“The Bends”- a moment of science

Storm Team 2

Last week I went over the gases that make up the air we breathe. Here’s a quick recap: 78% nitrogen, 21% oxygen, and the final nearly 1% is made of up trace gases.

Even though it takes up the overwhelming majority of air, nitrogen sits on the bench as the star while oxygen goes to work maintaining life as we know it on Earth. Nitrogen is crucial to life as well, but not in its gas form which just passes in and out of our body without any positive or negative effects… on the surface. If you take a trip underwater, through SCUBA diving, you better consider nitrogen for your own safety. 

Here’s Jeff Eidenberger, divemaster and owner of Carolina Dive Locker, explaining what happens when divers breathe pressurized air.

“This affects us in that our body tissue absorbs that nitrogen. That nitrogen could come out of solution and block blood flow. Most frequently witnessed by pain in your joints. And that’s why they came with the nickname the bends.”

The bends, or decompression sickness, occurs when divers don’t follow established guidelines on how fast they ascend. This results in too much nitrogen in their bloodstream. 

Hold up a minute. The air in these tanks are no different than the air we breathe. So why does diving result in more nitrogen in your body? 

A can of soda can help explain.

Soda gets its fizz from dissolved carbon dioxide. In order to keep your coke tasty and not flat, soda and other carbonated drinks have to be stored under higher pressure in cans. Henry’s Law states that the concentration of a gas dissolved in a liquid is proportional to the pressure of the gas above the liquid.

If pressure goes up- there will be more gas dissolved in that liquid. Just like your soda! Once you pop it open- the pressure inside the can lowers and the bubbles follow. 

Great in your soda, not great in your bloodstream as the same thing applies to divers.

As a diver goes deeper underwater, pressure increases and along with it higher concentrations of the air they breathe. Oxygen gets used by their bodies to keep them swimming, but nitrogen builds up. To avoid the bends caused by higher concentrations of nitrogen, divers take it slow and steady.

“When it comes time to come to the surface, they would slowly decompress so that their bodies would have sufficient time to off gas and equalize to the appropriate nitrogen level that they’re at,” says Eidenberger.

The consequences for not respecting the laws of physics is quite severe- as decompression sickness is potentially deadly.

“With the proper training and adequate safety protocols, you’re really in a limited amount of risk. So that’s why it’s important to be certified by a qualified instructor. We’d be happy to help with that at our facilities here at Carolina Dive Locker.” 

Storm Team 2 Meteorologist David Dickson

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