Cumulative Cyclic Exposures to 8000-ft Pressurization Equivalence and Attention Network Responses.

The literature is equivocal regarding the degree of cognitive impairment incurred at the 8000-ft (2438 m) maximal cabin pressure altitude equivalence for commercial aircraft. This study elaborates upon the investigation of the 8000-ft limit by introducing the cumulative effects of repeated daily exposures thereof. Pilots completed four daily high-altitude chamber flights at both sea level and 8000 ft. During each chamber flight, attentional processing and executive function were assessed using the Attention Network Test and the antisaccade task. Antisaccade task performance likely reflected a learning effect at both altitudes. Attention Network Test results, however, exhibited sensitivity to the fatigue and altitude interaction. Orienting network scores were affected by fatigue differently depending on altitude, with superior efficiency at 8000 ft compared to sea level (M = 44.9, SD = 25.0 vs. M = 29.0, SD = 18.1) in the last flight of the exposure cycle. Conflict network performance, however, suggested that while fatigue increasingly compromised executive control at both altitudes, marginally worse overall executive efficiency was observed at 8000 ft compared to sea level, notably in the last flight of the exposure cycle (M = 98.3, SD = 19.8 vs. M = 87.8, SD = 21.7). Executive control function, as measured by inhibition of interference in reconciling conflicting stimuli, degraded as a function of cumulative exposures to mild hypobaric hypoxia, though adaptive measures possibly compensated to preserve performance to a degree. This study serves as a baseline against which longer 8000-ft exposures, including long-haul flight, can be measured.