Mitigation of Altitude Related Brain Lesions in U-2/TR-1 Pilots
At what cost would you venture into the depths of outer space? A thousand dollars? A million dollars? For over 50 years, several United States Air Force U-2 “Dragon-Lady” pilots have paid an arguably priceless cost to push the boundaries of both their bodies and the stratosphere, continually performing missions above 70,000 feet. The U-2 is a high-altitude reconnaissance aircraft designed by Lockheed Martin to spy on the Soviets by flying at never-before-seen altitudes in order to go undetected. The journal Aviation, Space, and Environmental Medicine documents the prevalence of decompression sickness (DCS) and neurological decompression sickness (NDCS) in U-2 pilots over the span of sixteen years. Decompression sickness is an altitude related illness in which dissolved nitrogen forms bubbles in tissues and in the blood stream. Decompression/neurological decompression sickness symptoms include joint pain, slowed thought process, anomia, unresponsiveness, and permanent cognitive decline. The evidence in this study reflects an increasing trend towards neurological and pulmonary complications in these pilots. Between the years 1994-2010, the annual number of cases increased proportionally to the annual number of flight hours to meet operational needs. Radiological research suggests that tiny gas bubbles, called microemboli, arising in brain tissue lead to cerebral injury during prolonged exposure to altitudes above 18,000 feet.
Studies suggest that frequent changes in cabin and suit pressurization as well as limiting the consistency of hypobaric exposure reduce the chances of decompression related occurrences. The Air Force spent $9 million on reinforcing air-frame structure, replacing valves, upgrading the air system logic and various avionics in the cockpit of the U-2 in a program known as CARE (Cockpit Altitude Reduction Effort). Re-enforcing the structural integrity and pressurization components have resulted in increased cabin stabilization of the aircraft at altitudes exceeding 20,000 feet. While several systematic improvements have been made to the aircraft, minimal efforts have been made in the fitness and medical components to flight of the U-2 and for the prevention of DCS.
One proposed solution to improve U-2 pilots’ altitude toleration is to create an oxygen and nitrogen displacement training apparatus. Comparable to the altitude resistance masks frequently used by athletes, the O2/N2 (oxygen/nitrogen) displacement prototype will sit around the nose and mouth, simulating continually changing barometric pressures. By incrementally adjusting the O2/N2 breath ratio, the blood and tissue in the body will adapt to the shifting levels of dissolved nitrogen. This O2/N2 displacement regulator, paired with a regimented fitness program, can be used to improve stress tolerance when experiencing decompression sickness. Increased heart rate, blood pressure, and the release of hormones in exercise will improve the body’s responses to stress when in adverse barometric conditions.
Performing exercises such as stationary cycling and rowing with a gradual increase of nitrogen concentration via the O2/N2 displacement regulator, will allow the body to develop a toleration to DCS. While extensive research is needed to construct this apparatus and further justify the validity of this hypothesis, the notion of “practicing the way we play” is in effect. Similar to a vaccine, this regulator works by boosting the body’s natural defense against dissolved nitrogen in the system, so the body is able to more effectively resist the effects of decompression sickness at altitudes exceeding 70,000 feet.
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