Historical Look At Physiology And WWII Air War

Dr. Dean prepared a presentation on his historical research for April 7, at the Experimental Biology conference in San Diego. His presentation is entitled "High altitude physiology research and training platforms used by American physiologists during World War II: Innovative altitude chambers and high flying bomber aircraft."

Some early highlights of World War II Aviation Research

• Dr. Randy Lovelace of the Mayo Clinic, a leader in aviation physiology research during the war, studied the opening shock of a parachute by jumping from a plane at 40,200 feet on a static line, which opened his parachute immediately upon jumping. The force of deceleration as Lovelace left the speeding B-17 and his chute opened, blew off his gloves and knocked him unconscious. One of his hands suffered frostbite as a result of the jump, but he recovered.
• Physiologists later experimented with 150-pound dummies to determine opening shocks at varying heights, from planes traveling varying speeds.
• Still later, physiologists trained a 145-pound St. Bernard dog, Major, to parachute -- simulating the jump of a man. Major wore protective clothing and an oxygen mask and dog paddled during his descent.

Flight Still in Infancy

At the outset of the war, aircraft were neither pressurized nor heated, but air crews flew as high as possible to avoid ground fire and enemy fighters. Flying at 25,000-30,000 feet, roughly the height of Mount Everest, the crews suffered hypoxia from the lack of oxygen and decompression sickness from the low pressure, among other ills. Long range bombing missions could last for up to 8 to 10 hours under these grueling conditions.

Physiologists performed numerous experiments in hypobaric chambers to resolve these problems. These sealed chambers, also called high altitude chambers, mimic the low oxygen and low pressure of high altitudes.

At the beginning of the war in Europe, when physiologists were anxious to get to work and there were only three high altitude chambers in the U.S., they briefly considered using the elevators in the Empire State Building to study rapid changes in pressure. That suggestion never came to fruition, and U.S. scientists were able to build enough high altitude chambers quickly to get the research underway.

Among the problems the physiologists were able to work out using altitude chambers

• Decompression sickness, in which nitrogen bubbles form in the blood and tissue, can be reduced by breathing pure oxygen before takeoff and during ascent. This reduces the amount of nitrogen in the blood and tissues and so reduces bubble formation. This technique is still used today, including by astronauts prior to a space walk.
• Fliers could survive rapid decompression of a pressurized airplane with enough time to put on an oxygen mask before losing consciousness. Planes had not been pressurized, in part because of concerns that fliers could not survive a rapid decompression.
• Fliers could withstand a rapid decompression as long as their airway was open, allowing air to flow out of their lungs as the surrounding ambient pressure dropped. If their airway was sealed, as during mid-swallow, then their lungs could "over-pressure" resulting in tearing of lung tissue.

Physiological research also helped develop

• Ways to safely provide pressurized oxygen to air crews, helping them avoid hypoxia and decompression sickness.
• Ways to develop better fitting oxygen masks to avoid fogging and freezing of goggles, common problems for pilots early in the war.
• Ways to prevent blood from pooling in the lower extremities using a G-suit during violent dog-fighting maneuvers, thereby preventing "blackout" and loss of consciousness due to lack of blood flow to the brain.