Conformational risk factors of brachycephalic obstructive airway syndrome (BOAS) in pugs, French bulldogs, and bulldogs

Abstract

Extremely brachycephalic, or short-muzzled, dog breeds such as pugs, French bulldogs, and bulldogs are prone to the conformation-related respiratory disorder—brachycephalic obstructive airway syndrome (BOAS). Affected dogs present with a wide range of clinical signs from snoring and exercise intolerance, to life-threatening events such as syncope. In this study, conformational risk factors for BOAS that could potentially aid in breeding away from BOAS were sought. Six hundred and four pugs, French bulldogs, and bulldogs were included in the study. Soft tape measurements of the head and body were used and the inter-observer reproducibility was evaluated. Breed-specific models were developed to assess the associations between the conformational factors and BOAS status based on functional grading. The models were further validated by means of a BOAS index, which is an objective measurement of respiratory function using whole-body barometric plethysmography. The final models have good predictive power for discriminating BOAS (-) and BOAS (+) phenotypes indicated by the area under the curve values of >80% on the receiver operating curves. When other factors were controlled, stenotic nostrils were associated with BOAS in all three breeds; pugs and bulldogs with higher body condition scores (BCS) had a higher risk of developing BOAS. Among the standardized conformational measurements (i.e. craniofacial ratio (CFR), eye width ratio (EWR), skull index (SI), neck girth ratio (NGR), and neck length ratio (NLR)), for pugs EWR and SI, for French bulldogs NGR and NLR, and for bulldogs SI and NGR showed significant associations with BOAS status. However, the NGR in bulldogs was the only significant predictor that also had satisfactory inter-observer reproducibility. A NGR higher than 0.71 in male bulldogs was predictive of BOAS with approximately 70% sensitivity and specificity. In conclusion, stenotic nostrils, BCS, and NGR were found to be valid, easily applicable predictors for BOAS (+).

The impact of tongue dimension on air volume in brachycephalic dogs

“…Although the large tongue of brachycephalic dogs is readily appreciable by oral examination, it has been noted uncommonly and inconsistently in the peer‐reviewed literature, and, when mentioned, it is typically unreferenced or cited as an earlier anecdotal observation . Possibly because of the lack of robust documentation, macroglossia is not listed as a feature of brachycephalism in many major veterinary texts, so awareness of it may be low in the veterinary profession .…”

Anaesthesia of brachycephalic dogs

“…Previously, age, body condition and laryngeal collapse have been identified as negative prognostic factors for surgical success (Torrez & Hunt , Liu et al . , , ), although these associations are not consistently found. Postsurgical complication rates of 12 to 26·2% and a mortality rate of approximately 3% have been reported (Poncet et al .…”

“…In addition, there may be aberrant nasal turbinates, both rostrally and caudally, resulting in increased intranasal mucosal contact points and intranasal airway obstruction (Ginn et al 2008, Oechtering et al 2016. Studies have shown that brachycephaly predisposes to development of BOAS, with French bulldogs, pugs and English bulldogs being overrepresented (O'Neill et al 2015, Liu et al 2017b.…”

“…Surgical intervention, including palatoplasty, laryngeal sacculectomy and rhinoplasty, may improve the flow of air through the upper airways in up to 90% of dogs with clinical signs of BOAS (Poncet et al 2006, Torrez & Hunt 2006, Riecks et al 2007, Fasanella et al 2010, Haimel & Dupré 2015. Previously, age, body condition and laryngeal collapse have been identified as negative prognostic factors for surgical success (Torrez & Hunt 2006, Liu et al 2016, 2017a, 2017b, although these associations are not consistently found. Postsurgical complication rates of 12 to 26·2% and a mortality rate of approximately 3% have been reported (Poncet et al 2006, Riecks et al 2007, Fasanella et al 2010.…”

Brachycephalic obstructive airway syndrome

“…10 However, the most significant conformational factor in the three breeds is the degree of nostril stenosis (). Obesity is significant in pugs and the gender predisposition is interesting, with more male Frenchies and bulldogs being affected than females, and more female pugs being affected than males.…”