Brachycephalic airway obstructive syndrome

Overview

Brachycephalic airway obstructive syndrome (BAOS), also known as brachycephalic obstructive airway syndrome or BOAS, is a condition that affects brachycephalic (short-nosed, flat-faced) dog breeds such as Bulldogs, Pugs, Shih Tzus, and Boston Terriers. The syndrome results from anatomical abnormalities in the upper airway that cause varying degrees of breathing difficulty. These abnormalities include narrowed nostrils, elongated soft palate, hypoplastic trachea, and everted laryngeal saccules. BAOS is progressive and can significantly affect an animal’s quality of life, particularly in hot weather or during exercise.

Causes

BAOS is a congenital condition caused by the selective breeding of dogs to have brachycephalic (short and wide) skulls. The mismatch between soft tissue structures (such as the palate and tongue) and the shortened bony skull leads to airway obstruction. Specific anatomical abnormalities that contribute to BAOS include:

• Stenotic nares – narrowed nostrils that restrict airflow

• Elongated soft palate – overlaps the airway and partially blocks airflow to the trachea

• Everted laryngeal saccules – soft tissue structures that can protrude into the airway

• Hypoplastic trachea – an abnormally narrow windpipe

• Nasopharyngeal turbinates – abnormally large or misplaced structures in the nasal cavity

These defects can be present at birth and worsen over time due to chronic strain and inflammation of the airways.

Symptoms

The severity of symptoms can vary, but common clinical signs of BAOS include:

• Noisy breathing (stertor or stridor)

• Snoring and loud breathing even at rest

• Exercise intolerance – difficulty breathing during physical activity

• Gagging or retching

• Coughing or choking episodes

• Cyanosis – bluish gums or tongue due to lack of oxygen

• Collapse or fainting, particularly during excitement or heat stress

• Overheating – inability to regulate body temperature efficiently due to restricted airflow

Diagnosis

Diagnosis of BAOS is based on physical examination, breed history, and evaluation of respiratory sounds. Diagnostic procedures may include:

• Physical and breed assessment – identifying clinical signs and breed predisposition

• Airway endoscopy – direct visualization of the upper airway under anesthesia to assess the soft palate, larynx, and trachea

• Radiographs (X-rays) – to evaluate the size of the trachea and detect other anomalies

• CT scan – occasionally used for a detailed view of the nasal passages and soft tissues

• Pulse oximetry or arterial blood gas analysis – to assess oxygenation in severe cases

Treatment

Treatment depends on the severity of the condition and may include both medical and surgical interventions:

• Medical management (for mild cases):

  • Weight management to reduce respiratory effort

  • Anti-inflammatory medications to reduce airway swelling

  • Avoiding heat, stress, and overexertion

• Surgical intervention (for moderate to severe cases):

  • Stenotic nares resection – widening the nostrils to improve airflow

  • Soft palate resection – shortening an elongated soft palate

  • Laryngeal saccule removal – to open up the airway

  • Tracheostomy – in emergency cases or as a temporary measure post-surgery

• Postoperative care – includes restricted activity, anti-inflammatory drugs, and monitoring for complications

Prognosis

The prognosis for dogs with BAOS varies depending on the severity of the condition and how early it is treated. With early surgical intervention and proper management, many dogs experience significant improvement in breathing and quality of life. However, in severe or untreated cases, the condition can lead to chronic respiratory distress, heat stroke, or sudden death. Preventive measures such as avoiding extreme breeding for exaggerated facial features and promoting awareness among breeders and owners are essential for reducing the incidence of this syndrome.