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Feature—February 2008
Cold Shock and Swimming Failure
The real danger of cold water is not in the slow descent into hypothermia, but in the sudden symptoms of cold shock.
by Chris Brooks

It is well known by most sea kayakers that hypothermia is a serious risk. Getting chilled by exposure to water even as warm as 70°F (21°C) can eventually lead to a number of serious and even life-threatening physical and mental symptoms. Many kayaking books focus on the various stages of hypothermia, and while it is important to recognize them, the most serious and dangerous effects of cold water aren’t in a slow deterioration of abilities. For kayakers, a more realistic approach to the risks of cold-water immersion is to focus on the effects that happen in the first seconds of immersion and the following few minutes.

Water does not need to be drastically cold to kill you. You can drown very quickly if you are not mentally and physically prepared for sudden immersion. Since early times, the Inuit understood this danger. The waterproof paddling jackets—tuiliqs and kamleikas—used by early kayakers sealed together with their kayaks to provide full body coverage. Inuit whalers even developed dry suits. They consisted of sealskin or seal gut stitched together to form a complete covering that was worn by harpooners hunting whales from umiaks. The danger of exposure to cold water was well understood by the Arctic maritime peoples.

The presence of icebergs makes it obvious that kayakers should dress for cold water. On a warm summer day, when it may be comfortable to paddle in shorts and T-shirts, the risk of cold water may still be present, and dressing for the water is essential.

The Greek author Herodotus wrote about hypothermia back in 450 BC during the Persian/Greek wars commenting on mariners who died in sea battles in the Mediterranean Sea: “Those who could not swim perished from that cause, others from cold.” The first human experiment in cold water to test out the value of protective clothing, however, was not done until 1922. A doctor working for the Merchant Shipping Advisory Committee on lifesaving appliances, named Dr. Hill, immersed his laboratory assistant, Mr. Pergarde, in 62°F (16.6°C) water and concluded: “That the coverings wet or dry, protect a body from cooling down, and also that a rubber skin outside such coverings is a further great protection.”

The four stages where death can occur as a result of sudden cold-water immersion have been recognized by the scientific community since before World War II. These are: Cold Shock—kills in 3–5 mins. Swimming Failure—kills in 5–30 mins. Hypothermia—kills after 30 mins. Post-Rescue Collapse—kills during or hours after rescue.

The first two stages of immersion—cold shock and swimming failure—kill more than half the people who drown. It’s especially important to protect yourself from those first two stages, and to do that effectively, you need to know something about cold-water physiology and survival psychology. It’s also important to understand the denial of risk that is built into us all and causes many sea kayakers to paddle without wearing protective clothing or fail to make good plans and preparation prior to -launching. Up until about 50 years ago, no one really understood the reason why people suddenly immersed in cold water died. It was attributed to an inability to stay afloat and vague terms such as “exposure.” The steady loss of lives was simply accepted as fate and an occupational hazard.

As long as cold shock and swimming failure were considered only of academic interest, mariners and government regulators—and later survival training schools, outdoor-sportswear manufacturers and PFD manufacturers—concentrated their efforts on protecting people from the more protracted process of hypothermia. As a result, hypothermia is widely recognized and understood; however, even with today’s well established teaching programs, good regulations and much improved life-saving equipment, the two stages of immersion have often been overlooked. These are what I want to address.

Cold Shock
Over 15 years ago, Moulton Avery wrote an excellent article in this magazine (“Cold Shock,” SK, Spring ’91), noting that “immersion in cold water kills more sea kayakers than any other factor in our sport.” Cold shock has been observed in people sensitive to cold at water temperatures as high as 77°F (25°C). In water below 60°F (15°C), the effects of immersion become significantly life-threatening to everyone. The lower the temperature, the more severe the symptoms. The effects of cold shock are completely out of your conscious control. If you don’t protect yourself from cold water, they will happen to you whether you like it or not. If you really don’t believe that it will affect you, the next time you take a shower, turn the cold water on full blast and aim it at your belly button. You will soon be a believer.

Cold shock is caused by rapid skin cooling and can kill within three to five minutes after immersion. On initial immersion, you make a huge inspiratory gasp. Being immersed in near-freezing cold water is also extremely painful, and the sudden sensation of acute pain can accentuate the inspiratory gasp. The gasp is followed by severe hyperventilation: a fourfold increase in your breathing rate. It is not uncommon for you to be panting at a breathing rate of up to 65 times a minute in this critical stage, so there is no chance to hold your breath. Indeed, in water below 60°F, your breath-holding ability is reduced by 25–50 percent. If the water is near freezing, even after the effects of cold shock have settled, you’ll only be able to hold your breath for about 12–17 seconds.

The rapid breathing rate on its own can cause muscle spasms of the limbs and chest. All of these breathing irregularities increase the risk of drowning if you dip underwater or have a wave splash over your face. It only takes an inhalation of about five ounces (150 ml) of water to cause drowning. Drowning is a combination of cardiac arrest and suffocation. Your heart stops beating within one to two minutes after you have inhaled a significant amount of either fresh- or seawater. Water in the lungs compromises your ability to exchange oxygen, and because respiratory movements may occur for up to five minutes when underwater, water can continue to be drawn into your lungs.

Cold shock also causes a massive increase in heart rate and blood pressure. These cardiac responses may cause death, particularly in older, less healthy people.

The intense effects of cold shock last two to three minutes and will settle down after about five minutes of immersion. This period of involuntary reactions is just at the critical stage of sorting yourself out after your kayak has flipped and you’re working to adjust to the wind and waves and avoid inhalation of water.


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