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EXECUTIVE SUMMARY
1. Currently within Canada’s internal lakes and rivers,
there are numerous personnel being moved over water during the winter and
spring months in vessels without the provision of liferafts. Whether this is
an acceptable state of affairs is the question addressed in this research
paper.
2. The facts about the dangers of immersion in cold water
are as follows:
(a) There are four clear stages of immersion in which death can occur. These are:
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Cold shock (kills within 3-5 minutes after
immersion).
-
Swimming failure (kills within 30 minutes after
immersion).
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Hypothermia (kills after 30 minutes of immersion).
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Post rescue collapse (kills at the point of rescue
or up to several hours afterward).
(b) The cause of death associated with each
stage respectively is:
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Drowning, heart (circulatory) and respiratory
problems.
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Impaired physical performance leading to inability
to self-help, swimming failure and drowning.
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Deep body cooling leading to hypothermia and
drowning.
-
Collapse of arterial blood pressure leading to
cardiac arrest.
3. Up until 5-8 years ago, the problems associated with
stages 1-2 and 4 have largely been considered of academic interest only.
Stages 1, 2 and 4 can have a profound influence on survival probability as the
water temperature falls and the sea state worsens. With regard to the
condition of hypothermia, for a normally clothed "typical passenger"
this is accelerated if whole body exercise is performed in the water (i.e.
swimming).
4. Historically, there has been a preoccupation with
hypothermia. This has been reflected in the predictive survival curves based
on the time to reach hypothermia. Thus, excellent teaching and training
programs, standards and equipment have been developed aimed at reducing this
specific threat. However, it is now considered that the early responses to
immersion (stages 1 and 2) probably account for the majority of open water
immersion deaths.
5. Survival prediction curves are of limited value only.
This is because they do not take into account that death may occur from cold
shock, swimming failure and drowning during early hypothermia. The curves
should be revised to include these factors.
6. The initial responses (stage 1) peak in water between
10-15ºC. Swimming failure (stage 2) occurs much sooner in cold water than in
warm water, even in proficient swimmers. As a consequence, humans tend to
grossly over-estimate their swimming capability in cold water. This is a
little known, but central factor in the cause of death.
7. From all the combined research on cold water accidents
and scientific research, it has become clear that sudden immersion in cold
water, (i.e. below 15°C) is very dangerous. It should be avoided if at all
possible. Furthermore, a conscious decision to swim (and rescue oneself) or
stay floating still in the water should not be taken lightly without assessing
the pros and cons. It has now been shown that a person’s swimming ability in
warm water bears no relationship to that in cold water.
8. These scientific findings lead to practical advice
regarding the regulations requiring the carriage of liferafts and training of
operators of passenger carrying vessels.
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Wherever possible entry into water below 15°C should
be avoided. Direct entry into a life raft should be the objective.
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Transport Canada should use this philosophy in the
design, development and implementation of all new legislation. All vessels
operating in Canadian lakes and rivers at 15°C or below should carry
liferafts that can be easily launched and boarded by the entire crew and
passengers.
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The only exception to this should be where it is
physically or practically impossible to stow a liferaft. Under such
conditions the passengers must wear inflatable lifejackets when on board.
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Closeness to the shore or the carriage of EPIRB are
not a reason for waiving this requirement because death from cold shock will
occur within 3-5 minutes, and swimming failure in under 30 minutes. EPIRB
responses have averages between 90 minutes and 2 hours.
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The Marine Emergency Duties curriculum should be
amended to include the two new Canadian videos on cold shock, swimming
failure, hypothermia and post-rescue collapse.
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Even though there are well established teaching
programs, regulations and much improved life saving equipment, there are
still in the order of 140 000 open water deaths each year. What has been
overlooked is the significance of the first two stages - cold shock and
swimming failure as a cause of death. The precise details of these are
described in this report.
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