Brachycephalic obstructive airway syndrome (BOAS) in dogs

Summary

What is brachycephaly?

Brachycephaly means “short-headed” and describes dogs bred to have a shortened muzzle and relatively broad, flat skull.

Common brachycephalic breeds include:

• English bulldog
• French bulldog
• Pug
• Pekingese
• Boston terrier
• Boxer
• Lhasa Apso
• Shih Tzu
• Bull Mastiff
• Cavalier King Charles Spaniel

In these dogs, the bones of the face and skull have been shortened, but the soft tissues of the nose, mouth and throat have not necessarily reduced by the same amount. This can leave less room for the nostrils, tongue, soft palate and other airway structures.

Not every brachycephalic dog has clinically significant BOAS, and severity varies between individual dogs. However, more extreme flat-faced anatomy is associated with a greater risk of breathing problems.

What is brachycephalic obstructive airway syndrome (BOAS)?

BOAS describes a combination of anatomical abnormalities that restrict airflow through the upper airways of some flat-faced dogs.

A dog may have one or more of the following:

• Stenotic nares – abnormally narrow nostrils that restrict the amount of air entering the nose.
• An elongated or thickened soft palate – excess soft tissue at the back of the mouth partially obstructs the entrance to the airway.
• Everted laryngeal saccules – small pockets of tissue near the voice box are pulled into the airway because of the increased pressure required to breathe.
• Hypoplastic trachea – the windpipe is narrower than normal.
• Laryngeal collapse – chronic airway pressure can eventually weaken structures around the larynx, causing further obstruction.

Other anatomical features, including crowded nasal passages and a relatively large tongue, may also contribute to restricted airflow.

BOAS is not simply noisy breathing. It can affect a dog’s ability to exercise, regulate body temperature, sleep comfortably and, in more severe cases, obtain enough oxygen.

Symptoms of BOAS in dogs

Signs of BOAS can vary from subtle to severe and may become more obvious during exercise, excitement, hot weather or humid conditions.

Common signs include:

• noisy breathing, snorting or snoring
• breathing through the mouth when not exercising
• frequent or excessive panting
• tiring quickly during walks or play
• reluctance or inability to exercise normally
• difficulty coping with hot or humid weather
• gagging, retching or coughing
• regurgitation or vomiting
• excessive drooling
• difficulty swallowing
• restless or disturbed sleep
• sleeping in unusual positions to keep the airway open
• fainting or collapse after exercise, excitement or heat exposure.

Expert advice from Dr Felicia:

A lot of dog owners think that their dog having noisy breathing, snoring and snorting to be normal. This means that BOAS is  under-diagnosed in veterinary practice.

Gastrointestinal signs such as regurgitation and reflux commonly occur alongside BOAS because the increased effort required to breathe can affect pressure within the chest and abdomen.

When is BOAS an emergency?

Dogs with BOAS are particularly vulnerable to heat-related illness because an obstructed upper airway makes panting less effective.

Seek urgent veterinary care if your dog:

• is struggling or working very hard to breathe
• has blue, grey or very pale gums or tongue
• collapses or becomes weak
• cannot recover normally after exercise
• is severely overheating
• appears panicked or distressed because they cannot breathe
• has rapidly worsening noisy breathing or airway obstruction.

Keep your dog as calm and cool as possible while travelling to the veterinary clinic and avoid placing pressure on the neck.

What causes BOAS in dogs?

BOAS is primarily caused by the anatomical changes associated with breeding dogs for a shortened, flat-faced skull shape.

Genetics and conformation determine the underlying airway anatomy, but several factors can worsen the severity of clinical signs.

These include:

• excess body weight
• hot or humid weather
• strenuous exercise
• excitement or stress
• increasing age and secondary airway changes.

Obesity is particularly important because additional tissue around the neck and chest increases the effort required to breathe. Research from the University of Cambridge has found an association between obesity and impaired respiratory function in brachycephalic dogs.

BOAS can also worsen over time. Repeatedly breathing against a narrowed airway creates increased negative pressure within the throat, which can contribute to swelling, everted laryngeal tissue and eventually laryngeal collapse.

Expert advice from Dr Felicia:

Brachycephalic patients are also at higher risk of disease in other body systems including the middle ear and gastrointestinal tract due to abnormal anatomy and pressure from obstructive breathing.

Why is hot weather particularly dangerous for dogs with BOAS?

Dogs primarily cool themselves by panting. Air passing through the nose and mouth helps evaporate moisture and release heat.

In dogs with BOAS, narrowed airways make this process less efficient. As body temperature rises, dogs pant harder, which can create further airway swelling and make breathing even more difficult. This can create a dangerous cycle of increasing heat and respiratory distress.

During warm weather:

• exercise in the cooler parts of the day
• avoid strenuous activity and excitement
• provide constant access to cool water and shade
• use air conditioning where necessary
• never leave your dog in a parked car
• stop exercise immediately if breathing becomes unusually noisy or laboured.

If you suspect heatstroke, seek veterinary treatment immediately.

How is BOAS diagnosed?

Your veterinarian may suspect BOAS based on your dog’s breed, history, breathing sounds, exercise tolerance and physical examination.

The assessment may include:

• Nostril examination – stenotic nares can usually be assessed while the dog is awake.
• Breathing assessment – the vet will listen for abnormal airway sounds and assess breathing effort at rest and, where appropriate, after controlled exercise.
• Body condition assessment – excess weight can significantly worsen airway obstruction.
• Examination of the mouth and throat – evaluation of the soft palate, larynx and deeper airway often requires sedation or general anaesthesia because these structures cannot be adequately examined in an awake dog.
• Imaging – chest or neck x-rays, CT or other imaging may be recommended in some dogs to assess the trachea, lungs or other abnormalities and help plan treatment.

Some veterinary centres also use structured respiratory-function grading or exercise testing to assess BOAS severity.

BOAS functional grading

The University of Cambridge BOAS functional grading system classifies dogs from:

• Grade 0: clinically unaffected
• Grade I: mild respiratory signs but considered clinically unaffected
• Grade II: moderate BOAS
• Grade III: severe BOAS.

This type of functional assessment can help identify dogs whose breathing abnormalities may otherwise be dismissed as normal for their breed.

Treatment for BOAS in dogs

Lifestyle and conservative management

Dogs with mild BOAS may benefit from lifestyle changes that reduce the demand placed on their airway:

• maintaining a lean, healthy body weight
• avoiding strenuous exercise, particularly in warm or humid conditions
• exercising during cooler parts of the day
• avoiding overheating and excessive excitement
• using a well-fitted harness rather than placing pressure on the neck with a collar
• managing gastrointestinal problems such as reflux where these are present.

These measures can reduce symptoms but cannot correct the anatomical abnormalities causing BOAS.

Dogs experiencing an acute breathing crisis may require emergency treatment such as oxygen, cooling and other supportive veterinary care.

Surgery for BOAS

Surgery may be recommended when anatomical abnormalities are causing clinically significant breathing problems, exercise or heat intolerance, sleep disturbance or other complications.

Procedures may include:

• Widening stenotic nares – surgically enlarging the nostril openings to reduce resistance to airflow.
• Soft palate surgery – shortening and/or reducing the thickness of an elongated soft palate so that it obstructs the airway less.
• Treatment of everted laryngeal saccules – removal may be recommended in selected dogs.
• Additional airway procedures – some dogs require treatment of other obstructive structures depending on their individual anatomy.
• Tracheostomy – temporary or, rarely, permanent creation of an opening into the trachea may be required in severe airway obstruction.

Is it better to treat BOAS early?

In general, dogs treated before severe secondary airway changes develop tend to have a more favourable outlook. Chronic breathing against a restricted airway can contribute to progressive changes including laryngeal collapse. For this reason, owners should not wait for repeated collapse or severe respiratory crises before discussing treatment options with their veterinarian.

Surgical treatment can substantially improve airflow, exercise tolerance and quality of life in appropriately selected dogs, although it does not change the dog’s underlying skull shape and some animals continue to require lifelong management.

Is BOAS surgery risky?

Brachycephalic dogs have an increased risk of airway and recovery complications with sedation and general anaesthesia because their airway is already narrowed and they may also be prone to regurgitation and aspiration.

BOAS surgery itself can temporarily cause swelling around the airway, which is why close monitoring after the procedure is particularly important. Some dogs may need oxygen, temporary replacement of a breathing tube or, less commonly, a temporary tracheostomy during recovery.

Your veterinarian or surgical specialist will assess your dog’s individual risks against the expected benefits of improving their airway.

Expert advice from Dr Felicia:

Veterinary clinics will often have a specific protocols in place for brachycephalic patients, which includes treatment with anti-anxiety medication to keep them calm in hospital, pre-oxygenation prior to anaesthetic, use of medications to help with reflux and vomiting and longer post-op monitoring in recovery.

How much does BOAS treatment cost?

Treatment costs vary considerably depending on the severity of BOAS, which airway abnormalities require correction, whether specialist treatment is needed and whether complications occur.

According to PetSure’s 2024 claims data^Ø:

• the average cost to treat BOAS was $3,174
• the highest claimed treatment cost was $29,775
• brachycephalic dogs accounted for 93% of BOAS claims assessed during the year.

These figures are based on PetSure claims data and represent treatment costs rather than what an individual owner will necessarily pay. Costs can vary between veterinary clinics, individual dogs and the treatment required.

Prognosis for dogs with BOAS

The outlook for dogs with BOAS varies according to the severity of the airway obstruction, the abnormalities involved and whether secondary changes such as laryngeal collapse have developed. Dogs with milder disease may remain comfortable with careful weight, exercise and heat management, although their underlying anatomy does not change.

Many dogs that require corrective surgery experience meaningful improvement in breathing, exercise tolerance and quality of life. Younger dogs treated before advanced secondary airway changes develop generally have a better prognosis than dogs with severe, longstanding disease. Dogs with advanced laryngeal collapse or other significant complications may have a more guarded outlook and can require ongoing management.

Can BOAS be prevented?

BOAS cannot be prevented in an individual dog once the underlying brachycephalic anatomy is present. However, maintaining a healthy weight, avoiding overheating and having breathing abnormalities assessed early can reduce additional strain on the airway.

At a population level, responsible breeding is important. Breeding dogs should be selected for healthy respiratory function and less extreme conformational traits rather than pronounced flat-faced features.

Respiratory-function grading schemes are now available for some brachycephalic breeds to help identify dogs with clinically significant BOAS and support healthier breeding decisions.

In conclusion

BOAS is more than snoring or noisy breathing. It is a potentially progressive airway disorder that can affect a dog’s ability to exercise, regulate body temperature, sleep comfortably and breathe normally.

Flat-faced dogs vary considerably in how severely they are affected, so the most useful guide is how well the individual dog can breathe and function. Noisy breathing, poor exercise tolerance, heat sensitivity, gagging, regurgitation or disturbed sleep should be discussed with a veterinarian rather than accepted as normal for the breed.

Weight control and careful management can reduce symptoms, while corrective surgery can significantly improve quality of life for many dogs with clinically important airway obstruction. Severe breathing difficulty, blue or grey gums, collapse or overheating should always be treated as an emergency.

^ØBased on PetSure claims data, 2024 calendar year. Reimbursement for these claims under a pet insurance policy would be subject to limits, such as annual benefit limits or sub-limits, benefit percentage, applicable waiting periods and any applicable excess. Cover is subject to the policy terms and conditions. You should consider the relevant Product Disclosure Statement or policy wording available from the relevant provider. Please note that values calculated are based on all claims for that condition and medically related conditions in each calendar year.

Sources:

“Brachycephalic Syndrome”, American College of Veterinary Surgeons. https://www.acvs.org/small-animal/brachycephalic-syndrome/. Accessed 6 October 2026.

“Recognition & Diagnosis – Brachycephalic Obstructive Airway Syndrome”, University of Cambridge Department of Veterinary Medicine. https://www.vet.cam.ac.uk/boas/about-boas/recognition-diagnosis. Accessed 6 October 2026.

“BOAS Resources and Respiratory Function Grading”, University of Cambridge Department of Veterinary Medicine. https://www.vet.cam.ac.uk/boas/resources-1. Accessed 6 October 2026.

“Health Issues – Brachycephaly in Companion Species”, Royal Veterinary College. https://www.rvc.ac.uk/research/focus/brachycephaly/health-issues. Accessed 6 October 2026.

Wallace ML. “Surgical management of brachycephalic obstructive airway syndrome: An update on options and outcomes”, Veterinary Surgery, 2024. https://pubmed.ncbi.nlm.nih.gov/38952039/. Accessed 6 October 2026.

Dupré G, Heidenreich D. “Brachycephalic obstructive airway syndrome: much more than a surgical problem”, Veterinary Quarterly, 2022. https://pubmed.ncbi.nlm.nih.gov/36342210/. Accessed 6 October 2026.

Gruenheid M, et al. “Risk of anesthesia-related complications in brachycephalic dogs”, Journal of the American Veterinary Medical Association, 2018. https://pubmed.ncbi.nlm.nih.gov/30020004/. Accessed 6 October 2026.

“Understanding flat-faced breeds: Why anatomy matters”, PetSure, 2025. https://petsure.com.au/knowledge-hub/understanding-flat-faced-breeds/. Accessed 6 October 2026.