BOAS stands for brachycephalic obstructive airway syndrome. A brachycephalic dog is one with a short nose – brachy means short, and cephalic head, which means the skull bones are short and give the face and nose a squashed-up appearance. The short bones of the skull and nose lead to a distinctive anatomy, which also affects the soft tissues of the upper airways.

Breeds which can be described as brachycephalic include bulldogs (French and English), boxers, pugs, Shih Tzus and Pekingese. The anatomic configuration of these breeds faces, and nose can lead to a distinct set of breathing problems.

Brachycephalic obstructive airway syndrome is a collection of abnormalities which can impact upon the dog’s ability to breathe normally. 

Factors which can primarily contribute to BOAS include:

  • Narrow nostrils (“stenotic nares”) which restrict the amount of air which can flow into the nose. 
  • Abnormal nasal bones (turbinates). The nasal turbinates are scrolls of bone within the nose,m covered in soft tissue. As air passes through the nasal chambers, it is warmed and humidified. In brachycephalic breeds the nasal turbinate bones can extend into the throat and obstruct airflow.
  • Overlong or thickened soft palate. If the soft palate is too long for the length of the mouth it can partially block the entrance to the windpipe (trachea), this blocks air from freely flowing.
  • Laryngeal collapse (in pugs). The larynx (voice box) can be placed under chronic stress because of the restriction in airflow, this can cause it to collapse or narrow.
  • Tracheal narrowing (“hypoplasia”), the trachea can have a narrowed diameter, making it harder to breathe.

Brachycephalic breeds may experience one or a combination of the above problems. 

All of these anatomic problems contribute to increased resistance of air through the respiratory tract. This can lead on to secondary problems including:

  • Laryngeal collapse (abnormal narrowing of the voicebox and coughing)
  • Gastrointestinal signs such as excessive salivation, acid reflux, regurgitation and vomiting. 
  • Enlarged tonsils, or inside out (“everted”) tonsils (as the throat starts to collapse under the strain).

What symptoms might be seen in a dog with brachycephalic airway obstructive syndrome?

  • Noisy breathing, mouth breathing or snoring. (Whatever the breeder tells you, this is NOT normal! – Ed.)
  • Inability to exercise or lack of interest in exercise.
  • Overheating can occur as the nasal cavity helps a dog with temperature regulation. In hot weather dogs with BOAS struggle to keep cool.
  • Collapse or fainting if the dog cannot maintain the oxygen levels needed. This is more likely to happen in hot weather or during exercise. 

All of the abnormalities which contribute to BOAS cause increased resistance of air entering the respiratory tract. Essentially it is much harder for a dog with BOAS to breathe normally. The more significant the abnormalities which the dog has the more significant or severe the symptoms they will experience. A dog with BOAS may have noisy breathing even at rest and is often heard snoring when asleep. 

When exercising the dog may be heard to snort. They may have reduced tolerance to exercise, tiring quickly or struggling to perform any exercise at all because of the difficulty breathing. 

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How is BOAS diagnosed?

Often the clinical signs and breed presentation will make your vet suspicious about BOAS in your dog. Further investigation might be needed to find out exactly which parts of the upper respiratory tract might be contributing to the brachycephalic airway obstructive syndrome. Your veterinary surgeon might want to examine your dog’s throat under general anaesthesia. Other tests could include x-rays, CT scan or endoscopy. 

What can I do to help my dog?

  • Weight loss or ensuring your dog maintains a healthy weight will reduce the strain and severity of BOAS symptoms.
  • Keep your dog cool on hot days and prevent overheating. If your dog is struggling to keep cool there is a risk of collapse or life-threatening symptoms.
  • Use a harness rather than a collar. A collar can put pressure on your dog’s throat and could worsen the symptoms of BOAS.
  • Medication might be used in the short term to help alleviate symptoms. Your vet will be able discuss the options for your dog.

In severe cases, with significant symptoms, surgery might be advised. 

Surgery cannot address all the factors which contribute to BOAS but it might be used to:

  • Shorten the soft palate.
  • Widen the nostrils.

If you have concerns that your dog is struggling with its ability to breathe or it might be showing symptoms of BOAS it is best to book a check-up with your vet. If your dog is significantly struggling to breathe, then seek emergency treatment without delay. Although not all factors contributing to BOAS can be corrected, your vet will be able to work with you to help ensure your dog has the best quality of life possible. 

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