Can someone please explain to me the definition of partial pressure in a very simple simple way and how it applies to us?
Like the partial pressures of different gases in our bodies.. And why people get decompression sickness when they scuba dive.. And why having helium lessens the risk. Etc. Why are partial pressures important?
TIA!!
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It might be easiest to examine this from another perspective.
Think about an electronic scale. Let’s say I have three items: a toy car, a banana, and a dollar bill. I put them all on the scale. They weigh 2 pounds combined.
Now, the “partial mass” (note that this is a made up term) of an object would be the amount that it contributes to this total mass. If the car weighed a pound, the “partial mass” of the car would be a pound, as that’s what it contributes to this total weight.
This is largely what partial pressure is. If the pressure in a balloon is 5 psi, and there’s three different gases in there, they all contribute to that psi reading. If I (for example) determine that the partial pressure of the helium is 2 psi, I’m saying that if I had only the helium in the balloon, the balloon would have an air pressure of 2 psi.
Decompression sickness is semi-related. It’s known that as pressure increases, the solubility of a gas increases. This means that the farther underwater you go, the more of a specific gas can dissolve in your bloodstream. This is concerning, because that gas will become less soluble when you try to get shallower and will need to exit the bloodstream. If you go too quickly, this causes issues as the nitrogen exits the bloodstream.
Helium is less soluble in general, which means less gas will be in your bloodstream. This makes the decompression less dangerous as there’s less gas that needs to exit the bloodstream.
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