Inhaled air travels from the upper airways (nasal passage and trachea) to the lower airways of the lungs. Deep in the lung tissues, inhaled oxygen enters the blood stream to be exchanged with carbon dioxide, a metabolic waste that is exhaled out of the body. Cats with lung disease may cough, have labored breathing, and experience exercise intolerance. Radiography (x-rays) allows your veterinarian to visualize the lungs and diagnose problems such as pneumonia, heartworm infection, asthma, and cancer.