Rapid breathing

Question
Hi,
I have a 3 year old pekeniese, not sure if that is the right spelling that has been diagosed with heart failure, He is on  lasix, enderol,and a breathing pill.He is getting worse each day and this morning he has rapid breathing and seems real weak. He ate good last night but can not get him to eat today,Should I have him put to sleep as the vet says they cant do anymore for him. Why he breathing so fast?

Answer
He is breathing so quickly in an attempt to oxygenate his blood better while it is in his lungs.  This is to compensate for the fact that his heart is not working properly and therefore cannet pump enough blood round his body to keep the body tissues supplied with oxygen.  

That he is refusing to eat probably means his body has started to shut down his digestive system in order to conserve blood and therefore oxygen for more "important" tissues such as his brain.

Unfortunately once a dog reaches this stage there is nothing that can be done and he will probably go down hill very quickly.  It is likely his quality of life is not going to be very good from now on and he may start to be in pain in the near future.
If he were my dog i would certainly be thinking about making the decision to have him put to sleep in the next day or two, but only you can judge his condition and his level of suffering accurately as you know him best.  I would encourage you not to prolong his life for the sake of keeping him alive a few extra days though.  it is kinder to put him out of his misery when he starts to get distressed as with this condition it is unlikely he will die painlessly and peacefully in his sleep.  In my opinion putting him to sleep would really be the last and greatest act of kindness you could perform for him if you think he has had enough.
Hope this helps a little, i am very sorry for your situation.
Sarah