Brachycephalic Obstructive Airway Syndrome or BOAS

  • By: Mick Whitefield
  • Time to read: 9 min.

Brachycephalic Obstructive Airway Syndrome (BOAS) is the condition that affects the breathing of an animal, these breathing problems are a direct result of having a short head and/or a short nose which has been achieved through specific breeding programs. Your dog can have one, or all of the abnormalities which affect the airways through the nose and mouth, these are:
1. Stenotic nares.
2. An elongated soft palate.
3. Hypoplastic trachea.

These 3 breathing difficulties can create further problems within the upper respiratory tract leading to secondary abnormalities such as:
4. Everted laryngeal saccules.

5. Laryngeal or Tracheal collapse.
It is considered to be a pathological condition which is exacerbated by situations of exercise, stress, or heat, this leads to distress because of the inability to obtain oxygen to the lungs, thereby increasing respiratory rates and heart rates which can be life threatening for your dog.

Brachycephalic means – having a relatively broad but short skull.

Top Lap dogs is going to describe the problem and show you pictures of this troubling condition, you may be upset by some of the pictures shown.

Brachycephalic types from Mild to Extreme

Old English Bulldog Long Nose
Mild Brachycephalic
Bulldogs used to have longer noses
Old English Bulldog Puppies Short Nose
Extreme Brachycephalic.
These Bulldog pups have very short noses

                                                                                                Brachycephalic Obstructive Airway Syndrome is primarily a breed-related disorder that affects the breathing of your dog and has come about largely due to the results of selective breeding.

This condition can significantly compromise the health and welfare of any affected dog, particularly Extreme Brach’s as they will likely find it difficult to breathe normally at some time during their life. Noisy breathing, snoring, difficulty breathing causing heat stroke, excess nasal discharge and food regurgitation are just some of the integral problems associated.

There is a basic list of breeds that can suffer with this condition, but not all dog breeds on the list suffer from BOAS. Below is a picture of Top Lap Dogs rescued Shih Tzu. Shih Tzu’s are on the list but Bailey has a normal length nose and open nares and as such does not suffer any breathing problems, nor does he have a soft palate that causes him any internal breathing problems.

Boas Nares Open1
Bailey (Our Shih Tzu) has normal open nares.
Boas Side View Shihtzu
Baileys nose is a normal length, but not all Shih Tzu’s have a long snout
Boas Short Snout Bulldog
Here we have a French Bulldog with a short snout which is actually a result of specific long term breeding to attain this look.

Brachycephalic Obstructive Airway Syndrome or BOAS

Lets get a further description of each condition.

 Stenotic Nares

  • 1. Having Stenotic nares means the nostrils are pinched or narrowed, making breathing more difficult than it should be and causes these animals to snort and snore. It is a congenital trait, meaning these animals are born with it. In many cases vets can perform a simple surgery to help widen the nares.
4 Nare States
Boas Bulldog Nares
In this British Bulldog you can see that the nares (nostrils) are mild
and may or may not cause breathing problems

The drawing below shows the areas of Stenotic Nares (nostril) and
Soft Palate (back of the throat) that can block the airways.

Boas Possible Surgery Areas

The areas shown above may be considered for surgical removal.

Boas Stenotic Nare

Stenotic Nares (Nostrils) before Surgery

Essentially the nostril area has some flesh removed to allow the air to pass through the nose

Boas Stenotic Nare After Surgery 1

Stenotic Nares After Surgery

Your pet vet may recommend stomach acid reducer medication before surgery. The surgery entails the removal of the excess tissue that is causing the airway obstruction. It typically includes widening of the nostrils (nares resection), thinning and shortening the soft palate (palatoplasty), and removing the “balloon” structures or saccules (sacculectomy) in the back of the throat. Most brachycephalic dogs require all three procedures.


 Elongated Soft Palate

  • 2. An elongated or overlong, soft palate may partially obstruct airflow into the windpipe (trachea) and cause turbulent airflow in the voice box (larynx area). This further increases the level of effort required by the affected dog to breathe in and also out. Over time it can also cause inflammation of the upper airway. 
Soft Palate Side View
Soft Palate Cut Out Correct Rotated

Here the palate is cut away to allow good airflow
Boas Soft Palate Removal Double
After this treatment breathing should be normal

Hypoplastic Trachea

  • 3. Hypoplastic trachea is a congenital condition occurring when there is an abnormal growth of the cartilage rings that are the trachea (windpipe) which is the tube that connects the lungs to the larynx allowing the passage of air in and out of the lungs through the mouth and nose. The airflow through the trachea is restricted because the diameter of the windpipe is reduced.
Boas Trachea
On the Left (A) you can see the Trachea (Top Left) is restricted. On the Right (B) the airflow to the lungs is normal

Everted Laryngeal Saccules.

  • 4. Everted laryngeal saccules are usually the result of side effects from breathing difficulties associated with other aspects of BOAS. It is a condition in which the laryngeal tissue within the airway, directly in front of the vocal cords, is pulled into the trachea (windpipe) and can partially obstruct the airflow. It is often described as trying to breath through a straw.



Laryngeal Stages


Everted Laryngeal Saccules

The photo shows the Laryngeal Saccules are everted (overgrown with soft tissue) as shown in the cuneiform collapse in the drawing above. This is restricting the room for air to pass through to the lungs.

Clearly the option here is to remove the excess soft tissue to allow normal airflow for breathing.

If the tissue is not removed the dog can suffer with shortness of breath, noisy breathing, snoring, coughing and other associated BOAS problems.

Laryngeal or Tracheal collapse.

  • 5. Laryngeal  or Tracheal collapse is essentially a weak area of cartilaginous rings within the Trachea area that leads to a collapse of the windpipe. This condition is described as extrathoracic or intrathoracic which to put in simple terms describes whether the collapse occurs when breathing in or breathing out.
  • The treatment is essentially the same no matter extrathoracic or intrathoracic. The basic procedure is to insert a Stent (pipe) to avoid collapse and allow air to flow to the lungs.
  • Tracheal collapse is most commonly found in small dog breeds, including the Chihuahua, Lhasa Apso, Maltese, Pomeranian, Pug, Shih Tzu, Toy Poodle and Yorkshire Terrier.

Brachycephalic Obstructive Airway Syndrome (BOAS)

Dogs suffering from clinical BOAS may struggle to breathe when exercising and collapse because of lack of air (oxygen) to the lungs. Dogs rely on panting to cool themselves, making those that suffer from BOAS susceptible to overheating. Such animals can potentially develop very severe breathing difficulties when in hot places.

The extra effort needed to breathe-in leads to secondary problems due to the inability of the airway to cope with the increased negative pressures.

Dog Breeds Affected by BOAS

Many brachycephalic type animals (not all) have Brachycephalic Obstructive Airway Syndrome. The disorder is lifelong, often progressive, and affects an animal’s ability to exercise, play, and eat. The condition impacts a dog’s ability to engage in normal behaviours or live comfortably. 

Brachycephalic breeds have a characteristic short or squashed nose appearance. The most distinctive feature among these breeds is the short muzzle. 

Dog breeds most affected by Brachycephalic Obstructive Airway Syndrome include:

  • English Bulldog
  • French Bulldog
  • Boston Terrier
  • Dogue de Bordeaux
  • Japanese Chin
  • Boxer
  • Pug
  • Pekingese
  • Shih Tzu
  • Cavalier King Charles Spaniel
  • Lhasa Apso
  • Brussels Griffon
  • Bull Mastiff
  • Chinese Sharpei
  • Australian Bulldog
  • Chow Chow


Causes of Brachycephalic Obstructive Airway Syndrome

Several factors cause BOAS:

  • An excessively thick and long soft palate. The fleshy and thick bit at the back of the mouth’s roof can dangle over the airway to cause obstruction.
  • Narrow windpipe (trachea). The narrow windpipe tends to increase the resistance that the dog experiences when breathing in. The narrow trachea can be worsened by protruding fleshy structures (laryngeal saccules).
  • Larynx collapse. The larynx holds open the animal’s airway in the throat. The structure can collapse, narrowing the airway to increase resistance to air when the dog is breathing.
  • Stenotic condition. This is when narrowed nostrils increase the resistance of air flowing through the nose.

All these factors can contribute to varying degrees of obstructing the airway making breathing more difficult. The ensuing inflammation caused is usually progressive and typically gets worse over time. 

Symptoms of Brachycephalic Obstructive Airway Syndrome (what to look for)

A progressive disease, BOAS, usually presents in dogs between ages 1 and 4, but severe cases may become manifest after a few months of age. The symptoms are varied and can range in terms of severity. 

If you notice any of the following clinical signs, consult a veterinarian for advice. 

  • Snoring or snorting during exercise or at rest
  • Difficulty breathing when exercising
  • Clear nasal discharge
  • Sleep apnoea and restlessness at night
  • Poor or reduced exercise tolerance
  • Prolonged recovery following exercise or after exposure to warmer conditions
  • Poor tolerance to heat stress
  • Retching, vomiting, and regurgitation 
  • Collapse due to air deficiency.

If the brachycephalic syndrome is not treated, the resultant chronic increase in negative pressure in the dog’s pharynx may lead to laryngeal collapse as the animal ages. Laryngeal collapse occurs when the laryngeal cartilage has lost its rigidity, causing airflow obstruction. 

Diagnosing BOAS 

In many cases, the symptoms and animal breed are adequate for a diagnosis. Sometimes, however, it becomes necessary to examine the animal’s throat under anaesthetics. The back of the throat cannot be visualized when the dog is conscious. During the physical examination, the vet assesses your dog’s head anatomy and behavior in certain circumstances.

Most brachycephalic dogs experience some level of upper airway obstruction, typically evident as snoring or snorting noises. The key is for your veterinary surgeon to decide whether your four-legged friend is experiencing significant levels of symptoms or indicating an anatomical conformation that predisposes him/her to problems. This involves how your dog copes with warm conditions or exercise and also the possibility of secondary deterioration within the trachea.

However, only the nostrils (nares) can be adequately assessed without a general anaesthetic. Therefore, the diagnosis is initially based on the vet’s overall assessment, but confirming the diagnosis may require additional investigation.

Depending on the preliminary physical examination, several tests may be required. These might include blood tests, chest X-rays, and heart (cardiac) assessment. Full airway assessment requires the dog to be under anaesthetics. However, general anaesthesia in brachycephalic dogs is associated with an increased risk, especially during the recovery phases.

Your primary care veterinary may opt to refer cases that require full airway assessment to a specialist veterinary surgeon. The advantage is that surgical treatment can be performed under the same anaesthetic, reducing the post-surgery recovery risks. The surgeon might also decide to use an endoscope to examine the oesophagus for gastric reflux.

Treatments for BOAS 

To compensate for their malformations, brachycephalic dogs “pull” harder when breathing in. This action creates intense negative pressures in the chest, throat, and neck, which may eventually cause secondary digestive and respiratory diseases. This explains why brachycephalic dogs frequently vomit or regurgitate.

In mild cases of BOAS, conservative management may prove effective. Examples of areas to address include: 

  • Watch the weight: Excess weight worsens the symptoms and leads to a higher risk of complications. 
  • Avoid overheating: Brachycephalic dogs are more exposed to overheating than other breeds. Overheating comes with greater health risks. 
  • Use a harness: A harness when walking brachycephalic breeds helps prevent unnecessary pressure on the neck. 
  • Short-term measures: Oxygen therapy and anti-inflammatory drugs can be useful in controlling a breathing crisis. You may use antacids to treat regurgitation and gastric reflux.

In more severe BOAS cases, surgery should be considered. Surgery first involves taking a detailed history of the dog to understand the extent of symptoms a particular dog may have and provide clear expectations following surgery. Every animal has different anatomy and, therefore, the surgical outcomes are also different for each dog.

Surgery after Care

After surgery, the dog is treated with pain medication and is usually monitored in the clinic for 8-24 hours. The main post-surgical complications include airway swelling, regurgitation, vomiting, and aspiration pneumonia.

Recovery is usually speedy though, and the dog can often be discharged on the same day with pain relief medication, anti-inflammatory drugs, and some antibiotics.

Once released, the dog should rest for seven days, which means avoiding physical activity that causes barking and heavy breathing. The location of the surgery site demands that no undue pressure is placed on the neck. The dog should ideally be discharged from the pet hospital with a harness. 

Only short, light walks are recommended. The dog should not be allowed to play, which may mean keeping him away from the children and other pets. For a few days, feed the recovering pet with soft, low-fat intestinal food. At home, keep the recovering animal in a cool environment.

After two weeks, it’s expected that your dog will have significant improvement in their Brachycephalic Obstructive Airway Syndrome symptoms or even complete resolution of other symptoms such as snoring, snorting, and sleep apnoea. 









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