Eli5 how does decompression illness kill you?
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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.
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