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 kayaking and canoeing 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
occurred above 70 degrees, with 133 involving water between 40 – 60
degrees. 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 50 degree 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 36 degree
water wearing sweat suits 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 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 50 degree F. water.
– A 50 year old person in 50 degree 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 ineffective 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 34 degree 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
paddle craft 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 82 degree
water and 3.0 liter gasp in 50 degree water (i.e. nearly your entire
lung volume), and in 50 degree 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 41 degree 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 breath
holding 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 50 degrees, and near maximal gasp was reached at 52
degrees. 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
wet suit or dry suit. 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 > 2 degrees), the cardiac responses are
substantially reduced. The breathing problems unfortunately are much
less responsive to such efforts at training.

A
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 0 degrees to as high as 60
degrees. 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 wet suit/dry suit debate, I readily admit that I am a dry suit
chauvinist, finding a dry suit much more comfortable. For the
prevention of cold shock a well fitting wet suit 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 wet suit, many find that first cold water flush
unpleasant, and for long term survival in cold water a dry suit with
appropriate insulation can be 2- 3 times more effective in staving
off hypothermia. The newer lycra/fleece wet suits 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.

From
the Grand Canyon Private Boaters Association email list.