Download Pool Tip #22: Hypothermia (PDF format, 18KB)

Body heat is lost through four processes: radiation (still air surrounding the body), conduction (contact with a cold object), evaporation (sweating), and convection (air or water movement around the body). Swimming in an attempt to stay warm will actually increase the rate at which heat is lost through convection, and will speed up the onset of hypothermia. Immersion hypothermia is a lowering of the body core temperature which occurs when cold temperatures cause the body to lose heat faster than it can be produced. The onset of hypothermia is also affected by: wind velocity; air temperature as well as water temperature; length of exposure to the cold; the person’s age, body size, build, level of mental and physical fitness; and, the amount and type of protective clothing worn.

Initial symptoms of hypothermia include shivering, rapid and involuntary muscle contractions, and bluish coloring. Reduced blood flow to the extremities also occurs due to the “mammalian diving reflex”, a series of bodily functions that reduce circulation to most parts of the body except vital organs, and which is triggered by sudden face contact with cold water (less than seventy degrees F). Hypothermia will progress toward sleepiness, unconsciousness and eventual death. The proper response to unexpectedly finding oneself in cold water is to stay where you are, use clothing for flotation, and use either the heat escape lessening posture (H.E.L.P.) or huddle together if there is a group. Do not attempt to survival float or swim to safety.

To avoid the possibility of afterdrop which might trigger ventricular fibrillation, first aid for mild hypothermia involves gradual rewarming by showering, covering up, getting out of wet clothes, and drinking warm liquids. Alcohol should not be consumed because it causes blood vessels to dilate and increase heat loss. Also, hypothermic victims should not smoke since nicotine reduces circulation to the skin.