panhellenic asma 29 feb08
DESCRIPTION
Quantitative prediction of the effects of fatigue on human cognitionTRANSCRIPT
Application of Cognitive Modeling to Fatigue Management
4th Panhellenic Conference on Aerospace MedicineAthens, 29 February 2008
James C. Miller, Ph.D., CPEmillergonomics.com
[email protected](USAF Research Lab, Retired)
Topics
Fatigue context
Quantitative modeling of fatigue (SAFTE)
FAST software (Windows)
F/PAS Web site
Modeling examples
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
The Human in the Loop
Human Strengths: Better pattern recognition capabilities and decision-making skills than can be provided in software
Human Weaknesses: Much more performance variability than one finds in software and modern hardware, primarily in attention and vigilance
Sources of Fatigue Variability
Large amplitude, moment-to-moment fluctuations in attentiveness associated 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
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
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
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 fatigue cannot be accomplished in one good-quality, nocturnal sleep period
Types of Fatigue
The only known cure for physical fatigue, acute fatigue, cumulative fatigue, jet lag, and shift lag is good-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
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 are predictable; thus, we may model them
Predictive Model
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):
Circadian rhythms in metabolic rate and alertness Cognitive performance recovery rates associated with
sleep, and cognitive performance decay rates associated with wakefulness
Cognitive performance effects associated with sleep inertia
Quantitative Predictions of Fatigue
Validation Example
Predictive Software:FAST
Quantitative Predictions of Fatigue
The Fatigue 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
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
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)
FAST (zoom & variability)
Zero suppression * Copy/Paste * -30 percentile
FAST
Click and drag “grid” input function
FAST
Start End StatsDay Date Time Day Date Time Dur Eff %BCLFriz 11/9/2007z 13:00z Friz 11/9/2007z 20:59z 480 97.97 0Satz 11/10/2007z13:00z Satz 11/10/2007z20:59z 480 97.97 0Sunz 11/11/2007z21:00z Monz 11/12/2007z04:59z 480 96.42 0Monz 11/12/2007z21:00z Tuez 11/13/2007z04:59z 480 97.7 0Wedz 11/14/2007z05:00z Wedz 11/14/2007z12:59z 480 75.82 67.29Thuz 11/15/2007z05:00z Thuz 11/15/2007z12:59z 480 73.04 71.25Friz 11/16/2007z06:00z Friz 11/16/2007z12:59z 420 71.72 75
471.43 87.52 29.7
Tabular output
Copy/paste work period data
Predictive Software:F/PAS
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 the Intelligent 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)”
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
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 Interface for aircrews, mission
schedulers, and flight surgeons; irregular schedules Mishap Investigation Interface for both air and ground
mishaps Shiftwork Scheduling Interface; regular, cyclic schedules
F/PAS Mission Scheduling InterfaceUnder Construction.
Display looks much like FAST graph.Rapid input by Outlook-style Calendar.
F/PAS Mishap Investigation Interface (Questions)
F/PAS Mishap Investigation Interface (Mission Log)
F/PAS Mishap Investigation Interface (Dashboard)
F/PAS Mishap Investigation Interface (Graphic Output)
F/PAS Shiftwork Scheduling Interface (Known Plans)
F/PAS Shiftwork Scheduling Interface (Plan Options)
F/PAS Shiftwork Scheduling Interface (New Plan Wizard)
F/PAS Shiftwork Scheduling Interface (Analysis)
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
Modeling Examples
Ground Mishap in FAST (Phase)
Ground Mishap in FAST (BAC)
Dr. Miller’s Trip to Athens
Shiftwork
Additional Information
FAST (from NTI, Inc.): www.ntiinc.ms11.net
Dr. Miller: www.millergonomics.com(Presently, a consultant to NTI for F/PAS development)