Currently you can set your suit pressure to 11kPa, and it will give you a warning about oxygenation being at critical, but besides the warning there is no disadvantage to playing in this state. In fact there are large advantages, especially on hot planets, it can drop your oxygen tank consumption to less than 1/3 of what it would be if you were using a pressure that did not result in the warning (>40 kPa). Doing this should come with some sort of negative debuff to balance it, such as perhaps a movement speed loss.
#Add debuff for having oxygenation at critical
pale crane
In reality it would be impossible to breathe at these pressures regardless of the o2 partial pressure, as your blood would boil.
zinc kernel
even better, make the player go unconcious if they dont stop moving to oxygenate their blood
like literally running along, then the uncon % thing goes up till 100% and then you flop over
pale crane
haha that would be fun, once you pass out it slowly returns because you aren't moving
trail scarab
Oxygenation is an odd thing. I think you have to get below a certain % and then it slowly adds up a "oxygenation loss" health penalty and when it hits a certain point you start to gain unconsiousness.