BOAS is a conformational airway disorder, meaning it is caused by the physical structure of the upper airway rather than infection or a single disease process. In affected dogs, the shortened skull often results in narrowed nostrils, an elongated soft palate, and reduced airway space in the nose, throat, and windpipe. These structural limitations make it harder for air to move freely in and out of the lungs.
How BOAS Affects Breathing
Normal breathing relies on open and unobstructed airways from the nostrils to the lungs. In dogs with BOAS, several anatomical abnormalities may contribute to airflow restriction, including:
- Stenotic (narrow) nostrils
- Elongated soft palate
- Collapsed or narrowed trachea
- Excess soft tissue in the throat
These changes increase airway resistance, meaning the dog must work harder to breathe, especially during exercise, stress, or warm weather.
Clinical Signs
Clinical signs of BOAS can range from mild to severe and often worsen with heat, excitement, or physical activity. Common symptoms include:
- Loud or noisy breathing (stertor or snoring sounds)
- Snorting or gagging
- Exercise intolerance
- Rapid fatigue during activity
- Difficulty breathing in warm or humid conditions
- Bluish gums or collapse in severe cases
- Sleep disturbances due to breathing difficulty
Over time, chronic airway obstruction can lead to secondary complications, such as inflammation, airway collapse, and reduced oxygen intake, which may affect overall health and quality of life.
BOAS Breathing Test Procedure
The BOAS breathing test is performed by a veterinarian and typically includes both physical examination and functional respiratory assessment. Dogs are evaluated at rest and after controlled exercise (such as a short walk) to observe how efficiently they recover.
The assessment may include:
- Observation of breathing patterns and noise
- Measurement of respiratory rate and effort
- Physical examination of nostrils and throat
- In some cases, imaging or endoscopy for detailed airway evaluation
Dogs are often scored based on breathing effort and tolerance to exercise.
BOAS Severity Grading
Results are commonly classified as:
- Grade 0 (Normal): No evidence of breathing obstruction; normal exercise tolerance
- Grade 1 (Mild BOAS): Mild respiratory noise or slight exercise limitation
- Grade 2 (Moderate BOAS): Noticeable breathing difficulty and reduced exercise capacity
- Grade 3 (Severe BOAS): Significant airway obstruction with marked breathing distress or risk of collapse
Management and Treatment
BOAS is a lifelong condition, but symptoms can often be managed. Treatment options include:
- Weight management to reduce airway pressure
- Avoiding overheating and strenuous exercise
- Using harnesses instead of neck collars
- Anti-inflammatory medication in some cases
- Surgical correction (e.g., widening nostrils or shortening soft palate) in moderate to severe cases
Early intervention can significantly improve breathing efficiency and quality of life.
Importance in Breeding
BOAS testing is essential in breeding programs for brachycephalic breeds. Selecting dogs with healthier airway structure helps reduce the severity of BOAS in future generations and improves overall breed welfare. Breeding decisions based on respiratory health assessments are increasingly recommended by veterinary and kennel organizations.
Summary
The BOAS Breathing Test is a vital respiratory health screening tool that evaluates airway function, identifies breathing obstruction, supports early intervention, and promotes responsible breeding practices to improve long-term respiratory health and welfare in dogs.
