Table 1.
Functional grading system of brachycephalic obstructive airway syndrome (BOAS) based on respiratory signs before and after an exercise tolerance test (ETT)
| Respiratory Noisea | Inspiratory Effortb | Dyspnea/Cyanosis/Syncopec | ||
|---|---|---|---|---|
| Grade 0 | Pre‐ETT | Not audible | Not present | Not present |
| Post‐ETT | Not audible | Not present | Not present | |
| Grade I | Pre‐ETT | Not audible or mild | Not present | Not present |
| Post‐ETT | Mild | Not present to mild | Not present | |
| Grade II | Pre‐ETT | Mild to moderate | Mild to moderate | Not present |
| Post‐ETT | Moderate to severe | Moderate to severe | Mild dyspnea; cyanosis or syncope not present | |
| Grade III | Pre‐ETT | Moderate to severe | Moderate to severe | Moderate to severe dyspnea; may or may not present cyanosis. Inability to exercise. |
| Post‐ETT | Severe | Severe | Severe dyspnea; may or may not present cyanosis or syncope. | |
The grading system was established previously.18 The clinical grading was based on respiratory signs before (pre‐ETT) and immediately after a 3‐minute exercise tolerance test (post‐ETT) with trotting speed of approximately 4–5 miles/hour performed by the study investigators. Presentation of at least one sign in the highest grade determines the final grading result.
aRespiratory noise was diagnosed by pharyngolaryngeal auscultation. Mild: only audible under auscultation; moderate: intermittent audible noise that can be heard without stethoscope; severe: constant audible noise that can be heard without stethoscope.
bAn abnormal respiratory cycle characterized by evidence of increased effort to inhale the air with the use of diaphragm and/or accessory muscles of respiration and/or nasal flaring with an increase in breathing rate. Mild: regular breathing patterns with minimal use of diaphragm; moderate: evidence of use of diaphragm and accessary muscles of respiration; severe: marked movement of diaphragm and accessary muscles of respiration.
cDogs that have had episodes of syncope and/or cyanosis as documented by owner's report are classified into Grade III without ETT. Mild dyspnea: presents sign of discomfort; moderate dyspnea: irregular breathing, signs of discomfort; severe dyspnea: irregular breathing with signs of breathing discomfort and difficulty in breathing.