Brachycephalic Airway Syndrome (BAS) in Dogs

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Last updated on
6 min read

Key takeaways

Brachycephalic airway syndrome (BAS) is a group of anatomic deformities of the airway system common in dogs with flat, pushed-in faces.

  • Signs of BAS include noisy breathing, especially during inhalation, excessive panting, and snoring
  • Fainting, cyanosis, and sudden, life-threatening respiratory crises may also result, particularly in the heat or with exercise
  • Obesity typically exacerbates the condition
  • Some of the disorders are easily visualized by looking at the dog’s mouth and nose, but affected structures at the back of the mouth and larynx require sedation to identify
  • Surgical repair is recommended as the condition is likely to worsen over time
  • In a life-threatening emergency, such as a severe respiratory crisis, oxygen and anti-inflammatory medications are used for short-term relief
  • Prognosis relies upon the severity of abnormalities
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A closer look: Brachycephalic Airway Syndrome (BAS) in Dogs

Symptoms vary in severity. Many brachycephalic dogs live normally with their anatomic defects and have only a few limitations. The severity of symptoms varies according to how many abnormalities are present and how severe the abnormalities are. Symptoms may also worsen with humidity or in hot weather, and these breeds are more prone to overheating.

Brachycephalic airway syndrome (BAS) is potentially life-threatening because it partially obstructs the upper airways.

**BAS may lead to a sudden, severe, life-threatening respiratory crisis requiring emergency veterinary care. **

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Risk factors

Essentially all short-faced breeds experience at least some degree of BAS. Mildly affected dogs show only a little noisy breathing with exercise. More moderate symptoms may interfere with quality of life for both the dog and the owner who must listen to constant noisy breathing.

Brachycephalic dogs are more likely to suffer heat stroke and have a higher anesthetic risk due to BAS. Obesity is also an important factor as it increases breathing difficulties. The prognosis varies based on the extent of abnormalities present and the age of the dog.

Brachycephalic dogs might also suffer from other anatomic conditions that affect the eyes and the gastrointestinal tract.

Possible causes

The cause of BAS lies in the traits selected for when breeding brachycephalic dogs. The Greek term translates to “short head”, and it refers to breeds with short or pushed-in faces, such as pugs, boxers, and bulldogs. The short muzzle associated with these breeds compromises the breathing passages and creates several anatomic abnormalities.

The most common abnormalities are:

  • Stenotic nares: narrow nostrils that reduce the amount of air that flows into the nose.
  • Enlarged tongue (macroglossa): an abnormally large tongue that obstructs airway passage.
  • Elongated soft palate: long soft palate that blocks part of the passage to the trachea.
  • Everted laryngeal saccules: pouches inside the larynx that turn outward or are sucked into the airway.
  • Hypoplastic trachea: the trachea has a smaller diameter than normal.

Main symptoms

In severe cases, symptoms of a life-threatening respiratory crisis may arise.

Testing and diagnosis

Simply being a brachycephalic dog suggests the diagnosis.

Stenotic nares are usually easy to spot upon visual inspection. Identifying the other abnormalities usually requires sedation or general anesthesia.

Brachycephalic dogs are at a greater risk of complications from anesthesia, so they often undergo a full diagnostic workup with x-rays and bloodwork prior to anesthesia. Surgery is necessary to correct these defects, so it is common to schedule surgical correction in association with the examination under anesthesia so the dog only undergoes one anesthetic episode.

Steps to Recovery

The goal of surgical repair is to improve airflow in the respiratory tract and prevent serious complications of BAS. Surgical repair is scheduled as an elective procedure when the pet is healthy and may require referral to a specialist. When a dog presents with a severe respiratory crisis or conditions (e.g. heatstroke), life-saving care is needed which takes priority over surgical repair of anatomical defects.

Prognosis largely depends on the extent of the abnormalities that affect the dog and on age. Dogs under two years that undergo surgery typically experience better results with improved ability to breathe. Some brachycephalic dogs are able to live normal lives without ever needing surgical correction at all.

Comorbidities like allergies and obesity decrease the likelihood of a good postoperative outcome.


These conditions are part of having a brachycephalic dog, at least to some degree. Strategies to minimize their impact on overall quality of life include:

  • Weight control: obesity makes it harder for dogs to breathe normally
  • Using a harness instead of a collar to reduce the impact of trachea and larynx abnormalities
  • Keeping the dog sheltered from the heat
  • Avoiding stressful situations such as heavy exercise

Is Brachycephalic Airway Syndrome (BAS) in Dogs common?

Abnormalities of this sort are common in nearly all brachycephalic dogs. Stenotic nares are the most common.

Typical Treatment

In very mild cases, surgery isn’t necessary. Surgical repair is recommended when it is likely to either improve the dog’s quality of life or prevent severe complications. The earlier the surgery is performed in life, the better the outcome.

Treatment of a respiratory crisis resulting from BAS involves emergency use of oxygen and medications such as steroids and anti-inflammatories for short-term relief.


Malcolm Weir, DVM, MSc, MPH; Krista Williams, BSc, DVM; Cheryl Yuill, DVM, MSc, CVH - Writing for VCA Animal Hospitals
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner
Dr. David Diamond - Writing for PetPlace
No Author - Writing for American College of Veterinary Surgeons

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