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Fatigue Countermeasure Chat Questions

by Ray Oyung

February 20, 1998

I'd like to start by thanking everyone who participated in yesterday's chat with Susan Lee and me. It was loads of fun and I hope everyone had a chance to have their questions answered. If there are some questions that you might have thought of after the chat, please send them and ask for me. Your questions will get to me this way. There were some great questions and I enjoyed hearing from everybody. I noticed one question from Carl that I missed. I'll answer that one now. For those of you who missed the chat session, you can read through the thread at http://quest.arc.nasa.gov/aero/chats/2-19ro.html.

Carl asked about the weather in the places I flew to during my field studies. I mentioned a couple field studies that I participated in. One trip I mentioned took me from Taipei, Taiwan to Auckland or Christchurch, New Zealand about twice a week for 6 weeks. There was an interesting weather phenomenon on those trips. The flights were in July and August. Taiwan is in the northern hemisphere and was their local summer time (about 90 degrees F and 80% humidity. When the flight reached New Zealand, on the southern hemisphere, it was winter time (about 50 degrees F and rain). We had to put half our clothes in the hotel in Taipei (short sleeve shirts and light pants) and the other half at the hotel in Auckland (heavy sweaters and rain gear).

Sarah asked a question about the pilot who crashed in an airplane at Guantanamo Bay, Cuba and what that pilot could have done to avoid the accident. If you'd like to read more about this article before continuing, the information is in my second field journal. At the time this accident occurred, little was known about fatigue and the role it plays in aviation. Crew Resource Management (CRM) was just getting underway and the concepts were still being formulated. Very few organizations were implementing this important protocol into their standard operating procedures.

Education is a big piece of the solution. When science can be used to explain objectively the physiology behind human actions, we can then implement or apply these concepts into the operation. In this case, if the effects of fatigue were better understood and acknowledged, then the concepts of acute sleep loss, cumulative sleep debt, hours of wakefulness, time of day, or known sleep disorders would be tools available to the pilot to assess whether the safety of their flight could be compromised. The pilots in the accident at Guantanamo Bay performed their duties to the best of their abilities. We hope that our work has been, and will continue to be in the future, tools that can be provided to promote safety not only in aviation, but in all modes of transportation and 24 hour shift work operations.

Sarah asked another excellent question about the best tools people can use to avoid jetlag. I mentioned preventive and operational countermeasures. Preventive measures are used before the trip even starts. They include going to bed and waking up about the same time each day for a least 2 days before the trip. Everyone has a specific amount of time they need in order to be at their optimal performance during the waking hours. Some people need 6 hours of sleep and some people need 10 hours of sleep. I need 8 hours. How many do you need? You'll know what you're sleep need is, if you can go to sleep at a certain time (for me it's around 10:30 PM) and wake up without an alarm clock or someone waking you up.

Determine where you're going, what time your leaving, what time you'll arrive at the destination (local time) Then determine what you're home time would be at the destination. Here's an example. I'm going to Paris at 2:00 PM local time from San Francisco International Airport (KSFO). The flight to Paris is 11 hours and Paris is 9 time zones or hours away (time zones start from Greenwich, England on the Prime Meridian and increase by one meridian each direction around the Earth until reaching the 180-degree meridian on the other side). If you left SFO at 2:00 and the flight is 11 hours, the time at home would be 1:00 AM (2:00 + 11 hours later). Because Paris is 9 time zones away from SFO, the local time in Paris would be 10:00 AM (2:00 + 11 hours flight time + 9 time zones crossed). If the time is 10:00 AM arriving at the airport, then it would be about 3:00 AM (if the body were at home) upon arriving at the hotel. The body at this time thinks it's well past bedtime, but the sun is in the sky. This is where jetlag comes from.

With this information, and deciding you need to be awake after arriving in Paris, you could try to sleep on the plane for as long as you can. This will help relieve some of the sleep pressure thatŐs built up after cumulative hours of wakefulness. If you can get to sleep on the plane, try using ear plugs and an eye mask to help you stay asleep. The ear plugs will keep the noise from disturbing you and the eye mask will keep the light out.

Light plays an important role in the circadian system. It has an alerting affect and can shift the circadian rhythm backward or forward. So what exactly does light do? As light enters through the eyes, it follows a path to the back of the eyeball called the retina. The retina is where sensory cells begin to process this light. From there, the light follows through a cord called the optic nerve to the brain. There's a hormone in the brain that is secreted at night in the absence of light and stops secretion with the presence of light. This hormone is called melatonin. Have you heard of it before? Lots of studies are being performed at different labs around the country. It's considered useful to help folks get to sleep (just as we would want to try to get some sleep on the plane ride over to Paris). There are some great possibilities for melatonin use, but all the research to understand and properly use the substance has not been finished. Further studies are required to properly regulate it's use. Currently there are no regulations in place to standardize it's production.

There are some operational things that you can do too. In our chat, I mentioned caffeine. It's a chemical that's found in many drinks and food. Depending on individual differences (everybody has a different tolerance to effects of caffeine), caffeine will take effect about 15 to 20 minutes after consumption and last about 4 hours. If there is a reason you need to be awake at a certain time, try having a coke or chocolate bar (don't forget to brush your teeth). Since caffeine has an effect for about 4 hours, make sure not to take it if you want to be asleep within this time frame. Also note that caffeine is a diuretic. This means caffeine has a tendency to accumulate fluid in the bladder which makes you need to go to the bathroom.

If you want to read more about some of these concepts, check the Q&A from the questions archive at: http://quest.arc.nasa.gov/aero/question/humanfactors/.


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