Aviation Safety Vortex 2/2003

Perchance to Dream...

Fatigue. Everyone knows that it is bad, but excessive fatigue is often worn as a badge of honour — as if to show how hard we're working, instead of how dangerous we have become. Regulations attempt to govern it through duty times and mandatory rest periods, but the arguments as to their effectiveness continue.

The helicopter industry in Canada sees fatigue from many sources. We have ambulance pilots working 12-hour day and night shifts, spending endless hours waiting for the phone to ring. In the summer, VFR pilots routinely fly 10 or more hours on seismic, logging, or forest fires — often for weeks on end. Spray pilots fly only at dawn and dusk (frequently after a long ride to the spray block) with terrible sleep schedules that involve a few hours at night and a few more during the day. Maintenance is routinely performed at night, when the machines are not flying, and late-night or early-morning run-ups are common. Pilots in Arctic camps may sit for days in bad weather, only to see it clear at 2 a.m., and be expected to go flying.

If there is one thing we know about fatigue, it is that it leads to human error, and the consequences are seen everywhere. In June 2001, just north of Albury, Australia, a convoy of six tractor-trailers was involved in an accident that scattered wreckage over several hundred metres and closed the highway for hours. The convoy was "slipstreaming", a common practice in motor racing and trucking, which involves the lead vehicle effectively towing those behind in its wake. The Transport Workers Union claimed the practice was used to save fuel, and even to keep the vehicles going if the driver fell asleep. It was just one example, they said, of the measures drivers had taken to meet unrealistic deadlines.

There are other high-profile examples of accidents in which fatigue played a starring role:

• The managers who authorized the launch prior to the Challenger explosion in 1986 had had little sleep the night before.
  
  
• The pilot-in-command of the Cessna 177B Cardinal in which he, seven-year-old Jessica Dubroff and her father were killed, suffered fatigue that seems to have impaired his judgment, and he departed into weather that had convinced a Beech 1900 captain to delay his flight.
  
  
• The officer in charge of the Exxon Valdez was acutely sleep-deprived when she ran aground off Alaska in 1989.
  
  
• The nuclear accidents at Chernobyl and Three Mile Island, and the deadly chemical spill at Bhopal, India, all involved serious errors of judgment by tired operators.

In studies throughout the Western world, statistical data has proven that an incident rate spike occurs predictably during all night activities. This means your chances of having an accident in the wee hours may be greatly increased, due to degraded performance. In aviation occurrences, the initial investigations often reveal a puzzling lack of judgment by otherwise competent aviators.

It seems logical that to combat fatigue, we need sleep — but sleep is something we know little about. Until recently, the theory was that we slept to give body and mind a good rest; but that has come under question. We now know that the brain is highly active for some of the time we spend snoring, and that we actually use almost as much energy when asleep as we do when awake and resting. There are two different types of sleep, known as REM (rapid eye movement — this is when we dream, and the brain activity is similar to when we're awake), and non-REM. Various theories claim that REM sleep plays a part in brain development, maintenance, learning and memory. Babies spend much more time in REM sleep than adults — it starts to decline as we reach our mid-forties, and becomes minimal in later years.

We may not know exactly why we need to sleep, but it is clear that we cannot function properly without it. Sleep-deprivation experiments show that people become progressively less effective as they become increasingly tired. Preventing people from sleeping has been widely used as a form of torture that leaves the victims increasingly miserable, confused and suggestible, and may even kill them.

Long-term sleep deprivation studies have been performed on our little friends, the laboratory rats, by Professor Allan Rechtschaffen, Ph.D., the director of the Sleep Research Laboratory at the University of Chicago. Dr. Rechtschaffen and his colleagues constantly deprived an otherwise cheery group of rats of all sleep, and demonstrated a 100% mortality rate within two or three weeks. The rats became increasingly debilitated, developed skin lesions, edema and stomach ulcers. They lost weight despite eating more than usual, suffered a drop in body temperature of 6°C, and eventually died. In an interesting twist, if the rats were allowed some non-REM sleep but no REM sleep, they lasted twice as long but still died eventually, after a period of sexual hyperactivity. A control group of rats that were permitted limited amounts of both REM and non-REM sleep, survived.

It's not clear by what mechanism the rats died, but some of their symptoms pointed to a failure of their immune systems. This is supported by research that has shown a link between diminished immune response and lack of sleep, but other studies seem to have shown the opposite. The jury's still out on that one. Dr. Rechtschaffen has drawn a link between overeating and sleep deprivation, as a result of these experiments.

We have all felt the onset of serious fatigue. When the body is ready to sleep, not even the threat of grave and immediate danger will stop it — I have personally dozed off while driving a car, flying a helicopter, and riding a motorcycle, as I'm sure most of you have. When Charles Lindbergh made the first solo non-stop flight across the Atlantic in 1927, he discovered that staying alert for 33½ hours in the air proved agonizingly difficult. He wrote this passage in his journal, after completing only 9 hours of flight:

"My eyes feel dry and hard as stones. The lids pull down with pounds of weight against the muscles. Everything is uniform blackness, except for the exhaust's flash on passing mist and the glowing dials in my cockpit, so different from all other lights... My world and my life are compressed within these fabric walls... My mind clicks on and off. I try letting one eyelid close at a time while I prop the other with my will. But the effect is too much, sleep is winning, my whole body argues dully that nothing, nothing life can attain is quite so desirable as sleep. My mind is losing resolution and control".

To combat fatigue, we must take a multi-faceted approach that involves the individual and the organization. On a personal level, we can strive to attain sufficient sleep, and be sure that it is of good quality. Sleep deprivation can be the result of everyday factors such as work patterns, jetlag, lifestyle, having young children, the use of alcohol, tobacco, drugs, etc. Relief can often come from dark, quiet, and comfortable sleeping quarters, exercise, a healthy diet, and following a disciplined schedule.

From an organizational standpoint, tasks or assignments where the risk of fatigue is high (shift work, late shifts, long periods away, high-flying contracts, etc.) should be recognized and identified. Certain tasks could be re-scheduled to a different part of the day, when the employee is more alert. Company policies must be pro-active in combating fatigue, and managers should learn to recognize signs that an employee needs a break. Tired employees, left on jobs because there is no replacement, seems to be common in our industry, but we all know this is an accident waiting to happen.

Some things to be aware of when trying to prevent fatigue:

• Time continuously awake: It is ironic that the practice of extending a duty day can increase productivity when used sparingly but can result in a decrease in productivity if used excessively. In one study by Professor Drew Dawson and colleagues at The Centre For Sleep Research in Adelaide, Australia, it was found that performance impairment after 17 hours awake was equivalent to a blood alcohol concentration of 0.05 percent (for which most provinces now suspend a driving licence for 24 hours). However, this study does not suggest people are unable to complete any tasks successfully when they have been awake for an extended period. Simple, over-learned tasks are relatively unaffected by fatigue. This is not the case however, with tasks requiring reasoning or judgment. Performance on these tasks will be impaired and additional fatigue proofing may be necessary if this performance decrement is to be managed safely.
  
  
• Time of day: The consistency and effectiveness with which a task is completed during a day shift is higher than during a night shift. In addition, fatigue recovery during a night off-duty period is considerably more efficient than recovery during a day off-duty period. These differences occur because the body's internal clock follows a 24-hour cycle and controls many functions including temperature regulation, performance capability and mood (figure 1). (roughly 08:00 - 11:00 and 20:00 - 23:00) and two periods during the day when sleepiness is the greatest (03:00 - 06:00 and 15:00 - 17:00). As is the case with length of time continuously awake, additional defences may be required if tasks undertaken during circadian low periods (especially between 03:00 and 06:00) are to be completed to the required standard. Similarly, allowances must be made if off-duty time coincides with a period of maximum alertness.
  
  
• Fatigue prior to duty: Individuals need about seven to eight hours of sleep in order to cope with ordinary demands of everyday life. To the extent that this need has not been met (perhaps as a result of early morning starts, out of phase attempts to sleep, poor sleeping conditions, administrative requirements or poor sleep discipline) individuals will be suffering from acute fatigue. Consequently their performance, especially on tasks requiring reasoning and judgment, will deteriorate as their on-duty time increases. While it's true there are individual variations and some tasks can be successfully completed by individuals who have had less than their required sleep, these are the exception.
  
  
• Sleep Debt or Cumulative Fatigue: Unfortunately, the body cannot store sleep. Although the loss of a small amount of sleep on a single night may not have a significant effect on performance, sleep loss is cumulative — and should it continue for several nights, it will build into a sleep debt. For example, the loss of one hour of sleep for a single night will be undetectable, after the loss of a second hour on the second night the individual will feel its effects, after the third night the effects of sleep loss on performance will be noticeable to an external observer. To manage the fact that it is not always possible for individuals to get all the sleep they need every night, they must be offered periodic opportunities to recover this sleep loss. Research has established that two nights of unrestricted sleep are usually sufficient to recover from even a relatively severe sleep debt. Therefore, to prevent the accumulation of excessive sleep debt, everyone should be provided with the opportunity for recovery sleep.

Figure 1: Flight safety Australia

So far, we've discussed fatigue from quasi-voluntary factors, but much sleep deprivation is involuntary. Physiological problems such as chronic stress, illness, or pain, can deprive the body of sleep, as can sleep disorders like night terrors, sleepwalking, narcolepsy, or sleep apnoea. If you suspect you may have a physiological problem or sleep disorder, seek qualified help.

Some of these problems can go unrecognized or untreated because the sufferer may not know that they are sleep-deprived. People with sleep apnoea, for instance, literally stop breathing for short periods during sleep, but may never realize they have a disorder. As sufferers sleep, the soft tissue in the throat relaxes and obstructs the upper airways, causing them to snore loudly and eventually to stop breathing, which causes the brain to rouse and demand oxygen. This arousal interrupts the deep-sleep cycle, and may occur more than a hundred times in a night, without the sleeper's awareness. As a result, the victim can be chronically fatigued, even though they spent a considerable time asleep. It is estimated that this condition afflicts four percent of the population, usually overweight, middle-aged men (so, does that make us helicopter pilots a high-risk category?).

Whether its cause is physiological or environmental, excessive fatigue does not belong in the cockpit, around the helicopter, or in the maintenance hangar. Be vigilant of yourself and your colleagues for signs of fatigue around your operation. Try to encourage a personal and company culture that recognizes and reacts to fatigue issues. Get to know the relationship between fatigue and drugs like caffeine, alcohol, and prescription and non-prescription medicines. Be aware of the risks associated with shift work and extended hours. Strive to get optimal rest, both physically and mentally, when off duty. Eating well, staying hydrated (see Vortex 3/2002), and maintaining a healthy lifestyle will all help prevent chronic fatigue. And by all means, take a nap if you need one!

Cats — The world's best sleepers

Thanks to Civil Aviation Safety Authority, Australia, Flight Safety Australia, article "Dead Tired", July-August 2001 http://www.casa.gov.au/.