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Bronchitis is inflammation of the small airways in the lungs. It can be acute and short – lived with reversible changes, or chronic with irreversible changes. It can be insidious in onset and the pet may not show signs of disease until it is advanced with severe changes to the respiratory tract.   It is usually seen in middle aged or older small breed dogs and causes a persistent. It must be differentiated from other diseases causing chronic cough such as congestive heart failure, pneumonia, and lung cancer. The causes of bronchitis are poorly understood, but thought to be secondary to numerous factors such as chronic infection, exposure to pollution or aerosolized irritants, and second hand smoke exposure. It may also be a sequel to allergic airway disease.

The inflammatory response leads to excessive mucus production in the airways. Smaller bronchi can become occluded by thick mucus plugs and the mucosa (lining) of the bronchi can become thickened. Once the bronchial walls weaken, they can begin to collapse causing further impedance of airflow into and out of the lungs. Compare the normal bronchi in Photo 1 to collapsing bronchi in Photo 2).   Clinical signs include persistent, intractable coughing with gagging; cough that is exacerbated by exercise; a cough that is unproductive, loud and harsh during the day, but productive at night; cyanosis (bluish color to mucus membranes due to lack of oxygen), collapse and exercise intolerance; or increased effort to breathe out. Diagnosis involves ruling out other diseases, usually with radiographs (xrays), followed by endoscopic examination of the airways. Usually samples are taken for culture and cytology to rule out infection or other diseases.   

Since the disease is not curable, treatment is directed at trying to improve the patient’s quality of life. Treatment falls into several categories: eliminating any environmental irritants, weight control, cough suppression, treatment of infection, treatment of airway inflammation and obstruction, and oxygen therapy if needed. Often dogs with chronic bronchitis are overweight. This extra weight over the ribs and the increased amount of fat in the abdomen increase the work of breathing leading to more consumption of oxygen. With weight reduction, patients can improve their ventilation and oxygenation, increase their exercise capabilities, and decrease the stress on their heart. Anti-inflammatory therapy usually involves the use of corticosteroids – either orally or via inhalers once infection has been ruled out. Bronchodilators may help to open airways and provide better oxygenation and help to expel accumulated mucus. Airway nebulization can help to thin the mucus allowing better clearance, and light exercise after a treatment may assist in dislodging mucus plugs. Cough suppressants are not used initially because the cough is important in expelling excess secretions. However, once the cough becomes more non-productive, cough suppressants can be beneficial. Oxygen therapy can be used for temporary support during a crisis situation, but an animal that requires oxygen therapy usually has advanced disease and a poor prognosis.