11 yr old shephard cross, stopped eating and tongue turning purple

Our dog Kiya is very ill. She is a food motivated animal who now has been existing on the tiniest bites of food for the last 10 days. She is still drinking some water daily. We took her to the vet May 11 as she was listless, had a kind of cough and was panting rapidly. He said her heart and temperature were fine and that she had an upper respiratory infection. He prescribed Clavaseptium and Torbutrol to be administered twice daily for 7 days. This prescription is almost finished, she is not responding well and her tongue is turning purple. She always looks eagerly forward to a daily walk through the woods but now has no desire and is losing weight rapidly. The only unusual happenstance was about three days before she became ill she caught a sparrow on her walk and gulped it down. She is a wonderful intelligent dog and a beloved pet to our children. We would be most grateful for any help at this moment. Thankyou.