What breed of dog is this?
Has the dog been vet checked?
Is the dog on a monthly heartworm preventative?
Thank you for that information. Coughing can be a sign of heartworm, heart problems, tracheal problems, kennel cough, upper airway illness such as bronchitis, bacterial or fungal infections, or lung worm. Given the age of the dog it is important to get the right diagnosis. Since there are so many reasons that can cause a cough I would have the dog examined. Each of the above would require different treatment.
Heartworm or a heart/lung problems would be a concern for an older dog. You can rule out kennel cough if the dog has not been around other dogs. Fungal or bacterial infections can easily be picked up anywhere. Fluid build up around the lungs would be another concern.
There is no definitive answer for a cough alone as it can mean so many things.
I don't see in the Chow profile that they are prone to anything that would cause coughing , such as tracheal or esophageal problems. Until you can get the dog in for an exam keep the dog rested with little activity.
I am going to direct you to asite on coughing which will tell you possible causes and tests that may be needed.