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Tactical aircrew sometimes report physiological or cognitive impairment during flight. One hypothesis proposed to explain these events is that obstructions in the valves of the flight mask may disrupt respiration and lead to symptoms. This study investigated whether obstructions in the inhalation valve of a flight mask are a plausible contributor to physiological events in the cockpit.

This study was approved by the Naval Medical Research Unit Dayton Institutional Review Board. Sixteen qualified active-duty participants flew 2 profiles in a hypobaric chamber-1 with a normal flight mask and 1 with a modified mask. We measured outcomes related to respiratory behavior as well as subjective symptoms and cognitive performance while participants sat quietly and while reading aloud.

The modified mask caused several differences in pressures and the flow of gas through the breathing system, as well as differences in respiratory behavior, particularly when reading aloud. Symptoms were also reported more frequently when using the modified mask than the normal mask. We did not observe any differences in symptom severity or cognitive performance across the 2 masks.

Obstructions in the inhalation valve of the flight mask are a plausible contributor to reported events in flight.