[header] How to diagnose coughing in dogs [title] Notice what time of day the coughing occurs. [step] Coughing in dogs has many causes, including heart disease. The cough is a symptom and can't always be used to determine the cause; however, certain conditions do have distinctive types of cough, which can help point towards the source of the problem. 
Noticing what time of day your dog coughs can help determine the cough's cause. [substeps] Coughing during the night can be caused by congestive heart failure, fluid buildup in the lungs, or tracheal collapse.