How can my dog have so much boundless energy when she can't even breath?

She is really, really laboring to breath. That tumor in her throat is just getting bigger and bigger. I wish Rick was here. I’m just about ready to take her in…but then she does what she just did and that was she came hurtling off the couch, ran out the open door and FLEW off the deck and ran all around the back yard. I don’t understand how she’s able to do that.