PERCLOS as an Indicator of Slow-Onset Hypoxia in Aviation

<jats:p><jats:bold>BACKGROUND:</jats:bold> PERCLOS is a metric that has been primarily studied in the domain of driver fatigue to predict performance decrements, but there is comparatively less research applying it to aviation, where hypoxia is a safety concern. Hypoxic exposure was expected to increase blink activity, possibly by means of impairing blink inhibition behavior, thereby leading to increased eyelid closure time.<jats:bold>METHODS:</jats:bold> PERCLOS, blink rate, and blink duration were measured using head-mounted eye-tracking on pilots using a flight simulator inside a hypobaric chamber. Pilot subjects were tasked with programming the autopilot of a G-1000 console according to instructions from a simulated air traffic controller. Data was collected at 5% decrements in blood oxygen saturation (S<jats:sub>p</jats:sub>o<jats:sub>2</jats:sub>) through progressive decreases in hypobaric pressure to model slow-onset hypoxia.<jats:bold>RESULTS:</jats:bold> PERCLOS, blink rate, and blink duration increased significantly and linearly as a function of decreasing S<jats:sub>p</jats:sub>o<jats:sub>2</jats:sub>, and largely recovered in the posthypoxia normoxia condition. The greatest change in PERCLOS relative to the prehypoxia baseline occurred in the 80% S<jats:sub>p</jats:sub>o<jats:sub>2</jats:sub> condition, whereas the greatest change in blink rate and duration occurred at 75% S<jats:sub>p</jats:sub>o<jats:sub>2</jats:sub>. As S<jats:sub>p</jats:sub>o<jats:sub>2</jats:sub> decreased, a higher frequency of long blink durations was observed.<jats:bold>DISCUSSION:</jats:bold> The increase in blink rate and duration in the absence of task demand manipulation could suggest hypoxia-induced sympathetic excitation and impairment of adaptive blink inhibition behavior. The effect of hypoxia on oculomotor features is also likely task-specific. In consideration of the extensive demand made upon the visual modality in flight, increased PERCLOS may further tax visual information processing.<jats:bold>Thropp JE, Scallon JFV, Buza P. <jats:italic>PERCLOS as an indicator of slow-onset hypoxia in aviation</jats:italic>. Aerosp Med Hum Perform. 2018; 89(8):700–707.</jats:bold></jats:p>