There has certainly been increased awareness amongst owners but many symptoms are still seen as ‘breed traits’ or ‘normal’ for the breed.

Early recognition of symptoms can help to slow down what is a progressive airway condition.

BOAS is also a complex condition and not all dogs will have all signs, in fact the issues can vary between breeds.

To understand the disease components of BOAS it’s important to understand the upper airway anatomy of the dog.

Dogs are obligate nasal breathers when resting. Air enters their nostrils or “nares” at the top when breathing in.
It then passes through the nasal cavity which houses small membrane covered bony structures called turbinates. These warm and humidify and filter the air as it passes through to the next area, the nasopharynx. The nasopharynx is the upper part of the throat behind the nose. It lies above what is known as the soft palate. The nasopharynx connects the nose and throat. It leads to the trachea (wind pipe) and oesophagus (food pipe). Air passes through the larynx (voice box) to get to the trachea and ultimately the lungs.

In theory, air should pass through these areas without obstruction.

In brachycephalics the foreshortened skull shape does not always allow enough room for the corresponding soft tissues (tongue and soft palate) and these can be overlong and thickened. Nostrils may be pinched (stenotic) and the turbinates within may also be over crowded or pointing in the wrong direction. Some brachycephalic can also have a narrowed windpipe (tracheal hypoplasia) and a thickened tongue base.

Credit:Giselle White

All these things cause increased obstruction/resistance to air. The dogs will have to work harder to keep their airways open and air flowing. If left unchecked, continuous wear and tear on the airways can then lead to irreversible secondary affects to the respiratory system and gastrointestinal system. BOAS can impair the dog’s quality of life making it harder to play, eat and sleep.


Narrowing (stenosis) can occur not only in the external opening but also just inside in an area called the alar fold. The degree of stenosis both inside and outside can vary and your dog may show various symptoms related to this.

A pug with severe stenosis


Dogs use both their mouths (panting) and nose (heat exchange via the turbinates) to cool themselves down, as air moves in and out.

Any resistance to this airflow such as pinched nostrils and overcrowded nasoturbinates, a thickened palate exerting pressure from below, or even a small trachea can consequently mean that cooling is harder and therefore may take longer. This is why dogs suffering with BOAS, switch to open mouth panting much faster than those without BOAS, even during normal exercise. It can be even more dangerous in warm or humid weather with the possibility of heat stroke. Left unchecked and exacerbated by weight, heat stroke can cause secondary swelling of the airways, increased temperature, cyanosis and death.

Overheating French Bulldog


A small amount of nasal noise does not necessarily mean that your dog has BOAS. However, it is a progressive condition so should be monitored.

There are different types of noise that may cause an issue. The different types of noise may indicate particular problems in certain areas or ‘lesion sites’.


This sounds like a rattle or a snore. Some dogs may do it only when excited or over exerted. Others may do it intermittently. It is the vibration of the soft tissues in the nasopharynx, pharynx or larynx and may be sign that the soft palate is over long or too thick. If the palate is too long, it will overhang the entrance of the trachea. When the dog pants, the palate gets sucked in and out of the trachea, obstructing the airflow. Respiratory effort increases to try and get the palate out of the way so that air can pass through.

French bulldog with stertor


A much higher pitched wheezing noise mostly heard on inspiration as air struggles to pass through the larynx due to narrowing or collapse. The latter being secondary to the continuous high pressures on the laryngeal cartilage that supports and keeps open the larynx

Laryngeal stridor in a pug dog


Some BOAS free dogs will snore. This can often be influenced by the position they sleep in.

BOAS affected dogs tend to snore and snort continuously when asleep and awake. This may be caused by stenosis of the nose, especially inside the nasal cavity. Whilst asleep, dogs use their noses to breath. Crowded turbinate bones and pinched nares make air flow difficult. Dogs with BOAS usually snore loudly and often look like they are struggling to get air in when sleeping. They sometimes even wake up whilst sleeping.

Dogs with a collapsed nasopharynx may also heavily snort when awake (nasal steror).

Nasal obstruction whilst awake with flaring of the area of skin around the nasal cavity
Nasal obstruction whilst sleeping


Although not a disease in itself, it can be an indicator of airway problems. It is also a symptom that owners often miss as it occurs at night. You may find that your dog sleeps a lot during the day and lacks enthusiasm to go for walks. In severe cases sleep apnoea can occur during which time they may not take a breath for up to 20 seconds, followed by a gasp that wakes them.

Sleep Disruption


Dogs with BOAS often find it hard to sleep in the normal lying down position. When their mouths are closed a thickened tongue or palate adds further pressure upwards on the nasopharynx. This impedes the movement of air. They are known to sleep sitting up, standing, with their heads raised on objects or even sleep with objects (toys) in their mouths as this opens the airways

Sleeping whilst sitting or standing up


It is not unusual to find concurrent symptoms that seem unrelated to the airways but are in fact secondary to airway disease. Some dogs struggle to eat as they have to ‘come up for air’. If the soft palate is too long it may block the oesophageal opening, impeding swallowing. Also if they eat too fast, the palate may get stuck in the trachea. They may ‘hack’ a lot during and after meals.

BOAS can have secondary effects on the stomach. These excessive breathing pressures can cause weakness in the muscles where the oesophagus enters the stomach. The stomach slowly starts to get sucked into the chest cavity, or herniates. This is usually intermittent though it can be permanent. It can lead to vomiting and regurgitation. Regurgitation can be very subtle, known as ‘silent regurgitation’. Belching, swallowing and licking can indicate silent regurgitation.

When dogs find it difficult to eat or swallow, excess air may be gulped. This may also lead to increased flatulence. They may also be at higher risk of aspiration of food and water and subsequent lung damage.


Brachycephalic dogs may have reverse sneezing. This is usually not a serious clinical sign but may indicate nasal irritation.

Reverse Sneezing