Hypoxia Hangover and Flight Performance After Normobaric Hypoxia Exposure in a Hawk Simulator.

The incidence of hypoxia-like symptoms in military aviators is on the rise. Cases can be related to On-Board Oxygen Generating System (OBOGS) malfunction, air contamination, loss of cabin pressurization, hyperventilation, or a combination of these issues simultaneously. Normobaric hypoxia training in tactical fighter simulations has been conducted in the Finnish Air Force since 2008. This training helps aviators to recognize their individual hypoxia symptoms and refreshes hypoxia emergency procedures in a realistic cockpit. A flight mission included three set-ups and a return to base (RTB) after the third set-up. In a tactical Hawk simulator, different concentrations of oxygen were used (8%, 7%, and 6% oxygen in nitrogen) to create normobaric hypoxia exposures. During the RTB, the flight instructor evaluated the subjects' flight performance ( = 16) in order to estimate cognitive functions after hypoxia. A control flight was evaluated before or after the flight with normobaric hypoxia exposure. Instrumental flight rule performance during RTB decreased significantly from 4.81 to 3.63 after normobaric hypoxia and emergency procedures. Some pilots reported fatigue, headache, memory problems, and cognitive impairment as adverse effects up to 12 h after normobaric hypoxia training. Hypoxia has a significant effect on flight performance during RTB, even 10 min after hypoxia emergency procedures. Since 100% oxygen was used as emergency oxygen, as in a real aircraft, the oxygen paradox may decrease flight performance. Hypoxia training in tactical fighter simulations provides an opportunity for pilots to also understand the effects of the "hypoxia hangover" on their flight performance.