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!!
In: 3
DCS isn’t exactly caused by partial pressure. It’s caused by nitrogen that has been under pressure and thereafter entering into solution in the blood stream/entering tissues entering a reduced pressure environment (by surfacing too quickly) and forming bubbles in the body. Bubbles in the wrong spot can hurt you or kill you (eg you spine, your lungs, your brain) and aren’t too pleasant to have as a rule. If the pressure is released more slowly (controlled surfacing, decompression stop) then the nitrogen is less likely to form those types of bubbles and you’re less likely to get bit by DCS.
Helium doesn’t exactly lessen the risk of DCS. What it does (in tri mix or bi mix [heliox] technical diving) is it lessens the proportion of both oxygen and nitrogen in you breathing gas mixture. So, obviously, if you’re breathing less nitrogen you’re less likely to get nitrogen bubbles in your blood stream (also lessens potentially the occurrence of nitrogen narcosis). But it also reduces the risk of oxygen toxicity. Oxygen under certain partial pressures/at certain depths can become neurotoxic. To offset that, sometimes technical divers that are going (well) beyond recreational depths will dive hypoxic gas mixes that you can’t really breath at the surface but which you can breath at significant depth. Helium, as an inert gas, is used to fill up the remaining balance of your gas mix.
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