CANINE CHRONIC BRONCHITIS

Coughing is different from reverse sneezing or retching to vomit. The dog in this video is coughing.
(video from Greg Jahnke on YouTube)

When the bronchi are injured by irritants (cigarette smoke, air pollution, biochemical products of infection etc.), they respond with a healing process which is inherently inflammatory. When the injury becomes ongoing, the inflammatory/healing process also becomes ongoing and the end result involves excessive mucus production in the airways. The mucus obstructs the smaller bronchi which stimulates coughing, which in turn leads to irritation and then to inflammation and then to more mucus. A vicious cycle results.

Once the vicious cycle (of mucus production to coughing to inflammation to mucus) has become entrenched in the patient, it is unlikely to be cured and therapy is geared towards controlling the symptoms.

WHAT MAKES BRONCHITIS CHRONIC?

Bronchitis can be temporary, as in short-term infectious disease such as Kennel Cough, or it can be chronic, which basically means it has been going on for a long time. To fit the definition of “chronic”, the cough must be present daily for at least a couple of months. There are many causes of ongoing cough; bronchitis is certainly not the only one. It is very important to determine whether or not a reversible underlying cause is present. The character of the cough (wet, dry, “honking,” productive etc.) is not particularly helpful in determining the cause of the cough.

DIAGNOSIS

It is important to realize that there are many conditions that make dogs cough chronically including but not limited to:

• Pneumonia
• Tracheal Collapse
• Fungal infection in the Lung
• Lungworms
• Cancer
• Heart Failure
• Heartworm Infection

(Note that asthma is conspicuously missing from this list. Asthma involves recurring episodes of airway inflammation and narrowing rather than the continuous (non-episodic) airway inflammation. Asthma is not a natural clinical entity in the dog though it is certainly a well-described condition in the cat.)

Chest radiograph of a dog with bronchitis. The heart is the oval structure in the center.
The lacy white texture of the lungs comes from mucus and other
inflammatory secretions clinging to (and visually highlighting) the airway walls.
(original graphic by marvistavet.com)

Radiographs of the lungs are crucial in ruling out conditions that have a specific treatment. In bronchitis, mucus in the airways tends to outline the shape of the airways in patterns that look like parallel lines (so-called “tram lines") when looking at an airway’s side view or circles (so-called “doughnuts”) when looking at an airway end on. The airways may be dilated in bronchitis as well, especially if the case is advanced. Other conditions tend to have characteristic radiographic appearances of their own but there is definitely room for ambiguity.

In a perfect world, bronchoscopy can be performed and samples of the airway secretions can be analyzed. In bronchoscopy, a small video camera is inserted down the airway system. The color and character of the airway walls can be examined and a fluid wash can be used to aspirate out samples of secretions. General anesthesia is required for this procedure.

Bronchoscopy and sampling of airway secretion
(video from Wildlife Surgery on YouTube.com)

Alternatively, a tracheal wash can be done to obtain samples using special tubing and fluid washes. In this procedure, only samples are taken and there is no camera involved and no visual inspection of the airways. Sedation is generally needed.

Sedation and anesthesia are not without risk in patients with lung compromise so the benefit of obtaining diagnostic information must be weighed against patient risk. Often invasive procedures are skipped and trial courses of medication are used.

TREATMENT OF BRONCHITIS

There are several aspects to the treatment of bronchitis. Often a weight loss program relieves so much chest restriction that medications become unnecessary. Physical therapy techniques can be used to clear secretions. Medications can be used to relieve inflammation, dilate airways, and reduce secretions but some trial and error is often needed to get the right combination. Newer inhalant therapies can spare the patient many potential drug side effects.

TRIAL COURSES OF MEDICATION

Different individuals respond to different medications and in bronchitis there are several options to choose from and even combine.

Corticosteroids

Corticosteroids such as prednisone relieve inflammation and cut secretions like no other medication can. Typically a short course is used to control symptoms initially followed by a lower dose maintenance course. This helps dry up the mucus in the airways and stop the cough-irritation vicious cycle. The problem is that oral steroids have side effects potential with long term use. Further, because they are suppressive to the inflammatory process it is especially important to have ruled out infectious causes of coughing which might be made worse with steroid use.

Cough Suppressants

The cough itself is involved in the vicious cycle of irritation described above. Suppression of the cough reflex through medication may be helpful in establishing patient comfort. On the other hand, we want our patient to be able to clear the mucus from the inflamed airways if there is an excess of mucus present. Common medications used are hydrocodone and butorphanol. Over-the-counter human products are often ineffective and may be combined with harmful additional medications such as decongestants or pain relievers.

Never medicate your pet without checking with your veterinarian first
about what product to use and how to dose it.

Airway Dilators

Although, airways technically do not constrict in chronic bronchitis, it may be helpful to relax them allowing air to pass through bronchi that had previously been so small as to be occluded by mucus. Common medications include: albuterol, terbutaline, and theophylline. These are frequently used in combination with corticosteroids to enhance reduction in cough.

Mucolytics

An over-the-counter supplement called N-acetylcysteine may be helpful. This supplement works by breaking down sulfur bonds in the airway mucus creating a more watery secretion. Thinner secretions may be easier to clear. The use of this supplement has not been formally studied for this use but it is an option that might be helpful.

Antibiotics?

Chronic bronchitis is not an infectious disease but all the inflammation and mucus in the lung certainly compromises the patient’s normal resistance to infection and ability to clear inhaled bacteria. Sometimes antibiotics are a helpful temporary addition to the therapies listed above.  More commonly antibiotics are used early in the treatment course to rule out infectious causes of cough before the use of corticosteroids which are immune suppressive.

Coupage is a form of respiratory physical therapy which allows for moistened secretions to be moved into more central airways so they can be coughed up. See video below for details.

How to Perform Coupage.
(video from themorrishospital on YouTube.com)

Obesity Management

Pressure on the chest from body fat hampers the patient’s ability to take a deep breath. Many patients with chronic coughs do not require medication after excess weight has been lost simply because the chest can then expand properly.

For more details on pet weight loss click here.

Chronic bronchitis represents an ongoing airway change that generally cannot be cured; however, symptoms are manageable for most patients. Discuss the options for therapy with your veterinarian, expect some trial and error to be necessary, and it is likely the outcome will be a system that keeps your pet comfortable.

Minimize Airway Irritants

It will be especially important to minimize irritants circulating in the air. If possibly, smoking cigarettes should be limited to outdoor areas. If house painting, cleaning, or remodeling is planned, the pet should probably be boarded or stay elsewhere until any fumes have dissipated. It may be a good idea to get a good air filter for home use to minimize dusts, pollens or molds in the air. 

 Page posted: 11/18/2014
Page last updated: 6/2/2020