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By Elizabeth Goldbaum, Live Science

When dolphins dive deep below the water's surface, they avoid succumbing to decompression sickness, or "the bends," likely because the massive sea creatures have collapsible lungs, a new study finds. These lungs allow dolphins to inhale and exhale two to three times quicker than humans.

Understanding how dolphins breathe rapidly and maintain lung functionality under immense pressure could help scientists keep humans safe when they are in similarly extreme situations, such as under anesthesia during surgeries, the researchers said.

Unlike humans, dolphins do not need to be strapped to an oxygen tank to achieve their impressive diving feats. This is because dolphins have compressible lungs that help them withstand high pressures deep in the ocean.

"The deeper [dolphins] go into the ocean, the smaller the volume of gas or air in the lungs gets," said study lead author Andreas Fahlman, a professor of biology at Texas A&M University in Corpus Christi.

The study was published this month in The Journal of Experimental Biology.

Fahlman found that dolphins can replace as much as 95 percent of the air in their lungs in a single breath. For comparison, humans are capable of replacing only as much as 65 percent. Dolphins exhale and then inhale above water before diving back down with lungs filled with air — each breath consumes and releases a certain amount of oxygen that energizes the animals as they swim the ocean.

The researchers studied six male bottlenose dolphins at Dolphin Quest Oahu, a dolphin training facility in Hawaii that is open to the public. The dolphins were free to swim away from the researchers whenever they wished, Fahlman said, though the animals were trained to sit still and breathe into a mask, called a pneumotachometer. This device essentially functioned as a "speedometer for the lungs," Fahlman said.

Studying animal breathing rhythms and capacities can help scientists better understand respiratory disease in marine animals, which is a major cause of morbidity and mortality among marine animals in the wild and under human care, Fahlman said.

Humans are exposed to pollen, debris and other airborne pollutants that many dolphins and other mammals are unable to remove from their blowholes. This can make some animals susceptible to certain diseases like lung disease.

Fahlman said he plans to expand his research to beluga whales and porpoises to investigate their breathing patterns. He said there is especially high concern around mammals living in waters near oil rigs.

Researchers are planning to travel to Alaska and the Arctic to study the mammals before oil reserves there are exploited, to establish a baseline for animal health, he added.

This is a condensed version of a story that appeared on Live Science. Read the original here. Elizabeth Goldbaum is on Twitter. Follow Live Science @livescience, Facebook & Google+.

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