Measuring sleep (ir)regularity: Current metrics and applications

Kurzfassung

Introduction: In view of the latest technological developments in commercial aviation, flights with reduced crews appear possible. In so-called extended minimum crew operations (eMCOs), one pilot is in control of the aircraft ('Pilot Flying') while the other pilot is allowed to rest and sleep ('Pilot Resting'). Sleep inertia - a state of cognitive impairment immediately after waking up - is a potential safety risk if the Pilot Resting has to act upon awakening. In addition, fatigue and boredom can increase for the Pilot Flying due to flying alone for an extended period. This study aimed to examine how eMCO segments in a high-fidelity flight simulator scenario affect sleep, sleep inertia, fatigue, boredom and crew performance of commercial pilots. Materials and methods: Five crews (n = 10 pilots) participated in the study at the AVES flight simulator center of the German Aerospace Center and completed one of two conditions: aborted vs. non-aborted eMCO segment. In both conditions, the crews flew together for 30 minutes, followed by an eMCO segment in the new Pilot Flying (PF) and Pilot Resting (PR) roles. In the aborted condition, the eMCO segment ended unexpectedly after a 60-minute sleep opportunity for the PR, with an engine fire occurring immediately upon awakening. In the non-aborted condition, the eMCO segment ended as planned after 2.5 hours without interruption, with the engine fire occurring 30 minutes after the end of the eMCO segment. Sleep was objectively recorded using a wireless EEG system and a flexible, unobtrusive electrode grid with high wearing comfort. Self-assessments of fatigue, workload and boredom were collected every 30 minutes. Crew performance was operationalized as speed and success in handling the engine fire. Results: In the non-aborted condition, pilots slept for 99 minutes on average out of a 130-minutes sleep opportunity. Beneficial effects of the nap on subsequent fatigue levels were mixed. Fatigue and boredom of the PF were higher during the eMCO segment than before or after the segment. Workload during the engine fire was perceived as slightly higher in the aborted eMCO than the non-aborted eMCO condition. Out of three crews in the aborted eMCO condition, one PR did not deem himself fit to act upon awakening, leaving the PF to -successfully- deal with the fire on his own. Crew performance speed (i.e., how fast the fire was resolved) did not differ between the two conditions. Conclusions: In this particular scenario and based on a limited sample size, sleep inertia, fatigue and boredom had no effect on crew performance when an engine fire occurred. The investigation of further safety-relevant eMCO scenarios, e.g. increasing sleep inertia during night flights, is warranted. Acknowledgments: We thank all participating crews.