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What Is Brachycephalic Obstructive Airway Syndrome (BOAS) In Dogs?

Aimee Labbate
  • Aimee Labbate

  • RCVS: 700039


What Is BOAS in dogs?

BOAS is a condition seen in flat faced (brachycephalic) breeds such as pugs, French bulldogs, shih tzu, boxers and bulldogs. It refers to a combination of issues that can restrict the free flow of air into the airways thereby causing breathing difficulties.

BOAS is normally caused by a combination of different factors – a dog may be variable affected by one of more of the following:

  • An over long and thick soft palate potentially causing it to obstruct the back of the throat
  • A narrowed windpipe (trachea)
  • Narrowed nostrils and compacted nasal cavity
  • Tongue that is too large for the size of the mouth
  • Laryngeal collapse

These structural abnormalities within the airways can lead to secondary changes within the airways and digestive tract over time. These changes can cause further worsening of the breathing together with retching, gagging, regurgitating and vomiting.

What causes BOAS in dogs?

Brachycephalic breeds have a compacted skeleton compared to other breeds, leading to several structural malformations, such as those seen with BOAS. These are due to the fact that there is a mismatch between their smaller skeleton and the normal amount of skin and soft tissue that they still have, causing folds and partial obstructions to the airways.

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Poor breeding using dogs that are severely affected can further contribute to these issues, by selecting for more extreme variations.

What are the symptoms of BOAS in dogs?

The signs of BOAS vary between dogs but can include:

  • Snorting and snoring
  • Reduced exercise tolerance and difficulty breathing when exercising
  • Prolonged recovery after exercise or exertion
  • Poor heat tolerance and tendency to overheat
  • Retching, regurgitation, vomiting
  • Restless at night
  • Collapse

Importantly, dogs suffering from BOAS are at an increased risk of suffering from heat stroke, so if you have a brachycephalic breed then please be extra careful with them in the warmer months.

How is BOAS in dogs diagnosed?

The diagnosis of BOAS is often made based on the clinical history together with the physical examination findings. Further tests are usually then carried out to determine the severity of the abnormalities. These may include examination of the back of the throat under general anaesthetic; a CT scan of the head to further assess the nasal cavities and soft palate, and endoscopy to see up the nose.

How can BOAS in dogs be treated?

Where changes are severe enough to be causing difficulties for the dog then treatment is usually surgical, to correct the abnormalities where possible. For example, affected dogs often have their nostrils widened and their soft palate shortened. These procedures will often lead to a dramatic improvement in clinical signs. Occasionally, in dogs that are severely affected, further procedures may be needed.

Dogs that are showing digestive issues will also be prescribed medication to help with these signs – these drugs can usually be stopped after a month or so following surgery.

What is the prognosis for dogs with BOAS?

This varies greatly between individual dogs depending on the severity of the structural abnormalities and the degree of secondary changes present. Most cases respond well to surgery and have a dramatically improved quality of life thereafter.

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