Terraforming and Atmosphere

[EDG]

Really interesting and useful numbers there. I guess for a world that has a stable but higher pressure atmosphere then the people and creatures on it would be adapted for that environment with more resilient lungs etc.

Creatures that evolved there would, yes. Humans can acclimatise to an extent, but without actual genetic engineering we won't survive long. People live (and are born in and spend their whole lives) in low O2 ATA conditions in villages high in the Himalayas on earth, but even though they're used to it, they still have health problems. (another cool thing about low pressure - water boils at lower temperatures there. So making food there has to be adapted to the pressure in order to cook food properly - IIRC they basically use pressure-cooker type technology rather than just heating things directly with fires, which also are harder to light up there).

I'm guessing that higher pressure atmospheres are on planets that are larger or have denser earth / core than ours.

Not necessarily. If a planet can hold onto a gas, then it can hold onto as much as it likes of it. Look at Venus - it's slightly less massive than Earth and yet its atmosphere is 90 times thicker. But generally, more massive planets will have higher pressure - pressure is proportional to gravity, so if we suddenly and magically increased the earth's mass so that surface gravity was 1.5Gs (but we kept the radius the same) and didn't change our atmosphere at all, the atmospheric pressure at the surface would be 1.5 atms, not 1 atm. It all really depends on how much gas there is, which may be a lot or may be a little depending on the circumstances and history.