The Altitude Problem

The interface between humans and technology was no less important for those early pioneers, who, for the first time in history, were start­ing to reach for the sky. Human factors research in aeronautics did not, however, begin with the Wright brothers’ first powered flight in 1903; it began more than a century earlier.

Much of this early work dealt with the effects of high altitude on humans. At greater heights above the Earth, barometric pressure decreases. This allows the air to expand and become thinner. The net effect is diminished breathable oxygen at higher altitudes. In humans operating high above sea level without supplemental oxygen, this trans­lates to a medical condition known as hypoxia. The untoward effects on humans of hypoxia, or altitude sickness, had been known for centu­ries—long before man ever took to the skies. It was a well-known entity to ancient explorers traversing high mountains, thus the still commonly used term mountain sickness.[298]

The world’s first aeronauts—the early balloonists—soon noticed this phenomenon when ascending to higher altitudes; eventually, some of the early flying scientists began to study it. As early as 1784, American physician John Jeffries ascended to more than 9,000 feet over London with French balloonist Jean Pierre Blanchard.[299] During this flight, they recorded changes in temperature and barometric pressure and became perhaps the first to record an "aeromedical” problem, in the form of ear pain associated with altitude changes.[300] Another early flying doctor, British physician John Shelton, also wrote of the detrimental effects of high-altitude flight on humans.[301]

During the 1870s—with mankind’s first powered, winged human flight still decades in the future—French physiologist Paul Bert conducted important research on the manner in which high – altitude flight affects living organisms. Using the world’s first pressure chamber, he studied the effects of varying barometric pressure and oxygen levels on dogs and later humans—himself included. He conducted 670 experiments at simulated altitudes of up to 36,000 feet. His findings clarified the effects of high-altitude conditions on humans and established the requirement for supplemental oxygen at higher altitudes.[302] Later studies by other researchers followed, so that by the time piloted flight in powered aircraft became a reality at Kitty Hawk, NC, on December 17, 1903, the scientific community already had a substantial amount of knowledge concerning the physiology of high-altitude flight. Even so, there was much more to be learned, and additional research in this important area would continue in the decades to come.