Forehead-mounted reflectance oximetry for in-cockpit hypoxia early detection and warning

Effective hypoxia-related mishap prevention relies upon aircrew rapid recognition of hypoxia symptoms. The objectives of this experiment were twofold: to compare the effectiveness of a forehead-mounted reflectance oximeter and finger-mounted pulse oximeter for application in a hypoxia early warning detection system, and to determine whether the forehead-mounted sensor could be placed within an aviation helmet.

Subjects donned an aviation flight mask and were instrumented with a forehead reflectance oximeter, a finger pulse oximeter, a blood pressure cuff, and a skin temperature sensor. Following instrumentation, subjects breathed ambient air for 10 min through the Reduced Oxygen Breathing Device (ROBD) to allow for acclimation. The baseline period was followed by one of two counterbalanced ascent profiles used to model rapid exposures to altitude. Data were collected at 1 Hz from both sensors for the duration of the protocol.

Analyses indicated an exceptionally strong agreement between the forehead and finger sensors at all ranges of desaturation. The sensitivity data revealed that the forehead sensor was significantly faster when responding to rapid changes in SpO2 than the finger. The sensor was successfully integrated inside the helmet; however, once donned by the subject, there was considerable artifact due to pressure fluctuations.

While these data may seem to suggest that the forehead sensor is accurate and sensitive to altitude induced changes in SpO2, major drawbacks exist for the technology utilized in the current study. Significant improvements aimed at diminishing noise, curbing motion artifact, and improving reliability are required to reduce errant measurements.