A New Method for Combined Hyperventilation and Hypoxia Training in a Tactical Fighter Simulator

INTRODUCTION: Physiological episodes are an issue in military aviation. Some non-pressure-related in-flight symptoms are proved to be due to hyperventilation rather than hypoxia. The aim of this study was to validate a new training method provoking hyperventilation during normobaric hypoxia (NH) training in an F/A-18 Hornet simulator.METHODS: In a double-blind setting, 26 fighter pilots from the Finnish Air Force performed 2 setups in a WTSAT simulator in randomized order with full flight gear. Without the pilot's knowledge, 6% O₂ in nitrogen or 6% O₂ + 4% CO₂ in nitrogen was turned on. Ventilation (VE) was measured before, during, and after hypoxia. S_po₂ and ECG were monitored and symptoms documented. The subjects performed a tactical identification flight until they recognized symptoms of hypoxia. Thereafter, they performed hypoxia emergency procedures with 100% O₂ and returned to the base with a GPS malfunction and executed an instrument landing system (ILS) approach with the waterline HUD mode evaluated by the flight instructor on a scale of 1 to 5.RESULTS: Ventilation increased during normobaric hypoxia (NH) from 12 L · min^-1 to 19 L · min^-1 at S_po₂ 75% with 6% O₂, and from 12 L · min^-1 to 26 L · min^-1 at S_po₂ 77% with 6% O₂ + 4% CO₂. ILS flight performance was similar 10 min after combined hyperventilation and hypoxia (3.1 with 6% O₂ + 4% CO₂ and 3.2 with 6% O₂). No adverse effects were reported during the 24-h follow-up.DISCUSSION: Hyperventilation-provoking normobaric hypoxia training is a new and well-tolerated method to meet NATO Standardization Agreement hypoxia training requirements.Leinonen AM, Varis NO, Kokki HJ, Leino TK.