As most continents around the world are suffering from severe heat waves due to climate change, some doctors, physiologists and experts have explained what happens to the human body in such temperatures.
The hot and humid weather will quickly dehydrate the body. Photo: AP
How does heat attack the body?
The body's resting temperature is normally around 37 degrees Celsius. Ollie Jay, professor of heat and health at the University of Sydney in Australia, says it only takes a 4-degree increase in temperature for severe heatstroke to occur.
During heat waves, anyone who comes to the hospital with a fever of 102 degrees Fahrenheit or higher and no apparent source of infection should be considered for heat exhaustion or severe heatstroke, said Dr. Neil Gandhi at Houston Methodist Hospital.
Heat can kill in three main ways, according to Dr. Jay. The first is heatstroke—a severe rise in body temperature that causes organ failure. When the internal temperature gets too hot, the body diverts blood flow toward the skin to cool down. But that diverts blood and oxygen away from the stomach and intestines, and can cause toxins that are normally confined to the intestines to leak into the circulatory system.
“That creates a cascade of effects: blood clotting throughout the body and multiple organ failure, ultimately death,” he said.
The second and biggest cause of death is stress on the heart, especially in people with heart disease. This starts with blood rushing to the skin to help cool the body, but also causes blood pressure to drop. The heart responds by trying to pump more blood to keep the body from passing out.
“The heart is forced to work harder than it should. For someone with heart disease, it's like running for a bus with a hamstring injury,” says Jay.
Hot weather is very dangerous to human health and even life. Photo: AP
The third cause is dangerous dehydration. When people sweat, they lose so much fluid that it can severely strain their kidneys, Jay said. Dehydration can progress to shock, which causes organs to shut down due to lack of blood, oxygen, and nutrients, leading to seizures and death.
“Dehydration can be very dangerous and even fatal if the condition becomes severe, but it is especially dangerous for people who have medical conditions and are taking certain medications,” said Dr. Renee Salas, a professor of public health at Harvard University.
Effects on the brain
Heat also affects the brain. Some doctors say that excessive heat can make a person confused or have difficulty thinking.
"One of the classic definitions of heatstroke is a core body temperature of 40 degrees Celsius along with cognitive dysfunction," said W. Larry Kenney, professor of physiology at Pennsylvania State University.
Humidity problem
Some scientists use a complex measure of outside temperature called Wet Bulb Globe Temperature (WBGT), which takes into account humidity, solar radiation, and wind. It is an empirical index of the heat stress to which an individual is exposed.
Previously, it was thought that a wet bulb temperature of 35 degrees Celsius was when the body started to have problems, said Professor Kenney, who runs a hot box lab and has conducted nearly 600 tests on volunteers.
But the reality is that his tests show that the danger level for wet bulb temperatures is closer to 30.5 degrees Celsius. He says that figure has already started to appear in the Middle East. For older adults, the danger point is a wet bulb temperature of 28 degrees Celsius.
“Humid heat waves kill more people than dry heat waves,” Professor Kenney concluded, because humidity affects the evaporation capacity of sweat.
Ngoc Anh (according to AP)
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