December 15, 2017

Characterization of Brachycephalic Obstructive Airway Syndrome in French Bulldogs Using Whole-Body Barometric Plethysmography

Brachycephalic Obstructive Airway Syndrome (BOAS) is a respiratory disorder that is common in brachycephalic breeds such as pugs and French Bulldogs. With the recent spike in popularity of French Bulldogs, there is concern about the frequency of this disorder in the breed due to accelerated inbreeding to meet demands. Furthermore, there is very low disease recognition in owners of French Bulldogs therefore the disease often goes undiagnosed. Previously, noninvasive measures to diagnose BOAS included a face mask and pneumotachograph these methods were not particularly accurate therefore there was no perfect way to diagnostic test for BOAS. 

There were two key objectives in this study. First, the authors aimed to use Whole-Body Barometric Plethysmography (WBBP) to characterize respiratory cycles in non-brachycephalic control dogs and French Bulldogs (FB) with ranging respiratory characteristics. Second, they wanted to create a scoring system, (BOAS Index) to categorize the respiratory cycles of French Bulldogs with moderate to severe Brachycephalic Obstructive Airway Syndrome (BOAS) and those without significant symptoms. 

The subjects used in this study include Patient FBs who were FB that were referred for BOAS consultation at the Queen's Veterinary School Hospital, QVSH) and study FB who were volunteered by UK owners and breeders for the study. For controls they used non-brachycephalic dogs from QVSH and non-brachycephalic staff owned dogs. 

The scientists then created a functional grading system for BOAS. In this system, Grade III denoted severe BOAS, Grade II signified moderate BOAS, Grade I as mild BOAS, Grade 0 means BOAS free. These groups were then consolidated, Grade III/II were BOAS+ and Grade 0/1 were BOAS-. 

Data collection was performed with the dog inside a transparent Perspex chamber, measurements were recorded for 20 minutes after the dog adjusted to the new environment for 5-10 minutes. The selected respiratory parameters include: tidal volume (TV), inspiratory time (Ti), expiratory time (Te), peak inspiratory flow rate (PIF), peak expiratory flow rate (PEF), respiratory rate (RR) and minute ventilation (MV) and were used to characterize the WBBP flow waveform. 

After undergoing the WBBP test for 20 breaths, the dogs then underwent physical re-examination and were then functionally graded (0-III). They were then divided into two groups, a training group and a test group of 20 new dogs. Quadratic discriminant analysis (QDA) was then used to place each dog into a group based on six variables. Then, a predictive index was constructed by scoring the posterior possibilities of being classed into Grade 'X' with intervals of disease severity for each grade. These were then placed into the binary classification of BOAS+/-. 

The results identified 0.54 prevalence of BOAS+ in the total sample group (n=89) and 0.43 prevalence of BOAS+ for the study FB (n=70). To support the belief that there is a fair amount of low disease recognition for this disorder, the study found that 60% of BOAS+ dog owners claimed their dogs never showed signed of trouble breathing or symptoms of the disorder. Also, the study found that male HB have a prevalence risk ratio of BOAS + 1.90 times higher than female FBs. 

They then used a multivariate analysis to classify BOAS- FB and BOAS+ FB and several statistical modelling approaches to test the classifications. Throughout all of these tests the QDA application performed well. The QDA results showed that the classification accuracy for four-group classification had a 84.06% accuracy and binary group analysis had 94.2% accuracy. Conclusions, the QDA classifier was a very accurate and effective means of classifying the features of interest, creating a successful assessment of BOAS status.

Citation: Citation: Liu N-C, Sargan DR, Adams VJ, Ladlow JF, 2015. Characterisation of Brachycephalic Obstructive Airway Syndrome in French Bulldogs Using Whole-Body Barometric Plethysmography. PLoS ONE 10.

Reviewed by: Harper Lane