Use of ultrasound to estimate tracheal diameter in unclipped brachycephalic dogs: A pilot study

A significant contributory factor to the brachycephalic obstructive airway syndrome index of bulldogs is the diameter of their tracheas. Bulldogs are predisposed to tracheal hypoplasia. A non-invasive, financially reasonable and widely accessible screening test for tracheal diameter would be useful for assessing the most appropriate dogs to breed from within bulldog populations and may help in predicting results following upper airway surgery.

A prospective method comparison study involving 10 client-owned brachycephalic dogs was conducted. Each patient underwent tracheal ultrasonography using a handheld ultrasound device (Butterfly IQ+) followed by extubated computed tomography (CT) scanning of the head and neck. Ultrasonographic tracheal measurements were compared with CT tracheal measurements and analysed for agreement, accuracy, and inter-observer and intra-observer repeatability.

Bland‒Altman analysis showed there was good agreement between the ultrasound and CT tracheal measurements; however, the 95% limits of agreement were wide (+0.43 and ‒0.29 cm), indicating that the ultrasound measurements lacked a high level of accuracy. Ultrasound in general overestimated the tracheal diameter by 0.07 cm (p < 0.05). Intra-observer repeatability (mean range: 0.12 cm, average coefficient of variation [COV]: observer one;7.36%, observer two;5.53%, observer three;6.10%) was more consistent than inter-observer repeatability (mean range: 0.26 cm, average COV: 8.47%).

The accuracy of tracheal diameter measurements using an affordable handheld ultrasound device in unclipped brachycephalic patients was relatively low. However, technique modifications may significantly improve results, and further investigation is warranted to explore the utility of this method as a screening tool for tracheal hypoplasia in bulldog populations.