We all know about altitude sickness. I felt it personally at an altitude of 13,000 feet in the Rocky Mountains, although I haven’t been any higher than that. There seems to be a threshold altitude above which humans can no longer acclimatize; the region at and above this altitude is called the death zone, and this threshold altitude is at 8,000 m (Wikipedia: Effects of high altitude on humans).
What do you think about the existence of a similar death zone at extremely low altitude regions below sea level? Death Valley is only 282 ft below sea level at its deepest point, and the Dead Sea is just under 1,300 feet below sea level at its surface. If there were land areas that were far deeper than these two particular locations, below sea level by as much as 8,000 m (as much as the dead zone is above sea level), and we had standardized testing rooms at every altitude (in 1000 m intervals) between -8000 m and sea level where the interior of the room was cooled to room temperature (72 degrees F) but the room’s interior air pressure would equilibriate to the external air pressure at that altitude (the pressure would therefore increase as we went down from 0 to -8000 m), do you think that there would be a threshold altitude below which we could not descend strictly due to air pressure, and not due to temperature. (It would probably become much hotter as we descend further and further below sea level, but you’re inside that testing room where it’s nice and comfy!)
In other words, do you think there is a death zone below us as well as the death zone that we know is above us at 8000 m, and if so, how far down do you think it is? Do you think an optimal elevation exists, and if so, do you think that this optimal elevation is below our current sea level or above it? Is there such a thing as too high of an air pressure (provided that we are not subjected to a sudden increase in air pressure but a gradual acclimatized increase)?
There definitely are problems associated with breathing air at sufficiently elevated pressure: Scuba divers can encounter nitrogen narcosis and oxygen toxicity. Apparently, some individuals begin to see symptoms starting at depths as low as 100 ft, and many will experience problems if they spend considerable time at depths exceeding 150 ft.
But my calculations say that the ambient pressure at the bottom of an 8000m (~26,200 ft) hole is around 2.4 atmospheres, which is what a diver at a depth of 46 ft experiences. This appears to be well short of the pressure needed to produce troublesome symptoms.
Would that 8000m hole at 2.4 atmospheres, assuming the same oxygen percent by volume composition as the sea level atmosphere, lead to improved physiological performance in a similar way as a marathon runner who runs at sea level rather than at, say, Denver, CO which is about a mile above?
I am guessing that it might be able to raise an average person’s aerobic capacity and athletic performance to the level of an elite athlete, but I don’t have any evidence for that statement other than extrapolating the improvement that is shown from high altitudes to sea level to sea level to below.
End of the day for me so just a quick note. Cave divers who started using Helium Oxygen mixes rather than nitrogen oxygen mixes claimed that even at rather shallow depths that it was quite apparent that nitrogen narcossis (which helium doesn’t cause) was significant. One major player even claimed he could beat anybody at checkers at 30 or 60 feet (with him on helium and the other guy on nitrogen) or some such.