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Thermal Underwear Cold Weather Survival for Seafarers

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Hypothermia icy cold weather winter survival medical information for the marine professional for keeping warm with thermal underwear

Dear Seafarer,

If your ship ever goes to cold countries, you should undoubtedly have heard of Hypothermia. If you haven't, you should learn something about it. Your very life may depend on knowing the information below:

Hypothermia is a condition marked by an abnormally low internal body temperature. It develops when body heat is lost faster than it can be replaced. Normal muscular and cerebral functions become impaired and death can follow if it becomes worse. This takes place below 96 F and lower.

Signs of hypothermia include confusion or sleepiness; slurred speech or shallow breathing; weak pulse or low blood pressure; stiffness in the arms or legs or poor control over body movements. Severe hypothermia can cause an irregular heartbeat, leading to heart failure and death.

Symptoms of Hypothermia

  • Shivering is typically the first sign of hypothermia. It eventually becomes uncontrollable. However with severe hypothermia, shivering stops. One of the key indicators that the victim has moved from mild/moderate hypothermia to severe hypothermia is that he/she is no longer shivering.
  • Behavior changes like complaining, difficulty in speaking, and uncoordinated movements. Victims will struggle to perform simple tasks like walking a straight line or zipping up their coat. With severe hypothermia, behavior changes from erratic to apathetic to unresponsive. Uncharacteristic behavior like inappropriate excitement or lethargy, poor judgment, and poor decision making are common.
  • Cold, pale and blue-gray skin due to constricting blood vessels. May develop into a coma, with dilated pupils making it difficult to determine if the victim is alive or dead.

How Heat is Lost from the Body

  • Convection: Heat is carried away from the body by currents of air or water. Wind chill is an example of convection.
  • Conduction: Transfer of heat between two contacting surfaces. Water conducts heat 25 times faster than air and steel is even faster than water. Generally conductive heat loss accounts for only about 2% of overall loss. However, with wet clothes the loss is increased 5 times.
  • Evaporation: Heat loss when water is removed from the body during sweating and respiration.
  • Radiation: The loss of radiated heat from a warm body to a surrounding colder environment. This is more significant on cold, cloudless nights. Factors important in radiant heat loss are the surface area and the temperature gradient.

    It is important to recognize the strong connection between fluid levels, fluid loss, and heat loss. As the body moisture is lost through the various evaporative processes the overall circulating volume of water in the body is reduced, leading to dehydration. This decrease in fluid level makes the body more susceptible to hypothermia.

Field Treatment for Hypothermia

The basic principles of re-warming a hypothermic victim are to conserve the heat they have and to replace the body fuel they are burning up to generate that heat.

  • Reduce Heat Loss. Find shelter from the wind, and cold. This could be under a tree, in tent, or in a sleeping bag. If at all possible, get the victim off of the ground (a foam pad would be ideal). Remove any wet clothing and replace with layers of dry clothing, increased physical activity.
  • Add Fuel and Fluids. Keep a hypothermic person adequately hydrated and fueled. Give them warm, sweet liquids but NO coffee or tea - and NEVER ALCOHOL!
    • Alcohol - a vasodilator - increases peripheral heat loss
    • Caffeine - a diuretic - causes water loss increasing dehydration
    • Tobacco/nicotine - a vasoconstrictor, increases risk of frostbite
  • Provide Heat Source. Light a fire or a stove.
  • Seek Medical Attention as quickly as possible. Never leave a hypothermic victim alone.

Prevention of Hypothermia
  • Dress Appropriately. Wear clothing to keep the warmth. Avoid cotton!
  • Stay Dry - be aware that water comes from both the outside (environment) and the inside (perspiration). Stay out of the wind if possible.
  • Keep Your Body Burning. Stay hydrated, and eat foods like carbohydrates and proteins to provide energy.
  • Conserve Your Energy. Exhaustion leads to a quicker onset of hypothermia.

Man Overboard

If you fall overboard, is it better to swim or not to swim? Consider your circumstances carefully before deciding to swim.

  • Swimming is an option but this leads to faster heat loss and exhaustion.
  • Even a strong swimmer would not be able to swim more than one kilometer in calm water. Cramp and hypothermia develop more quickly, usually a victim becomes semiconscious and is likely to drown.
  • Swimming increases heat loss (increase by 35-50%) and is not recommended if you are more than one kilometer away from shore. Adopt a heat conserving strategy (help or huddle) instead.
  • Treading water also leads to rapid heat loss. Avoid if possible. Wear a PFD (Personal Floatation Device) Do not remove clothing or shoes, they provide insulation (a jacket can also be used to trap air and assists floatation).


It's important to keep warm and dry during the windy, cold, winter months. Dressing appropriately can make a big difference. Wear several loose, warm layers. Thick wool socks and a cap can combat winter's chills. At night, use extra blankets because hypothermia can develop during sleep. Thermal underwear are excellent for keeping the heat in your body.

Get plenty of rest. Fatigue makes you more vulnerable to subnormal heat and cold. Eat nutritious foods, and exercise moderately. Limit your alcohol intake because alcohol speeds up body heat loss.

I hope this information will serve you well when you travel to the extremely cold regions of the world.



Marine Engineer World


P.S. We have located the perfect thermal underwear for you here. These should be standard clothing for every professional seafarer and marine personnel working in Cold Regions. They have given me excellent comfort even in icy arctic cold weather conditions and I want you to experience that freedom too! The military has also tested many products that will withstand extreme weather.


2003 Yoon Chee Tuck    Contact me

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