Sleep Deprivation

- by Fernanda Morley R.N. C.C.R.N

Sleep deprivation is inevitable on a long passage.

It is crucial to address this issue because decisions made by a tired crew have frequently been the cause of groundings, navigation errors or vessel failures. Studies of young soldier's cognitive abilities and vigilance demonstrate deterioration after just one night of sleep loss. After three nights of sleep loss, the soldiers exhibited severe impairment and in certain cases, paranoia and hallucinations.

To manage the deprivation part, we must understand what sleep represents.

WHAT IS SLEEP?

Sleep is a biological state that is caused by the discharge of specific neurons in certain parts of the brain. It involves an alternate cycle of non-rapid eye movement (NREM) and rapid eye movement (REM). The cycle consists of 80 minutes NREM followed by 10 minutes of REM. This 90 minute cycle is repeated 3 to 6 times during the night.

• Sleep occupies one third of our existence.
• It is necessary for our physical and mental health.

Sleep affects almost every physiological and psychological process. The body has normal low cycles called circadian rhythm lows. The most dramatic low time is between 2 A.M. and 6 A.M. The second rhythm low is not as dramatic in presentation and occurs between 2 P.M. and 6 P.M. These lows are represented by increased sleepiness.

When we do not get enough sleep, our body will physically try hard to make us sleep and psychologically we crave it. As a veteran shift worker, the primary focus of our night shift conversations was comparing how many hours of sleep we had that day. We were obsessed about sleep!

SIGNS OF SLEEP DEPRIVATION

Within a 24 hour period, the maximum sleepiness usually occurs in the middle of the night. When forced to be awake at this time, we can experience:

• increased sleepiness and fatigue
• weariness
• Poor attention and motivation span, especially for boring tasks requiring sustained concentration. Watching for freighters would be an example...boring but necessary and dangerous without sustained concentration.
• memory lapses
• decreased initiative,judgement ability and decision making
• increased irritability.

We learned that a nod and exchange of pertinent information with watch changes was sufficient for us on long passages...we like staying married!

MANAGEMENT

Sleep debt occurs since sleep loss is cumulative in nature. Prevention is important. The only cure is sleep.

• Allow at least 4 hours of uninterrupted sleep each day during sustained operations to maintain minimal performance.
• Encourage frequent naps...20 minutes or 90 minutes in length. A 60 minute cycle causes waking during the REM cycle of sleep. The person wakes up feeling more irritable less refreshed and disorientated.
• Plan naps before watches to enhance performance. Sleep can be cumulative as well...like storing it in a sleep bank.
• Try to change watches at circadian rhythm lows. Sleep deprivation exacerbates normal sleepiness during these times. The person relieving will be more more refreshed and can overcome the circadian rhythm low sleepiness more effectively than the person who has already been on watch for several hours.
• 3 to 4 hour watches are good intervals for a crew of 2 people. Remember to plan a 4 hour block of uninterrupted sleep after midnight.
• Use stimulants, like coffee, sparingly.
• Avoid use of alcohol, antihistamines, tranquilizers, motion sickness medications or any drugs that will sedate.
• Dimenhydrinate(Gravol) may be used to help you sleep once you are off watch. It is short acting and usually does not have a "hangover" effect. If you are taking certain medications, check with your Doctor about drug compatibilities before taking this drug. Be aware of your drug allergies. It is also a good idea to try this drug while on land. Find out what kind of response you have from it before heading offshore. You do not want any detrimental surprises!
• Create a comfortable below deck sleeping arrangement that is conducive to your sleep pattern. In my case, brushing my teeth and washing my face helps set up the pattern of sleep...sometimes an inconvenient time for a 20 minute workout!
• While on watch, have frequent small snacks of high carbohydrate foods. Avoid large amounts of protein. The carbohydrates will provide energy to fuel body function and prevent drowsiness. The large amount of protein will exacerbate drowsiness because the body must break down and digest the protein.
• After your watch and about 20 minutes before you plan to sleep, have a snack of high protein. This will help sustain your hunger longer and you will have a more uninterrupted sleep.

With proper management sleep deprivation can be reduced to a necessary nuisance instead of being a threatening issue when doing a long passage. Here's to safe passages!!!

Fernanda Morley R.N. CCRN. Morley Yachting Services
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See also: You Are Your Own 911 by this author.