I've seen an overabundance of the misuse of two words of late: breath and breathe. They are not interchangeable, folks.
Breath, according to the Merriam-Webster online dictionary has several meanings. You can be out of breath from running up the stairs. There can be a breath of fresh air after a spring breeze. The air exhaled or inhaled through your mouth, nose and lungs is your breath. And sometimes, your breath stinks. It is in short, a noun.
Breathe also has a few meanings on Merriam-Webster online, but generally only the one really counts. You breathe when you have an intake of air into or out of your lungs. It is a verb. To breathe. I breathe. He breathes. She breathes. They breathe. And so on.
You do not catch your breathe, breath heavily or any of the other atrocities that have been floating around lately. And I must admit that most of these I see on Facebook where the young have apparently slept through their grammar class.
I can tell you from harsh experience that the grammar check on Microsoft Word is pretty damn wonky. There are a few things that a widget like that should always highlight: its/it's and they're/there/their for one. Its/it's it does okay. The other one it seems to not even try half the time. I would love it if it could catch things like breathe/breath but it doesn't seem to care about noun-verb agreement so much. *sigh*
And don't even get me started on Blogger's on again/off again spell check. (Do you know, it thinks Blogger's is misspelled? And the word doesn't above. But not this one in the previous sentence. Kiss my ass, Blogger spell check.)