Breed-specific anatomical risk factors of brachycephalic obstructive airway syndrome: A comprehensive computed tomographic study from nares to cervical trachea

The severity of brachycephalic obstructive airway syndrome (BOAS) can vary in dogs with similar external traits. This study aimed to identify breed-specific upper airway lesions measured on computed tomographic (CT) images and their associations with the BOAS index (a measure of airway obstruction). This was a prospective cross-sectional study including 40 pugs, 52 French bulldogs, and 21 bulldogs. All subjects underwent whole-body barometric plethysmography respiratory function testing to obtain a BOAS index and CT of the head/neck. Eleven validated CT measurements were recorded from nares to cervical trachea. Multivariate linear regressions were used to assess the associations between the breed-specific upper airway lesions and BOAS index. Pugs with a higher soft tissue proportion at the rostral nasopharyngeal meatus (β=0.639, p < .001) or with Grade III laryngeal collapse (β=15.099, p = .009); French bulldogs with a smaller nasopharyngeal index (β=-0.142, p < .001), or with Grade I (β=18.939, p < .001) or Grade II (β=26.503, p < .0001) laryngeal collapse (when compared to Grade 0); and bulldogs, with a smaller trachea perimeter (β=-1.46, p = 0.012), or smaller nasopharyngeal index (β=-0.119, p = 0.041) or higher skull index (β=247.525, p = 0.004) were associated with higher BOAS indices. The contributory lesions of BOAS are different between the three breeds. Some of these lesions are unfortunately not amenable to surgical correction. While breed specific surgical considerations are required, lesions such as the hypoplastic trachea in bulldogs should be eliminated by breeding selection. • The contributory lesions of BOAS are different between pugs, French bulldogs, and bulldogs. • In pugs, intra-nasal obstruction and advanced laryngeal collapse predicted BOAS severity. • In French bulldogs, nasopharyngeal dimensions and laryngeal collapse predicted BOAS severity. • In bulldogs, tracheal hypoplasia and broad skull correlated with BOAS severity. • Inoperable lesion such as hypoplastic trachea in bulldogs should be eliminated by breeding selection.