Pressure effects on the nose by an in-flight oxygen mask during simulated flight conditions

Background: Dutch F-16 fighter pilots experience oxygen mask inflicted nasal trauma, including discomfort, pain, skin abrasions, bruises and bone remodelling. Pressure and shear forces on the nose might contribute to causing these adverse effects. In this study, it was evaluated how flight conditions affected the exerted pressure, and whether shear forces were present. Methods: The pressure exerted by the oxygen mask was measured in 20 volunteers by placing pressure sensors on the nose and chin underneath the mask. In the human centrifuge, the effects on the exerted pressure during different flight conditions were evaluated (+3G_z, +6G_z, +9G_z, protocolised head movements, mounted visor or night vision goggles, NVG). The runs were recorded to evaluate if the mask’s position changed during the run, which would confirm the presence of shear forces. Results: Head movements increased the median pressure on the nose by 50 mm Hg and on the chin by 37 mm Hg. NVG, a visor and accelerative forces also increased the median pressure on the nose. Pressure drops on the nose were also observed, during mounted NVG (-63 mm Hg). The recordings showed the mask slid downwards, especially during the acceleration phase of the centrifuge run, signifying the presence of shear forces. Conclusions: The exerted pressure by the oxygen mask changes during different flight conditions. Exposure to changing pressures and to shear forces probably contributes to mask-inflicted nasal trauma.