What is "Heat Stress?"

The human body is designed to operate at 98.6^o. When the air temperature, combined with humidity moves the Heat Stress Index (see HSI scale) above 90o, the human body becomes stressed. In order for the core body temperature to be maintained at a safe level, two elements are necessary: 1.) Convection (wind) and 2.) Evaporation (sweating).  As the Heat Index rises, the body produces more sweat in order to cool itself. Prolonged exposure drains the body of vital fluids.  This lowers the circulatory volume.

HEAT STRESS INDEX RELATIVE HUMIDITY

Heat Exhaustion and Heat Stroke can follow if preventative measures are not employed.  

Commonly observed signs of heat stress are profuse sweating, rapid breathing rate and rapid heart rate.  Because of excessive fluid loss, this disorder gives adequate warning by increasing fatigue, weakness, anxiety, and drenching sweats, leading to circulatory collapse with slow thready pulse; low or imperceptible blood pressure; cold, pale, clammy skin; and disorientation followed by a shock-like unconsciousness.

Exposure to high ambient temperature may lead either to excessive fluid loss and dehypovolemic shock (heat exhaustion) or to failure of heat mechanisms and dangerous hyperpyrexia (heatstroke), an abrupt onset of heatstroke is sometimes preceded by prodromal headache, vertigo, and fatigue. Sweating is usually but not always decreased and the skin is hot, flushed, and usually dry. The pulse rate increases rapidly and may reach 160 rpm. Respirations usually increase but the blood pressure is seldom affected. Disorientation may briefly precede unconsciousness or convulsions. The temperature climbs rapidly to 41C (105 F) and the patient feels as if burning up. Circulatory collapse may precede death; after hours of extreme hyperpyrexia, survivors are likely to have permanent brain damage.  

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