Dolphins: Why They Don't Get 'the Bends' During Deep Dives

The bends... any deep-water diver can tell you that this unusual 'decompression sickness' is no joke. It can cause serious and immediate damage, but can also leave organs permanently marred, cutting short a diver's career if not their life. Interestingly this condition should affect all mammals, not just humans; so why don't dolphins seem to suffer from it? A new study has the answer.

"Our measurements provide novel data for respiratory physiology in cetaceans (whales, dolphins, and porpoises), which may be important for clinical medicine and conservation efforts," the authors of the study, which was published in The Journal of Experimental Biology, reported.

So what exactly did these researchers measure? Study lead author Andreas Fahlman, a biologist with Texas A&M University in Corpus Christi, recently explained to Live Science that dolphins can pull of their impressive deep-diving feats in the first place thanks to lungs capable of holding an impressive amount of oxygen.

That alone is somewhat obvious, but what is special about these lungs is that they are also able to become quickly compressed - an ability that allows dolphins to avoid the rapid decompression of their oxygen as they torpedo back to the surface after a long hunt. (Scroll to read on...)

To determine this, Fahlman and his colleagues measured the breathing of six male bottlenose dolphins at a dolphin training facility in Hawaii with a device called a pneumotachometer, which sits on the animals' blowholes and the backs of their necks.

Using this "speedometer of lungs" as the researcher calls it, Fahlman was able to determine that dolphins can move air in and out of their lungs two to three times faster than humans overall. More importantly, exhaling - which is done to avoid the bends while surfacing - boasted a speed of 34 gallons (130 liters) of air per second. Comparatively, ever experienced human divers can only steadily exhale at a measly rate of four gallons (15 liters) per second.

The team determined that this is largely due to the fact that dolphin lungs can even collapse their alveoli - the pitted sacks that monitor air flow in a lung. That' according to the researchers is impossible for humans.

So why is knowing this important? Fahlman explained that understanding the normal breathing capabilities of an animal can help conservationists and veterinarians understand when something is wrong. Water contaminants and air pollution, for instance, are two issues that can be better addressed if we know how exactly dolphins should be breathing.

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