If you regularly do any sort of recreational diving, then you have probably heard of the dreaded diver’s disease known as “the bends.” It’s more formally known as decompression sickness, and it’s something that any diver should be wary of, breath-hold divers included.
Decompression sickness is caused by a few major factors: breathing compressed air, how deep the dive was and the time spent at that depth, as well as how fast one ascends.
Since snorkelers, freedivers, and spearos don’t breathe compressed air (most do breath-hold dives), they might appear to be immune to getting the bends, but that’s not true, since the other factors apply to them.
Can you get the bends if you’re a freediver? While it is unlikely, you can get decompression sickness from freediving, or any sort of breath-hold diving. It would take many hours of diving with inadequate surface intervals, but at some point, even a freediver can start to feel the effects of the bends.
In this article, we’ll go over in more detail what exactly decompression sickness is, how freedivers can be affected by it, as well as the steps they can take to keep the risk of getting the bends to a minimum. Let’s dive in.
What is decompression sickness (“the bends”) exactly?
So that we are clear on what is being discussed, since not all breath-hold divers were necessarily educated on the dangers of decompression sickness a.k.a. “the bends” (whereas it’s one of the first things you’ll learn in the Open Water Diver course), so let’s go over exactly what we are dealing with.
It’s no secret that scuba divers rely on breathing compressed air stored in their scuba tank, and that’s how they are able to dive to incredible depths for impossibly long times that a breath-hold diver can only hope to achieve. However, this comes at a price: an increased risk of decompression sickness.
Since the water pressure increases the deeper you dive underwater, scuba divers are subjected to several atmospheres of pressure. For instance, at a depth of 20 m, they are experiencing three times the pressure compared to the surface. The pressure also affects their air supply – squeezing the total amount of air into a smaller volume.
Effectively, what’s happening is that each breath of breathing gas a scuba diver inhales contains a highly concentrated amount (e.g. at 20 m, there is three times the pressure, so that’s three times the amount squeezed into a single breath), and this is explained by Boyle’s Law.
This causes their air supply to be used very quickly, but the issue of interest for this article is that this also causes an unusually high amount of nitrogen to enter a scuba diver’s tissues (remember that air is 78% nitrogen, 21% oxygen, and 1% other gasses).
Keep all of this background information in mind as we move on to how scuba divers get the bends.
The bends, or decompression sickness, occurs when a diver ascends too quickly and the extra nitrogen in their tissues gets released too quickly. If the ascent is too quick, the nitrogen will form bubbles in the bloodstream and this results in all of the symptoms of the bends, and is essentially what decompression sickness is.
If this is hard to picture, imagine opening a can of a carbonated drink. In its sealed (pressurized) environment, it just appears to be a regular liquid. However, once you break the seal, you can immediately hear the fizz as bubbles and foam start to rise. Imagine that is happening inside your body.
The bubbles will cause a veritable cornucopia of symptoms, and some of these can result in permanent damage and even death.
According to the Diver’s Alert Network (DAN), the symptoms of DCS include:
- Unusual fatigue.
- Skin itch.
- Pain in joints or arm, leg or torso muscles.
- Dizziness or vertigo.
- Ringing in the ears.
- Numbness, tingling and/or paralysis.
- Shortness of breath.
- A blotchy rash.
- Muscle weakness or paralysis.
- Difficulty urinating.
- Confusion, personality changes or bizarre behavior.
- Amnesia.
- Tremors.
- Staggering.
- Coughing up bloody, frothy sputum.
- Unconsciousness or collapse.
However, now you might be asking the question: freedivers do not breathe compressed air nor do they dive for as long as scuba divers, so is decompression sickness even a risk?
So why is this a problem for freedivers?
The bends is less of a problem for freedivers, but the risk is not completely eliminated. Even though breath-hold divers do not breathe compressed air, the single breath of air they do breath will be subjected to the pressure at depth.
Even though you are not inhaling greater than normal amounts of nitrogen, the nitrogen in your breath can still enter your tissues due to the pressure underwater as they try to reach equilibrium. Thus, when you start to ascend and the pressure decreases, the process will get reversed and the nitrogen will be released.
Now, the nitrogen being released will be a very small amount compared to scuba divers. A very, very small amount, hence why we say the risk is minimal.
However, what if you were to do 50 more dives? Also, what if you were to have short surface intervals so there is less time for the nitrogen in your system to off-gas?
Over a long enough period of time, say several hours, then during one of your ascents you may start to feel the effects of decompression sickness.
Be aware of these predisposing factors that can increase the chances of you experiencing DCS from freediving:
- Dehydration.
- Having alcohol in your system.
- Being cold.
- Scuba diving earlier in the day.
- Exercising before your freediving session.
If any of these factors apply to you, then you are at a higher risk of getting DCS even if you are not a scuba diver.
How can freedivers avoid the bends?
Knowing all of the risk factors that increase your chances of getting DCS, then you must try to avoid these factors at all costs.
Follow these steps to drastically reduce your chances of getting DCS:
- Limit how many dives you do in one session.
- Limit the duration of the dives you do.
- Increase your surface intervals (recommended 3 times the length of your bottom time assuming the dive is less than 30 m deep, e.g. a 2 minute dive to 20 m requires 3 minutes of rest at the surface. At a depth greater than 30 m deep, multiply the bottom time by 4).
- Wear appropriate thermal protection, e.g. an appropriately thick wetsuit.
- Stay hydrated – drink water or electrolytes.
- Avoid drinking alcohol before or too soon after a dive.
- Don’t freedive after scuba diving.
- Don’t do intense exercise before freediving.
You can also follow the same steps that scuba divers take to avoid DCS:
- Ascend slowly as you approach the surface (say, 1 meter per second).
- Do a safety stop before you surface.
Now, these extra steps are easier said than done, considering you are likely running low on air at this point. However, that is why you should factor a slow ascent into your calculations when doing a breath-hold dive. Save enough time and energy to perform these steps and you will basically ensure that you will never suffer from DCS.
