Panhellenic AsMa 29 Feb08

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Quantitative prediction of the effects of fatigue on human cognition

Transcript of Panhellenic AsMa 29 Feb08

  • 1. Application of Cognitive Modeling to Fatigue Management
      • 4 thPanhellenic Conference on Aerospace Medicine
    • Athens, 29 February 2008
    • James C. Miller, Ph.D., CPE
    • millergonomics.com
    • [email_address]
    • (USAF Research Lab, Retired)

2. Topics

  • Fatigue context
  • Quantitative modeling of fatigue (SAFTE)
    • FAST software (Windows)
    • F/PAS Web site
  • Modeling examples

3. The Human in the Loop

  • The most unpredictable component in any weapon system is human cognition
  • After training and currency, the greatest contributor to that human variability is fatigue
  • Good human-machine system design exploits human strengths and protects the system from human weaknesses

4. The Human in the Loop

  • Human Strengths : Betterpattern recognitioncapabilities anddecision-makingskills than can be provided in software
  • Human Weaknesses : Much more performance variability than one finds in software and modern hardware, primarily inattention and vigilance

5. Sources of Fatigue Variability

  • Large amplitude, moment-to-momentfluctuations in attentivenessassociated with fatigue; average performance may be at an acceptable level
  • Brief periods when responses are extraordinarily delayed or absent for a half-second to a minute (" lapses "); often called "distractibility;" fatigued system operators are more easily distracted than non-fatigued operators
  • Microsleeps ; i.e., falling asleep on the job for more than a minute

6. Types of Fatigue

  • Fatigue and sleepiness are caused primarily by lack of sleep, with the exception of physical fatigue caused by brief physical work and task-specific fatigue
  • For practical purposes, we sort the generators of fatigue into six categories:
    • Physical
    • Circadian
    • Acute
    • Cumulative
    • Chronic
    • Task-specific

7. Types of Fatigue

  • Circadian Effects.Malaise and fatigue due to:
  • Night Work .the pre-dawn period when sleep drive and sleepiness are highest and body temperature and alertness are lowest.
  • Jet Lag .a time zone change that is faster than about one time zone per day and exceeds about three time zones; re-synchronization of internal circadian rhythms to new external time cues, especially the daylight-darkness cycle.
  • Shift Lag .a change from day work to night work and vice versa.The main external time cue, the daylight-darkness and social cycles, inhibits re-synchronization.For most night workers, re-synchronization never occurs

8. Types of Fatigue

  • Acute Fatigue.Acute fatigue builds up normally and unavoidably within in one waking period; recovery from acute fatigue occurs as the result of one good-quality, nocturnal sleep period
  • Cumulative Fatigue.Cumulative fatigue builds up across major waking and duty periods when there is inadequate recovery (due to inadequate sleep) between the duty periods; recovery from cumulative fatiguecannotbe accomplished in one good-quality, nocturnal sleep period

9. Types of Fatigue

  • The only known cure for physical fatigue, acute fatigue, cumulative fatigue, jet lag, and shift lag isgood-quality nighttime sleep
  • All other treatments, called fatigue countermeasures (including prescription drugs), are "Band-Aids" that counter the symptoms of fatigue
  • Eventually, the individual must sleep to recover from these types of fatigue

10. Nature of Fatigue

  • Ubiquitous:fatigue affects everybody
  • Pervasive: fatigue affects everything we do, physically and cognitively
  • Insidious:often when we are fatigued, we are quite unaware of how badly we are performing
  • Fortunately, the biological changes and rhythms that cause fatigue-induced declines, lapses and variability in human performance arepredictable ; thus, we may model them

11. Predictive Model 12. Quantitative Predictions of Fatigue

  • A world-class applied model (or simulation) was developed during the 1990s, primarily with US DoD funding
  • The Sleep, Activity, Fatigue and Task Effectiveness ( SAFTE ) is a 3-process, applied model of human cognitive performance effectiveness (Hursh et al., 2004):
    • Circadianrhythms in metabolic rate and alertness
    • Cognitive performance recovery rates associated withsleep , and cognitive performance decay rates associated withwakefulness
    • Cognitive performance effects associated withsleep inertia

13. Quantitative Predictions of Fatigue 14. Validation Example 15. Predictive Software: FAST 16. Quantitative Predictions of Fatigue

  • TheFatigue Avoidance Scheduling Tool( FAST ) was based upon the SAFTE applied model
  • It is a Windows program that estimates the average effects of various work-rest schedules on human cognitive performance by examining manually-entered work and sleep data in any of several formats
  • Geophysical model allows jet lag calculations
  • Autosleep function fills in best sleep estimate when needed

17. Quantitative Predictions of Fatigue

  • FAST was developed initially as a US Air Force product to deal specifically with R&D on Air Force mission-scheduling issues(Dr. Miller was the Government contract technical monitor)
  • The FAST software development effort concluded in 2006 with version 1.5; FAST is available commercially

18. FAST Cognitive performance (%) Cursor for I/O Dashboard Sleep (blue; model input) Work (red; captures data output) Daylight/darkness (gray) Circadian phase (thin red curve) 19. FAST (zoom & variability) Zero suppression*Copy/Paste*-30 percentile 20. FAST Click and drag grid input function 21. FAST Tabular output Copy/paste work period data 22. Predictive Software: F/PAS 23. Quantitative Predictions of Fatigue

  • A follow-on contract was awarded by the USAF in 2006 to create the "son of FAST" software(Dr. Miller was the Government contract technical monitor)
  • Its working name was theIntelligent Scheduling Tool( IST )
  • FAST is Windows-based; the IST is browser/Web-based
  • This new software is now called the Fatigue/Performance Assessment System( F/PAS )

24. Quantitative Predictions of Fatigue

  • F/PAS uses the SAFTE model and its core software has all of the functions of FAST
  • F/PAS gains two new functions that were unavailable in FAST:
    • Pharmaceutical effects (caffeine, go pill, no-go pill)
    • Generalization of the Autosleep function from a single time zone to transmeridian travel

25. Quantitative Predictions of Fatigue

  • F/PAS also gains three new interfaces that are being designed with a user-centered method
  • The new interfaces replace the original, graphic interface in FAST that was designed to support fatigue scientists
  • The interfaces include the:
    • Mission Scheduler Interfacefor aircrews, mission schedulers, and flight surgeons; irregular schedules
    • Mishap Investigation Interfacefor both air and ground mishaps
    • Shiftwork Scheduling Interface ; regular, cyclic schedules

26. F/PAS Mission Scheduling Interface

  • Under Construction.
  • Display looks much like FAST graph.
  • Rapid input by Outlook-style Calendar.

27. F/PAS Mishap Investigation Interface (Questions) 28. F/PAS Mishap Investigation Interface (Mission Log) 29. F/PAS Mishap Investigation Interface (Dashboard) 30. F/PAS Mishap Investigation Interface (Graphic Output) 31. F/PAS Shiftwork Scheduling Interface (Known Plans) 32. F/PAS Shiftwork Scheduling Interface (Plan Options) 33. F/PAS Shiftwork Scheduling Interface (New Plan Wizard) 34. F/PAS Shiftwork Scheduling Interface (Analysis) 35. FAST-to-F/PAS Transition

  • Presently, the user interfaces are in early alpha phase and usability testing; thus, too early for formal plan and schedule
  • F/PAS will read the fas data files created by FAST
  • For owners of FAST, there will probably be a discounted upgrade program to F/PAS

36. Modeling Examples 37. Ground Mishap in FAST (Phase) 38. Ground Mishap in FAST (BAC) 39. Dr. Millers Trip to Athens 40. Shiftwork 41. Additional Information

  • FAST (from NTI, Inc.):www.ntiinc.ms11.net
  • Dr. Miller:www.millergonomics.com
  • (Presently, a consultant to NTI for F/PAS development)