Dogs breathe heavily for several reasons, one of which is to lower their body temperature through panting. According to WebMD, when dogs pant they evaporate water from the mouth, tongue and lungs. The warm air in their bodies is replaced with cooler air from the atmosphere.
When a dog is at rest they will normally breathe around 10 to 30 times a minute. If the dog is breathing heavily but is not hot or tired, this could be a sign of an underlying problem.
If a dog has rapid, labored or noisy breathing, he should be taken to a veterinarian. It could be a sign of distress indicating one or more of the following health issues:
- Heat stroke or dehydration
- Congestive heart failure
- Lung Disease
- Ketoacidosis associated with diabetes
- Kidney failure
- Obstruction in the nasal passages
Dogs can have stridor, or croupy breathing, which has a raspy, high-pitched sound. Dogs can make this noise when they exercise. If the onset of this sound is sudden, however, this could be a sign that something is lodged in the dog's voice box.
If a dog is wheezing, the trachea or bronchi could be having spasms or narrowing. Bronchitis, heart failure or tumors somewhere in the airway can cause this. Dogs with broken ribs or severe bruising may take very rapid, shallow breaths because of pus, serum or blood in the chest cavity that is preventing a full range of motion.