Journal of the Royal Naval Scientific Service. Volume 27, Number 2 ...

Hypothermia in Divers: Bevan 109
Figures in square brackets [ ]
indicate number of measurements
contributing to the average.
suffering from acute hypothermia and could
even be responsible for the death of the
victims after rescue. (41
IN DIVE
ELEVATION
REWARMING
0 10 20 30 40 50 60
ELAPSED TIME IN MINUTES
FIG. 4 Average response of deep body
temperature.
against heat loss. In the light of more recent
investigations the benefit of peripheral vasoconstriction
can be seen to be largely dependent
on the thickness of the subcutaneous fat.
Following the initial elevation, the deep-body
temperature was observed in most cases to
fall and on the completion of the dive continued
to fall for a period afterwards to a
mean of 055°C below pre-dive levels. This
apparently paradoxical situation whereby the
temperature continues to fall, even after
removal from the cold water environment, is
partly explained by Keatinge' 4 ' who postulated
that the skin temperature may remain low and
thus maintain the thermal gradient responsible
for the loss of deep-body heat. Furthermore, as
the cold induced vaso-constriction of the skin
subsided, the increase in the blood circulation
would increase the conductivity of the superficial
layers, thus briefly accentuating the fall
in deep-body temperature. This after-drop in
deep-body temperature was not of a very large
magnitude in this experiment. However, it
would be of great significance to persons
Survival
The extremely, inhospitably cold environ
ment that bathes the diver has mothered
inventions of effective protection against its
insidious dangers, among them the "wet-suit".
Following the introduction of the wet-suit into
world-wide use, this suit has now ramified
from diving usage to many other water-borne
activities, notably those of yacht crews and
water skiers. Thus an increasing number of
coastal accidents include survivors wearing
effective thermal-insulating garments.
This is of enormous importance to Search
and Rescue (SAR) organisations such as the
Royal National Lifeboat Institution (RNLI).
Whereas just a few years ago a lifeboat might
confidently return to base after a period of
searching knowing full-well that anyone remaining
in the water after a particular period
would most certainly be dead from hypothermia,
today those survivors might be wearing
wet-suits.
The question therefore arises, how long
should a search for such individuals be maintained
? The answer is particularly elusive,
mainly due to an almost complete lack of
information in this new field. To quote one of
the few data available (reported by the Daily
Telegraph, 20.11.1967) "The skin-diver Mr.
. 29, of Penzance who disappeared at
noon on Saturday scrambled ashore
at 4.30 a.m. (Sunday) after \6{ hours
in the water ". This man was in relatively good
condition when he came ashore having been
exposed to cold water for a period more than
four times longer than he could have hoped
to have survived had he not been wearing a
wet-suit.
In the absence, therefore, of sufficient background
information, one can only calculate
and extrapolate from existing knowledge as
to what might be the maximum survival times
that a wet-suited man can expect. The closest
relevant information comes from G. W.
Molnar' 7 " from a survey of several hundred
reports of survival in sea-water of different
temperatures between 1942 and 1945, Molnar
was able to construct a graph showing the
maximum survival time that might be expected
of ship wreck survivors. This graph is reproduced
in Fig. 5. It can be assumed that the
longest lasting survivors are those with the