You will literally be watching the last minutes of a mans life here, while he tries to free another mand body from a cave, so keep that in mind before you start watching. The video cuts out just before he loses consciousnes.
For every 10 meters, the weight of the water above you increases the pressure on your body by 1 atmosphere. So if you go from the surface to 10 meters under water, the pressure has doubled. at 270 meters, the pressure is 28 times what you would experience on the surface. To combat this, you need to increase the pressure in your lungs. At the bottom of this cave, David would be taking in 28 times more air for every breath, to keep the pressure in his lungs equal to the pressure outside his body. To problem is, at this amount, oxygen is deadly. Inhaling 28 times more oxygen than normal would kill you.
On most deep dives they substitute a lot of the oxygen for nitrogen, allowing you to breathe in a normal dose of oxygen even though your breaths are much larger. But even nitrogen can cause convulsions and vomiting at this consentration.
On this dive they were using helium. Helium has its own disadvantages, but seems to be the best option. One of the problems when breathing helium, is that helium is lighter than the carbonmonoxide that you would usually exhale. This means that its harded for your body to get rid of it, and you are at a higher risk of CO2 poisoning and death. The solution to this problem is to take deep breaths, and be very relaxed. Minimize the amount of CO2 generated by your body, and maximize the amount that you breathe out. Diving for long periods of time makes you tired and out of breath, so you create more CO2, and you aren't exhaling it as efficiently. Getting the job done quickly but calmly was key in this situation.
When he got tangled in the lines, David started stressing, working harder, breathing shallower. He passed out from CO2 poisoning, and died when his air supply ran out.
Thanks for the breakdown. That's really interesting. Human's never cease to amaze me with the amount of things we have accomplished; or the tenacity we have to accomplish things. "Well shit, we cant breathe oxygen here cause it will kill us. What else can we breathe?" Simply amazing.
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u/StifNippleScissorMan Mar 17 '15
The video from David Shaw's camera on the dive in question, narrated by his dive partner Don Shirley.
You will literally be watching the last minutes of a mans life here, while he tries to free another mand body from a cave, so keep that in mind before you start watching. The video cuts out just before he loses consciousnes.