as in virus "colds" as we know them. Yes there is a virus-bacteria combo involvement yielding Kennel Cough, but over all things like "flu" are almost non-existent in dogs.

However they can get opportunistic bacterial infections of the lungs if their immune systems become suppressed. In older dogs especially bacterial infections in the lungs, leads to fluids in the lungs, which in turn can yield congestive heart failure and death.

Labored breathing is a classical sign of lung infections. You need to take the dog to a Vet for antibiotics (e.g. Clavamox, Baytril), and a diuretic to get rid of any fluids.

After the infection clears you then need to find out what precipitated it. In older dogs one always has to suspicion the possibility of cancer in the background. After the infection has cleared, you should get a blood panel workup. If anything turns up suspicious (e.g. high WBCs, high calcium, low RBCs/hematocrit, low platlets), then an ultrasound should be performed.

In general aspirin is bad for dogs. There is a high chance of ulcers developing. Even with acid blockers there is a possibility of stomach irritation. NSAIDs such as Deramaxx can be obtained from a Vet that will be less harsh, and provide better pain relief for arthritis. But for now, arthritis if present is secondary to other possible problems.