What is chronic bronchitis?
Chronic bronchitis (CB) is a long-term inflammatory condition that affects the pulmonary or respiratory system. This condition is irreversible and is slowly progressive. This condition may also be known as chronic obstructive pulmonary disease (COPD).
What causes chronic bronchitis?
No definitive underlying causes of chronic bronchitis have been determined. However, long term airway inflammation may result from exposure to inhaled irritants such as tobacco smoke, air pollutants or allergens, bacteria associated with dental disease, or from recurrent infections of the respiratory system.
Are there other factors that can make chronic bronchitis worse?
Yes. Obesity is a complicating factor and will worsen the symptoms. Dental disease increases the risk that bacteria will travel from the mouth into the lungs and cause a serious secondary infection. Dogs with chronic bronchitis may also have other concurrent respiratory abnormalities such as tracheal collapse or bronchiectasis (dilated lower airways).
"Chronic bronchitis is a condition of the lower respiratory tract."
What part of the respiratory system is involved in chronic bronchitis?
In general terms, the respiratory system is divided into two parts. The upper respiratory tract consists of the nose, nasal sinuses, throat, and trachea (windpipe), while the lower respiratory tract consists of the small airways (bronchi and bronchioles) and the alveoli (the small air sacs deep in the lung tissue where oxygen exchange occurs). Chronic bronchitis is a condition of the lower respiratory tract. Initially it affects the small airways, although in advanced cases it will progress to also affect the alveoli.
How does chronic bronchitis affect the dogs lungs?
In its early stages, chronic bronchitis causes inflammation in the small airways. Persistent inflammation will cause blockage of the small airways and will ultimately result in reactive changes in the lungs, including dilation of portions of the small airways (bronchiectasis) or scarring in the lungs (pulmonary fibrosis). This condition develops slowly and is progressive.
Does it affect all breeds and ages of dogs?
Chronic bronchitis occurs in all breeds of dogs but may be more common in small-breed and toy-breed dogs such as West Highland White Terriers and Cocker Spaniels. It most often affects middle-aged and older dogs.
What are the signs of chronic bronchitis?
In its early stages, the main sign of chronic bronchitis is chronic coughing or coughing that persists for longer than a month. The cough is usually 'dry' or harsh, and gagging is common after coughing.
As the disease progresses, difficulty breathing, decreased exercise tolerance (tires easily), or even fainting with overexertion may occur. Breathing may become noisy, and the pet may wheeze when exhaling. In later stages, the gums may develop a bluish tinge as a result of lack of oxygen. Dogs with chronic bronchitis rarely have a fever and usually their appetite remains normal. Chronic coughing may also be a symptom of heart disease, infection of the lungs, or some types of cancer.
How is chronic bronchitis diagnosed?
Your veterinarian may suspect chronic bronchitis based on your pet's history and the results of a physical examination. When the chest is listened to with a stethoscope, wheezes, or ‘crackles’ (harsh crackling or popping sounds), may be heard when the dog breathes in and out. With chronic bronchitis, the heart rate is usually normal or lower than normal and there is often a pronounced sinus arrhythmia (an irregular heart rate that is associated with the breathing cycle).
A series of tests may be required to confirm the diagnosis and to exclude other diseases that could be causing the symptoms.
- CBC and biochemistry profile will assess the general health of your dog, and specific blood or fecal tests may be recommended to rule out parasitic diseases such as heartworm or lungworm.
- Thoracic radiography (chest X-ray) often shows characteristic changes in the lungs and may be helpful to eliminate other types of heart or lung disease. Magnetic resonance imaging (MRI) or computed tomography (CT) may also be utilized, but generally only at referral hospital settings.
- Cytology using bronchoscopy. A bronchoscope is used to directly examine the inner surfaces of the airways in an anesthetized dog, looking for characteristic changes associated with chronic bronchitis. After completing the visual examination, cytology samples, or samples of the cells lining the bronchi and bronchioles can be collected for microscopic examination and culture for microorganisms such as bacteria.
- Bronchoalveolar lavage (BAL). The pet is usually placed under sedation or anesthesia, and a thin, flexible, sterile catheter is passed into the lower part of the lungs. A small amount of sterile fluid is flushed forcefully into the area and then promptly suctioned or aspirated back out. The recovered fluid contains mucus and a small number of cells that can be cultured for microorganisms and examined under the microscope as discussed previously.
What is the treatment for chronic bronchitis?
Many dogs with chronic bronchitis can be treated as outpatients. However, if the pet is experiencing severe respiratory distress, hospitalization for oxygen therapy and/or intravenous medication to stabilize the condition may be required.
Specific medications that may be prescribed to treat chronic bronchitis include bronchodilators to dilate the airways and help clear secretions, cough suppressants, antibiotics if there is evidence of a secondary bacterial infection, and/or corticosteroids to decrease the inflammation and ease the coughing. There have also been some anecdotal reports of using maropitant (Cerenia®), a drug normally used for vomiting, as a cough suppressant.
In some patients, the use of metered dose inhalers (puffers) may be an option to administer corticosteroids and / or bronchodilators directly to the lungs. Your veterinarian will discuss all the options with you and help you decide which options are best for your pet.
Non-specific treatments for chronic bronchitis include diet modification and mild exercise to promote weight loss and using a harness instead of a collar for restraint. Avoidance of irritants such as smoke or airborne allergens will help lessen the chance of relapses. Your veterinarian may prescribe supplements that have antioxidant, anti-inflammatory or immune stimulant functions as supportive treatments.
To reduce the risk that bacteria will induce further inflammation or cause an infection in the respiratory tract, it is important to maintain good oral hygiene in the dog with chronic bronchitis. It is important to brush their teeth on a daily basis. Regular oral examinations including a complete dental descaling, cleaning, and polishing under general anesthesia are part of a comprehensive oral hygiene program.
"It is important to maintain good oral hygiene in the dog with chronic bronchitis."
What is the success rate for treatment of chronic bronchitis?
This condition is non-reversible and is often slowly progressive. Appropriate treatment will slow the progression of the disease and will relieve distressing symptoms. With proper management, most dogs with chronic bronchitis enjoy a normal life expectancy and an excellent quality of life. Relapses may occur when the seasons change or if air quality is poor.
Adjustments to medication dosages may be necessary at these times. Consult your veterinarian for the appropriate advice if this occurs with your pet.
