BOAS is not a single disease but a conformational airway syndrome caused by anatomical restrictions in the upper respiratory tract. Because of selective breeding for shorter skulls, these dogs often have narrowed nostrils, excess soft tissue in the throat, and elongated soft palates. These structural changes reduce airflow and increase the effort required to breathe normally.
How BOAS Affects Breathing
In a healthy dog, air flows freely through the nostrils, nasal passages, throat, and windpipe into the lungs. In dogs affected by BOAS, one or more of the following abnormalities may be present:
- Stenotic (narrow) nostrils, restricting air entry
- Elongated soft palate, partially blocking the airway
- Narrowed or collapsing trachea
- Excess tissue in the throat (laryngeal obstruction)
These abnormalities increase airway resistance, causing the dog to work harder to inhale and exhale, especially during exercise, stress, or hot weather.
Clinical Signs
Dogs with BOAS may show a range of respiratory symptoms, including:
- Loud or noisy breathing (snoring, snorting, or stertor)
- Exercise intolerance or early fatigue
- Gagging or retching, especially during excitement
- Rapid or labored breathing
- Difficulty in warm or humid conditions
- Collapse or fainting in severe cases
- Restlessness during sleep due to breathing difficulty
Over time, chronic breathing restriction can lead to reduced oxygen intake and secondary complications affecting heart and lung function.
BOAS Breathing Test Procedure
The BOAS breathing test is performed by a veterinarian or trained assessor and is designed to evaluate functional respiratory performance under standardized conditions. The assessment typically includes:
- Resting evaluation – observation of breathing noise, effort, and posture
- Physical examination – assessment of nostrils, throat, and general airway anatomy
- Exercise test – a short controlled walk (usually 3–6 minutes)
- Recovery assessment – monitoring how quickly breathing returns to normal after exercise
Some protocols also include body condition scoring, as obesity can significantly worsen BOAS symptoms.
BOAS Severity Grading
Results are typically classified into functional grades:
- Grade 0 (BOAS-Unaffected): Normal breathing with no clinical signs
- Grade 1 (Mild BOAS): Occasional noise or mild exercise intolerance
- Grade 2 (Moderate BOAS): Clear breathing difficulty during activity and slower recovery
- Grade 3 (Severe BOAS): Significant respiratory distress at rest or with minimal exertion
Management and Treatment
While BOAS cannot be fully reversed without addressing anatomy, symptoms can often be improved through management and surgery. Treatment options include:
- Weight control to reduce airway strain
- Avoidance of overheating and intense exercise
- Use of harnesses instead of collars
- Anti-inflammatory medications in some cases
- Surgical correction (e.g., widening nostrils, shortening soft palate, or airway reconstruction)
Early diagnosis and intervention can greatly improve breathing comfort and overall quality of life.
Importance in Breeding
BOAS testing is essential in brachycephalic breeding programs. It helps identify dogs with better airway function and supports breeding decisions aimed at reducing respiratory disease severity in future generations. Many veterinary organizations recommend routine BOAS screening before breeding to improve long-term breed health and welfare.
Summary
The BOAS Breathing Test is a critical respiratory assessment that evaluates airway function, detects breathing obstruction, guides medical or surgical intervention, and supports responsible breeding practices to improve long-term respiratory health in brachycephalic dogs.
