Influence of Breed on Tracheal Diameter and Endotracheal Tube Size Selection in Dogs: A Retrospective Analysis.

Selecting the correct endotracheal tube (ETT) size is critical for safe anesthesia in dogs. Current ETT size recommendations are largely based on body weight (BW), although some breeds, particularly brachycephalic dogs, may receive smaller ETTs than predicted from BW alone. This two-part retrospective study was performed to evaluate the effect of breed on ETT selection. In Part 1, computed tomography (CT)-measured tracheal diameters (TD) were compared among five small dog breeds weighing 4-5 kg and having a body condition score of 5/9. In Part 2, an expanded clinical cohort of 512 dogs from eight breeds was used to compare clinically selected ETT sizes with BW-based predictions. Statistical models assessed whether breed influenced clinically used ETT sizes after accounting for body mass using the cube root of BW. CT measurements revealed that TD differed significantly among breeds within a similar body-weight range. In the Part 2 clinical cohort, clinically selected ETT size was significantly associated with breed, the cube root of BW, and their interaction. Shih Tzus, French Bulldogs, Pekingese, and Boston Terriers had clinically selected ETT sizes smaller than BW-based predicted sizes, with a median discrepancy of approximately 0.5 mm in Shih Tzus and approximately 1.0 mm in French Bulldogs, Pekingese, and Boston Terriers. These findings suggest that the magnitude of discrepancy from BW-based predictions varies among brachycephalic breeds, indicating that breed may warrant consideration when estimating ETT size.