DURATION OF EXPOSURE
a. The duration of exposure resulting in immersion foot varies according to the
ambient (air) temperature of the water and, therefore, with season and latitude.
Immersion of the torso and extremities in water below 50F, as in northern latitudes,
may result in death in less than one hour due to excessive lowering of body temperature
b. The average duration of exposure resulting in trench foot is three days at a
temperature range of 32 to 50F with a time range of from a few hours to 14 days.
c. The average duration of exposure resulting in frostbite is 10 hours, with a
usual range of 1 to 20 hours, but this varies for different types of activity. For patrols
and other offensive maneuvers, the period of greatest susceptibility usually begins at
that time when walking ceases either because of arrival at an ambush site or because
of being pinned down by the enemy. In stationary guard situations, the same can be
said for the time of posting of the guards; in vehicular movements, for the time of
mounting; and in defensive maneuvers (fox holes), for the time immobilization begins.
A decrease in physical activity reduces the exposure time necessary to produce cold
a. Symptoms and Signs During Exposure. The lack of warning symptoms
emphasizes the insidious nature of cold injury, which unfortunately, is casually
overlooked by many troops and commanders. The only warning symptoms may be
tingling, stinging, or at most a dull aching sensation of the exposed part followed by
numbness. The skin briefly may appear red and then becomes pale or waxy white. At
this stage, the affected part may feel "like a block of wood." If freezing has occurred,
the tissue appears "dead white," and is hard or even brittle, with complete lack of
sensation and movement. Medical personnel rarely see these stages of cold injury, as
thawing or rewarming with the development of the manifestation of the injury has
usually occurred. Data from previous wars indicate that medical officers saw less than
two percent of cold injury casualties before rewarming had occurred.
b. Differentiation. The differentiation of types of cold injury, that is, freezing vs.
nonfreezing, may be difficult early after rewarming has occurred. The classification into
trench foot, immersion foot, and frostbite is of use chiefly as a description of the mode of
injury. Tissue injury is largely the result of blood vessel damage and hence will be
similar in all forms of cold injury, the major variable being the severity. The type of cold
injury usually encountered is a graded injury, which may involve superficial and deep
frostbite. The actual severity of the injury cannot be accurately evaluated at this time.