Hypothermia is a medical condition where the body loses heat faster than it produces it, leading to a dangerously low core body temperature. While often associated with extremely cold temperatures, hypothermia can occur in 60-degree Fahrenheit water. The human body maintains a core temperature of about 98.6°F (37°C), and hypothermia begins when it drops below 95°F (35°C). Water conducts heat away from the body much more efficiently than air, posing a risk even at seemingly mild temperatures.
How the Body Loses Heat in Water
The body constantly generates and loses heat. In water, heat loss primarily occurs through conduction and convection. Conduction is the direct transfer of heat to a cooler substance, like water, through physical contact. Convection involves heat transfer through the movement of liquid molecules across the skin.
Water is a significantly more efficient conductor of heat than air; your body loses heat up to 25 times faster in water of the same temperature. This rapid transfer is due to water’s higher thermal conductivity and specific heat capacity. Several factors influence this rate. Body size and shape play a role, as individuals with a larger surface area-to-mass ratio lose heat more quickly. Body fat acts as an insulator, helping retain heat. Wet clothing increases heat loss through conduction and evaporation. Activity level also influences heat loss; vigorous movement initially generates heat but increases blood flow to extremities, leading to more rapid cooling.
Understanding Hypothermia’s Progression
Hypothermia progresses through distinct stages, each with specific signs. In mild hypothermia (90-95°F / 32-35°C), individuals experience uncontrollable shivering, the body’s attempt to generate heat. Other signs include pale, cool skin, numbness, increased heart rate and breathing, mental confusion, clumsiness, slurred speech, or difficulty with coordination.
As hypothermia advances to the moderate stage (82-90°F / 28-32°C), shivering often stops, indicating failing regulatory mechanisms. Symptoms include a decreasing conscious state, increased confusion, slowed heart rate and breathing, enlarged pupils, and paradoxical undressing.
Severe hypothermia occurs below 82°F (28°C). The person becomes unconscious, unresponsive, and muscles may become rigid. Breathing and heart rates become very slow, difficult to detect, and potentially irregular before stopping. Pupils no longer respond to light, and the individual may appear lifeless. This stage is life-threatening and requires immediate medical attention.
Responding to Cold Water Emergencies
Immediate action is important in a cold water emergency. First, get the person out of the water quickly and gently to prevent further heat loss. Once out of the water, remove wet clothing, which rapidly draws heat away, and replace it with warm, dry blankets or clothing. Focus on warming the core of the body, such as the chest, neck, and groin, using warm compresses or blankets. Warm the person gradually, avoiding rapid rewarming methods like hot baths or heating lamps, which can stress the heart. If the person is conscious and able to swallow, offer warm, sweet, non-alcoholic drinks. Monitor breathing; if it stops, begin cardiopulmonary resuscitation (CPR) immediately if trained. Call emergency services (911 or local equivalent) as soon as hypothermia is suspected.
Preventive measures are important for cold water activities. Always check water temperatures and weather forecasts. Wearing appropriate gear, such as wetsuits or dry suits, provides insulation and can significantly extend survival time. Dressing in layers of insulating clothing, even under a wetsuit, can provide additional warmth.
Having a buddy system ensures that someone can provide help if an emergency occurs. If an accidental immersion happens, try to remain calm and avoid panicking, as excessive movement can increase heat loss. If wearing a life jacket, assuming a Heat Escape Lessening Posture (HELP) by pulling knees to the chest and wrapping arms around them can help retain body heat. If with others, huddling together can also reduce heat loss.