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Fatigue is defined as “a physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member’s alertness and ability to safely operate an aircraft or perform safety-related duties.”
Two types of fatigue have been identified i.e. “transient" and “cumulative” fatigue.
Transient fatigue may be described as fatigue that is dispelled by a single sufficient period of rest or sleep.
Cumulative fatigue occurs after incomplete recovery from transient fatigue over a period of time.
“FREQUENTLY ASKED QUESTIONS CONCERNING: PERSONAL STRATEGIES FOR FATIGUE MANAGEMENT IN FLIGHT CREW”
1. How do I predict when I am most likely to be fatigued?
Your level of fatigue at any point in a duty is influenced by a few major factors:
Time since last major sleep – the longer it is, the more likely you are to be fatigued.
Time on duty – the longer it is, the more likely you are to be fatigued.
Time of day (according to your body clock).
2. How does the body clock work? Is it important?
Most physical and mental functions vary throughout the 24-hour day, and most, especially mental functions, are worst between the hours of 0100 and 0500, which is the time one naturally feels most sleepy. These daily or “circadian” (which means “about a day”) rhythms are controlled by brain chemicals which are regulated by exposure to sunlight.
Note that there is a second sleepy period during the day which occurs in the mid-afternoon. This latter period of sleepiness is sometimes called the “post-lunch dip”, although it occurs whether or not lunch has been eaten.
This means your naturally sleepy periods will correspond to 0100-0500 and mid-afternoon at home time; these are the hours that you should target for sleep.
3. Can I train myself to require less sleep?
No. The only effective remedy for fatigue is sleep. Although the amount of sleep required per day varies between people, we cannot sustain sleep deficit for long periods without our performance
and safety being compromised. Missing a few hours of sleep each night will cause significant impairment of performance after two or three days.
4. What can I do to help me get to sleep?
Timing — the sleep should be timed to coincide with the naturally sleepy periods, as mentioned above; if it is daytime sleep, time it for the afternoon sleepy period.
Light — sunlight should be blocked out, using blackout curtains or eyeshades or both.
Sound — use earplugs, with or without background “white noise” (such as a fan or air conditioning) to mask external noises which might disturb you.
Temperature — most people sleep better if the temperature is close to 21C (70F).
Anxiety — ensure that there are reliable alarms set so that you will not oversleep. Ensure you are not under time pressure and have had a period to “wind down” from undertaking any stressful activities before resting.
Exercise — it will help to be physically fit, and exercise can improve sleep; however do not undertake vigorous and prolonged aerobic exercise within two hours before resting.
Stimulants — avoid caffeine, tobacco (and food) for a few hours before bed. Caffeine can take 4-6 hours to disappear from the system.
Alcohol — although alcohol can help you fall asleep, it disrupts the normal sleep cycle of the brain and causes sleep to be restless. Any more than one drink has the potential to impair your sleep.
Expectation — follow a routine or ritual prior to going to bed; if you are sleeping during the day, the routine should match your normal night-time routine, this provides the brain with an expectation of sleep.
Diet — eat before day sleep to avoid wakening due to hunger but avoid overeating (> 20 percent of daily energy intake) one to two hours prior to the main sleep episode.
5. Surely naps are a bad idea, because I feel worse afterwards?
Naps can have a powerful effect on restoring alertness and improving safety. Even after 10 minutes a nap can produce an improvement in alertness and help maintain performance, although this cannot be sustained indefinitely. Note that naps beyond about 45 minutes will result in a sleepy feeling on waking, known as “sleep inertia” which can impair your performance for 20 minutes or longer. Beware of this effect.
6. What about sleeping tablets?
As a crew member you should only use sleeping tablets on the advice of a doctor who understands the medical considerations of aviation.
7. Doesn’t melatonin fix jet lag?
Melatonin is a hormone produced by the brain at night which regulates the body’s circadian rhythms. Studies have shown that taking it can help synchronize circadian rhythms to a new time
zone. However, for pilots or cabin crew, adjusting to local time is very often not achievable or desirable. In these cases, melatonin is usually not useful.
8. How about caffeine and other stimulants?
Caffeine can sustain wakefulness, but most people use it so regularly that much of this benefit is lost because they develop tolerance to it. If you are serious about using caffeine to remain alert, use it only when it is necessary to be awake and avoid using it at other times. Be aware that it may take 4-6 hours for the stimulant effect to wear off.
9. Why do some people use an air pump device to help them sleep?
There are a few medical conditions that affect sleep. One of these is called “sleep apnoea” which literally means that breathing stops during sleep. When breathing stops for a period, brain oxygen levels decrease until the individual wakes slightly; this can have harmful effects, including a high level of daytime sleepiness. Since the problem can develop slowly, and tiredness is common in aviation operations, the affected person may not be aware that there is a problem. If you are feeling more tired during the day than colleagues working similar schedules, especially if you are overweight and a snorer, you should ask your doctor about sleep apnoea.
Tests can be undertaken, usually involving a night in a sleep laboratory to monitor your breathing pattern. If you are found to be suffering from sleep apnoea, it is likely you will be given a “CPAP” pump device to provide you with additional oxygen while you sleep; this treatment is virtually 100 percent successful and does not normally affect medical certification.
10. What’s the most important thing I can do?
Sleep! Although stimulants like caffeine can produce some short-term benefits, the only thing that really remedies fatigue is sleep. Make it a priority to get some sleep during the day prior to working all night. Some sleep is always better than none.
SLEEP HYGIENE:
This can be described as habits that promote normal sleep which, if disrupted, can adversely affect it. To an extent, good sleep hygiene follows a common sense approach such as: within a few hours of a sleep opportunity avoid caffeine, heavy exercise, alcohol intake exceeding a small amount, and large meals. Any pre-sleep “ritual” should be followed when away from home to help promote falling asleep.
OBSTRUCTIVE SLEEP APNOEA:
Obstructive sleep apnoea (OSA) is a condition in which, during sleep, the upper airway is obstructed due to loss of tone in the pharyngeal musculature. The obstruction may be complete, leading to cessation of airflow (an apnoea) or partial, leading to a markedly reduced inspiratory flow (a hypopnoea).
OSA can be defined as the presence of five or more obstructive events (either apnoeas or hypopnoeas) per hour of sleep. The obstructive sleep apnoea syndrome is defined as the presence
of OSA with daytime sleepiness.
OSA is also associated with an increased risk of coronary artery disease, hypertension and stroke.
Risk factors for OSA include increasing age, obesity, hypothyroidism and a family history of OSA.
CPAP is the treatment of choice in those with the OSA syndrome.
All crew with OSA syndrome should be assessed as temporarily unfit and referred to a sleep laboratory or appropriate specialist physician for a sleep study. Because of the associated cardiovascular risk, the usual risk factors should be assessed and treated.
Most crew members with significant OSA and certainly OSA syndrome should be treated with CPAP treatment in addition to appropriate advice regarding weight loss. Once satisfactory CPAP is established, demonstrated by reduced daytime sleepiness and absence of snoring on treatment, return to flying should normally be allowed.
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For further information read (ICAO Manual DOC8984 Chapter 17.)
https://www.icao.int/publications/pages/publication.aspx?docnum=8984
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