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Bronchitis: Chronic, Sterile Disease Articles Home |
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Bronchitis: Chronic, Sterile
About the Diagnosis In dogs, as in people, the lungs are the organ that allows oxygen to enter the body and that expel the waste gas, carbon dioxide, from the body through the breath. In terms of structure, the lungs are made up of tissue (parenchyma) arranged into clusters of tiny, gas-exchanging chambers called alveoli. These alveoli-each one smaller than a pinhead-have a single channel for air inflow and outflow. These channels merge together to form the airways, or bronchi, and in turn, the bronchi merge together to form the trachea or windpipe. The result is that when air is inhaled the airflow enters into a single tube in the back of the mouth and nose (the trachea) and travels down the tube, splits to go into the bronchi, and then branches again many times so that the air travels through increasing numbers of smaller and smaller tubes until reaching the several million alveoli that make up the lungs. This is the normal process of each breath. Bronchitis is the name given to irritation or inflammation of the branching tubes and airways-the bronchi. Irritation and inflammation cause swelling, and swelling of the bronchi narrows their width, restricting the amount and ease of airflow. It is a similar problem as asthma, except that in asthma, the bronchi become narrowed as a result of an allergic reaction, whereas in bronchitis, the bronchi become narrowed because either an infection or irritant particles like dust or smoke have landed on the bronchial surface and triggered both irritation and mucus (phlegm) production. Chronic sterile bronchitis and chronic obstructive pulmonary disease are the two names given to the same, common, age-related respiratory disease of older dogs in which the bronchi are irritated by noninfectious causes (in other words, by pollens, dusts, air pollution, and so on), triggering a nagging and recurrent cough. Initially with bronchitis, symptoms are subtle or nonexistent because of the ability of the lungs to compensate for slightly decreased airflow. As the bronchitis worsens, coughing, wheezing, and increased respiratory effort develop, with the exact nature of symptoms depending on the severity and progression of the irritant process in the airways. If the bronchitis becomes severe enough, serious deficiencies in oxygen delivery can occur that can lead to weakness, respiratory distress, and collapse. In severe cases, bacterial pneumonia is a secondary problem that can occur with bronchitis. Chronic bronchitis can produce symptoms that mimic other respiratory diseases. Therefore, to pinpoint whether chronic sterile bronchitis is the cause of symptoms, your veterinarian will ask you questions about the symptoms you have observed, such as coughing, and how long they have been occurring, whether the severity has stayed the same, worsened, or waxed-and-waned, and so on. Your veterinarian will also examine your dog closely, including listening to the chest with a stethoscope, to try to identify clues that would make chronic bronchitis more likely or less likely. All dogs suspected of having chronic sterile bronchitis need chest x-rays and often other tests as well, such as a routine blood screen. Finally, if there is a suspicion that an infection may be present in the airways, your veterinarian will likely recommend a transtracheal wash or a bronchoalveolar lavage, which are procedures that retrieve a sample of respiratory secretions for analysis while your dog is sedated or under general anesthesia. Living with the Diagnosis Chronic sterile bronchitis, as the same indicates, is a longstanding (chronic) disorder not caused by infections. Therefore, the main symptom, cough, can be a nuisance to the affected dog and to family members, but the condition is rarely life-threatening. Therefore, the cornerstones of dealing with chronic bronchitis are:
The longstanding nature of chronic bronchitis and the worsening that occurs with age mean that complete elimination of cough is rarely possible. By the time chronic sterile bronchitis causes symptoms (coughing), often there is some degree of permanent tissue damage to the airways. The lungs have a great ability to compensate for damage, destruction, and temporary dysfunction. Therefore, treatment is based around maximizing the function of the remaining tissue and trying to prevent further degeneration of the airways. Treatment Short-term care revolves around supportive care (hospitalization, oxygen supplementation if necessary, bronchodilators, anti-inflammatories, etc.). Such intensive measures are RARELY necessary, since chronic bronchitis usually produces a nagging, longstanding cough and not respiratory difficulty or distress. Long-term care and management involves the steps mentioned above. Specific medications that are used for treating chronic bronchitis include: bronchodilators, to decrease the coughing reflex and reduce the speed of airflow during coughing; cough suppressants, to break the cycle of coughing and airway irritation and bring comfort to a chronically coughing dog; possibly antihistamines, if an allergic component is thought to be part of the trigger for coughing; and weight loss, if there is any sign of obesity because excess weight worsens lung function and reduces airway diameter. As a last-ditch effort, it may be necessary to give pills or syrups that contain corticosteroids (cortisone-like drugs). These are excellent anti-inflammatories but they also cause significant weight gain and can decrease immune function, potentially creating problems in the long term. Inhalation therapy ("puffers") that administers bronchodilators or corticosteroids has been an important part of management of bronchitis and asthma in human medicine. In the recent past there have been good inventions (specialized inhaler masks) to help appropriately supply these medications to dogs and cats, and this form of treatment is revolutionizing treatment for chronic respiratory disease in dogs and cats. Most animals are surprisingly tolerant to this form of treatment, and it is easy to perform. If your dog is diagnosed as having chronic sterile bronchitis and requires treatment, you should ask your veterinarian about inhalation therapy, or he/she may refer you to a respiratory specialist (a Diplomate of the American College of Veterinary Internal Medicine, specialty of Small Animal Internal Medicine). DOs
DON'Ts
When to Call Your Veterinarian
Signs to Watch For
Routine Follow-Up
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