fatigue.docx

8/14/2019 Fatigue.docx

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Definition

The medicine definition of Fatigue refers to:A condition characterized by a lessened

capacity for work and reduced efficiency of accomplishment, usually accompanied by afeeling of weariness and tiredness. Fatigue can be acute and come on suddenly or chronic

and persist [Medicine Net (20089)].

Author Hawkins [7]defines fatigue as a source of difficulty which has tended to generateconfusion and retarded progress.

Medicine Health [8]defines Fatigue as:Fatigue, also known as weariness, tiredness,exhaustion, or lethargy, is generally defined as a feeling of lack of energy.

Theoretical frame

Fatigue have a varied range of interpretations with a wide concept which may defers from

one person to another [Medicine Net (20089)]. Fatigue can be interpreted in four ways.Firstly, it may reflect on inadequate rest, sleep, the symptoms of being disturbed, by

stressors or sufferer such as jetlag, excessive physical activity disturbance or excessivecognitive work being undertaken [Hawkins (19887)]. Fatigue can be said to be like stress

which is an umbrella term which encompasses many different perspective [Green, Muir,

James, Gradwell, & Green (19966)]. Fatigue causes can be also group asAcuteFatigue(immediate) or Chronic Fatigue(long term build-up).

Fatigue is a major risk in aviation, and implementation of countermeasures, bothorganisational and individual, are need to minimise this risk. Fatigue is a condition that is

hard to determine, its effects are very widespread and contribute more to aviation risk than

actually perceived. As aviators, an understanding of the causes of fatigue is helpful inavoiding this syndrome. Circadian desynchrony, sleep debt, hypoxia, zietgeber shifts and

workload contribute significantly to fatigue. However, careful planning by the organisation,technical advances and individual responsibility may reduce the risk of fatigue in theaviation industry.

The reduced state of physical and mental function associated with tiredness is known asfatigue (Caldwell & Caldwell, 2003). Deprivations of rest, circadian desynchrony or zeitgeber

shifts (i.e. light or temperature cues for time) increase the rate of fatigue in an individual.Kirsch (1996) writes that 4-7% of aviation accidents can be attributed to fatigue, however

this is not an accurate representation of the problem. The actual extent of its effects isextremely hard to determine, as there are no testing methods available that can accurately

measure the level of fatigue in an individual (Petrilli, Roach, Dawson & Lamond, 2006). The

effects of fatigue, however, can be observed from an individuals behaviour (Caldwell &

Caldwell, 2003). According to research (Pilcher & Huffcutt, 1996 as cited in Passer & Smith,2008), fatigue has negative effects on mood, cognitive and physical performance. Adverselyaffecting mood causes irritation, poor decision making and therefore increase

miscommunication between flight crew. Likewise, an aircraft technician might also find it

difficult to assemble complicated aircraft components due to cognitive and physicalimpairment. In addition, fatigued individuals incorrectly perceived an increase in

performance although their cognitive and physical had been impaired by sleep deprivation(Passer & Smith, 2008). Hence, individuals often lay blame of an incident on other

confounding factors such as complicated displays or un-cooperative team members,


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although the root cause may be fatigue. It can be assumed that fatigue contributes to moreaircraft accidents than statistically reported.

Heinrich illustrated in his safety pyramid that for each major accident there are an

estimated 300 near misses. In addition, further research indicates that an estimated 600

incidents without mishap go unreported (Phimister, Oktem, Kleindorfer, Kunreuther and

Yen, 2000). Therefore, even though a small number if accidents can be directly attributed tofatigue, the actual number may be in fact much larger, signalling an urgent need for the

aviation industry to take steps in reduce fatigue related risks. Suitable countermeasuresshould be adopted on the organisational as well as the personal level to combat the rootcauses of fatigue. Unfortunately, with the improvement of the aviation industry and the

onset of new low cost carriers, (International Air Transport Association, 2007), pilots are

made to fly multiple sectors while maximising the limits on flight duration allowed by theAirline Operators Certificate (Fatigue Managment, n.d.). Commute time and other personal

necessities also reduce the amount of time available for sleep. In a single international

pattern around the world, international pilots experience many difficulties; they cross manytime zones, work long shifts, Experience early flights and flying at night. However, the

human body is unable to re-adjust its sleep wake cycles to the new time zones immediately,causing circadian desynchrony or otherwise known as jet lag (Petrilli et al, 2006). Caldwell

and Caldwell (2003) noted that normal recovery from jet lag takes 2 to 3 days, and that theeffect is more pronounced on an eastward followed by a westward route than vice versa.

Pilots fatigue increases as they fly an international pattern with many sectors (Petrilli et al,

2006), a situation aggravated by the loss of sleep credits (Passer & Smith, 2008). Accordingto Passer and Smith, 1 sleep credit is equivalent to 1 hour, therefore sleeping 7 hours a day

instead of 8 results in a loss of 1 sleep credit. Caldwell and Caldwell (2003) wrote thatorganisations often plan shifts without taking into account their workers commute time and

time for other necessities, assuming that all time spent off work is spent resting. Hence,

international patterns with many ports of call are planned with layovers too short for pilotsto rest. The loss of sleep credits forces the brain to sleep involuntarily, and this often goes

unnoticed(Petrilli et al, 2006). This effect, known as microsleep, compromises safety as

pilots are effectively not in control of the aircraft during that short period Caldwell andCaldwell (2003). Our brain is a complex organ that runs on oxygen. However, the external

air pressure decreases as an aircraft climbs; an individuals respiratory system absorbs lessoxygen at higher altitude than at seal level and this causes a condition known as hypoxia(Whitt, n.d.). Although hypoxia has many symptoms such as dizziness, shortness of breath,

etc. Whitt writes that these symptoms of hypoxia contribute significantly to aviation fatigue.

Smoking also aggravates this situation by reducing oxygen absorption into the lungs,therefore, even if an airplane is pressurised to a certain cabin altitude, the smoker would

feel as if he is breathing at an altitude of much higher, increasing the rate of fatigue(Nesthus, Garner & Mills, 1997).

Our circadian rhythm is influenced and controlled by external cues or zeitgeber.

Temperature and light fluctuate during the day and our bodies match our sleep/wake cyclesto match these changing patterns (Green, Muir James, Gradwell & Green, 1996). It was

found out that 59% of surveyed pilots responded that night flying was a major cause of

fatigue (Bourgeois-Bougrine et al., 2003 as cited in Petrilli et al., 2006). This occurs whenthe human body increases melatonin production in the body, lowering heart rate and bodytemperature in preparation for sleep (Passer & Smith, 2006). The amount of workload is

also a factor that determines the rate of fatigue. Pilots are constantly faced with theresponsibility of monitoring multiple cockpit instruments, radio communications,surrounding traffic, aircraft heading and many other aspects of flying including the actual


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control of the aircraft (Hancock & Desmond, 2001). According to Hancock and Desmond, the

cockpit workload fluctuates with the progression of the flight peaking prior to take-off and

landing, increasing the rate of fatigue in aircrew. Therefore, while increasing workload alsoincreases fatigue risk, decreasing workload decreases, however, organisational efficiency aconstant balance that the aviation industry maintain.

The effects of fatigue are often grossly underestimated; it affects almost every humanfactor involved and may have accounted for more accidents in aviation that actually

perceived. However, organisations can help counter the effects of fatigue in their staff byplanning duties according to the circadian rhythm. Technology assists relieving fatiguethrough ergonomics, environment simulation and automation. Most importantly, the

individual has the responsibility to increase their resistance to fatigue, and take steps toreduce it if they are on duty.

Classification of Fatigue

There are mainly three types of fatigues.

Physical FatiguePhysical fatigue refers to various physical issues such as muscle soreness, lack of oxygen,poor nutrition, tiredness caused by lack of sleep or illness [Stokes & Kites (199413)].

Mental Fatigue

It is associated with task demanding intense concentration, cognitive information processingor other high cognitive skills. Such metal fatigue can be seen in examples such as single

pilot flying in Instrument Flight Rules (IFR) during night. Mental fatigue can be arise fromprolong activity as well [Stokes & Kites (199413)].

Emotional Fatigue

Emotional fatigue can be also known as burnout which simply refers to the wearying effect

of working under psychological disagreeable task. This type of fatigue can be seen whenindividual starts complaining saying its tired, bored, routine or from consistent arguing inworkplace or domestically [Stokes & Kites (199413)].

Causes of Fatigue

Internal Drive for Sleep

Sleep duration or the amount of sleep obtained will influence the level of fatigue. AuthorDijk and Czeisler [3]stated that the sleep homeostat or the bodies demand for sleep willincrease throughout the day of wakefulness will contribute to the amount and quality of

sleep at night. Thus if sleep has been prevented or shorten, it will result in physical fatiguefor an individual.

Circadian Biological ClockOur bodies sleep clock that influences the sleep duration and quality is critical in the level offatigue one will experience. As the circadian system helps to maintain our wakefulness

during the day, with sleep rarely being initiated during the day. If this system getsdistorted, fatigue level will increase as sleep will be consistently being initiated at the wrongtime, creating a decrease in individuals performance [Dijk & Czeisler (19953)].


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Jet Lag

After travelling to and fro from time zones, individuals circadian clock will be out of its

preset local day-night cycle. Thus the circadian clock can adapt the time of bothphysiological and behavioural variables [Signal, Ratieta, & Gander (200612)]. Thus

consistent jetlag will eventually distorts ones bio clock which will increase the probability offatigue causing, slower reactions, degrading performance, and defective memory which

inevitably increases the outcome of human error in any situation [Hawkins (19887)].

Shift WorkShift work schedules are referring to working hours distortion which requires sleep to bedisplaced from its normal night time slot. Thus this distorting inevitably affects the

characteristics of circadian rhythm, which might be a source for fatigue [Signal, Ratieta, &

Gander (200612)]. The symptoms are similar to jetlag as their cues for sleeping are oftendisturbed from their different shift working rosters. Thus the consistent changing of sleep

rhythm will affect ones performance as fatigue due to the lack of sleep or the irregularities

of sleep cycle from disturbance of the bio clock will result in degrading humanperformances.

Consequences of Fatigue

The precise nature of fatigue can be said to be diverse and insidious. As fatigue level in one

individual increases, accuracy and timing degrade with lower performance level which areunconsciously accepted without self-detection [Signal, Ratieta, & Gander (200612)].Narrowing of attention (similar to stress) occurs thus increasing the risk of human errors in

any situations. As sleepiness increases, performance decreases and the effects of suchrelationships worsens during night hours [Dinges & Kribbs (19914)]. Problem solving andreasoning skills are slower then normal while psychomotor skills are degrading with anincrease rate of false responses [Caldwell (19971)]. Furthermore, fatigue will reduce social

interaction with others and eventually loses group or team performance level. This isextremely critical for pilots operating an aircraft.

Biological limitations imposed by fatigue will impair performance of even the most highlyskilled or motivated individuals [Caldwell (19971)]. In addition, the effects of fatigue

cannot be overcome either by training or experience, or negated by monetary or otherincentives [Signal, Ratieta, & Gander (200612)].

Prevention of Fatigue

Here are a few ways to prevent fatigue as recommended FAA and ICAO for pilots. Totalprevention of fatigue is impossible, thus the recommendations will significantly reducedfatigue only.

First, to ensure restful, quality sleep, the sleep environment should be cool, dark, andquiet. It is also best to avoid working or reading in bed, as this may actually contribute to

problems in falling asleep. The bed should be associated only with sleeping and sexualactivity. If you desire to read before going to bed, do this in a chair outside the bedroomand then go to bed

Adjustment of shift work to prevent circadian dis-synchronization. This can be

accomplished by maintaining a consistent sleep/wake schedule even on days off. It is also

important, when on the night shift, to avoid exposure to daylight from dawn to 1000. Wear


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sunglasses if you cannot go to sleep before the sun rises (as long as this does not pose a

safety hazard), and while asleep consider wearing a sleep mask to avoid any exposure to

light. Exposure to light before you go to sleep will interfere with the quality of your sleep.You may eat a light snack before going to sleep, but do not go to sleep too full or too

hungry. Also avoid caffeine consumption for about 6 hours prior to going to sleep. Nappingis a good strategy for coping with sleep deprivation during continuous operations or other

times when it is difficult to get a good nights sleep

Maintain good physical health with regular fitness programmes which will enable the bodyto resist the effects of fatigue.

Get plenty of natural sleep. It is also important when treating fatigue to maintain areasonable work schedule during waking hours. It makes no sense to try to catch up on

sleep and then exhaust oneself during the day. Also ensure that you eat properly to giveyour body the fuel it needs to recuperate.

After 24 - 48 hours of sleep deprivation DO NOT sleep overly long during the recoveryperiod. This could interfere with your normal sleep/wake cycle and cause sleeping problems

the next night.

When trying to sleep outside your normal bedtime, prepare for sleep as you normallywould have - wear the clothes to bed that you would normally wear, darken the room, and

keep noise to a minimum.

Supporting evidence

The accident report compiled by the NTSB (2000 [10]) on Korean Air Flight 801 suggests a

classical example and evidence of fatigue in aviation. After the investigation andexperimentation, investigators were able to identify the fatigue factor of the captain. The

accident occured at 00:42 hours in the flight crew's home time zone on 6 August 1997.

According to most of the research, pilots are vulnerable to poor alertness and higherpossibility of errors during midnight. More importantly, captain must have been sleeping ifhe were on his usual flight schedule. He was suffering from fatigue and was preoccupied

with glidesope and lost the position of the aircraft. Consecuently he was too late to execute

a "go around" approach, resulting into crash of aircraft at a hill near Guam InternationalAirport killing 228 of 254 people.

A research carried out by Powell, Spencer, Holland and Petrie (2008 [11]) on fatigue levelson two-pilot operations found an interesting result. For 12 weeks several pilots having 3-12

hours flight timings were allowed to complete Samn-Perelli fatigue ratings just before their

descent at the end of their flights. Total of 3023 usable ratings, including 74 per cent ofdouble sector pilots and 26 per cent of single sector pilots, were collected. The results

showed that highest levels of fatigue were observed in the night between 2 am to 6 am. Itwas found the fatigue is correlated to length of the duty. Moreover, fatigue levels werehigher at end of two-sector duties that single sector duty.

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