| As the weather cools and we start
dreaming of tropical vacations for this winter, there is still lots of
great paddling up north. With summer crowds gone we have the opportunity
to enjoy our time on the water in a more quiet and intimate manner. In
addition to great delights, fall and winter paddling also provides greater
dangers, particularly for those unprepared for up close and personal
contact with chilling waters. Cold water and its effects are involved in
virtually all kayaking and recreational boating deaths. For example,
between 1985 and 1995, of the 182 deaths in the waters of the Pacific
Northwest, only 2 occured above 70o , with 133 involving water
between 40 - 60o . This article will review some information
which helps explain what makes cold water exposure so potentially risky,
review some strategies to minimize that risk, and raise a few hairs with
some stories of tragic, and mostly preventable, cold water deaths.
Some stories and some statistics
- an 18 year old canoeist capsized into 50o
lake water, and sank to the bottom before a rescuer towing the canoe could
rescue him. He was wearing jeans, a shirt and no PFD.
- nine elite marines, water survival instructors, capsized in 36o
water wearing sweatsuits and no PFDs. None of them survived the attempted
100 yard swim to shore.
- sixteen (16) Danish fishermen jumped into the icy waters of the North
Sea when their trawler sank in a storm. They were in the water for a 2 - 3
hours before being rescued. They walked across the deck of the rescue
vessel and went down into the galley to warm up. Each and every one
collapsed and died in the galley.
- an average adult person has a 50/50 chance of surviving a 50 yard swim
in 50o F. water.
- a 50 year old person in 50o F water has a 50/50 chance of
surviving for 50 minutes
what does it all mean?
Cold water can kill in three ways. The canoeist
probably suffered cold shock resulting in ineffective breathing,
rapid onset of panic, confusion, and inneffective swimming, struggling
briefly at the surface and then sinking. The marines may have managed the
initial cold shock, but the cold water rendered their extremities
neuromuscularly dysfunctional within several minutes, causing death by
drowning. The fishermen were a more classic case of severe
hypothermia, with body chemistry dysfunction causing cardiovascular
collapse and death.
The vast majority of kayaking deaths in cold water occur well before body
core temperature has fallen to the point of being dangerous. Even an
unclothed person in 34o water will maintain core temperature
for at least 20-30 minutes, so in this I article will concentrate on
understanding and preventing cold shock and drowning.
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).
The respiratory effects of cold shock have been estimated to account for a
third of cold water deaths, including many extremely fit and healthy
people. Review of reports of kayaking deaths by Charles Sutherland and
others suggests to me that a much higher percentage of paddlecraft deaths
are caused by cold shock. This has not been a favored topic of medical
research, but study of work done by Dr. Michael Tipton and others makes it
easy to understand the high level of risk that cold waters bring to the
unprepared in our sport(details below).
!!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 liter
gasp in 82o water and 3.0 liter gasp in 50o water
(i.e. nearly your entire lung volume), and in 50o 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 kayaker 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 50o, and near maximal
gasp was reached at 52o. These are summertime water
temperatures in some of the Northeast, and in most of it by November. This
information is not meant to scare people away from cold water paddling,
but certainly to caution them. Wonderful experiences may be had paddling in
these conditions, but if we wish not to become Coast Guard statistics we
must understand the risks and take measures to protect ourselves.
first, buy some protection
No, not that protection, this is about
Safe Paddling, 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 PFD is essential to keeping the head
out of water and prolonging survival.
does practice make perfect?
A definite maybe. It does appear that
repetitive immersions in cold water will allow the body to adapt and
moderate the cold shock response. After 6 - 8 immersions (daily, each time
long enough for core temperature to drop>2o), the cardiac
responses are substantially reduced. The breathing problems unfortunately
are much less responsive to such efforts at training. An more
important type of practice is to actually try out your cold water
clothing in a variety of conditions. The studies referenced in this
article seem to show a fairly consistent set of responses across a range
of water temperatures from 0o to as high as 60o .
There is individual variation though, and gear that works for your
paddling partner may not be adequate for you. Most people find it very
revealing to try floating in 30, 40, or even 50 degree water.
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. The newer
lycra/fleece wetsuits can however be a very comfortable, moderate cost,
no-excuse-for-not-wearing-it form of protection if you are confident that
your paddling does not put you at risk of prolonged immersion.
what about hypothermia?
There are many excellent resources on
prevention, recognition, and management of hypothermia. Some internet
resources are listed below so just a few points. Recognize and manage
hypothermia early - thought processes become quickly impaired and can
rapidly lead to decision making which turns an unpleasant situation into a
dangerous one. In a non-immersion situation, the greatest heat loss is
through the head and neck, insulation for these areas is most important.
In maintaining extremity function good head protection has been shown to
be more useful than better gloves or socks. Get out of the water! Water
will cool 20 - 30 times faster than air. Movement in the water, such as
swimming, will make this even worse. Severe hypothermia is a medical
crisis. The victim must be handled gently and knowledgably.
“No previously healthy person should die of hypothermia after he has been
rescued and treatment has been started.” (Cameron C. Bangs, M.D.).
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