Brachycephalic Obstructive Airway Syndrome (BOAS)

Author: Dr. Nina Samuel, VMD, DACVS-SA

What is brachycephalic obstructive airway syndrome (BOAS)? 

BOAS is a collection of upper airway abnormalities that result from the shortened skull structure seen in brachycephalic dog breeds (e.g., English Bulldogs, Pugs, French Bulldogs, Shih Tzus). These anatomical changes often lead to partial or complete airway obstruction, which can result in respiratory distress and other complications. There are different components contributing to BOAS, including both primary and secondary changes. As these breeds have become more popular, it is helpful to have a thorough understanding of this syndrome and what can be done to help these patients. 

What are primary anatomical changes associated with BOAS? 

1. Stenotic nares 

2. Elongated/thickened soft palate 

3. Hypoplastic trachea 

4. Aberrant nasal turbinates 

5. Macroglossia 

What are secondary changes associated with BOAS? 

1. Everted laryngeal saccules (stage 1 laryngeal collapse) → this can progress to more advanced stages of laryngeal collapse 

2. Everted/inflamed/hypertrophic palatine tonsils 

3. Hiatal hernia (sliding/dynamic) 

Determining severity of BOAS 

1. History and clinical signs: Discuss sleeping, stertor/snoring, exercise tolerance, regurgitation 

2. Physical examination a. Visual exam - conformation, nares 

b. Exercise - have patient trot for 2-3 minutes and evaluate tolerance of the exercise and increased stertor/respiratory effort 

3. Sedated airway examination a. Evaluate tonsils, laryngeal function, laryngeal saccules, soft palate 

b. Use Doxapram to stimulate laryngeal function and more accurately assess laryngeal function 

c. Endoscopy can be used in conjunction with a sedated airway examination to provide magnification and documentation of the exam 

4. Cervical/thoracic radiographs a. Hypoplastic trachea 

b. May catch a dynamic hiatal hernia 

5. Fluoroscopic swallow study a. This is useful to diagnose dynamic hiatal hernias 

b. Considerations: Risk for aspiration pneumonia 

What can be done surgically? 

1. Soft palate: A variety of surgical procedures to address elongated and thickened soft palates have been described, including but not limited to staphylectomy, folded flap palatoplasty, and H-pharyngoplasty 

2. Everted laryngeal saccules: Sacculectomy to remove this extra tissue 

3. Erythematous, everted tonsils: Tonsillectomy to remove tonsils that are everted from the crypts and enlarged 

4. Stenotic nares: A variety of surgical procedures to address stenotic nares have been described, including but not limited to Trader’s technique, rhinoplasty, and ala vestibuloplasty 

5. Aberrant nasal turbinates: Laser-assisted turbinectomy (LATE) has been described, but is only currently being performed at limited institutions in the United States 

6. Macroglossia: This is a newer recognized component of BOAS and while midline glossectomy has been described, it is not commonly performed 

7. Hiatal hernia: Hiatal hernias can be repaired with either an open abdominal approach or laparoscopically. I generally recommend addressing the upper airway first and then pursuing hiatal hernia repair at a separate surgical event ~4 weeks after surgery. This minimizes anesthesia time and also allows for decrease of inspiratory pressure. 

Brachycephalics are at an increased anesthetic risk due to their conformation. This is compounded by performing surgery on the airways, and post-operative upper airway obstruction is a real risk that should be discussed with owners, including the potential for re-intubation and tracheostomy placement. Close monitoring of the patient during recovery and availability of oxygen therapy are both important! While we’re never going to make our brachycephalics into Greyhounds with surgery, the goal is to improve their quality of life, which may involve a combination of medical and surgical management.