Hypothermia & Cold Water Survival
Hypothermia is defined as subnormal body temperature - a lowering of the body core temperature. Unconsciousness can occur when the body core temperature drops from normal [98.6 F (37 C)] to approximately 86 F (30 C).
Cold Water Kills
Safety experts estimate that half of all drowning victims actually die from the fatal effects of cold water, or hypothermia, and not from water filled lungs. Loss of body heat is one of the greatest hazards to survival when you fall overboard, capsize or jump into the water. Cold water robs the body of heat 25-30 times faster than air. When you lose enough body heat to make your temperature subnormal, you become hypothermic.
Sudden immersion in cold water cools your skin and outer tissues very quickly. Within 10 or 15 minute, your core body temperature (brain, spinal cord, heart and lungs) begins to drop, your arms and legs become numb and completely useless. You may lose consciousness and drown before your core temperature drops low enough to cause death.
Body Hot Spots
Certain areas of your body are "hot spots" that lose large amounts of heat faster than other areas. These "hot spots" need special protection against heat loss to avoid hypothermia. The head and neck are the most critical areas. The sides of the chest and armpits, where there is little fat or muscle, are major areas of heat loss from the warm chest cavity. The groin region also loses large amounts of heat because major blood vessels are near the surface.
How Cold is "Cold Water"?
Cold water does not have to be icy ... it just has to be colder than you are to set water hypothermia in motion. A person who is wet, improperly dressed and intoxicated can become hypothermic in 70 degree F weather. The rate of heat loss depends on water temperature, the protective clothing worn, percent body fat and other physical factors, and most importantly the way you conduct yourself in the water.
NOTE: In waters of 40 degrees F or less, a person without a survival suit loses functional use of their limbs within minutes. Unconsciousness soon follows.
Different activities in the water consume varying amounts of body heat. The more energy (heat) you expend, the quicker you body temperature drops, reducing your survival time. As shown below, wearing a PFD (life jacket) can add hours to your survival time.
Hypothermia is defined as subnormal body temperature - a lowering of the body core temperature. Unconsciousness can occur when the body core temperature drops from normal [98.6 F (37 C)] to approximately 86 F (30 C).
Cold Water Kills
Safety experts estimate that half of all drowning victims actually die from the fatal effects of cold water, or hypothermia, and not from water filled lungs. Loss of body heat is one of the greatest hazards to survival when you fall overboard, capsize or jump into the water. Cold water robs the body of heat 25-30 times faster than air. When you lose enough body heat to make your temperature subnormal, you become hypothermic.
Sudden immersion in cold water cools your skin and outer tissues very quickly. Within 10 or 15 minute, your core body temperature (brain, spinal cord, heart and lungs) begins to drop, your arms and legs become numb and completely useless. You may lose consciousness and drown before your core temperature drops low enough to cause death.
Body Hot Spots
Certain areas of your body are "hot spots" that lose large amounts of heat faster than other areas. These "hot spots" need special protection against heat loss to avoid hypothermia. The head and neck are the most critical areas. The sides of the chest and armpits, where there is little fat or muscle, are major areas of heat loss from the warm chest cavity. The groin region also loses large amounts of heat because major blood vessels are near the surface.
How Cold is "Cold Water"?
Cold water does not have to be icy ... it just has to be colder than you are to set water hypothermia in motion. A person who is wet, improperly dressed and intoxicated can become hypothermic in 70 degree F weather. The rate of heat loss depends on water temperature, the protective clothing worn, percent body fat and other physical factors, and most importantly the way you conduct yourself in the water.
NOTE: In waters of 40 degrees F or less, a person without a survival suit loses functional use of their limbs within minutes. Unconsciousness soon follows.
Different activities in the water consume varying amounts of body heat. The more energy (heat) you expend, the quicker you body temperature drops, reducing your survival time. As shown below, wearing a PFD (life jacket) can add hours to your survival time.
PREDICTED
SURVIVAL TIME [for an average adult in 50 degree F (10 C) water] |
|
Drown
Proofing* |
1.5
Hours |
Swimming
Slowly |
2
Hours |
Treading
Water |
2
Hours |
Holding
Still |
2.75
Hours |
H.E.L.P.
Position |
4
Hours |
Huddle |
4
Hours |
Wearing
a PFD |
7
Hours |
| *Drown Proofing is a warm water survival technique. In order to conserve energy you relax in the water and allow your head to submerge between breathes. This technique is NOT RECOMMENDED FOR COLD WATER, since about 50% of heat loss is from the head. | |
How to Survive in Cold Water
If you suddenly find yourself in the water don't panic! Calmly follow the procedure below to increase your survival time. Minimize body heat loss. This is the single most important thing you should do. Take the following steps:
If you suddenly find yourself in the water don't panic! Calmly follow the procedure below to increase your survival time. Minimize body heat loss. This is the single most important thing you should do. Take the following steps:
- Do not remove clothing, despite what you have been told. Instead, button, buckle, zip and tighten cuffs, collars, shoes and hoods. Cover your head if possible. A layer of water trapped inside your clothing will be slightly warmed by your body and help insulate you from the colder water, slowing your rate of body heat loss. Put on a PFD if available.
- Devote all your efforts to getting out of the water. Act quickly before you lose full use of your hands and limbs. Climb onto a boat, raft or anything floating. Right a capsized boat and climb in. Most boats will support you even if they are full of water. If you cannot right a capsized boat climb on top of the hull. The object is to get as much of yourself out of the water as possible.
- Do not attempt to swim unless it is to reach a nearby boat, another person or a floating object on which you can climb or lean. Unnecessary swimming "pumps" out warmed water between your body and your clothing circulating new cold water to take its place. Unnecessary movement of your arms and legs pumps warm blood to your extremities, where it cools quickly, reducing your survival time by as much as 50%.
H.E.L.P. (Heat Escape Lessening Position) - Hold you knees to your chest to protect the trunk of the body from heat loss. Wrap arms around legs and clasp hands together.
Huddle - Huddling together with one or more people will extend survival time 50% longer than swimming or treading water.
Remain as still as possible, however painful. Intense shivering and severe pain are natural body reflexes in cold water which will not kill you but heat loss will.
First Aid for Hypothermia
Any person pulled from cold water should be treated for hypothermia. Symptoms include intense shivering, loss of coordination, mental confusion, cold/blue (cyanotic) skin - especially around the lips or fingers, weak pulse, irregular heartbeat and enlarged pupils. Once shivering stops, core body temperature begins to drop critically.
Your goal in treating hypothermia is to prevent further body cooling. Severe cases call for rewarming by trained medical personnel. In all cases, arrange to have the victim transported to a medical facility immediately.
What to do:
Any person pulled from cold water should be treated for hypothermia. Symptoms include intense shivering, loss of coordination, mental confusion, cold/blue (cyanotic) skin - especially around the lips or fingers, weak pulse, irregular heartbeat and enlarged pupils. Once shivering stops, core body temperature begins to drop critically.
Your goal in treating hypothermia is to prevent further body cooling. Severe cases call for rewarming by trained medical personnel. In all cases, arrange to have the victim transported to a medical facility immediately.
What to do:
- Gently remove victim to warm shelter. (Treat gently to prevent heart fibrillation/stress.)
- Check breathing and heartbeat. In cases of hypothermia, you should check very closely for as long as two minutes. Start CPR if necessary.
- Remove victim's clothing with a minimum of movement, cut them away if necessary.
- Lay victim in a level face up position with a blanket or other insulation beneath them.
- Wrap victim in warm blankets, sleeping bag or other warm covering.
- Apply heating pads or hot water bottles (wrapped in towels to prevent burns) to the head, neck, chest and groin.
- Do not apply heat to arms and legs or give them a hot bath. This forces blood out through the cold extremities and back to the heart, lungs and brain, which will further drop the core temperature. This can cause"after drop" which can be fatal.
- Do not massage or rub the victim. Rough handling may cause cardiac arrest.
- Apply warmth by direct body to body contact. Have someone remove their clothing and lay next to the victim, skin to skin. Wrap both in blankets.
- If person is alert enough, you can give them hot drinks. If they are unconscious or stuporous do not give them anything to drink. Never give alcoholic beverages.
Cold Water Drowning
Some apparent drowning victims may look dead, but may actually still be alive! A phenomenon called the "mammalian diving reflex" can be triggered by cold water. This reflex common to whales, porpoises and seals, shuts off blood to most parts of the body except the heart, lungs and brain and slows the metabolic rate. What little oxygen remains in the blood is circulated where it is needed most. Do not assume that a person is cyanotic and who has no detectable pulse or breathing is dead. Administer CPR and transport the victim to a medical facility as quickly as possible for specialized rewarming and revival techniques. People have been revived after being submerged for extended periods, some in excess of 45 minutes! So don't give up!
Material borrowed from www.hypothermia.org.
Some apparent drowning victims may look dead, but may actually still be alive! A phenomenon called the "mammalian diving reflex" can be triggered by cold water. This reflex common to whales, porpoises and seals, shuts off blood to most parts of the body except the heart, lungs and brain and slows the metabolic rate. What little oxygen remains in the blood is circulated where it is needed most. Do not assume that a person is cyanotic and who has no detectable pulse or breathing is dead. Administer CPR and transport the victim to a medical facility as quickly as possible for specialized rewarming and revival techniques. People have been revived after being submerged for extended periods, some in excess of 45 minutes! So don't give up!
Material borrowed from www.hypothermia.org.