Chris Kouwenhoven

Sporadic wheezing

Today we are once again dipping into the "e-mail box" to address a question sent in by one of our subscribers. I hope this may answer some questions for you about your pet's health.

"Once every couple of days my male 3 year old suddenly starts to wheeze as if he is trying to clear his throat or congestion in his airway. Sometimes I detect a congested sound when I put my ear to his side. He is very healthy, otherwise, great appetite and very playful. What do you think?" (Submitted by Les Kelvin).

Thanks for the question, Les! The respiratory system, like the heart, must function throughout life. Most of the time it does so "in the background" and we are really not aware of it. Only when there are problems do we recognize its function. Respiratory distress may be caused by a variety of factors:

**Upper Respiratory Infection (URI): Bacterial and/or viral infection, usually accompanied by coughing and/or sneezing. Generally lasts only about a week to ten days.

**Bacterial or viral infection of the lungs (pneumonia): Although the body is exposed to a staggering amount of potential disease causing organisms (pathogens) almost every moment, most otherwise healthy animals, including humans, do not become infected by these pathogens. Many of these pathogens are airborne and may be present in the next breath you or your pet inhale. The complex system of airways which warm and moisten every breath trap many of these potential disease organisms. Small hairs, called cilia, present in the nasal mucosa which lines the respiratory passages, also help to trap these small airborne particles and keep them from reaching the lungs. If, despite all these protective measures, pathogens reach the lungs and cause pneumonia, the decrease in available oxygen transport via the lungs to the RBCs (Red Blood Cells) may cause labored breathing.

**Constriction of the respiratory airways: This constriction may be due to inflammation from inhaled material or an allergic reaction to substances present in the air. The swelling of the cells in and around the smaller respiratory passages, called bronchioles, narrows these areas and decreases the amount of air able to reach the lungs.

**Pneumothorax: (air in the pleural cavity). Normally there a slight negative pressure in the chest (thorax) that allows the lungs to inflate with each intake of breath. When a puncture wound, such as a bite, allows outside air to enter the chest, this makes filling the lungs much more difficult, and respiratory distress is quickly seen.

**Hemothorax (blood in the pleural cavity): Very similar to pneumothorax, except that it is free blood, rather than air, in the pleural cavity that restricts the inflation of the lungs. This is often caused by trauma, such as being hit by a vehicle or receiving a blow to the chest area.

**Pulmonary edema (fluid in the lungs): Edema is simply a collection of excess fluid in the interstitial (outside cell membranes) spaces. We often see edema as a swelling following an injury, such as a sprained ankle. It is an attempt by the body to immobilize the injury and to bathe the damaged cells in extra fluids to hasten repairs. In the lungs and smaller respiratory passages, this edema may be due to the body's response to infectious organisms or, more rarely, inhaled chemicals. Naturally, the presence of edema makes obtaining sufficient oxygen more difficult and a wheezing sound may be heard as air attempts to get by such swelling.

Of course there are other reasons Les' pet may be exhibiting the symptoms he has described, including swollen tonsils, ingested fibers and hair, and even a genetic narrowing of the respiratory passages, but only a through physical exam can pinpoint the exact cause(s) for this sporadic wheezing. As long as it is only sporadic, he is otherwise healthy, playful, and eats well, such episodes can probably wait until time for the next visit to your pet's veterinarian for routine vaccinations. If, however, the episodes should increase in frequency or duration, you should seek professional care as soon as possible. Upper respiratory infections accompanied by sneezing and copious nasal discharge should be reason for a visit to your veterinarian, especially in multi-cat households.