Diagnosis OF BOAS

Currently, the best method for diagnosis of brachycephalic obstructive airway syndrome is a combination of:

  • A full physical examination

  • Questionnaire about current clinical signs, exercise tolerance and sleeping habits

  • Exercise tolerance tests such as the respiratory function grading scheme

  • Visual airway inspection under heavy sedation or general anaesthesia

  • Diagnostic imaging (e.g. Xrays)

PHYSICAL EXAMINATION

The physical examination is important for assessing body condition, grading narrow nostrils, observing for noisy breathing, and checking for other common health conditions in brachycephalic breeds.

Stenotic nares or narrowed nostrils, can be a problem in our squishy face breeds. Open nostrils are important for clear passage of airflow. We know that French Bulldogs with moderate to severe narrowing of their nostrils are 20 times more likely to develop brachycephalic obstructive airway syndrome (BOAS).

We grade nostrils as:

  • Open: nostrils are wide open

  • Mild stenosis: slightly narrowed nostrils but the outer nostril wall does not touch the inner nostril wall. This means there should be a visible “slit”. The nostril wings should move open on inspiration.

  • Moderate stenosis: the outer nostril wall touches the inner nostril wall at the top part of the nostrils and the nostrils are only open at the bottom. The nostril wings are not able to move and there may be nasal flaring.

  • Severe stenosis: nostrils are closed or almost closed. The dog may switch to oral breathing from nasal breathing with stress or very gentle exercise such as playing.

Exercise tests

Any dog showing obvious symptoms of BOAS on examination at rest does not necessarily need to have an exercise test. In fact, for severe BOAS cases, it can be dangerous to perform an exercise test.

Where exercise testing may be helpful is in those dogs that appear symptom-free at rest. For these dogs, a 3-minute trotting exercise tolerance test is suggested, known as the respiratory function grading (RFG) scheme.

The RFG scheme for brachycephalic dogs was developed by the Cambridge University BOAS research team. Kennel clubs around the world are adopting this scheme to detect the presence and severity of brachycephalic obstructive airway syndrome using an exercise tolerance test.

Currently, the test is only validated for French bulldogs, Pugs and British Bulldogs and can only be performed by veterinarians who have undergone further training to be an assessor. Dr Melissa Kozaruk is an accredited assessor.

Dogs are examined for the presence of respiratory signs at rest, then they are trotted for 3 minutes and re-examined at the end of the test.

Dogs are graded as:

  • 0 - “clinically” unaffected

  • 1 - mild

  • 2 - moderate

  • 3 - severe

The objectives of the scheme are:

  • To identify dogs at risk/subject to BOAS. Grade II and III are considered clinically BOAS-affected and they require management and/or treatment such as multi-level corrective airway surgery.

  • Give breeders the best available information in terms of the appropriateness of using a dam/sire in a breeding programme. Grade 3 dogs should be removed from breeding programs.

  • To provide data and statistics in terms of BOAS to monitor the frequency and progress in the breed affected for ongoing research for the overall improvement of the relevant breeds.

You can find out more about diagnosis and the respiratory function grading test at the Cambridge University website.

You can perform a version of this test at home or at the dog park - try trotting your dog for 3 minutes – a normal dog should not experience breathing noise or shortness of breath after such a short period of activity. Observe if any symptoms occur during longer periods of exercise.

It is important to note that the grading scheme is not used as a singular diagnostic tool, but rather a way of assessing the severity of respiratory distress in brachycephalic dogs.

Some grade 1 dogs may also benefit from surgery if they have other clinical signs suggestive of BOAS (e.g. snoring, regurgitation, heat intolerance). For these dogs, a longer exercise test (e.g. 10-20 minutes) may be required.

A thorough physical examination, history, clinical signs, exercise tests, diagnostic imaging, and other tests are still essential to make an assessment.

VISUAL AIRWAY INSPECTION & IMAGING

Airway examination under anaesthesia can also be a useful tool to guide planning for surgery.

Some of the components we assess are:

•Nares – are they stenotic?

•Soft Palate – is it elongated? Thickened? Ulcerated?

•Tonsils - are they everted or enlarged?

•Larynx – are laryngeal saccules everted? Is there laryngeal collapse?

•Trachea – is there a hypoplastic trachea?