Defining, Measuring, and Predicting Fatigue · Fatigue is operationally defined … Subjectively by...
Transcript of Defining, Measuring, and Predicting Fatigue · Fatigue is operationally defined … Subjectively by...
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Defining, Measuring, and Predicting Fatigue
Gregory Belenky, M.D.
Sleep and Performance Research Center
Washington State University
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Fatigue Operationally Defined …
Fatigue is operationally defined … Subjectively by self-report, e.g., “I am tired.”
o Karolinska Sleepiness Scale (KSS)
o Samn-Perelli Fatigue Scale
Objectively by degraded performance, for instance
o Psychomotor Vigilance Task (PVT)
o FOQA-derived metric
Fatigue is unmasked by increasing time on task
Qantas simulator-based fatigue study When fatigued better at detecting errors
When fatigued worse at managing errors
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Fatigue a function of….
Fatigue is function of three factors … Time awake (sleep/wake history) – in use
Time of day (circadian rhythm phase) – in use
Time on task (workload) – under development
…. All three are modulated by individual differences
At a minimum to study fatigue we need
Objective measures of sleep
Objective measures of performance
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Actigraph and Hand Held Psychomotor Vigilance Task (PVT)
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Measuring Sleep with the Actigraph…
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Measuring Performance with the PVT …
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70
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Van Dongen and Hursh, 2011
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An experiment…
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Fatigue as the Integration of Sleep Loss, Circadian Rhythm, and Workload
Wesensten, et al., 2004
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Time Awake, Time of Day, and Time on Task
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Another Experiment …Sleep Restriction and Performance
Belenky, et al., 2003
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Mathematical Models …
Mathematical models integrate … Homeostatic sleep drive (time awake/sleep/wake history)
Circadian rhythm phase (time of day)
Workload (time on task)
… and individual differences
Mathematical models combine sleep/wake history, circadian rhythm phase, and workload in order to predict performance
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Activity, Sleep Scoring, Performance Prediction…
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Integration of Fatigue Risk Management into Rostering and Scheduling
Personal biomedical status monitoring Sleep/wake history (by sleep watch)
Circadian rhythm phase (by technology TBD)
Predict performance in real time person by person (by biomathematical performance prediction model)
Validate with embedded performance metrics
o Lane deviation (trucking)
o Metrics derived from FOQA (commercial aviation)
Integrate performance prediction into rostering and scheduling Integrate into objective function of rostering and scheduling software
Optimize along with other constraints
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Gregory Belenky, MDResearch Professor and DirectorSleep and Performance Research CenterWashington State University P.O. Box 1495Spokane, WA 99210-1495
Phone: (509) 358-7738FAX: (509) 358-7810Email: [email protected]
Point of Contact
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Predicting Performance from Sleep/Wake History and Circadian
Phase•Linear Decline during Waking
•Charging Function during Sleep
•Circadian Rhythm
•Combined (decline, charge, circadian)
A Nap
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Predicting Performance from Actigraphically-Derived Sleep Wake History