During the late 1970s, when oil exploration and extraction from the
North Sea were at a peak, there was increasing concern about the number
of episodes of unexplained confusion, loss of consciousness and deaths
Previous field measurements on divers had demonstrated that divers
became hypothermic with little or no sensation of cold, despite suit
heating using tepid water pumped from the surface.
This thesis describes laboratory experiments designed to document and to
determine the cause of 'insidious' hypothermia. Initially, it was shown
that uniform skin cooling in tepid water could produce subnormal body
temperatures in all subjects tested, whether or not they had been
acclimatised to cold.
This symptomless fall in deep body temperature could be reversed by
further chilling the hands and feet using a separate water circulation
system, while the rest of the body remained in tepid water. The rise in
deep body temperature was shown to be due to an increase in metabolic
rate caused by shivering, with cold-acclimatised subjects shivering
The main cause of 'insidious' hypothermia is therefore inadequate skin
stimulation of thermoregulatory reflexes by lukewarm water, with previous cold water exposure further reducing responses.
The next series of experiments was designed, to assess the impairment of
memory and reasoning processes by oold, since most previous evidence find
been inadequate or anecdotal. Psychological tests were administered
during the unusual physiological circumstances on rewarming after oold
immersion, where subjects felt warm and comfortable, but had a low or
falling deep body temperature.
The results clearly showed that the ability to form new memories was
seriously impaired, even by mild falls in temperature, and that reasoning
processes were greatly prolonged, although remaining accurate.
The current work has therefore successfully determined the cause of the
hypothermia which occurs in lukewarm water, and has shown that mental
abilities are seriously affected early in the development of hypothermia.