What happens to a climber's lungs as they go up a mountain?

Question

The answer is supposed to relate to pressure and gas laws. What also happens to a diver's lungs as they descend into the ocean floor?

Answer 1

As a climber goes up a mountain, due to change in pressure, with decreasing pressure, the lungs will expand more, increasing the lung capacity.  They will have difficulty breathing though because there is less oxygen higher up, and your body will straight to breathe due to the pressure difference that your thorassic cage produces with the diaphragm.

The reverse happens with a diver, as they go further to the ocean floor, there is increased pressure from the volume of water above them, so their lungs and chest cavity is compressed smaller as gas is compressible.  This makes it harder to breathe, however with gas tanks, they use less oxygen because the lungs are smaller.  This though is problematic because they will end up increasing breathing rates to get the same amount of oxygen into their bodies since the exchange is smaller due to less gas volume in the lungs