Basic HTML Version
Chapter 27 — 5
PREVENTION
Alcohol and other drugs may predispose to hypothermia by dilating peripheral blood vessels
and losing heat by conduction into the water.
Diving in cold water is the commonest cause, but even in tropical waters loss of body
temperature during a dive is likely if the diver is not effectively insulated.
The most popular and convenient insulator is the
wet suit
(see Chapter 5). Air bubbles
enclosed in synthetic rubber provide an insulating barrier between the diver and the water
without the need for the suit to be waterproof – hence the term "wet suit". They are available
in various thicknesses depending on the expected water temperature. Wet suits have the
disadvantage of compression of the air cells at depth, which reduces their insulation and
causes inconvenient changes in buoyancy.
This problem is reduced in professional diving operations by the use of a "
dry suit
" which
uses air as the insulating material. Other variations include electrical, chemical or hot water
warming procedures, or even an inflatable air pocket enclosed in a wetsuit.
When immersed and in a survival situation, heat loss in an uninsulated person can be
minimised by floating in the H.E.L.P position, a curled-up posture ("foetal" position) with the
knees near the chest and the arms by the side, so covering the body areas which lose heat the
most (axilla and groin). This can obviously be done only if the diver has a flotation aid.
Huddling together with other survivors may be of value. Restriction of movement will also
minimise heat loss.
To reduce heat loss, it is best not to swim more than a short distance, as although swimming
generates some metabolic heat, this is more than offset by heat lost into the water during
movement.
Divers should abort dives once they start feeling cold, and should ensure adequate time on the
surface, in a protected and warm environment, before returning to dive. Hours are needed to
regain the deep core body temperature. Sweating is a good sign that hypothermia no longer is
a problem.