Highest ever altitude dive

[aquaregia]

Oh, it's because it's ratio deco?

(still just guessing here)

 

[boulderjohn]

I have no training in deco diving, so I was hoping for a bit more clarification on this. I'm assuming the thinking is that Tahoe's around 0.75atm, so it's only the equivalent of 10ft deeper? I'd rather consider that "double surface" would occur at 16ft, "triple surface" at 41ft, "quadruple surface" at 66ft, etc. Or is the idea that you run straight down the mountain so you offgas at sea level?

Again, no experience or training in this at all, so I'm sure some of my thoughts are way off.

I am not sure I understood your question.

The issue of altitude and diving is fairly complicated.

The major concern is the difference in pressure both in the water but more especially when surfacing. When you surface, you do not want to have too great a pressure differential between your body and the air you are breathing. When you are at 34 FFW, your ambient pressure is one atmosphere (from the 34 FFW) plus whatever the pressure is from the air above you. At sea level, that would be 2 atmospheres, but at altitude it is less. Because the water weighs the same at altitude as it does at sea level, the difference is greatest near the surface, and the biggest change you will have comes when you leave the water itself. The difference in pressure between the N2 in your body and the N2 in the atmosphere will be greater at altitude.

Most decompression tables, computers, and software will adjust for this. For example, let's say I want to plan a 150 foot dive (breathing a mixture of helium, oxygen, and nitrogen) for 30 minutes bottom time in fresh water. Using a typical decompression software program (V-Planner), I would be required to do 32 minutes of decompression (using EANx 50) if I were doing the dive at sea level. If I were doing it at Lake Tahoe, the program would want me to do 42 minutes of decompression.

 

[Blackwood]

Oh, it's because it's ratio deco?

(still just guessing here)

Well, whatever you call it, it's not a traditional buhlmann-type of approach where you chase the m-value with your fast tissues.

Whether there's any merit behind it I can't speak to.