Investigating novel anatomical predictors for endotracheal tube selection in dogs

The selection of an appropriate endotracheal tube (ET) for orotracheal intubation in dogs is based largely on experience, with no well-established guidelines available. This study examined relationships between several novel and published methods for selecting endotracheal tubes in a heterogenous population of 79 adult dogs. The following measurements were included: left and right nare width, nasal septum width, sum of left and right nares width plus the nasal septum width, total nose width and height, tracheal width, metacarpal and digital footpad width and height, and body mass. Using the Bland and Altman ratio method, the calculation of Cube Root Mass provided the greatest accuracy and precision, predicting actual ET size use within 3 to 4 tube sizes. A simpler to calculate, but less precise method was Width of Nose/3. The majority of published methods for estimating ET size performed poorly, including nasal septum and tracheal width.