Overheating is rarely an issue during diving because even relatively warm tropical water cools the body since its temperature is less than the normal temperature of a human body. But too much heat is a common problem before and after a dive especially in areas with hot climates and cool water thus requiring thick exposure suits or tropical areas with very warm waters.
When your body temperature rises either through exposure to a warm environment, heavy exercise or a combination of these, several physiological cooling processes begin to protect your core body temperature from rising.
Initially your skin capillaries dilate allowing heat from the blood to radiate through your skin. Next you begin to perspire cooling the skin and thus your blood through evaporation. If your core temperature remains high your heart rate and pulse accelerate
to circulate blood more rapidly to your skin for cooling accompanied by a breathing increase.
These responses remain until the core temperature returns to normal which usually means when you stop exercising or reach a cooler environment, for example entering the water. If this doesn’t happen soon enough your body can only continue its cooling efforts to your physical limit. The more physically fit you are and the less body fat you have the better you can handle hyperthermia, but beyond the limits of the human body’s cooling system you can experience heat exhaustion or heat stroke.
Hyperthermia or Heat Exhaustion
Thermoregulation is the ability of the human body to keep its temperature within certain boundaries even when the surrounding temperature is very different. When the surrounding temperature is high the body’s thermoregulation system is working at full capacity to cool.
Hyperthermia or heat exhaustion is elevated body temperature due to failed thermoregulation that occurs when a body produces or absorbs more heat than it dissipates.
Signs and symptoms of hyperthermia include weak rapid breathing, weak rapid pulse, cool clammy skin, profuse sweating, dehydration, nausea, etc.
A diver with heat exhaustion should remove the exposure suit, seek shade, drink non alcoholic fluids and rest until they cool off.
Extreme Hyperthermia or Heat Stroke
If a diver with hyperthermia remains hot or continues to heat the physiological control mechanisms will eventually fail and result in heat stroke.
Heat stroke is a type of severe heat illness that results in a body temperature greater than 40 °C.
Symptoms of heat stroke include red dry or damp skin, headache and dizziness. The pulse is strong and rapid, perspiration ceases and the skin is flushed and hot. At this point, the core temperature rises because the body’s cooling mechanisms have failed. Without medical attention, heat stroke can cause brain and organ damage, and even death is possible.
A diver with heatstroke should remove exposure suit, rest in a cool environment and contact emergency medical care immediately.
Miha Frlec PADI CD 