Im obviously confused somewhere. But let me explain further.
You have a metal container, carrying your breathable gas mix (depending on your depth). If this container doesn’t actually physically compress further due to the rigidity of the metal at say 800ft, then why would breathing a 80-20 mix of Ni and O in a compressed container cause any effects?
I understand that free diving, or diving in mailable suits will obviously cause your body to compress under the weight of the water around you. But saturation divers are very different. Are they not safe from the ‘physical’ pressure of the water, yet unsafe from the compression of air? What is the difference between our bodies not compressing at this depth, compared to the oxygen in our lungs compressing?
Edit: another question. If the oxygen inside the container is already at an extreme pressure, then why would releasing it cause any change to us physically from breathing it at sea level, compared to 1mile under the sea?