Brachycephalic Airway Obstruction Syndrome (BAOS) is a common condition in many dogs and cats that is due to upper airway obstruction from anatomical abnormalities. Brachycephalic refers to the breeds that are characterized by having the smashed face appearance. Examples of breeds of dogs considered brachycephalic are English Bulldog, Pug, and French Bulldog and breeds of cats are Persian and Himalayan. Because of the compressed face and poorly developed nose airflow is restricted. These animals need to produce a higher negative pressure on inspiration to be able to get adequate airflow; this increased pressure leads to inflamed and swollen tissues in the airways which further exacerbates the obstruction. If allowed to continue airway failure can occur which in some cases becomes an emergency.
Signs that a dog or cat is experiencing upper airway obstruction are snoring, wheezing (high pitched whistling sound), mouth breathing, gagging, restlessness, choking/gagging when eating, and rapid breathing. In more severe cases the animals may collapse, have blue tongues or gums, or experience hyperthermia because they cannot cool themselves adequately by panting. Stress, exercise, or heat can quickly exacerbate the signs leading to an emergent situation.
Through breeding the anatomy of the respiratory tract has been changed leading to the clinical signs associated with BAOS. The common anatomical abnormalities area:
1) Stenotic nares: Narrowing of the “nostrils” causes occlusion of air passage and therefore increased effort with inspiration. Over time this increased inspiratory pressure causes other airway anatomy to worsen.
2) Elongated soft palate: The roof of the mouth (hard palate) becomes the soft palate toward the back. Because of the increased inspiratory effort the soft palate becomes stretched over time. Eventually the soft palate lengthens to the point it hangs into the larynx causing a true obstruction. If this continues the soft palate will become thickened and swollen further lessening airflow through the larynx.
3) Everted laryngeal saccules: Each side of the larynx has a saccule (pouch of tissue). The negative pressure associated with BAOS pulls these saccules and eventually they evert into the airways leading to more obstruction. Think of your pant pockets as the saccules; if you pull your pockets out they are everted and don’t lie nice and flat.
4) Laryngeal collapse: The larynx is a cartilage structure at the back of the throat that opens and closes to control airflow and keep food, etc from entering the lower airways (trachea and lungs). Over time the cartilage in the larynx weakens and the larynx collapses further causing narrowing of the airways and obstruction.
5) Tracheal hypoplasia: The trachea is the structure that takes air into and out of the lungs. Commonly in brachycephalic animals the trachea does not develop well and is small (narrow diameter) which further decreases airflow.
Luckily there are some treatments that can be done for BAOS to decrease the complications associated with it. The best outcomes are with early intervention, sometimes as early as 4-6 months. During the puppy/kitten booster series the nose shape and breathing noises are evaluated. If noisy or obstructive breathing is found it is recommended to open the nose and correct the soft palate at the time of the spay/neuter surgery. If the saccules are everted these are trimmed as well. It has been shown that correcting the obstruction early in life has a positive outcome by helping with airflow and therefore progression of the obstructive nature of the syndrome. If not corrected it can progress to an emergency situation where the pet is in respiratory distress due to the obstruction of the airways.
This is Sophie. Her owner noticed she was very noisy when breathing and especially loud when sleeping. During evaluation it was determined her soft palate was the cause of the problem, her nose is not stenotic. The owner elected to proceed with surgery to trim the palate. Sophie did great and the owner is thrilled with the outcome. Not only does Sophie breathe quietly but her risk of a respiratory emergency due to the obstruction is much reduced.