Brachycephalic Airway Syndrome: What You Need to Know

                                                By Loren W. Noblitt, DVM, MS

The old phrase, "variety is the spice of life," is truly exemplified by the canine species as a whole.  Case in point: the dog's head.  As we all know, dog heads come in all shapes and sizes, but did you know that there are technically three major categories that they fall in to?  They are as follows: 1) Mesaticephalic-a skull of intermediate length and width.  This classification includes dogs like the Beagle, the Labrador Retriever, and the Rottweiler; 2) Dolichocephalic-a relatively long skull.  This classification includes dogs like the Greyhound, the Whippet, and the Collie; and finally, 3) Brachycephalic-a skull that is broad and short.  This includes dogs like the Pug, Boston Terrier, Boxer, Bulldog and Shi tzu.  The brachycephalics have been bred to have compressed faces, shallow eye sockets, and narrow nostrils (or nares) which, although making them all-the-easier to love, also seriously predisposes them to difficulty recruiting fresh oxygen into their lungs. 

Brachycephalic Airway Syndrome (BAS) is any combination of the following abnormalities: a) Narrowed (stenotic) nostrils, b) Elongated soft palate, c) Laryngeal saccule (the useless soft tissue masses adjacent to the vocal cords) eversion, d) Collapsed larynx, and e) Hypoplastic (narrow) trachea (windpipe).  Of these, the elongated soft palate, narrowed nostrils and trachea are considered to be present at birth.  The everted saccules and laryngeal collapse occur secondarily to the effects of the congenital defects (explained below).  Because any of the 5 components of BAS abnormalities can lead to obstruction of oxygen flow into the lungs, the condition often progresses to include inflammation and fluid accumulation of other important upper respiratory tissues like the epiglottis and tonsils, making it even harder for the animal to breathe-BAS is, in this way, very much a vicious circle.
 
     Let's now look at each component of BAS individually.  Nostril narrowing usually occurs on both sides, and when present, contributes to the severity of dyspnea (difficult breathing) making the dog work harder to pull air into his or her lungs-this increase in negative pressure draws the soft palate deeper into the larynx.  The normal function of the soft palate, in conjunction with the epiglottis, is to prevent food from entering the nasal cavity during chewing and swallowing.  In normal animals, the border of the soft palate is near the tip of the epiglottis and if the soft palate is longer than this, it frequently will obstruct airflow through the larynx creating friction with the epiglottis.  Friction results in inflammation during each respiration, further lessening air flow into the lungs.  As increased breathing effort continues in an effort to overcome these anatomical handicaps, increased negative pressure in the airway develops and encourages eversion of the laryngeal saccules, further blocking airflow.  Anxiety from the labored breathing occurs and often leads to excessive panting.

    There are several components of BAS that can be addressed surgically. Surgical correction or widening of stenotic nares may be desirable as part of an overall strategy to decrease upper airway airflow resistance in animals with multiple upper airway abnormalities.  Shortening an elongated soft palate is routinely done by cutting the excess tissue with surgical scissors at the level of the tonsils and stitching the remaining palate back together.  Correction of the nostrils and palate can be done together and as early as 3 to 4 months of age.  Similarly, the laryngeal saccules can be excised with a curved scissor if they are obstructing air flow to make the dog more comfortable and further reduce resistance to air flow; however, this often does not need to be done because once air flow is improved by either/or trimming the soft palate and widening the nostrils, the saccule swelling goes down in most breeds of dog and are no longer everted.  The recent exception to this rule appears to be the Norwich terrier, where everted saccules are felt to be a primary condition.

    As an owner of a brachycephalic dog, there are steps that you can take in lieu of (or in conjunction with) surgical correction, to help prevent severe BAS from occurring.  First of all, animals with severely compromised upper respiratory tracts due to congenital conditions should not be bred, as they will only perpetuate the BAS situation.  Obesity is a big risk factor for BAS so a healthy and controlled diet is imperative.  Along these same lines, exercise and excitement can trigger panting, subsequent airway inflammation, and obstruction, so as an owner be cognizant not to overdo it on walks or runs, especially in hot weather.  Cooling will help minimize panting, so some good suggestions are to place your dog in a quiet air-conditioned room or kennel after a long walk or bout of increased respiratory effort and always make sure that they have access to fresh, cool water.  Finally, the use of sedatives and analgesics in conjunction with your veterinarian may be used to help calm a distressed animal and to decrease severe panting episodes that come secondary to anxiety. 

    Your vet, or the vets at the Zionsville Animal Hospital can discuss with you whether or not your dog is a good candidate for any of the aforementioned surgical procedures. He or she probably will recommend doing a laryngeal exam under sedation to assess these structures.