CIRCUM-RESCUE COLLAPSE A condition that can occur once rescue is imminent, is in progress, or has just taken place. Muscles can fail and blood pressure can drop causing collapse and in some extreme cases, even death.
FREEBOARD The distance between the waterline and the top of the side (gunwale) of a boat. Airway freeboard relates to the water line and the airways.
HOMEOSTASIS The ability of the body to maintain core temperature in the normal range despite external temperature fluctuations.
HYPERVENTILATION An increased rate and depth of breathing above required levels.This can be a physiological response to rapid skin cooling and/or a psychological response to panic.
HYPOTHALAMUS The area of the brain that acts as the primary thermoregulation control center to regulate body core temperature within the normal range.
HYPOTHERMIA Abnormally low body core temperature that, in the extreme, can result in cardiac arrest.
RHIB Rigid hull inflatable boat.
THERMOGENESIS The process of heat creation in the body; this includes digestion, exercise and shivering.
THERMOREGULATION The process of adjusting body core temperature within a normal range.
VASOCONSTRICTION Narrowing of blood vessels that results in minimized blood flow, and therfore heat delivery, to the periphery of the body. This happens mainly in the blood vessels of the extremities (hands/feet) to decrease heat loss and preserve core body heat when cold. This process is normally initiated before shivering.
VASODILATION Widening of blood vessels allowing increased blood flow to the periphery of the body.  This occurs to promote heat loss and cooling of the body when too warm and may be accompanied by sweating.
VENTRICULAR FIBRILATION A potentially fatal abnormal heart rhythm that disrupts the effective pumping action of the heart.