Radiographic vertical tracheal diameter assessment at different levels along the trachea as an alternative method for the evaluation of the tracheal diameter in non-brachycephalic small breed dogs.

BACKGROUND: Tracheal narrowing due to congenital tracheal hypoplasia, acquired tracheal stenosis and tracheal collapse can lead to life-threatening respiratory distress. Tracheal hypoplasia has been identified in brachycephalic dog breeds, predominantly English Bulldogs, by measuring the tracheal diameter compared to the diameter of the thoracic inlet and creating a ratio. However, reference ranges for tracheal diameter have not been established for non-brachycephalic small breed dogs. It would be advantageous to have established tracheal diameters for non-brachycephalic small breed dogs, as these are the dogs most at risk of tracheal collapse. The main objective, of this study was to radiographically evaluate vertical tracheal diameter (VTD) at three standardized locations along the trachea of non-brachycephalic small breed dogs, in an attempt to further establish a screening diagnostic protocol for canine tracheal hypoplasia. Medical records and thoracic radiographs of non-brachycephalic small breed dogs without respiratory disease were reviewed. Right lateral radiographs were reviewed. The absolute and average VTDs at three locations (location A: caudal cervical VTD; location B thoracic inlet VTD; location C: intrathoracic VTD) were standardized by manubrium length (ML), as well as by the previously utilized thoracic inlet distance (Ti-D) and proximal 3rd rib width (PR3-W) to calculate manubrium-tracheal index (M-TI), thoracic inlet-tracheal index (Ti-TI), and proximal R3-tracheal score (PR3-TS), respectively. Correlations between averaged tracheal diameter and each of the ML, Ti-D, and PR3-W, and between M-TI and each of Ti-TI and PR3-TS were calculated. RESULTS: Eighty-one healthy dogs met the criteria for inclusion. Significant differences (P < 0.0001) were identified among the mean values of the absolute and standardized VTDs at levels A, B, and C. The smallest tracheal diameter was identified at the level of the thoracic inlet (Level B). The average VTD correlated better with ML (rs = 0.82, P < 0.0001) compared to Ti-D and PR3-W. A relatively strong correlation (rs = 0.77, P < 0.0001) was identified between the averaged manubrium tracheal index (M-TI) and thoracic inlet tracheal index (Ti-TI). CONCLUSION: M-TI is an appropriate alternative to Ti-TI and PR3-TS to radiographically evaluate VTD in dogs. M-TI < 0.43, < 0.34, or < 0.38 at level A, B, or C, respectively, may indicate tracheal hypoplasia in non-brachycephalic small breed dogs. Screening of canine VTD could be achieved using M-TI.

Comparison of intraocular pressure in healthy brachycephalic and nonbrachycephalic cats using the Icare® TONOVET Plus rebound tonometer.

OBJECTIVE: To compare intraocular pressure using the Icare® TONOVET Plus rebound tonometer in healthy brachycephalic and nonbrachycephalic cats. ANIMALS STUDIED: Both eyes of 78 healthy cats were investigated in this study. Cats were divided into two groups: brachycephalic (n = 39) and nonbrachycephalic (n = 39). PROCEDURES: Nose position and muzzle ratio were photographically recorded and analyzed. Physical and ophthalmic examinations were performed. Intraocular pressure was measured using the Icare® TONOVET Plus rebound tonometry instrument. Quantitative mean values were statistically compared using an unpaired t-test at a significance level of p < .05. RESULTS: Mean values of the nose position and muzzle ratio were significantly lower in the brachycephalic group (20.14 ± 5.43%, 9.61 ± 3.29%) compared with the nonbrachycephalic group (29.21 ± 4.30%, 13.97 ± 6.01%). The mean intraocular pressure for brachycephalic cats (15.76 ± 0.50 mmHg) was significantly lower (p < .001) than for nonbrachycephalic cats (18.77 ± 0.49 mmHg). CONCLUSIONS: Intraocular pressure was significantly lower in brachycephalic cats using the Icare® TONOVET Plus rebound tonometer. Intraocular pressure values obtained in this study could be used as a guideline for measurements obtained using this tonometry device in healthy brachycephalic and nonbrachycephalic cats.

Epidemiological associations between brachycephaly and upper respiratory tract disorders in dogs attending veterinary practices in England.

BACKGROUND: Brachycephalic dog breeds are increasingly common. Canine brachycephaly has been associated with upper respiratory tract (URT) disorders but reliable prevalence data remain lacking. Using primary-care veterinary clinical data, this study aimed to report the prevalence and breed-type risk factors for URT disorders in dogs. RESULTS: The sampling frame included 170,812 dogs attending 96 primary-care veterinary clinics participating within the VetCompass Programme. Two hundred dogs were randomly selected from each of three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) and three common small-to medium sized breed types (moderate brachycephalic: Yorkshire Terrier and non-brachycephalic: Border Terrier and West Highland White Terrier). Information on all URT disorders recorded was extracted from individual patient records. Disorder prevalence was compared between groups using the chi-squared test or Fisher's test, as appropriate. Risk factor analysis used multivariable logistic regression modelling. During the study, 83 (6.9 %) study dogs died. Extreme brachycephalic dogs (median longevity: 8.6 years, IQR: 2.4-10.8) were significantly younger at death than the moderate and non-brachycephalic group of dogs (median 12.7 years, IQR 11.1-15.0) (P < 0.001). A higher proportion of deaths in extreme brachycephalic breed types were associated with URT disorders (4/24 deaths, 16.7 %) compared with the moderate and non-brachycephalic group (0/59 deaths, 0.0 %) (P = 0.001). The prevalence of having at least one URT disorder in the extreme brachycephalic group was higher (22.0 %, 95 % confidence interval (CI): 18.0-26.0) than in the moderate and non-brachycephalic group (9.7 %, 95 % CI: 7.1-12.3, P < 0.001). The prevalence of URT disorders varied significantly by breed type: Bulldogs 19.5 %, French Bulldogs 20.0 %, Pugs 26.5 %, Border Terriers 9.0 %, West Highland White Terriers 7.0 % and Yorkshire Terriers 13.0 % (P < 0.001). After accounting for the effects of age, bodyweight, sex, neutering and insurance, extreme brachycephalic dogs had 3.5 times (95 % CI: 2.4-5.0, P < 0.001) the odds of at least one URT disorder compared with the moderate and non-brachycephalic group. CONCLUSIONS: In summary, this study reports that URT disorders are commonly diagnosed in Bulldog, French Bulldog, Pug, Border Terrier, WHWT and Yorkshire Terrier dogs attending primary-care veterinary practices in England. The three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) were relatively short-lived and predisposed to URT disorders compared with three other small-to-medium size breed types that are commonly owned (moderate brachycephalic Yorkshire Terrier and non-brachycephalic: Border Terrier and WHWT).