Flat-faced (brachycephalic) breeds such as Bulldogs, French Bulldogs, Pugs, and Boston Terriers are beloved for their “squishy-faced” appearance. Sadly, their anatomy predisposes them to brachycephalic obstructive airway syndrome (BOAS), a progressive condition that compromises quality of life, increases anesthetic risk, and often requires surgical intervention.
This article explains the features of BOAS, common clinical signs, treatment options, anesthetic considerations, and how the BRisk scoring system can help veterinarians evaluate and reduce risk.
What is BOAS?
BOAS is caused by a constellation of anatomical abnormalities that obstruct airflow:
- Stenotic nares: narrowed nostrils that restrict air intake
- Elongated soft palate: excess tissue extending into the airway
- Everted laryngeal saccules: tissue pulled into the airway from chronic negative pressure
- Hypoplastic trachea: abnormally narrow trachea relative to body size
These features create turbulent airflow, chronic airway resistance, and increased respiratory effort. Over time, BOAS can lead to permanent airway damage and even life-threatening collapse.
Clinical Signs of BOAS in Dogs
Dogs with BOAS may display:
- Loud breathing, snoring, snorting (stertor/stridor)
- Exercise intolerance and easy fatigue
- Heat intolerance or overheating during mild activity
- Gagging, retching, or vomiting due to airway turbulence and reflux
- Cyanosis (blue gums/tongue) during stress or exertion
- Collapse, sometimes requiring emergency stabilization
Gastrointestinal issues (e.g., reflux, regurgitation, hiatal hernia) frequently occur alongside airway problems, worsening overall morbidity.
Treatment Options
Medical management can help mild cases:
- Weight reduction to decrease airway load
- Limiting heat/exercise exposure
- Use of harnesses instead of neck collars
- Acid-suppressive therapy for reflux
Surgical intervention is often required, particularly for moderate to severe BOAS:
- Rhinoplasty (widening stenotic nares)
- Staphylectomy (soft palate resection)
- Laryngeal sacculectomy
- Occasionally addressing advanced collapse or tracheal hypoplasia
Early intervention (ideally before secondary airway changes develop) offers the best prognosis.
Anesthetic Concerns in BOAS Patients
Brachycephalic dogs present significant anesthetic challenges:
- Airway obstruction during induction and recovery
- Difficult intubation due to distorted anatomy
- Aspiration risk from regurgitation/reflux
- Rapid desaturation because of limited airway reserve
Steps to Reduce Anesthetic Risk
- Pre-anesthetic airway assessment and BRisk scoring
- Pre-oxygenation before induction
- Use of short-acting, reversible sedatives
- Availability of multiple endotracheal tube sizes and airway rescue equipment
- Delay extubation until fully awake and protecting the airway
- Prolonged post-anesthetic monitoring, as most complications occur during recovery
The BRisk Scoring System
To improve risk stratification, researchers developed the Brachycephalic Risk (BRisk) score, a preoperative tool that predicts complications in dogs undergoing BOAS surgery.
How the BRisk Score Works
The score is based on six independent variables assessed at presentation. Each contributes partial points; the total (maximum 10) stratifies the patient into risk categories:
- Breed
- French/English Bulldog → +0.5 points
- History of airway surgery
- No prior airway surgery → +1.5 points
- Concurrent non-BOAS procedures planned
- Yes → +1.5 points
- Body Condition Score (BCS)
- Overweight/obese → +1 point
- Airway compromise on admission
- Mild → 0 points
- Moderate (loud stertor, intolerance) → +1.5 points
- Severe (cyanosis, collapse) → +2 points
- Rectal temperature
- Hypothermic (<38°C / <100.4°F) → +0.5 points
Risk categories:
- ≤3 points: Low risk
- >3 points: High risk (≈9× greater chance of major complications in the original validation study)
- More recent validation showed dogs with scores >3 were 3× more likely to suffer major complications compared with those ≤3.
Clinical Use
- Helps veterinarians objectively assess anesthesia risk
- Guides decisions on referral, advanced airway planning, and recovery monitoring
- Improves owner communication by quantifying risk instead of relying solely on subjective impression
Final Thoughts
BOAS is more than “cute snoring.” It is a chronic, progressive disease that impacts both breathing and gastrointestinal function. Early diagnosis, surgical correction, and careful anesthetic planning are key to improving quality of life in brachycephalic breeds.
The BRisk scoring system adds an important layer of safety, allowing veterinarians to predict perioperative risk, tailor protocols, and set realistic expectations with owners. With thoughtful intervention, many brachycephalic dogs can breathe easier and live longer, healthier lives.
