Brachycephalic Airway Syndrome in Dogs

What does brachycephalic mean?

Brachy means shortened and cephalic means head. Brachycephalic dogs have skull bones that are shortened in length, giving the face and nose a pushed-in appearance. The shorter bones of the face and nose alter the related soft tissue structures they support. Some of these changes can cause physical problems, particularly with breathing. 

Brachycephalic breeds include bulldogs (French and English), boxers, Boston terriers, Pekingese, Chinese shar-peis, pugs, Lhasa Apsos, shih tzus, and bull mastiffs.

What is brachycephalic obstructive airway syndrome (BOAS)?

Brachycephalic obstructive airway syndrome (BOAS) refers to a particular set of upper airway abnormalities that affect brachycephalic cats and dogs. This syndrome is also called brachycephalic respiratory syndrome, brachycephalic syndrome, brachycephalic airway syndrome (BAS), and congenital obstructive upper airway disease. The upper airway abnormalities that occur in this syndrome may include one or more of the following:

Stenotic nares. Stenotic nares are abnormally narrowed or small nostrils that restrict the amount of air that can flow through the nostrils to the lungs.

Extended nasopharyngeal turbinates. Nasopharyngeal turbinates are ridges of bone in the nasal passages that are covered by tissue and help humidify and warm air that is inhaled. When these ridges extend past the nose into the pharynx (the area behind the nose and mouth), they obstruct airflow in varying amounts.

Elongated soft palate. The soft palate is the soft part of the roof of the mouth. An elongated soft palate is too long for the length of the mouth; the excess length partially blocks the entrance to the trachea (windpipe) at the back of the throat.

Laryngeal collapse. The larynx is the dog’s voice box. The cartilage in the larynx may collapse due to the chronic stress imposed on it by other abnormalities related to BOAS. Eventually, the larynx (voice box) is not able to open as wide as normal, causing further restriction in airflow.

Hypoplastic trachea. A hypoplastic trachea (windpipe) has a smaller diameter than normal.

Everted laryngeal saccules. The laryngeal saccules are small sacs or pouches that are part of the larynx (voice box). A dog with BOAS must work harder to breathe, causing increased pressure in the airway, which in turn can cause the laryngeal saccules to evert (turn outwards) or get sucked into the airway. Everted laryngeal saccules will further obstruct airway flow.

What other problems can occur due to BOAS?

BOAS has been linked to changes in the lungs, gastrointestinal tract, teeth, eyes, and skin.

• Bronchial collapse can occur when the bronchi (airways that connect the trachea to deeper airways in the lungs) weaken and collapse, causing further airway obstruction.
• Gastroesophageal reflux can occur when intestinal fluids flow back into the esophagus (the tube that connects the throat to the stomach).
• Teeth are often not lined up properly (malocclusion), which can lead to significant dental issues.
• Eyes often have abnormalities, such as chronic tearing, tear staining, and entropion (inward curling of the eyelids) due to the face conformation. These dogs are predisposed to corneal problems such as ulcers and pigmentary keratitis (discoloration on the eye’s surface).
• Skin infections can occur in the folds around the nose.

What are the signs of BOAS?

Any upper airway abnormalities can cause increased airway resistance, which increases the effort required to inhale. The more abnormalities that are present, the more severe the signs. Most dogs with this syndrome breathe more easily through their mouths than their noses.

Mildly affected dogs will have noisy breathing, especially with exercise, and most will snort when excited and snore when relaxed or asleep. Severely affected dogs have more pronounced airway noise, appear to tire easily with exertion, and may collapse or faint after exercise. Signs are often worse in hot or humid weather. Affected dogs are more prone to overheating, as their ability to pant and cool themselves is compromised. Dogs with impacts on their gastrointestinal tract may show signs including retching, vomiting, or lack of appetite.

Over time, dogs with this syndrome may develop other problems, including inflammation of other structures in the airways. In the long term, the increased effort associated with breathing can put increased strain on the heart. Most dogs are diagnosed with BOAS between one and four years of age. Both males and females appear to be affected equally. Dogs with multiple abnormalities tend to develop problems at an earlier age.

How is BOAS diagnosed?

This syndrome will be diagnosed based on your dog's breed, clinical signs, and results of a physical examination. Stenotic nares can usually be diagnosed with visual inspection. Diagnosis of an elongated soft palate, everted laryngeal saccules, or other associated anatomical changes in the mouth will require heavy sedation or full general anesthesia.

Since dogs with this syndrome have an increased risk of complications associated with general anesthesia, your veterinarian will recommend pre-anesthetic blood work and chest X-rays to evaluate your dog’s general health prior to the diagnostic procedure. If your dog undergoes general anesthesia to diagnose this condition, your veterinarian will likely recommend that any necessary surgical correction be performed at the same time.

What is the treatment for BOAS?

Obesity worsens the signs of BOAS, so weight loss is an important part of treatment if your dog is overweight. For dogs with mild or intermittent symptoms, the condition may be managed conservatively by controlling exercise levels, avoiding hot or humid conditions, keeping the dog in an air-conditioned area during the summer, and avoiding stress.

Corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and oxygen therapy may all be useful for short-term relief of airway inflammation or respiratory distress. However, medical management of this condition does not correct the underlying anatomical abnormalities.

Surgery is the treatment of choice whenever the anatomic abnormalities interfere with the dog’s breathing. Stenotic nares can be surgically corrected by removing a wedge of tissue from the nostrils, allowing improved airflow through the nostrils. An elongated soft palate can be surgically shortened to a more normal length. Everted laryngeal saccules can be surgically removed to eliminate the obstruction in the larynx. These procedures may be best performed at a referral center with a board-certified surgeon.

How successful is surgery?

The earlier that abnormalities are corrected, the better the outcome, since the condition worsens over time and may cause other abnormalities. Early correction of stenotic nares and/or an elongated soft palate will significantly improve airway function and may prevent the development of everted laryngeal saccules. In the early post-operative period, the surgical sites may swell and interfere with breathing, so your veterinarian will closely monitor your pet after surgery. The degree of monitoring necessary depends on the surgical procedures performed.

What is the prognosis for a dog with BOAS?

The overall prognosis for pets with BOAS depends on how many anatomic abnormalities are present and how old your dog is at the time of diagnosis and treatment.

Dogs under two years of age at the time of surgical correction have a better post-operative prognosis than dogs that are older. Dogs that only require surgical correction for stenotic nares and/or an elongated soft palate have a better prognosis than dogs with more defects. Dogs with hypoplastic trachea have a variable prognosis. Dogs that have other problems, such as allergic airway disease, or that have developed secondary problems from airway distress, have a poorer prognosis. However, appropriate management can significantly improve the quality of life for these dogs.

What else can I do to help my dog with BOAS?

Dogs with BOAS should be fitted with a harness that does not tug at the neck area. It is not advisable to use a regular neck collar for these dogs, since a collar can put undue pressure on the neck. In addition, affected dogs should be kept lean, as excessive weight can put more stress on their breathing.

This syndrome is directly related to the conformation or breed standard for brachycephalic dogs. Dogs with pronounced breathing difficulty or that require surgery to correct airway obstruction should not be used for breeding. It is usually recommended that these dogs be spayed or neutered at the same time as the surgical correction is performed. Unfortunately, this syndrome has been perpetuated by selecting and breeding dogs for their cosmetic appearance rather than their breathing abilities.