How to Survive in Cold Water

Post by: Dee White
11 September 2011

Drowning

Whether your preferred mode of transport is a small dinghy or a luxury yacht or cruiser, there is a chance that you might be unfortunate enough to fall overboard. WHAT HAPPENS THEN?

Remember – water is usually COLD

Normal body temperature is 37°C. Shivering and the sensation of cold can begin when the body temperature lowers to approximately 36°C. Amnesia can begin to set in at approximately 34°C, unconsciousness at 30°C and death at approximately 26°C. Sudden immersion in cold water, below 16°C, prompts a series of reflexes that will vastly increase one’s danger of drowning, unless interrupted.

The 4 stages of Cold-Water Immersion

Stage One – Cold Water Shock (CWS) – can be lethal in minutes.

  • Begins immediately, peaks in 30 seconds and lasts 2-3 minutes.
  • Characterised by instantaneous gasping, followed by rapid breathing. If the victim’s head is under water drowning can occur immediately, without the victim returning to the surface! The rapid breathing can decrease the normal levels of CO2 in the blood and can lead to confusion, dizziness or unconsciousness. Victims may not be able to differentiate between up and down.
  • Heart rate, blood pressure and cardiac workload increase which can result in heart attacks or cardiac arrest.
  • Breath holding ability decreases dramtically  from a minute or so to less than ten seconds, which may complicate the victim's ability to escape from a capsized boat.

Stage Two – Functional Disability

  • Sets in after the initial cold shock and lasts approximately 30 minutes.
  • Muscles and nerves in the legs and arms cool significantly.
  • Swimming efforts become increasingly difficult and ineffective.
  • Manual dexterity and grip strength are decreased. Victims find it increasingly difficult to grap lifelines or floatation devices, climb ladders or assist the rescuers.

Stage Three – Hypothermia

  • Usually begins after about 30 minutes of immersion.
  • Violent, painful shivering occurs.
  • Confusion and lethargy set in and efforts to remain afloat become feeble.
  • As core temperature drops, victims assume “instinctive drowning response” (loss of voluntary control of arms; arms extend laterally in an effort to press down on water, little or no supporting kick). Unconsciousness and/or submersion and drowning are only 20 to 60 seconds away!

Stage Four – Post – Rescue Collapse

  • The victim may be rescued, but they are still at risk. Core temperature may continue to drop even after rescue. If heart temperature falls to around 25°C, cardiac arrest can occur.
  • Hypothermia slows normal body responses to changes in posture or skin surface warming, so if a rescued victim is left upright, sudden drops in blood pressure may cause unconsciousness or cardiac arrest. Metabolic changes (e.g. acidosis) caused by hypothermia can also contribute to fatal cardiovascular events.

How to survive

Cold water robs the body’s heat approximately 25 times faster than cold air. If you should fall in the water, make every attempt to get out quickly.

  • Don’t fall in! Although many accidents are unavoidable, take every precaution to stay safe, even when your boat is moored or at anchor.
  • Life Jackets are probably the most important factor in cold water survival. They will keep the victim’s face above water in the initial cold shock phase, when gasping could lead to immediate drowning. They also allow victims to adopt heat-conserving postures (hands crossed over chest, arms pressed closely to sides, knees drawn towards chest, ankles crossed). Without a Life Jacket, the effort used to retain these positions could involve even more heat loss.
  • In the absence of a Life Jacket, victims should not remove clothing, as it actually provides buoyancy and helps conserve body heat.
  • Avoid swimming, as physical exercise causes the body to lose heat at a much faster rate than remaining still. Blood is pumped to the extremities and quickly cooled. Even strong swimmers only have a 50/50 chance of swimming half a mile in 10°C water. If swimming is absolutely necessary, use a stroke that keeps the head above water (i.e. breaststroke). Use small movements when treading water.
  • If floating wreckage is very close, get out of the water and stay out. The rate of body heat loss is around 25 times greater in water than in air of the same temperature, even when the body is wet.
  • Many accidents involve small boats which can be righted and re-entered. Most boats, even when filled with water, will support the weight of its occupants, so if you cannot right it, climb on top of it.
  • The major heat loss areas are the head, neck, armpits, chest and groin. If you are not alone, huddle together or in a group facing each other to maintain body heat.

Preparation

  • Make sure your boat and equipment are in first class condition.
  • Check the weather forecast before setting out.
  • Always tell someone where you are going and when you expect to return.
  • Dress in several layers of warm clothing.
  • Always wear your Life Jacket, or have it readily available to be grabbed at a second’s notice if conditions change. Be very aware though that some accidents occur when you are not expecting them and there are often no warnings. Life jackets are pointless unless used.
  • Clip on your Safety Line when weather and situation dictate it. Keep Life Jacket and Safety Line together and know where they are.
  • Make sure you practise “Man Overboard” drill regularly in a wide range of conditions.
  • Ensure you have a working VHF and mobile phone aboard.
  • Be aware of the water temperature.

Treatment

Mild hypothermia victims, who show only symptoms of shivering and who are capable of rational conversation, may just require removal of wet clothing and replacement with dry clothes and blankets. But they should be watched carefully in case their condition deteriorates.

  • In more severe cases, where the victim is semi-conscious, immediate steps must be taken to begin the rewarming process.
  • Get the victim out of the water and into a warm environment. Remove clothing only if it can be done with a minimum of movement of the victim’s body. Do not massage the legs or arms.
  • Lay the semi-conscious person face up with the head slightly lowered, (unless vomiting occurs). This allows more blood to flow to the brain.
  • Immediately attempt to warm the victim’s body core. If available, place the person in a bath of hot water at a temperature of 41 to 43°C. It is important that the victim’s legs and arms be kept out of the water to prevent “after-drop”. This occurs when the cold blood from the limbs is forced back into the body resulting in further lowering of the core temperature. After-drop can be fatal.
  • If a bath is not available, apply hot, wet towels or blankets to the victim’s head, neck, chest, groin and abdomen. Do not warm up legs or arms.
  • If nothing else is available, a rescuer may use their own body heat to warm up a hypothermia victim.
  • Never give alcohol to a hypothermia victim.

Some important facts to remember

Most victims recovered in cold water in “near drowning” cases show these typical symptoms of death.

  • Cyanotic (blue) skin colour
  • No detectable breathing
  • No apparent pulse or heartbeat
  • Pupils fully dilated (open)

However, these symptoms do not always mean that the victim is dead, but they are the body’s way of increasing its chances of survival. Scientists call it the “mammalian diving reflex” and it is most evident in marine mammals such as whales, seals and porpoises. The blood is diverted away from the arms and legs to circulate (at the rate of only 6-8 beats a minute in some cases) between the heart, brain and lungs. Marine mammals have developed this ability to the point where they can remain under water for extended periods of time (over 30 minutes in some species) without brain or body damage.

In humans the diving reflex is not so pronounced as in other mammals, but factors which can enhance it in humans are :-

  • Water temperature – less than 21°C or colder, the more profound the response and perhaps the more protective to the brain
  • Age – the younger the victim, the more active the reflex
  • Facial immersion – facial cold water stimulation seems to set off these reflexes.

The diving reflex is a protective mechanism for humans in cold water immersions, but the symptoms may confuse the rescuer into thinking the victim is dead. CPR should be started immediately, remembering that many victims have been successfully resuscitated after what may have seemed like a fatal length of time in the water.

Author - Dee White