What is asthma?
Asthma in our veterinary patients is very similar to asthma in humans. Asthma is a recurring respiratory compromise where the airways are constricted or narrowed. Asthma consists of airway inflammation, airway hyper-responsiveness (overreaction to stimuli) and airflow limitation (due to constricted airways). Extra mucus forms, the airway walls then swell with inflammation and then the airway muscles spasm and constrict which leads to exercise intolerance, coughing and wheezing (trapping of air on exhale).
How is asthma diagnosed?
A diagnosis of asthma in our cats may be based on both diagnostics and clinical signs. Because the airways are constricted, the volume of air a patient can move is reduced resulting in an increased respiratory effort. Cats may use their abdominal muscles to push out air or may attempt to breath with their mouth open.
The first step toward making a diagnosis of feline asthma is the chest radiograph, assuming the cat is not in too much distress for this procedure. Classically, this radiograph will show what is called air-trapping, meaning that the small airways have constricted so that inhaled air cannot be exhaled. The lungs are larger in appearance than normal as they are over-inflated. The diaphragm may seem flattened due to this over-inflation. If the classic signs are present a diagnosis is easy, however some cats have very normal radiographs (present in up to 23% of cats with asthma) . A specialist can perform a wash of the airways and collect mucus from deep in the lungs which can also be helpful in a diagnosis.
Response to therapy is also useful as a diagnostic test. If a cat responds to the classic treatment for asthma (steroids), a diagnosis is also made.
The cornerstone of asthma treatment is steroids, which reduce inflammation in the airways. Steroids can be given as pills, liquid, transdermally (for hard to medicate cats), through injections or via an inhaler. Usually treatment is initiated with oral steroids. These medications are relatively inexpensive and a good response to them helps confirm the diagnosis. Oral steroids can have drawbacks long term, including heart disease, weight gain and the development of diabetes. Therefore, in many of our asthmatic patients, we try to transition them over to inhaled steroids +/- bronchodilators. Cats are generally started on a combination of oral prednisolone and the metered dose inhaler then gradually maintained on only the metered dose inhaler. A special device called an Aerokat used to administer the inhaled steroid. This device can be purchased online and most patients get used to it quickly. Unlike oral medications or injections, inhaled steroids often take 4 to 6 weeks to be effective, but have minimal systemic side effects.
Fluticasone is the most commonly prescribed inhaled steroid. Generally cats are maintained on twice a day dosing. Also similar to humans, albuterol (a medication used to dilate the airways) can be administered “as needed” with the Aerokat device in the event of a crisis. Albuterol is useful as a “rescue” medication for acute asthma attacks, not for long term daily use.
Photo courtesy of AeroKat
Other Treatment Options
- Airway Dilators
- Terbutaline and theophylline are airway dilators commonly used in the management of asthma. Both terbutaline and theophylline are oral medications. Terbutaline can also be given as an injection during a crisis at the veterinary hospital.
- Cyclosporine (atopica)
- Cyclosporine is an immunomodulator often used to treat auto-immune diseases. It has been used occasionally in cats where adequate suppression of inflammation has not been possible with combinations of the other medications listed or when the cat is unable to take corticosteroids for other reasons.
- Cerenia is a prescription anti-nausea medication. It can be used off-label in cats and recently has been shown to be effective in reducing inflammation in the airways.
- Antibiotics may be prescribed if a secondary underlying infection is suspected. Cats with asthma have a decreased ability to clear inhaled particles and therefore are more prone to secondary infections.
- Antihistamines like zyrtec (cetirizine) are sometimes recommended to reduce the allergic response in the airways.
Additional At-Home Care
Minimizing irritants in the air is always helpful to an asthmatic cat.
- Do not allow cigarette smoke in the cat’s environment.
- Use dustless cat litter.
- Consider non-topical insecticides. No sprays, either.
- Regularly replace air filters at home.
For more details including a video on the use of the aerokat and inhaler, we recommend visiting fritzthebrave.com. This is a website set up by one family devoted to their asthmatic cat. It has grown into a detailed instructional site for both pet owners and veterinarians interested in the details of inhalers for feline asthma treatment.