You probably know something about the dangers of scuba diving: drowning, shark attacks, boating accidents... But there's one problem that's more common than the others, and it doesn't hit until you're already out of the water. That problem is decompression sickness, or as it's more commonly known, "the bends." It can cause fatigue, pain, and even in some rare cases, death, But what exactly is this strange and serious health problem, and why does it hit you the way it does?
The first thing you need to know is that the bends is that it happens when you surface too quickly. That shouldn't be a big deal, right? Well, it may sound like a small mistake, but it actually sets off a chain reaction of pain and havoc throughout your blood and joints. In fact, what happens to your body when you get the bends is as fascinating as it is frightening. Spoiler alert: you're going to cringe at some of this.
So before you go scuba diving, it's time for us to give you a little lesson on why surfacing slowly is more important than you ever would have guessed.
So, first off, let's talk about why decompression sickness happens in the first place. Maybe you have to get to the surface because there's a problem with your gear, or maybe there are sharks coming after you, or maybe you're out of air. Either way, you suddenly have to get to the surface very quickly. Maybe you even just make a mistake and don't pay attention to how fast you're heading up. While this doesn't sound like a big deal, this is actually a huge deal, and here's why.
When we're on dry land, our bodies are at "normal" pressure, or a pressure we're used to because there's just air around us. In water, however, the pressure is much greater, so our bodies are under much more pressure. As you dive, this pressure makes your lungs contract, so it takes twice as much air to fill them because the pressure is twice as high. When you come back to the surface, the air expands again, so your lungs go back to normal. Also, when you scuba dive, the air coming out of the tank has the same pressure as the pressure that the water is exerting around you. So if you come up too quickly, your lungs and body cannot adjust to the air in your system and how quickly it's expanding back to normal.
That's when things start to go really wrong...
Once you hit the surface, your body will already be beginning to act strangely on the inside, but you won't feel it instantly. It can take up to 12 hours before you start to notice signs and symptoms, though in rare cases it can take even longer. However, initial symptoms are usually visible after the first 15 minutes of being out of the water. Very rarely, you can feel symptoms as soon as you break the surface.
Once you start feeling symptoms, it's time to head to a hospital, because the symptoms are only going to get worse.
When you surface too quickly and your body can't adjust to the change in pressure and air in your body, it reacts in some pretty intense ways. When you stay deep under the water for a long time (usually half an hour or longer), nitrogen from the air you're breathing will begin to dissolve in the water in of your body, in your blood. If you surface slowly, and take breaks on the way up, the nitrogen is gradually expelled through your breathing.
However, when you surface too quickly, the nitrogen is suddenly under less pressure, it separates from your blood and tissue, and it impacts the way your blood flows. Think of it as having a bunch of tiny nitrogen bubbles moving through your bloodstream, blocking off the flow. Not a good thought already, right?
Your blood isn't the only thing that's having problems with nitrogen. When the nitrogen from breathing out of a tank deep underwater dissolves into the water in your body, it also gets into your muscle tissue and other soft tissue. Then, upon surfacing, those bubbles separate and can actively start destroying your tissues!
The air bubbles can block blood flow to parts of the body by cutting off the smallest blood vessels. The longer the blood is blocked, the worse the damage can be. In some situations you can actually rupture lung or brain tissue, but we'll talk more about that horrifying complication a little later.