Radiographic and computed tomographic evaluation of tracheal diameter and length in kittens

Daeyun Seo DVM , Kyuyong Kang DVM, PhD , Seongsoo Lim DVM , Beomkwan Namgoong DVM , Ahreum Choe DVM , Heesung Uhm DVM , Hyeajeong Hong DVM , Nanju Lee DVM , Isong Kim DVM , Seunghun Heo DVM , and Min-Su Kim DVM, PhD

Background: The authors aimed to evaluate the tracheal diameter and length in kittens using radiography and CT and to compare the measurements obtained with these two modalities. They also wanted to provide information for endotracheal intubation (ETI) in kittens, which is a procedure that can cause complications if not done properly.

Study: The study retrospectively analyzed the radiographic and CT images of 15 kittens with an estimated age of 12 weeks and a mean body weight of 1.49 kg. They measured the tracheal length and diameter at five different sites along the trachea and calculated the cross-sectional area and the transverse and vertical diameter ratios.

Methods: A digital radiography system and a 64-slice CT scanner were used to obtain the images. They used consistent criteria to measure the tracheal length and diameter on both modalities. They also used SPSS Statistics 26 to perform descriptive statistics, paired t tests, and linear regression analysis.

Results: The authors found that the cross-sectional area of the trachea was largest at the level of the C2-3 intervertebral disk space and decreased from the cranial end of the manubrium sterni to 1 cm cranial to the carina. The tracheal shape was most circular at the level of the C2-3 intervertebral disk space and 1 cm cranial to the carina, whereas it was elliptical from the level of the C4-5 intervertebral disk space to the level of the second rib. The vertical diameters of the trachea on radiography and CT did not differ significantly, but the tracheal length measured on radiography was about 6 mm longer than that measured on CT. The authors also found significant correlations between body weight and tracheal diameter and length.

Limitations: The authors acknowledged some limitations of their study, such as the lack of control over the respiratory cycles and the neck angles of the kittens, the small sample size and the predominance of domestic shorthair kittens, and the potential influence of superimposition, magnification, and image orientation on the measurements.

Conclusions: The authors concluded that their study provided the mean length, diameter, and morphological characteristics of the trachea in kittens, which could help reduce ETI-related complications. They suggested using the first rib as an anatomical reference for ETT placement and using regression equations based on body weight to predict tracheal diameter in emergency situations. They also recommended using a cuffed ETT in kittens, as it may be safer than an uncuffed ETT. They called for further research on kittens of various breeds and ages and under consistent respiratory cycles and optimal imaging positions.

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