True, that's the way breathing works. But it only works because G-d makes it work, if He chose not to for even one moment the process would simply... stop.
this is a really late reply but I love religious debates so I'm wondering, if your god is so perfect, how come he failed to make a universe which could operate independently from him. It seems he would be closer to perfection if we could breathe without him needing to focus on us to make it happen. But then I guess if he was capable of that, there really wouldn't be any need for him in the present because nature seems to be handling itself fairly well.
Also the whole 'g-d' thing was one of the reasons I became an atheist, because I realised that different people had different ideas about what was required to avoid hell (such as avoiding the entire spelling of 'god'), then I thought it would be pretty ridiculous for people to be sent to hell on trivial technicalities like that, and then I realised that pretty much all the sins that weren't technicalities were basically common sense (excluding stuff like homosexuality obviously) and I wouldn't commit them due to fear of my own guilt. So I just decided I didn't need moral guidance, and even if there is a god, he gave me rational thought for a reason and wouldn't want me wasting it on faith in a a god whom there is no evidence for. And yes I'm procrastinating