The science behind FRMS : the causes of fatigue Philippe Cabon, PhD - - PowerPoint PPT Presentation

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The science behind FRMS : the causes of fatigue

Philippe Cabon, PhD

From intuition to science

 Fatigue is not only a scientific concept, it is used

in the daily life and it is a subjective experience

 Everybody has the feeling of being a “fatigue

expert” based on her/his own experience

 Fatigue is linked to physiological mechanisms but

the way we perceive it is linked to psychological, social and cultural factors

 The way we perceive fatigue influences the way

we behave

FRMS Symosium, ICAO, Montreal

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“Fatigue is a biological drive for a recuperative rest”

Rest Sleep Adapted from Williamson et al, 2011

Fatigue

Sleepiness Accident

Time

• f Day

Time awake Task related factors

Impaired Performance Capabilities

Alertness components

6 12 18 24 30 36 42 48 54 60

2 4 6 8 10 12 14 16 18 Time since sleep (h) Alertness

Process S (homeostasic need for sleep)

2 4 6 8 10 12 14 16 18 20 22 24 Time of day (h) Alertness

Process C (endogeneous circadian pacemaker) Process W (sleep inertia)

Hours 0800 0800 1600 2400 Primary gate

Schematic representation of time periods favoring sleep onset (taken from Stampi, 1989)

Sleep gates and forbidden sleep zone

High Low Drowsiness Forbidden sleep zone Secondary gate

Main fatigue factors in aviation

Operational factors

 Irregular hours of work  Long duty times  Time Zone transitions

Internal factors

 Circadian factors  Homeostasic sleep  Sleep inertia

Task related factors

 Workload  Monotony

Main effects of sleep loss

 Microsleeps  Increased reaction time  Unstable cognitive state (more variability of

performance)

 Divergent thinking is more impacted than

convergent thinking

=> creative, innovative decision are more impacted than procedural decision

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FRMS Symposium, ICAO, Montreal

Microsleeps

FRMS Symposium, ICAO, Montreal

P.Cabon

Microsleeps can occur even during critical phase of a flight

Microsleeps in the last 90 mn of the flights

Number of microsleeps 18 16 14 12 10 8 6 4 2 90-60 60-30 30-0 Time before landing (mn)

Outward flights Return flights

Chronic sleep deprivation is incidious….

Van Dongen et al, 2003

Objective and subjective sleepiness during night driving

Alert

Subjective evaluation

(U.A.)

Sleepy

2 4 6 8 10 12 14 D P1 P2 P3 F 20 40 60 80 100

Ratio (%)

Increased risk of accident

Objective sleepiness

.

Subjective sleepiness

The complexity of fatigue

 Fatigue is a normal physiological state !  Fatigue is not only caused by the time on task but

by a complex interactions of various factors

 Fatigue and the way we perceive it are influenced

by a large inter-individual variability (sleep needs, chronotype,..) and by social factors

 More researches are needed to understand the

complexity of the link between fatigue and safety

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FRMS Symposium, ICAO, Montreal

From science to regulation

 Science can improve the design of rules and rosters  But the complexity of fatigue makes the design of

“perfect” rules or rosters impossible

 Hours of work regulations focused on limited aspects

• f fatigue and cannot address its complexity while

coping with operational/economics requirements

 FRMS is a promising way to better integrate the

complexity of fatigue mechanisms in work schedules management

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FRMS Symposium, ICAO, Montreal