Computed tomographic evaluation of tracheal anatomy of tigers (Panthera tigris)

To describe tracheal dimensions of male and female tigers using computed tomography (CT) scans, and to assess correlation between body mass and theoretical maximum endotracheal tube (ETT) size (Max ETT size).

Retrospective case series.

A group of 19 anesthetized tigers (Panthera tigris).

Medical records of tigers that underwent general anesthesia and CT scan between June 2014 and August 2024 were collected, and CT images selected according to inclusion criteria were evaluated. Tracheal length, vertical and transverse diameters and their ratio (T:V) and cross-sectional areas (CSA) were spot-measured at five locations (M1, 1 cm caudal to the cricoid cartilage; M2, at the level of C4-C5 intervertebral disc; M3, at cranial end of the manubrium sterni; M4, at the level of second costae; and M5, 1 cm cranial to origin of the most cranial bronchus) along the tracheal length and averaged. Minimum cross-sectional area (CSA_min) was calculated and compared with the CSA of commercial ETTs to obtain the Max ETT size. Correlations between body mass and averaged tracheal measurements were analyzed using Pearson's correlation. Significance was set as p < 0.05.

At M1-M5, T:V ratios were 0.9, 0.9, 1, 1 and 1, respectively. Based on the tracheal mean CSA_min [858.2 mm² ± 308.3 (mean ± standard deviation)], the Max ETT size was 22 mm ± 3.0 (ETT internal diameter). CSA_min was not significantly correlated with body mass (p = 0.416), nor were other tracheal measurements, including length of the trachea.

The trachea of Panthera tigris was elliptical with a mild latero-lateral flattening in the cervical portion and circular along the rest of its length. This information characterizes the tracheal anatomy of tigers and provides the basis for further investigations to better understand the optimal ETT diameter and airway management for this species.