What is Feline Asthma?
Asthma is a recurring respiratory disease in which there is constriction of the small airways of the lungs. This is due to excess mucus formation, inflammation of the smaller airways, and then spasm of the smaller airway muscles which leads to the constriction. The constriction then leads to coughing, difficulty breathing, difficulty exercising, and wheezing- though these do not always happen all at once. Sometimes the asthma can be secondary to an allergic reaction to an environmental agent, or it can happen spontaneously.
How Asthma is Diagnosed in Cats?
Physical exam: Oftentimes cats with asthma have difficulty breathing because the constricted airways do not allow for enough air to enter into the lungs. These cats can have increased labor and abdominal effort when trying to breathe, and may even breathe with their mouths open. Many may also have a chronic cough or intermittent coughing spells, and, as mentioned above, a veterinarian may hear wheezing when listening to the lungs with a stethoscope. Sometimes the wheezing can be heard without a stethoscope.
Chest x-rays: A commonly seen change in the lungs of cats with asthma is a thickening of the smaller airways within the lung fields, due to mucus and inflammation. Lungs can also be larger than normal because air is trapped in the airways and cannot get out due to the constriction, and sometimes because of this the diaphragm can appear flattened. Many, but not all, asthmatic cats will have these changes on their x-rays. However, some cats can have normal appearing x-rays even if they do have asthma.
Obtaining cells from smaller airways: This can be done either via tracheal wash or bronchoscopy. The idea is that either a small tube or a scope is placed down into the lower airways, and warm saline is flushed, then retrieved back. With it come cells and material from within the lungs which can then be assessed to make a definitive diagnosis. In cases of feline asthma, the most common cell type seen in these samples is the eosinophil, which is a white blood cell that is commonly seen in conjunction with allergies. Eosinophils can also be seen in normal cat respiratory secretions and with parasitic infections, but other tests can be performed to rule those out.
In an emergency situation where asthma is highly suspected, actions must be made quickly. Most cats with asthma will respond within minutes to epinephrine, and within 30 minutes to terbutaline which is used to dilate the airways. Short-acting steroids can also be given in an emergency situation to decrease the inflammation.
Longer term management of asthma typically involves corticosteroids. These are typically given orally when treatment is initially started, however inhalers are also used and can be very beneficial. An inhaler delivers the steroid directly to the lower airways. Long-term administration of steroids can have side effects, but these are not seen commonly in cats who are maintained with inhalers. In order to make sure that a cat receives the medication via inhaler appropriately, a spacer is used (similar to that used in children). The spacer consists of a tube that connects to the inhaler on one end and has a mask on the other end that connects to the cat’s face. The most common spacer is seen at www.aerokat.com. Most cats seem to tolerate this surprisingly well, though it can take some practice!
Other potential long-term treatments may include the following:
Small airway dilators: these may include drugs such as Theophylline and Terbutaline. They come in oral and injectable forms.
Cyproheptadine: This inhibits serotonin, which is an internal chemical that directly causes constriction of the smaller airways.
Cyclosporine: This is an immunomodulator, which may be beneficial in cats whose inflammation is not well controlled with the aforementioned therapies.
There are some other experimental medications that may be beneficial for this condition if no other treatments have helped.
Another important aspect of treatment involves decreasing possible airborne irritants. These include: using cat litter that does not contain dust, refraining from smoking near asthmatic cats, and regularly replace air filters at home.
Importantly, if you notice that your cat is having difficulty breathing, open-mouthed breathing, or struggling, please call your veterinarian or take your pet in to be seen immediately. A respiratory crisis associated with asthma can be life-threatening, so by doing so, you may save your cat’s life!