Hangar Talk: Editorial
Go, No-Go Decisions
By Stephen W. Roberts, MD, AME
... Fatigue, a normal physiological response of the human body to sleep loss and circadian rhythm disruption, is characterized by decreased physical and mental efficiency.
Common signs and symptoms of fatigue include sleeplessness, overall discomfort, irritability, depression, apathy, physical an emotional isolation from others, loss of appetite, slurred speech, visual fixation and impaired visual perception, decreased alertness, difficulty concentrating, slowed reaction time, need for increased sensory stimulation to react, impaired short-term memory, poor judgment, loss of accuracy and control smoothness, unawareness of errors, and responses to become increasingly more dependent on previously acquired habits (good or bad).
In these manifestations can be aggravated by individual exposure to other stressors, including low barometric pressure, noise, vibration, linear and angular acceleration (G forces), high ambient temperature, and low humidity. Furthermore, self-imposed stressors, such as poor physical fitness, inadequate diet or nutrition, inadequate hydration, excessive body weight, drug and alcohol use or abuse, use of medications, excessive caffeine consumption, and tobacco use can predispose you to becoming fatigued..They also can aggravate fatigue.
Sleep is a period of rest for the body and mind, during which bodily functions are partially suspended and consciousness is temporarily interrupted. Sleep is as necessary as food and water for the well-being of an individual. The average healthy adult is accustomed to a single, prolonged sleep of approximate eight hours. During a typical 24-hour day, there are two normal periods of sleepiness: between the hours of 3-5 a.m. and 3-5 p.m. Sleeping less than eight hours per day can result in sleep loss, which can become cumulative.
After sleep loss, the most notable feature of recovery sleep is its increased depth, rather than its duration. This means the following sleep loss, you do not have to sleep the same number of hours that you lost. Sleep loss can be caused by circadian rhythm disruptions, sleep disorders, stress, alcohol and drug use or abuse, excessive caffeine consumption, bad sleep habits, uncomfortable sleeping environments, use of sleeping pills, etc.. In addition, with increased age, sleep becomes less deep and more disrupted, and nocturnal sleep decreases. The main physiological effect of sleep loss is an increase in sleepiness, which causes fatigue.
Circadian rhythm defines a biological cycle of approximately 25 hours that determines the physiological behavior of all body functions. They are influenced by the succession of day and night, changes in ambient illumination, and timing of food consumption, physical activity, and social activities. Circadian rhythms can be affected by a sudden change in individual work-a rest schedules (shift work), sudden relocation to a different time zone, use of medications to sleep and stay awake, alcohol and drug use or abuse, etc.
Various factors affect your ability to adapt to new circadian rhythms:
- Adaption takes longer with increasing age.
Manifestations of circadian desynchronization,or incomplete adaptation to a new circadian rhythm, include difficulty falling asleep, difficulty remaining asleep, daytime sleepiness, decrease physical and mental performance, gastrointestinal problems, and other signs and symptoms associated with fatigue.
Here's what you can do to prevent fatigue:- Develop a practice of an appropriate sleep routine that includes at least eight hours of high quality sleep in a quiet, dark environment in a comfortable bed.
- Try to get as much sleep per 24 hours during a trip, as you would at home.
- Use physical or mental relaxation techniques to fall asleep. Sometimes it is as simple as a hot shower or bath before going to bed.
- Do not eat a heavy meal or drink large amounts of liquids before going to bed.
- Eat a balanced diet to prevent in-flight hypoglycemia.
- Do not consume any alcohol or caffeine for at least 3-4 hours before going to bed.
- If you're having difficulty getting to sleep, get up and try activity that helps you fall asleep. For example you could read, listen to soft music, watch a relaxing television program, take a hot bath etc. Counting sheep only works for a few.
- Avoid using sleeping pills to promote sleep and stimulants to promote wakefullness unless they are prescribed by flight surgeon (not likely). The same advice applies to the use of melatonin.
- Take a nap of no longer than 40 minutes immediately before your scheduled flight, if you didn't get enough sleep the night before. A nap can acutely improve alertness because it decreases the length of continuous wake fullness before a flight. Consider it a re-charge of your batteries.
Common misconceptions about fatigue:- Eight hours of rest are as beneficial as eight hours of sleep.
- I know exactly how tired I am.
- I have lost sleep before, and I did just fine.
- I motivated enough to just push through it.
- I am a highly experienced and capable pilot and can still fly aircraft even if I am tired.
- I don't need more than three or four hours of sleep every night.
- If I'm tired, all that I need is a cup of coffee (or two... or three) to feel better.
- There is a quick and easy fix for fatigue.
- One cure will work for everyone.
Stephen W. Roberts, MD, AME
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