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Welcome to this information section - here you
will find results of research we have done into the effects of cold water when
you fall into cold water.
Over the next few web updates we will produce further results on Wind Chill
factors, Hypothermia etc.
read about
Hypothermia
Please let us know if you have any comments
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Cold Water Immersion
Cold water immersion
has an immediate and severely debilitating effect on the body. Cold water shock
results in a variety of problems, predominant among these is gasping for air.
This can result in the inhalation of water and subsequent choking. Additional
effects include loss of coordination, muscle spasm, disorientation,
hyperventilation, and even possible cardiac arrest. Any of these effects can
make it difficult, sometimes impossible for a sailor to swim. Cold water
immersion is often a sudden, serious, and potentially deadly situation.
It seems that many sailors just don't
realize how cold the water they are sailing in really is, or how quickly they
can succumb to it's effects. Generally speaking, immersion in water with a
temperature of less than 10 ° c can produce the effects noted above.
Cold Shock
Cold shock occurs when rapid cooling of the skin triggers a cluster of heart and
breathing responses. The cardiac responses include an increase in heart rate of
40 -50%, and an increase in cardiac output of 60 - 100%, which combined with
vasoconstriction of the extremities results in an average blood pressure
increase to 175/93. Although a substantial strain on the heart, these changes
are not likely to be a problem for a healthy, fit person but may be dangerous
for those with underlying heart disease or hypertension (there have been cases
of apparently near instant cardiac arrest on cold water immersion).
!!Gasp!!
Sudden immersion in cold water results in an involuntary (that means you can not
stop it, and yes, that means all of us) gasp, followed by 1 - 3 minutes of
involuntary (yes, that still means all of us) hyperventilation.
Specific data are: 2.0 litre gasp in 26 ° c water and 3.0 litre gasp in 10 ° c
water (i.e. nearly your entire lung volume),
and in 10 ° c water a 600 - 1,000
percent increase in ventilation (air in and out) in the first minute. This
hyperventilation results in a profound lowering of blood carbon dioxide levels
and raising of blood pH levels, which causes a large risk of ventricular
fibrillation (“cardiac arrest”), muscular tetany (cramps), and cerebral
vasoconstriction which starves the brain of oxygen, causing disorientation and
confusion.
These effects, coupled with changes in lung mechanics caused by the pressure of
water on the abdomen and chest result in subjective feelings of inability to
breathe and panic typically lasting 1 - 3 minutes. Most importantly for survival
of a capsized dinghy sailor is a sharp reduction of maximal breath holding, for
example - in one study from a mean of 45 seconds pre-immersion to a mean of 9.5
seconds on immersion in 41o water, with one subject averaging less than one
second breath holding upon immersion. It is easy to see how these effects of
gasp, hyperventilation, and impaired breatholding would result in prompt
catastrophe upon a fall into choppy water or a capsize.
How
cold is cold water?
Not, apparently, all that cold. The maximal hyperventilation response is reached
at , and near maximal gasp was reached at 11 ° c. These are summertime water
temperatures in some of the Northeast, and at the beginning of the season
temperatures can easily have fallen to 5 ° c by March. This information is not
meant to scare people, but to caution them.
First,
buy some protection
No, not that protection, this is about Safe Sailing, not Safe S*x, but wearing
the right stuff can still make a big difference.
That means a wetsuit or drysuit. Protecting the front of the torso and back of
the chest will have the most profound effect on moderating the respiratory
responses, while protecting the extremities has the greatest benefit in
moderating the cardiac responses.
Most of these responses are worsened by head immersion, which also markedly
hastens the progression of hypothermia (if you manage to survive the cold
shock), so head protection is important. Since both cold shock and later
hypothermia inhibit effective swimming, wearing a buoyancy aid is essential to
keeping the head out of water and prolonging survival.
Make mine dry, very dry
In the wetsuit/drysuit debate I readily admit that I am a dry suit chauvanist,
finding a drysuit much more comfortable.
For the prevention of cold shock a well fitting wetsuit will be more than
adequate, provided it is truly well fitting and substantially slows the contact
of cold water with your torso.
If loosely fitting, with overgenerous neck and arm openings there may still be a
sufficient gush of frigid water to trigger these cold shock responses. Even with
a well fitted wetsuit many find that first cold water flush unpleasant, and for
long term survival in cold water a drysuit with appropriate insulation can be 2
-3 times more effective in staving off hypothermia.
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