Connecticut Water Trails Association
|
Connecticut Water Trails Association |
|---|
|
Connecticut Water Trails Program Paddling Safety Cold Water Safety - Cold Water Immersion
Some Stories and 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 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 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.
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 paddling 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, this 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. A much higher percentage of
paddlecraft deaths are caused by cold shock and it makes it easy to
understand the high level of risk that cold waters bring to those
unprepared in our sport. !! 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 paddler 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 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 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 you wish not to become Coast Guard statistics you must understand the risks and take measures to protect yourselves.
First Buy Some Protection This is about safe paddling and wearing the right
stuff can 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. Dressing Wet or Dry ? For the prevention of cold shock a well fitting
wetsuit is 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 and some find a drysuit more comfortable. What About Hypothermia 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.
| |||||||||||||||||||||||||||||||||||
 |
|
