Eli5 how does decompression illness kill you?
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It usually doesn’t, but it can mess you up for life. When it does kill you it’s catastrophic (uncontrolled ascent after a long period under pressure) and a nitrogen gas bubble causes a fatal embolism (blocks blood getting to the heart, lungs or brain), otherwise it’s a bit more chronic. Chronic cases aren’t going to be lethal on their own, just very painful and potentially disabling depending the degree of joint and nerve damage.
You know how if you open a 20 oz bottle of soda, it will bubble and fizz? When your body is under pressure, and then suddenly not under pressure, your blood will bubble and fizz.
Bubbles in your blood prevent blood from reaching vital organs. It’s like blood clots but made of gas.
The deeper you dive, the more compressed gasses become. Let’s say at a certain depth, oxygen is compressed by 2 times. If you were to surface immediately, you would have twice the oxygen volume in your lungs. That’s why divers rise slowly – the gasses gradually expand as they rise, so they can breathe out the gasses slowly.
Your blood also has gasses dissolved in it. The same property applies here. As another user said, this basically causes blood clots, but formed by gasses instead.
At depth, the pressure forces nitrogen gas to dissolve into your blood. If you ascend too quickly, that nitrogen gas all comes out of solution and turns back into gas at the same time, which can form bubbles in your bloodstream. In extreme cases those bubbles can block blood flow through your arteries, causing effects similar to what is seen in a heart attack or stroke.
In diving decompression illness is actually a couple different potential things.
The most common one that people refer to is the bends, this is when nitrogen comes out of solution in the bodies tissues. This happens because while diving you are under pressure, every 10 meters (or 33.3 feet) you gain one atmosphere of pressure. At sea level the atmospheric pressure is 1 bar (approx. 15psi) so a dive to 30 meters (approx. 100 feet) your body is under a total of 4 bar (approx. 60 psi). A rapid ascension would almost certainly cause bubbles to form in the soft tissues (joints, heart, muscle, lungs, etc.) which will cause a lot of pain and potential death. To mitigate this as a diver we do our best to ascend no faster than 1 meter per 3.3 seconds (1 foot per second) and perform a safety stop at 5 meters (approx. 15 feet) for at least 3 minutes. We also avoid flying for at least 24 hours after a dive has ended as flying can still cause decompression illness.
The other version we also refer to as and treats the same is lung over expansion. This tends to happen when someone panic’s and holds their breath during ascension often along with a rapid ascent. Basically your lungs are similar to a balloon and start to burst. This happens because as in above when the external pressure increases the amount of air in our lungs also increases. It’s referred to as Boyle’s law.
For both we treat with oxygen in as high of a concentration as available (most boats carry emergency O2 but even using something like EAN32 (Enriched Air Nitrox 32% oxygen) will help. The rest of the treatment is to get the person with DCS to a hospital and generally they will end up in a hyperbaric chamber.
For more information about DCS [https://dan.org/health-medicine/health-resource/dive-medical-reference-books/decompression-sickness/](https://dan.org/health-medicine/health-resource/dive-medical-reference-books/decompression-sickness/) is a good place to look.
As a bonus take a look at nitrogen narcosis and oxygen toxicity.
FYI I am a SCUBA diver certified as a rescue diver (just recreational level, not professional) and have dove to just over 100 feet under water. DCS is something that we go over at EVERY training level along with the treatment concepts. As a rescue diver we simulated a lost diver under water, recovered them, removed gear, applied rescue breaths, and removed that person from the water for our passing requirements.
Well, decompression is the opposite of compression, so pushing outward rather than squeezing inward. So your body can expand only so far before it will explode. However, the little gas bubbles and liquids inside you will explode or go where it shouldn’t long before your bones and meat will.
I used to date this girl and her dad is an anesthesiologist. He explained that at higher pressures blood can absorb higher volume of air. When you decrease the pressure rapidly there are air bubbles that form in the blood which can cause various issues including brain embolism.
Well simply when your body is under a ton of pressure your blood fizzles and creates bubbles, this is already bad as bubbles prevent the flow of blood in veins. Now what’ll really get you is that the tiny bubbles in your bloodstream once subjected to lesser pressure becomes ***big*** bubbles and that’s no bueno. Omce that happens the bubbles will travel to your brain restricting flow and causing parts of your body to die.
Bubbles form as gas comes out of tissues, not just blood. Generally gas in blood gets to the lungs where it then goes into the atmosphere, not recirculating round the body to become bigger bubbles. Bubbles come out of all tissues including spinal column, cartlidge. Bad decompression problems are generally those that damage nerves, Bubbles forming on the spine or brain stem, expand and put pressure on nerves, damaging and killing them & also stopping blood flow to these areas. Fizzy pop is a good analogy for what goes on. Fast release of pressure causes a mass of Bubbles.
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