Brachycephalic obstructive airway syndrome

Boston Terrier running through the fields

What is brachycephalic obstructive airway syndrome?

Long-term breathing difficulties and an inability to cool down normally are commonly seen in extremely brachycephalic dogs. This breathing disorder is called brachycephalic obstructive airway syndrome, or BOAS, and is a progressive, lifelong disorder that can impair a dog’s ability to exercise, play, eat and sleep.

Why do some dogs get BOAS?

Abnormalities in the airway in brachycephalic dogs include narrowed nostrils and elongation of the soft palate, which obstruct the passage of air through the nose and throat. In some breeds, especially the Bulldog, this may be accompanied by narrowing of the trachea (wind pipe). These abnormalities restrict the airway and reduce the space available for airflow. This makes it difficult for affected dogs to breathe freely and get enough air into their lungs. Over time, the additional breathing effort required for affected dogs can lead to collapse of the larynx (‘voice box’).

What are the signs my dog may have BOAS?

Dogs with BOAS:

  • may make a lot of noise when breathing, even at rest, which may sound like snoring, snorting or wheezing
  • may show signs of struggling to breathe, including excessive panting, laboured or heavy breathing - the chest and stomach may heave when breathing
  • may not be able to exercise normally and might have to rest on walks
  • might have a blue or grey tinge to their gums (a sign of low blood oxygen)

BOAS and hot weather

In addition to difficulty breathing, restrictions to the flow of air through the nostrils and internal nose structures can make it challenging for brachycephalic dogs to cool down, as the nose is the main area in a dog’s body where heat exchange occurs.

Brachycephalic dogs are at high risk of overheating in warm weather, even in the UK. In warm weather, BOAS signs may become more pronounced and other signs of overheating (‘heatstroke’) may occur including:

  • heavy panting
  • elevated body temperature
  • glazed eyes, increased pulse
  • vomiting / diarrhoea
  • excessive thirst
  • dark red tongue
  • excessive drooling
  • staggering

Overheating can be life threatening, and dogs may seizure, collapse, become unconscious and, in some cases, may sadly die.

Summer warning

If you notice any signs of overheating in your dog as described above, take immediate action while contacting your vet for help. Move your dog to a cool, shaded place, soak them with water to cool them down, and provide them with a small amount of water to drink to rehydrate.

BOAS and sleeping

Dogs with BOAS may find it difficult to sleep normally, often snoring while sleeping and sometimes waking up due to brief periods where their breathing stops. Dogs with BOAS may try to prop their head up while they are asleep to keep their airway open.

BOAS and eating

Some dogs with BOAS may also show problems with their gastrointestinal system, signs of which may include regurgitation, vomiting and coughing up foamy saliva. The signs of BOAS are progressive and often worsen over time.

Tips for keeping your dog lean 

Owners should aim to keep their brachycephalic dogs lean to avoid exacerbating clinical signs. This may include:

  • restricting the number of treats you give your dog
  • feeding your dog specifically formulated obesity diets
  • maintaining regular exercise

Learn more about dog obesity.

What should I do if my dog shows signs of BOAS?

If your dog shows any of the above signs, you should seek veterinary advice immediately. Treatment options are available that aim to reduce the amount of obstruction to your dog’s airway and improve their breathing abilities. Early intervention is often recommended as this may prevent or slow further progression of symptoms.

How will my vet diagnose BOAS?

Your vet will take a history of your dog’s clinical signs, and will assess the degree of respiratory compromise in your dog – this may include a ‘walk test’ to see how they cope with a short amount of exercise, and visual inspection of your dog’s nostrils. 

Assessment under general anaesthetic

If your vet suspects your dog has BOAS, they may recommend that your dog’s airways are assessed under general anaesthetic, where their nose and throat can be closely looked at. If abnormalities are seen, e.g. their soft palate is overly long and/or thick and obstructing their airway, their larynx is showing signs of collapse or their nostrils are significantly narrowed, your vet may recommend surgery.

BOAS surgery

Surgery may include opening up their nostrils, trimming away their excessive soft palate, and removing collapsed parts of the larynx. Some specialists may offer advanced laser surgery to reduce further obstruction inside your dog’s nose (behind their nostrils), where present.

Post-BOAS surgery precautions

Surgery helps many dogs with brachycephaly enjoy a better quality of life, but owners should be aware that their dog will not be ‘normal’ even after surgery, and precautions should still be taken to avoid exacerbating airway problems in their dog. This includes:

  • keeping your dog lean (obesity exacerbates breathing problems)
  • avoiding taking your dog out in hot weather
  • taking your dog on regular short walks to avoid putting stress on their airways while maintaining fitness
  • using a harness instead of a collar to avoid putting pressure on their airway

BOAS and obesity

Obesity is common in modern days, affecting an estimated 20-40% of dogs. Many dogs with BOAS are overweight or obese, which may in part be due to their reduced ability to exercise normally. This is problematic as a high body condition score is a risk factor for BOAS, and is associated with an increased severity of clinical signs.

To assess your dog’s body condition score, view the World Small Animal Veterinary Association's body conditioning scoring information. 

Find out more about brachycephalic dog health and welfare

Article author

This article was written by Dr. Rowena Packer from the Royal Veterinary College who has given The Kennel Club kind permission to replicate it. Dr. Rowena Packer is a Research Fellow at the Royal Veterinary College. Her research interests include many areas of canine inherited disease including brachycephalic health and canine epilepsy.

Think your dog may be affected?

If you're worried about your dog's health, always contact your vet immediately!

We're not a veterinary organisation and so we can't give veterinary advice, but if you're worried about any of the issues raised in this article, please contact your local vet practice for further information.

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If you're looking for a vet practice near you, why not visit the Royal College of Veterinary Surgeons' Find a vet page.

Find out more about issues that can affect flat-faced dogs in our brachycephalic hub.

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