The Bends

Written by: Antonia Beevor

Humans have always explored – this is a fact that has remained unchanged throughout history. And as our technology has adapted, this has allowed us to explore places that have never been seen by people, including the depths of the ocean.

Over seventy percent of the Earth’s surface is covered in water, and it represents a vast and unknown landscape for many. The human body can adapt to being deep underwater (as proven by the deepest free dive of 214 meters) thanks to very well-designed biology. Your Eustachian tubes – which connect your throat and nose to the middle ear – allow divers to equalise the internal pressure of their ears with the pressure underwater.

But holding your breath can only take you so deep, and for years, we have been trying to find a way to dive deeper and longer. We can trace these attempts as far back as 332BC, where Alexander the Great was lowered into the ocean in a ‘diving bell’. Later, during the Renaissance, DaVinci designed his own underwater breathing apparatus, made of tubes connected to an air source near the surface. But it was only around the 18th century that the first self-contained underwater breathing apparatus (SCUBA) was created by Henry Fleuss.

But for over 50 years, one of the great mysteries for divers was the bends. It was referred to as such because the joint pain experienced led to the afflicted bending over, but these days it’s more commonly called decompression sickness. In addition to joint pain, decompression sickness can manifest as a skin rash, amnesia, vertigo and many other symptoms.

Divers usually breathe compressed air when diving- a mix of 21% oxygen and 79% nitrogen. When you breathe out on land, the nitrogen is also exhaled. But underwater, the gas you breathe is under pressure, so instead of being breathed out, nitrogen begins to be forced into body tissue. When in its tissue, the nitrogen is dissolved, but when a diver ascends too quickly, the pressure exerted on the diver’s body changes rapidly, causing this nitrogen to come out of solution and form bubbles in the blood.

These bubbles can form anywhere in the body, and the varied symptoms of decompression sickness show this. The most effective way to treat decompression sickness is recompression therapy. Patients are placed in recompression chambers, where the pressure is increased, allowing the nitrogen bubbles to redissolve, where it can then be harmlessly respired.

Decompression sickness can be avoided by limiting the amount of nitrogen that dissolves during a dive. This can be done by limiting the depth and length of dives, ascending slowly, and stopping at points during ascent, which allows the excess nitrogen to escape.

Despite the risks associated with diving, the innovation and ingenuity that has taken us from diving bells to equipment that allows divers to spend hours underwater is a testament to humanity’s desire to discover.