Brachycephalic Upper Airway Obstruction Syndrome

Brachycephalic Upper Airway Obstruction Syndrome

Brachycephalic upper airway obstructive syndrome (BUAOS) is associated with a collection of anatomical deformities that are typically seen in brachycephalic (short-nosed) breeds of the dog and cat. The English bulldog, Pekingese, pug dog and Persian cat being more commonly affected, but a variety of other breeds (Cavalier King Charles Spaniel, Staffordshire Bull Terrier, various terriers) are also seen.

What causes the disease?
The defects are due to a mismatch between skeletal growth (which is “dwarf-like” due to a defect in the cartilage development), and the soft tissue structures that would normally develop. Abnormalities that may be seen in animals with BUAOS include:

  • Stenotic Nares (narrow nostrils)

  • Elongated soft palate

  • Hyperplastic (enlarged) tonsils

  • Everted laryngeal saccules

  • Laryngeal collapse

  • Hypoplastic (narrow) trachea


The brachycephalic animal may have one, or a combination of these conditions, with variable effect on airway dynamics.

What are the signs of this condition?
Mildly affected animals will have increased upper airway noise (snorting or snoring), especially with exercise. Severely affected animals have more pronounced airway noise, reduced tolerance of exercise, or collapse after exercise. Exercise, hyperthermia, or any stress may exacerbate the clinical signs. 

These dogs are very prone to hyperthermia even in a cool environment since their most important method of thermo-regulation, panting, is compromised. Vomiting, regurgitation and retching are also commonly observed signs.

Is corrective surgery necessary?
Early correction of anatomical abnormalities such as stenotic nares and elongated soft palate may result in a significant improvement of airway dynamics, and may prevent subsequent deterioration during the animal’s lifetime.

Stenotic nares and elongated soft palate have a significant influence on airway dynamics, and the most readily corrected anomaly present. They result in an increased respiratory effort, and significantly increase the amount of negative pressure generated within the airway lumen. As a result, they play a significant role in promoting dynamic airway collapse and causing permanent structural deformity of airway anatomy. Skeletal narrowing of the nasopharynx and nasal chambers also exists, but nothing can be done to correct this.
Obesity can play an important role in worsening a dog’s airway condition. A weight control programme may be discussed as part of any treatment. 

How will my vet diagnose this condition?
Diagnosis is made on the basis of breed, history and clinical examination. Other diagnostic aids include radiography and visual assessment of the larynx and pharynx. Radiography can be used to assess the length of the soft palate, and to evaluate the lungs and trachea. A definitive diagnosis is made on direct visual assessment of the tonsils, soft palate, pharyngeal mucosa and the larynx. The overlong palate may be inflamed and thickened, as may be the pharyngeal wall. The larynx will be examined for evidence of laryngeal collapse or eversion of the laryngeal ventricles. Other investigations that may be performed include blood and other laboratory tests, and examination of the bowel, particularly if vomiting or retching are observed.

What treatment options are there?
A variety of options will be considered in the management of this condition. Individual elements of disease will determine which treatment is ‘right’ for a specific dog.

a. Stenotic Nares
Correction of stenotic nares is a straightforward, and relatively benign surgical procedure. As a therapeutic technique (in animals presenting with signs of respiratory distress), the procedure will almost always be performed in conjunction with some other plastic procedure, usually resection of an overlong soft palate.

b. Elongated Soft Palate
Shortening of an overly long soft palate can be difficult surgery, largely due to the reduced surgical access into the back of the mouth. Care is necessary to ensure the palate is not shortened too much as food may then be allowed to enter the back of the nose, causing sneezing and a chronic discharge. Swelling of the area after surgery may cause interference with breathing, and very close monitoring is essential in the post-operative period. Experience with the surgery and associated nursing care is therefore important, if complications are to be avoided.

c. Tonsillectomy
The tonsils are frequently enlarged in these dogs due to long-term irritation. They may contribute to irritation and retching, and may narrow the airway in some animals. Where they are enlarged, the dog may benefit from their removal. 

d. Everted Laryngeal Ventricles 
The increased inspiratory effort secondary to stenotic nares and/or elongated soft palate frequently results in eversion and oedema of the laryngeal saccules (the tissue lining the laryngeal ventricles). This condition further complicates the airway obstruction. If this condition is present, the saccules will be removed at the time of corrective surgery. 

e. Laryngeal collapse
Laryngeal collapse occurs due to a progressive loss of structural integrity of the laryngeal structure as a result of chronic upper airway obstruction. “Tie-back” of the vocal folds, or partial removal of some of the larynx has been recommended for these dogs but was successful in only half of the animals in one study. Permanent tracheostomy may provide an effective solution, but requires considerable owner compliance for stoma cleaning and care. Some amendments to the animal’s lifestyle may also be required.

How successful is this treatment?
Successful management of the dog with airway disease requires a comprehensive evaluation of all of the potential components that may be contributing to the clinical signs. Anatomical defects are frequently at fault, and may require surgical correction. In other animals, other considerations may be equally important (e.g. obesity, bowel disease, allergic airway disease). Appropriate management can result in considerable improvements in a dog’s lifestyle.

If you have any further questions about airway disease in the brachycephalic dogs you should speak to your veterinary surgeon who will be able to discuss this condition with you more fully.
