How does Ant Man Breathe?

I watched the movie Ant Man last week. Not a good movie to watch if you suffer from myrmecophobia because not only is there Ant Man, but there are his ant minions. Lots of them.

And while it was enjoyable and fun, I had one big question: How does Ant Man breathe?

***SPOILERS ALERT***

Ant Man uses a suit (invented in the 1980s, but never mind that) to shrink himself down to the size of an ant. But he retains all his strength when he does so. Okay, I can deal with that.

But the problem I had was, how does Ant Man breathe. Here's the problem. Humans breathe oxygen. In the air, oxygen is a molecule of two oxygen atoms, or O2 (I can't subscript). Our lungs are designed to use take oxygen molecules from the air and pass them into our lungs through osmosis. That means the tissues between the lungs and the blood vessels have to be able to let the oxygen molecule pass but not the blood.

So Ant Man shrinks down to the size of an ant. Suddenly, the oxygen molecule is huge compared to his tissues. I doubt it would make the lung-blood transition anymore. Insects, such as ants. have tubes that bring in oxygen because they evolved to breathe even being so small. Humans did not.

Okay, then at one point in the movie, Ant Man shrinks down to be small enough to slip between atoms of titanium. So now he's smaller than an oxygen molecule. Yet he still breathes. He continues to shrink until he's smaller than a proton, and yet he still breathes.

Now, if he had an oxygen tank on his back and the oxygen shrunk with him, it would work. But he didn't (this could also be another restriction on his ability: "You only have 30 minutes of oxygen!").

So, I'm still pondering: how did Ant Man breathe, especially when he was smaller than an oxygen atom.

Yes, this is the kind of thing I think of while watching movies.