Instruction manual

PROFICIENCY IN SURVIVAL CRAFT AND RESCUE BOATS OTHER THAN
FAST RESCUE BOATS
13 1
13. Hypothermia
Hypothermia is the term given to the condition when deep body
temperature is lowered to less than 35 degrees C (95 degrees F) when normal
body function would be impaired. Loss of life may occur when deep body
temperature falls below 30 degrees C (86 degrees F).
In a cold environment, body heat production will automatically increase in
an effort to balance heat loss. However, if the rate of heat loss exceeds the rate
of heat production, then the body temperature must fall. The rate of heat loss is
many times greater in water than in air.
The rate of heat loss will vary depending on the difference in the
temperature between the body and the water. In tropical water hypothermia can
still occur but is likely to take far longer than in colder water, where death by
hypothermia can occur in less than 1 hour. In addition, death by drowning is a
frequent consequence of weakness caused by hypothermia. Crewmembers
should be aware that almost all seas in the world are at a temperature which can
be classed as a cold environment.
Hypothermia should always be suspected in every individual rescued at
sea.
There are three stages of uncomplicated hypothermia:
• excitation - indicated by marked shivering, confusion and disorientation
• adynamic - indicated by amnesia, slowing of the heart and possible
abnormal rhythms
• torpor.
The torpor stage may terminate in a comatose state, which can be difficult
to distinguish from death. The casualty is unconscious, there are no reflexes and
the pupils are dilated. The respiratory rate is very slow with only two or three
movements a minute, the pulse is imperceptible and heart sounds cannot be
heard, even with a stethoscope.