight. Above 15,000 feet, all occupants of the aircraft must be on continuous oxygen. At nighttime, oxygen is required when flying above 5,000 feet. Many experts feel these standards may be too liberal. Such guidelines may reassure even the most experienced pilot to the point of complacency. It cannot be overstated that each individual’s unique need for supplemental oxygen at altitude is a dynamic situation and must be An individual might be able to stay awake and functional for 20-30 minutes at 18,000 feet. This can decrease to 15-20 SECONDS by 40,000 feet. recognized as such. Many professional pilots will start on oxygen as low as 9,000 feet during the day, and as we all know, the experience of our colleagues is one of our best teachers. Another step is to be completely familiar with one’s oxygen equipment, whether it be portable or built-in. Much like every other piece of equipment used in flight, it must be in perfect working order and ready to use at a moment’s notice. This equipment needs a preflight check just as all other systems. Moreover, every pilot should be able to do simple equipment troubleshooting so that a simple problem doesn’t result in an aborted flight (or worse). Again, pilots who choose to take advantage of the opportunity to take a ride in an altitude lab invariably find it a very enlightening and educational experience. A chamber ride can be accomplished in just a few hours. NATA-Med powered by AirDocs is proud to be able to offer this opportunity to NATA members. More informa- tion can be found at www.nata.aero/natamed. The value in knowing one’s personal hypoxia symp- toms cannot be overstated, and may even be life-saving. A healthy respect for altitude and hypoxia, along with conservative personal standards, will ensure high-alti- tude flight remains a positive experience and does not become “the enemy above.” Aviation Business Journal | Summer 2020 27
