Test and evaluation of exercise-enhanced preoxygenation in U-2 operations

Background: Preoxygenation to prevent decompression sickness (DCS) during U -2 reconnaissance flights requires considerable time and occasionally does not provide adequate protection. Increasing preoxygenation within a practic al period of time provides marginally increased protection and is not alway s operationally feasible. Including exercise during preoxygenation to incre ase muscle tissue perfusion, cardiac output, and ventilation can improve th e quality of the denitrogenation. Methods: A pilot, who reported two cases of DCS during his first 25 U-2 high flights involving cabin altitudes of 29 ,000-30,000 ft, volunteered to test exercise-enhanced preoxygenation. He pe rformed 10 min of strenuous upper and lower body exercise at the beginning of preoxygenation prior to subsequent high flights without increasing total preoxygenation time. Results: The exercise was performed at 75% of maximal oxygen uptake based on the estimated maximal oxygen uptake determined duri ng an Air Force aerobic fitness test and heart rate. The pilot's next 36 hi gh flights, using exercise-enhanced preoxygenation, were completed with no reports of DCS. Conclusions: This statistically significant operational tes t reinforced the laboratory studies. Implementation of this procedure for r educing DCS in susceptible U-2 pilots and collecting additional data from t he U-2 pilot population is recommended.