Dynamic respiratory endoscopy in 67 Thoroughbred racehorses training under normal ridden exercise conditions

There are potential advantages to imaging the upper portion of the respiratory tract (URT) of horses during ridden exercise. With the advent of a wireless endoscope, this is now possible. However, there has been no detailed validation of the technique and findings have not been compared to ridden speed.

To assess the combined use of a Dynamic Respiratory Scope (DRS) and global positioning system (GPS) receiver for examining the URT of a group of Thoroughbred racehorses randomly selected from a single flat racehorse training establishment.

Horses were selected randomly from a population of Thoroughbred horses in training at the same training yard. Endoscopic images of the URT were recorded during a ridden exercise test on an 'all-weather-gallop' and were reviewed post testing. Speed was measured using a wrist mounted GPS receiver.

A total of 67 (34%) of the 195 horses in training were examined. Endoscopic findings included: normal URT function (44 cases); dorsal displacement of the soft palate (DDSP) (13 cases); laryngeal asymmetry (4 cases); and axial deviation of the aryepiglottic folds (3 cases). Maximum speed obtained by individual horses ranged from 41.8-56.3 km/h. Ridden speed was variably affected by DDSP.

The DRS provides a safe effective system for imaging the equine URT during ridden exercise at speed. The abnormalities of the URT identified were similar to those observed during treadmill endoscopy studies reported in the literature. The effect of URT abnormalities on ridden speed requires further investigation.

This technique can be used to diagnose common causes of URT associated with poor performance in horses during normal training. This has substantial implications for future clinical diagnosis and treatment of URT pathology.