In the other bed, somebody was having trouble with his breathing.

He could see them rise and fall with her quiet breathing.

But it sounds like there is something wrong with John's breathing.

He seemed to be having a little difficulty with his breathing.

Both have to do with breathing (though, come to think of it, so does everything else).

He or she might have problems with breathing and feeding.

I let him pull it out, being far more concerned with my breathing.

He was having trouble with his breathing, and hiding it.

Possibly it had something to do with the creature's breathing.

Silent, the only sound was his heart beating in time with her breathing.