ELi5: What causes decompression sickness, and is there such a thing as compression sickness?
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decompression sickness is caused by nitrogen bubbles forming in the blood vessels, kind of like how when you take the cap off a soda it starts bubbling. compression sickness isn’t a thing because by the time getting more compressed hurts you it’s just breaking your ribs/crushing you in other ways.
Edit: as pointed out by others on this post, there is actually “compression sickness”, go give them upvotes.
Ever seen someone get run over by a train? That’s compression sickness
As depth increases then the absorbtion of a gas in liquid increases, depending on depth & time, decrease depth too fast and that gas will come out of solution and form bubbles. These bubbles, depending on where in the bloodstream they are can cause serious problems especially if in the brain or spinal chord.
Yes, there is such a thing as compression sickness. In very deep diving, divers breath a mixture of Helium & Oxygen and will be compressed in a surface chamber initially. If the compression rate is too fast it has a very bad effect on the bodies nervous system this is called HPNS and can lead to permanent disability. A company working in Australia has very recently been convicted of allowing this to happen during a deep diving operation [DOF Subsea](https://www.nopsema.gov.au/blogs/dof-subsea-australia-pty-ltd-convictions)
You’ve got an answer about decompression. Now about compression.
There’s no “compression sickness”, but there’s nitrogen narcosis. With pressure high enough, the nitrogen instead of staying in the blood, passes through cell membranes and disturbs chemical activity of cells – in particular, messing with brain, at first making you feel light-headed, a bit like drunk, and in increased amount making you lose consciousness. That’s why depth divers use special mixes of oxygen with gases other than nitrogen, and need time to adapt – eject the nitrogen from their bloodstream, when descending deep.
It’s also a leading factor of why cave diving is so goddamn dangerous. There’s a bunch of quite darn simple safety rules about cave diving and you’re perfectly safe if you adhere to them all. Except you won’t, because your judgment is impaired, your thought process compromised, you get panicky, you take stupid risks, you make stupid decisions you’d never make normally, and you die.
When you get underwater you are compressed. Every ten meters (~30 feet I think) pressure increased by one atm. Volume of the air you breathe does not change but its density changes since it is compressed by increasing pressure. In 10 meters amount of the o2 you will inhale will double by this math. In every ~2 meters (~6 feet) you also have to equalize the inner pressure of your body with outer pressure otherwise your ears will hurt like hell.
Now as pressure increase some nitrogen break free since they are now turning liquid instead of gas, and leak into the other parts of your body.
While getting out of pressure you have to be slow and careful otherwise these liquid nitrogen cannot get back to its rightful place fast enough and turns into gas wherever it is at that point, be it in your joints, muscle, brain… you don’t want bubbles in your brain, right?
I got my open water diver certificate two decades ago, that’s how they told me about it
Decompression sickness occurs because of dissolved nitrogen turning back into a gas in your blood as the air pressure outside decreases rapidly causing the soluble nitrogen to form nitrogen bubbles. Think of it the same way a bottle of coke fizzes when u crack the seal the first time. Because the bottle when sealed is in a high pressure environment inside and thus the carbon dioxide gas is all dissolved in the coke.
Well the same is true for being in high pressure emvironements like scuba diving under deep sea. Nitrogen gas in the air becomes more soluble in your blood in this high pressure environment and dissolves in there. Now when you crack the seal of the coke and all the CO2 fizzes, this is because the pressure inside the bottle has suddenly normalised with the air pressure outside the bottle which is much lower and is where CO2 (and nitrogen) normally exist as gasses and thus it bubbles out of the coke, well if a diver was to suddenly raise out of the water over a short period of time, the nitrogen would all suddenly bubble out of there blood like in a coke bottle forming little air bubbles in the blood vessel which is not cool at all.
This is fixed by divers slowly rising up from the deep sea as the slow rise allows nitrogen to gradually become less soluble in the blood and as each lil amount of nitrogen reaches the threshold to become a gas, it is expelled in an exhale by the diver, so by the time they reach the top, they have breathed out nearly all the nitrogen bubbles, as opposed to them all being bubbled out into the blood at once with no where to go
Sorry for the waffle lol
There is also HPNS. High Pressure Nervous Syndrome. Too much pressure too fast. Only a factor in deep mixed gas diving.
There is a compression related sickness called oxygen or nitrogen narcosis. Basically you can get too much nitrogen or oxygen in your blood due to the compressed air, and it makes you similar to being drunk. I can lead to death. Usually caused by diving too deep for too long on the wrong air mix.
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