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Cold-Water Protection (Pg
24-25)
Water draws heat
from the body 25 times faster than air. Like wind chill, the effects
of cold water increase when the current is fast. Sudden immersion in
snowmelt or spring runoff is extremely debilitating, causing a
substantial loss of strength, coordination, and judgment rather
quickly. All cold-weather paddlers should select the gear needed for
the insulation required to stay warm.
Drysuits and
wetsuits both work effectively in cold water. In a wetsuit, air is
trapped inside the neoprene material, and the suit fits snugly
enough to keep most cold water out. What little water gets inside is
quickly warmed by the user's body heat. Drysuits create an actual
barrier between the environment and the paddler, eliminating that
initial “cold-water shock.” Paddling drysuits are made of a
waterproof material with latex seals at the neck, wrists, and
ankles. The paddler regulates the inside temperature by adding or
removing layers of insulation, such as pile or polypropylene. In
milder weather, a water-proof shell top or paddle jacket can be
combined with pile clothing or a wetsuit for comfort.
The first goal is
to protect the torso, which shelters the "core" of the body. The
greatest heat loss occurs in the armpits and crotch. Next, pay
special attention to the extremities. The head radiates a surprising
amount of heat. If the helmet alone is not warm enough, pile or
neoprene liners can be worn inside. Neoprene booties cover the
paddler's feet, and if the sole is thick enough they can be used
alone. Another alternative is to wear lightweight neoprene socks
inside sneakers. In cold weather a boater's hands quickly lose the
strength and sensitivity needed for effective paddling. Neoprene
gloves or mittens are one answer; mittens are warmer than gloves,
but more awkward and harder to find. Pogies (mittens that cover both
the hand and the paddle) permit direct hand-to-paddle contact for
maximum control with a kayak paddle. In borderline weather, carry
hand protection along for possible use later in the day.
Hypothermia (Pg 129-130)
The human body
functions only within a narrow temperature range. Warmth must be
maintained to support the chemical and metabolic functions
sustaining life. When the body cools below acceptable levels
(hypothermia), there is a significant loss of strength,
coordination, and alertness. Patients suffering from hypothermia may
become unable to paddle effectively or to assist in their own
rescue.
Paddlers must often contend with water that is dangerously cold. The
effects are felt with surprising speed. Just like the effects of
windchill, those of moving water produce an enhanced cooling effect
that multiplies the impact of co!d water. But hypothermia does not
always occur in cold weather. Unexpected summer storms can soak an
unprepared boater, or the wind can steal heat from his body. An
unprotected boater who takes a long swim on a cool, overcast day may
find it hard to rewarm. An injured victim may experience hypothermia
as shock sets in
Levels
of Hypothermia
The human body has three layers; an outer superficial layer, an
intermediate layer; and the inner core. The superficial layer
consists of the skin and subcutaneous tissue; the intermediate layer
is made up of the extremities, skeletal and muscular tissues, and
some lesser organs; the inner core contains the most critical
organs; the heart, lungs, and brain. When hypothermia sets in, the
body prioritizes heat distribution. It works to keep the vital core
warm, hoarding the additional calories required to heat parts of the
body that are not necessary for survival,
As the body begins
to chill, the first signs of hypothermia come in the form of muscle
tension and goose bumps. This non-shivering heat generation can
double the metabolic rate. As the core temperature continues to
drop, shivering begins. These uncontrolled contractions can increase
the metabolism to five times the normal rate. Now the body is
burning roughly 400 calories per hour. That's approximately the
number of calories in two Snickers candy bars. Under the right
conditions, the body can still re-warn itself.
At some point, the
body starts to realize it is beginning to lose its battle to heat
all its layers and decides it can survive without the superficial
one. By shunting the blood flow away from the skin and outer
tissues, it reduces the flow by about I to 2 percent. Strenuous
activity could increase heat output, but the body has limited stores
of fuel. Heating the entire body might burn what reserves are left
and leave the victim to cool even more quickly.
When core body
temperature fails below 95°F, shivering diminishes. The patient may
become confused; reasoning becomes clouded. With continued heat
loss, the body decides to sacrifice parts of itself so that the
brain can survive. By reducing the area being heated, life is
prolonged. First, the body decides it doesn't need the extremities,
and carbon dioxide and lactic acid build up in these areas. Then it
begins to shut down blood flow to unnecessary organs. And finally,
it will limit flow to the three organs that sustain life itself.
As the body
continues to cool, the victim begins to lose touch with reality. In
some cases. they experience atypical mood swings and may become
argumentative or combative when assistance is offered. Once the core
body temperature drops to 90°F, shivering is replaced by muscle
rigidity, and mental facilities are severely impaired. The victim is
semiconscious, progressing toward unconsciousness. As the core
temperature continues to drop, the metabolic rate diminishes, oxygen
consumption drops, and respiration slows. Cardiac output also slows
and weakens, resulting in further reduction in blood flow.
As lung and cardiac
function diminish, cardiac arrhythmias develop, and ventricular
fibrillation, a spasm of the heart muscle, eventually leads to
cardiac arrest. A review of hypothermia symptoms follows:
-
Temperature above 95°F. Conscious and alert.
Vigorous uncontrollable shivering, pain or numbness in
extremities, loss of manual dexterity, slurring of speech.
-
90° to 95°F. Conscious. Mildly impaired mental
facilities. Diminished shivering is replaced by muscle rigidity.
-
86° to 90°F. Semi- or fully unconscious. Severely
impaired mental abilities; may appear intoxicated. Rigid
muscles, cardiac arrhythmias.
-
80° to 86°F. Unresponsive, unconscious. Rigid
muscles, dilated pupils barely responsive to light, diminishing
or nonexistent pulse and respiration, blue-gray skin color.
-
80°F. Ventricular fibrillation, cardiac arrest.
Pupils fixed and dilated. Death.
Loss of body heat
occurs in a number of ways that may affect a paddler simultaneously:
-
Radiation: Heat is given off to a cooler
environment directly. The amount lost to cold water is many
times that of cold air.
-
Conduction: Heat passes out of the body directly
into a cooler object, such as the ground an injured person is
Iying on.
-
Convection: Heat rises away from the body into
the air. Clothing helps prevent this.
-
Evaporation: Heat is removed from the body as
water or perspiration evaporates and the skin dries. This is why
wet clothing should be removed from hypothermia victims.
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Respiration: Heat is continually lost as cold air
is drawn into the lungs, warmed, and then exhaled.
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