Non-freezing cold injury
1The lesson in plain words
Feet that stay cold and wet for many hours can be damaged without freezing. Keep them dry, warm them slowly, and never rub them.
What it is
Non-freezing cold injury (NFCI), also called trench foot or immersion foot, is damage to the nerves and blood vessels of the feet or hands. It is caused by hours or days of cold and wet at temperatures above freezing. Sailors get it in wet boots on long cold watches, in a flooded cockpit or in a liferaft.
Signs
At first the feet feel cold and numb, and look white or blotchy; the casualty may feel clumsy or as if walking on cotton wool. After warming they turn red, hot and swollen, and become very painful. The pain and sensitivity to cold can last for weeks or months, so early care and prevention matter.
First aid
Remove wet boots and socks, dry the feet gently and keep them in room-temperature air, raised a little. Warm them slowly: do not use hot water, a heater, or rubbing and massage, which damage the tissue further. Avoid walking on badly affected feet. Pain often gets worse as they warm. Get radio medical advice.
Prevention
Change into dry socks every watch, and keep a dry pair in a sealed bag. Avoid tight boots and socks that cut off the blood flow. Move your toes and feet often, keep your whole body warm and fed, and check your feet daily. Do not smoke: it narrows the blood vessels.
Frostbite
Frostbite means tissue has frozen; NFCI damages cold, wet tissue without freezing.
2Key data
- Cause
- Hours to days of cold and wet, above freezing
- Early signs
- Cold, numb, white or blotchy feet
- After warming
- Red, hot, swollen, very painful
- First aid
- Dry, room-temperature air, raise; no rubbing, no hot water
3Key points
- 1
NFCI comes from long cold and wet, without freezing.
- 2
Numb, white feet that turn red, swollen and painful after warming.
- 3
Dry the feet and warm them slowly in room-temperature air; never rub or use hot water.
- 4
Prevent it: dry socks every watch, loose boots, move your toes, check feet daily.
4Frequent mistakes
Wrong: Plunge cold, numb feet into hot water to warm them quickly.
Right: Warm them slowly in room-temperature air. Rapid heat damages injured tissue.
Wrong: Rub numb feet hard to restore feeling.
Right: Rubbing and massage cause more damage. Dry them gently and raise them.
5Practice case & exam keys
After 36 hours of a wet, cold delivery trip in sea boots, a crew member says his feet have been numb since the morning. Under the socks they look white and wrinkled.
Show the answer
Suspect non-freezing cold injury. Take off his boots and socks, dry his feet gently, rest them slightly raised and let them warm slowly at room temperature; keep his body warm. Do not rub his feet or put them in hot water. Expect pain and swelling as they warm. Get radio medical advice, keep him off his feet, and change the whole crew into dry socks.
Exam keys
- NFCI (trench or immersion foot): long cold and wet, not freezing.
- Signs: numb, white feet; then red, hot, swollen and painful.
- First aid: dry, slow warming, raise; no rubbing, no direct heat.
- Prevention: dry socks, loose footwear, movement, daily foot checks.
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