OP,
Our dog died two days ago with the exact symptom you described above but ours was in the far east.
Our dog was not feeling well two weeks prior to his death but when it seem that he was recovering he died. On the last evening my parents let him out into garden to walk about at around 8pm and got him in by 9pm. He was stumbling a bit when he got back and he went to sleep as usual. Heavy breathing and all that by 10.30pm he was gone.
He was a very healthy dog but two weeks ago things degenerated so I guess he never recovered. We gave him some medications which seem to work but only temporarily and we were thinking of getting him to vet soon but he died before that.
Ours was just a stray mongrel we rescued from dog hunters/catchers (they sold them to restaurants btw) when he was a young dog of not more than 1 year old then led a good life with us for another 7 years. He basically ran into our house and my mum and sister defended him from the dog catchers.
Well, his place is now take over and replaced by two more rescue dogs we have. One mongrel and the other one a kind of toy lion dog.
He is buried in our garden in front of the house.
Yes, we miss him.
😐