Linda Simon
Dr Linda Simon (MVB MRCVS, University College Dublin)
Boston Terrier at the vet

Brachycephalic Obstructive Airway Syndrome (BOAS) is a condition affecting the ability of brachycephalic (short-skulled, snub-nosed) breeds to breathe normally. It is due to the shape and size of their skull, as well as the excessive soft tissue present, that they have a hard time catching their breath and are often unable to keep up with their peers. For most, they are not only affected during exercise or hot weather, but in their day-to-day lives. Sadly, this is a progressive condition that worsens with time.

How affected a brachycephalic dog will be varies greatly from individual to individual. The more extreme the conformation (with a flatter face and smaller skull), the more a dog will struggle. Even those that seem minimally affected are working harder than the average canine to simply exist. While many of us now see the constant panting, snoring and snorting of the brachycephalic breeds as ‘normal’, we need to appreciate that these are all signs of a significant health issue and should not be ignored.

What Is Brachycephalic Obstructive Airway Syndrome (BOAS)?

When we talk about BOAS we are generally referring to a set group of congenital issues experienced by those with a brachycephalic conformation. Many will exhibit all of these issues to varying degrees, though dogs do not have to be affected with all of them to be classified as having BOAS.

Stenotic Nares

The nares are also known as the nostrils and stenotic means narrowed. This is one malformation that can be diagnosed easily without any special equipment. We simply need to look at the nose to appreciate that the nostrils are far narrower than they should be.

We grade nostrils on a ‘1 to 4’ scale, with 1 being wide open and normal and 4 being tapered, collapsed and almost closed. Those dogs with grade 4 nostrils will rarely breathe through their nose and will switch to open mouth breathing at practically any form of exertion or stress.

Elongated Soft Palate

The soft palate sits behind the hard palate in the mouth and functions to protect the airways when a dog swallows. For brachycephalics, the soft palate is overly long and thick and will block off a portion of the airway even when the dog is not swallowing. This is one of the main culprits for the excessive breathing and snoring noises that these dogs make.

Everted Laryngeal Saccules

The laryngeal saccules are soft tissue structures that can enlarge and evert to block a portion of the airway and reduce the space available for breathing. They become everted due to the increased pressure created by the abnormal breathing in these dogs.

Hypoplastic Trachea

A hypoplastic trachea is a windpipe that is congenitally narrower than it should be. It is the cartilage of the windpipe that is malformed and can even overlap in some cases. X-rays can be used to assess the dimeter of the trachea.

Other Issues

On top of the aforementioned conditions, dogs with BOAS often also have larger tongues than will fit in their mouths comfortably, laryngeal collapse and food-pipe and gastric lesions due to the chronic regurgitation associated with the excess negative pressure created when attempting to breathe. Sadly, with advanced respiratory disease, the excessive stress put on the heart can also lead to heart disease.

Which Breeds are Affected?

Shih Tzu on road

Shih Tzus canf be affected by BOAS

When we think of brachycephalic breeds, we generally think of a number of ‘poster child’ pedigrees, such as the Pug and Frenchie, but there are a wide range of breeds affected. Of course, many cross breeds can also suffer with BOAS. Some examples of the typical brachycephalic breeds include:

Why Are these Breeds Affected?

The fact of the matter is that these breeds have congenital breathing issues because of their genetic make-up and physical appearance. They have been bred by us to be this way. Their specific conformation simply means that air cannot enter and exit their body efficiently. Click here for a more detailed overview in our Brachycephalic Health article.

What Are the Signs & Symptoms?

Signs and symptoms will be worse in those with a higher grade of BOAS and will present at an earlier age in these individuals. They can vary depending on a dog’s lifestyle and personality. For example, those who are prone to anxiety will generally suffer more. Similarly, dogs who live in hot and humid environments will find it more difficult to cope.

It is hard to miss the signs of BOAS, as they can be heard loud and clear even when in the next room to the affected dog! These dogs tend to be very noisy and will pant, grunt and snort constantly. Excessive noise comes from their noses, larynx and pharynx. Even when they sleep they will make loud snoring noises and, for some, this can cause them to constantly wake up and suffer from sleep deprivation. While these signs are obvious, many owners ignore their significance and think of them as ‘normal’. Though they may well be the ‘expected’ for certain breeds, we need to understand that they are far from normal and indicate a significant underlying disease.

As well as the expected noises, these dogs may struggle to exercise normally and have an especially hard time in the heat as they are less able to regulate their body temperature. In fact, some may even collapse when exercising due to the lack of oxygen. As previously mentioned, many will experience chronic vomiting and regurgitation, which is caused directly by the abnormal pressures created when attempting to breathe. Reverse sneezing is also a frequent symptom in these guys, though is not thought to be pathological.

Diagnosing BOAS

Frenchie sleeping on floor

BOAS is not difficult to diagnose and is based on the dog’s physical appearance and the symptoms displayed, especially the noises made when breathing. Vets will ask owners about how their pet copes at home. Many vets will give those affected a grade. Grades are determined by a vet examining the dog’s breathing both at rest and exercise. Grading schemes are crucial as they allow us to determine which breed members (i.e. those with a high grade) should never be used for breeding.

Diagnostic Tests

Though a vet may have a high suspicion that a dog has all of the physical characteristics associated with BOAS, it is only the nares that can be visibly examined during a routine physical exam. To assess the rest of the respiratory tract, vets need to perform a full oropharyngeal exam under anaesthesia.

This may include a detailed CT examination and rhinoscopy. Often, if a corrective surgery is scheduled, this can be done at the same time as the diagnostic imaging. On top of visual assessments, exercise tolerance tests are widely used to determine the extent of the condition.

What Treatment Options Are Available?

Treating a dog with BOAS often entails both a surgical and non-surgical approach. Indeed, all those affected will benefit from certain lifestyle changes and non-surgical management. While surgery is often the gold standard therapy available, some may find it financially prohibitive.


All brachycephalic breeds should be maintained at a lean body condition score as we know that obesity inevitably worsens symptoms. To alleviate pressure on the respiratory tract, we should never use neck collars for walks as harnesses are far safer. Avoiding those situations that put pressure on the respiratory system (such as heat, humidity and stress) at all times is paramount.

Managing an episode of acute respiratory distress (for example, brought on by over-exercising or hot weather) requires immediate veterinary care. Dogs may be given a mild sedative to relax them and will be supplied with oxygen. Some will benefit from anti-inflammatory medications. If they require cooling, this will be achieved with fluid therapy and other methods.


There are a number of procedures available for those with BOAS. While some dogs will have all of them, others may only require one or two. The most common procedures performed are surgeries to widen the nostrils and shorten and thin the elongated soft palate. Some will also have their laryngeal saccules and/or tonsils removed.

Many general practitioners are now able to perform these operations in first opinion practice. Additional surgeries, such as correction of a laryngeal collapse, may be required in some patients. It should be noted that dogs experience more benefits from surgery the earlier it is carried out.

What Is the Prognosis for a Dog with BOAS?

Cavalier King Charles at the vet

Of course, prognosis is mainly determined by the extent of the disease and those with a milder form will have a much better prognosis. Those with a significantly hypoplastic trachea tend to have a worse prognosis. Similarly, animals that go on to develop secondary conditions (such as heart disease) or that have additional health problems will inevitably carry a poorer prognosis.

Prognosis is also determined by how the condition is managed, with those undergoing surgery generally doing far better than their counterparts. While most will almost certainly experience a reduced quality of life because of their impaired breathing, they can still manage to lead relatively normal lives.

Can you Prevent BOAS in a Brachycephalic Breed?

As a society that values animals and their well-being so highly, it is our duty to prevent this debilitating condition and our aim should be to eliminate it, to prevent ongoing suffering. BOAS significantly impacts on an animal’s wellbeing and also creates a financial and emotional burden on their owners. It is imperative that we work together to prevent BOAS in our canine companions. Here are some of the things that we can do:

Holland's Traffic Light System

Follow the example of countries like Holland. The Dutch government have introduced a ‘traffic light system’ that gives an animal a colour (red, amber or green) directly related to how brachycephalic they are. Red lights are given to those whose muzzles are shorter than a third of their skull. A red light means that it is now illegal for these dogs to be bred in the Netherlands.

Amber lights are applied to those whose snout is 1/3 to 1/2 the length of their skull and these dogs can potentially be bred if they meet certain health criteria. Finally, a green light means all dogs with muzzles 50% the length of their skull or longer can be bred from as normal. While this may seem somewhat harsh, it’s a law that is simply designed to protect the welfare of our dogs.

Raise Public Awareness

Informative campaigns educating potential owners on the significance of BOAS are vital in preventing the continued purchasing of brachycephalics from sources, such as puppy farms and backyard breeders, where they are being bred indiscriminately and with no regard for their health. We should also aim to prevent the media promoting those with severe brachycephalic conformations in their advertisements, which is known to drive public demand.

Raise Breeder Awareness

Ensuring that breeders are aware of the health tests and grading systems advised for those brachycephalic dogs that are to be used for breeding.

Raise Owner Awareness

Vets should be discussing BOAS with all brachycephalic owners so they can understand that the typical snores and snorts we hear should not be perceived as normal. They should be made aware of both the surgical and non-surgical treatment options available for their pets.

Spaying & Neutering

The spaying and neutering of those with significant airway disease should always be advised as these dogs should not be used for mating in any circumstance.