BRACHYCEPHALIC OBSTRUCTIVE AIRWAY SYNDROME (BOAS)

BOAS refers to a group of respiratory conditions resulting from the head conformation of dogs with short noses (brachycephalic breeds). For brachycephalic dogs, while the length of the skeletal nose is reduced, there is often no corresponding decrease in the size of the soft tissue contained within the skull. This results in a crowded nasal cavity with reduced air passage, and the partial obstruction of the pharynx and larynx by excessively long tissues.

Breeds commonly affected include English and French Bulldogs, Pugs, Boston Terriers, Shih-Tzus and Pekingese. Other breeds with longer noses such as Staffies and Cavaliers can also be affected.

The 5 main components of BOAS include;

1. Stenotic Nares – narrowed nostrils, reducing the air entering the respiratory tract.
2. Elongated soft palate – the soft palate (soft tissue at the back of the mouth that separates the nasal passage from the oral cavity) is often too long and thick in dogs with BOAS. These tissues obstruct the back of the throat and can enter the trachea (windpipe). This reduces airflow, leading to increased breathing effort, snoring, exercise intolerance and at worse, can lead to complete respiratory obstruction. Almost all brachycephalics suffer from this.
3. Everted laryngeal saccules – secondary airway changes due to turbulent airflow
4. Hypoplastic trachea – congenitally narrow windpipe
5. Caudal aberrant turbinates – abnormally formed cartilage scrolls in the nasal cavity that affects air passage through the nose.

BOAS can be progressive and lead to complete airway obstruction and collapse, particularly if not corrected at an early stage. Gastrointestinal symptoms such as oesophagitis and reflux can also develop due to changes in airway pressure.

The good news is that corrective surgery can be performed when brachycephalic animals are young. We routinely perform stenotic nares surgery at the time of desexing, and soft palate surgery from 12 months of age. This greatly improves airway function and can prevent or delay the secondary airway changes – significantly improving quality of life. Surgery can still be performed in later years with good results, but the results may not be as positive long term compared to early correction.