Loud breathing

Each time I pick up my old 16-17 year old girl she starts breathing loudly. I don't hear her doing it after she starts resting again but she does it when active too. So two nights now during play time she starts this. She does it when I pick her up to medicate her as well. She gets 1.5mg/ml of metacam at .1 ml twice a day for pain and inflammation for her chronic bumblefoot. She also gets 50mg/ml of gabapentin at .1 ml twice a day for pain. She gets sodium chloride twice a day every day, and flubiprofen twice a day on Monday, Wednesday, and Friday for corneal degeneration. She has been on the .1ml of metacam twice a day for 8 days now. She finished a treatment of enrofloxin a week ago for an infection in her foot. To me her foot looks red and puffy but the vet that does her laser therapy every week saw her Thursday and said she doesn't think it's infected.
The sound she's making while breathing is kind of a whistling sound. She's been doing it for two days now. I don't know how to upload a video or audio clip on the forum.

Metacam can cause slowed breathing in dogs, so it's possible it can happen in chins too. It's also possible she's just stressed from everything going on and handling her exacerbates it. Has she been checked for congestive heart failure?

She went into the vet yesterday. Of course she wouldn't do it then. She only seems to do it at night which is weird. The vet said her heart sounds ok and so do her lungs. She thinks she may be in pain from her feet saying that one is indeed infected. Thinking the antibiotics weren't done long enough to get rid of it so she's on a higher dose of baytril now. She also told me to increase her gabapentin to .2 ml every 12 hours or .15 ml three times a day. Unfortunately, it would be difficult for me to do three times a day so I'm doing twice. She did the breathing thing a little last night but not as loudly nor hard as before. My precious little baby is trying her best to hang in there.