JustinW:I would be very interested to learn the physics behind that dive. Thats 33.6 bar if my math serves me right. What is the oxygen toxicity at that depth and did he have to breath a gas mix below 21%? I would be interested to see a more detailed dive profile and a bit more into his diving history, if he has gotten bent before etc.
The physiology limitations are major factors when planning such dives. Yes, the bottom gas is usually a hypoxic (<21% oxygen) blend with a lot of helium to limit narcosis. Search on the term trimix.