John Arnott takes a look at why cetaceans don’t suffer from the bends
No. Cetaceans don’t suffer from the bends, or caisson disease, because they don’t hold their breath underwater in the same way humans do.
What causes the bends?
When humans dive, we breathe pressurised air, and nitrogen gas dissolves in our body tissues. If we return to the surface too quickly, the sudden reduction in pressure makes the nitrogen revert to gas, forming bubbles in our brains, central nervous tissue, blood vessels and joints, causing severe pain and even death.
- Can reptiles breathe underwater?
- Why whales have blowholes
- How can penguins dive so deep?
- Can fish drown?
Why don’t whales and dolphins suffer from the bends?
Instead of keeping air in their lungs when they dive, like humans, cetaceans store oxygen in their bloodstream and muscles. Humans do this, too, but whales have an abundant supply of haemoglobin and myoglobin proteins that help them to absorb a much higher concentration of oxygen than we can. And, of course, they have a lot more blood.
When a cetacean dives, the water pressure causes its lungs to collapse, forcing the air into the trachea (windpipe) where it cannot be absorbed into the bloodstream. This prevents nitrogen from saturating its blood, which is the main cause of the bends.
Despite their special adaptations, there have been cases of internal hemorrhaging and symptoms of the bends in some beaked whales. There seems to be a link between these symptoms and loud sounds, such as those produced during military exercises, which may cause cetaceans to surface unusually fast.
John Arnott