Frankincense is considered to oxygenate the body fairly well, though I'm having a hard time finding the data beyond the theory. Many believe that since oxygen molecules make up a significant portion of essential oil chemistry, this results in oxygenation of the cells as the oils degrade within our systems. Oils DO cross the BBB, (just inhale and there you go!). But I still have to find that missing link.
However, Peppermint will really open the sinus passages and increase physical oxygen absorption in this manner. This is something you can definitely feel.
MANY oils are shown to sharpen mental acuity; they've been shown to reduce neurotransmitter breakdown, but the research does not mention yet oxygenation. It mentions limitation of the action of acetylcholinesterase, thereby preventing the breakdown of acetylecholine - making more available. Oils shown to improve 'smarts' through diffusion include Lemon, Sage, Rosemary, and many bright, herbal oils.
If anyone can quote the data, I'd be interested too, and will keep an eye out for it