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 practical period of time provides marginally increased protection and is not always operationally feasible. Including exercise during preoxygenation to increase muscle tissue perfusion, cardiac output, and ventilation can improve the 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 performed 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 during an Air Force aerobic fitness test and heart rate. The pilot's next 36 high flights, using exercise-enhanced preoxygenation, were completed with no reports of DCS. CONCLUSIONS: This statistically significant operational test reinforced the laboratory studies. Implementation of this procedure for reducing DCS in susceptible U-2 pilots and collecting additional data from the U-2 pilot population is recommended.

A comparison of heart rate, eye activity, EEG and subjective measures of pilot mental workload during flight.

BACKGROUND: Mental workload is a major consideration in the design and operation of modern aircraft systems. Objective measures of mental workload that are sensitive and diagnostic are required to meet the needs of both pilots and designers. Due to the multifaceted nature of these complex mental demands multiple measures are required. HYPOTHESIS: Psychophysiological and subjective measures provide unique information about mental workload during flight. METHODS: Cardiac, eye, brain and subjective data were collected during an actual flight scenario designed to provide tasks which required different piloting skills at several levels of mental workload. RESULTS: Heart rate was sensitive to the demands of flight but not diagnostic with regard to determining the cause of the workload. Heart rates increased during take offs and landings and to an intermediate level during instrument flight rules (IFR) segments. By showing sensitivity to only the visual demands of the various segments of flight eye activity was more diagnostic. The theta band of the EEG demonstrated increased power during those flight segments which required inflight mental calculations. The subjective measures showed trends suggesting different levels of mental demand but demonstrated few statistically significant differences. CONCLUSIONS: Multiple measures, especially psychophysiological measures, provide a comprehensive picture of the mental demands of flight. The measures used in this study were shown to provide unique, non-overlapping information. Because of the continuous nature of the psychophysiological data it may be possible to develop systems which provide on-line monitoring of mental workload that can provide feedback to the pilot and aircraft systems.