Know the hazards of cold exposure on board

Gino Bottino, M.D.


Onboard cold exposures pose a hazard to boaters, especially when air and water temperatures start to fall. Knowing what to look out for can help you prevent and treat cold exposure injuries.

Local cold injuries are usually categorized as one of the following:

  • chilblain
  • immersion injuries of the hands and feet
  • trench foot
  • frostbite

Full-body exposure can be divided into three categories:

  • cold stress
  • hypothermia
  • immersion hypothermia


Although common, chilblain frequently goes unrecognized. Some people are especially prone to it, especially thin people and those with conditions such as diabetes and autoimmune disorders. Chilblain affects the skin, mostly the hands and face but also the lower extremities. It occurs in temperatures above freezing to 60 degrees Fahrenheit.

In chilblain, the skin appears bluish red with mild swelling. Sufferers may also feel itching, burning and occasionally pain when moving their fingers, hands and feet. If the exposure occurs regularly, chilblain can become a chronic persistent condition, leaving the skin discolored for long periods.

To treat, remove the offended areas from exposure, rewarm those areas and apply a soothing ointment (with or without steroids) to the skin.

Local immersion exposures and trench foot

Unlike chilblain, these incidents occur when the extremities are immersed in cold water or feet have been left in shoes immersed in water usually below 60 degrees but above freezing. Wet feet lose heat 25 times faster than dry feet and the body restricts blood flow to these areas, causing injury from a buildup of toxic products and a lack of oxygen after prolonged exposure.

Clinical manifestations include swelling, skin discoloration and blistering as well as numbness, tingling, pain, itching and muscle cramping. Like chilblain, trench foot can be chronic, and secondary infections are common. Treatment is the same as for chilblain.


The term “frostbite” is reserved for those injuries where tissue destruction has occurred. Pain happens early on or not at all. As the tissues freeze, only a sensation of numbness remains. The patient may not even be aware of the frostbite until someone mentions it. When the damage is superficial, the surface feels hard, but the underlying tissues feel soft when gently and firmly depressed. In deep frostbite, the entire area feels hard. Frostbite can cause permanent injury leading to amputations.

Treatment involves getting the patient to a medical facility followed by immediate, rapid thawing and rewarming of the exposed areas. In deep frostbite, the rewarming process can lead to serious complications and death, which is why patients should be transported to a treatment facility before rewarming occurs. Even moderate-size superficial frostbite can lead to serious complications and must be taken seriously. In situations when transportation to a treatment facility may be delayed, provide general warmth to the patient and plenty of fluids. Do not give alcohol, and do not attempt to rewarm the affected area; it’s safer to wait and transfer the patient to an adequate facility for medical attention.


Anytime you are exposed to temperatures below skin temperature, which averages around 92 degrees, you are subject to hypothermia. Six factors influence the development of hypothermia:

  • The severity of the exposure (how cold it is)
  • The physical medium of the exposure (water exposure cools the body 25 times faster than air)
  • The duration of the exposure
  • The degree of protection you are wearing or can achieve
  • Your body type, size and general condition as well as sleep deprivation
  • Alcohol, drugs and medications you take, and any diseases you may have.

It’s easy to recognize the signs and symptoms of hypothermia in others, but sometimes it’s hard to see them in ourselves. As the body’s temperature drops to less than 98 degrees, your skin becomes pale, you may develop a headache and start shivering. At under 95 degrees, you may have trouble thinking clearly, stop shivering and become uncoordinated, making completing tasks quite difficult. At body temperatures under 86 degrees, you enter a moribund state in which signs of death are present. Death occurs below 82 degrees.

All phases of hypothermia require treatment. Handle patients with a minimum of movement. Watch for vomiting. If it occurs, make sure the person vomits in a downward direction to avoid aspiration (suffocation).

Do not massage; this makes the inner body colder by forcing cold blood in. Rewarm the patient slowly by moving them into a warm area or shelter. If the person has advanced symptoms—no shivering, confusion, slow breathing and pulse, call for help and transfer them to a medical facility.

When you’re on board and transfer could be delayed, nude body contact with a warm individual under a regular blanket works best. A nude body on each side of the victim may be needed in severe cases. No alcohol or stimulants should be given. Provide warm liquids only. It’s important to provide emotional support and reassurance; a strong will to live greatly enhances survival.

Be aware that simply initiating treatment for severe hypothermia does not ensure survival. Rapid rewarming can lead to a sudden death syndrome, which can sometimes be reversed by cardiopulmonary resuscitation. This is why rewarming should be done in a medical facility if possible. Obviously, knowing CPR can be very helpful, and I encourage everyone to get training.

HELP and HUDDLE positions can extend hypothermia survival time

Immersion hypothermia

When a person is wet from any cause, their body temperature drops 25 times faster than when dry. It can occur in water temperatures under 70 degrees. In the water, use the HELP position to reduce heat loss (Heat Escape Lessening Posture). To assume this posture, cross your feet and bring your knees up to your chest, with your arms pulled into your sides across your knees. If you’re in a group, huddling in groups of two or three works best.

Treatment begins by removing the person’s wet clothes and drying them. Then, proceed as detailed previously.

Like everything else on board our boats, prevention is the key to a safe and happy trip. Knowing the dangers of cold exposures and how they occur will prepare you to handle these situations and avoid them when possible.

If you must enter cold water, always go feet first to lessen the shock to your system and allow for cold adaptation. Wear plenty of protection; clothes help by trapping air and warming the water around your body, reducing the circulation of cold water. Never dive into cold water as this can result in acute vertigo, disorientation, vomiting and cramps. Do not eat or drink (especially alcohol) before going into cold water. If it’s an emergency, wear as many articles of clothing as practical, and always wear a life jacket!

Gino Bottino, M.D.

Gino Bottino, M.D., has wide experience in medical practice and emergency medical matters. A member of United States Power Squadrons First Aid Support Team (FAST) and the Safety Committee, Gino also has a background in competitive sail racing and is familiar with health-related problems afloat.

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