Videoendoscopic evaluation of the upper respiratory tract in 93 sport horses during exercise testing on a high-speed treadmill

Abstract

Reasons for performing study: Videoendoscopy of the upper respiratory tract (URT) during high-speed treadmill exercise has proved to be invaluable in the assessment of URT dysfunction in racehorses. However, very little information exists regarding dynamic airway collapse in other sport horses used in nonracing equestrian disciplines. Objectives: To evaluate the videoendoscopic findings at rest and during exercise in a mixed population of sport horses referred for investigation of poor athletic performance and/or abnormal respiratory noise. Methods: Videoendoscopy of the upper airway was performed at rest and during high-speed treadmill exercise in 93 horses. Results: Dynamic airway obstructions were diagnosed in 77% of horses and were frequently complex in nature. The most common forms of dynamic collapse included soft palate dysfunction (54%), dynamic laryngeal collapse (38%), axial deviation of the aryepiglottic folds (24%) and pharyngeal wall collapse (18%). In the majority of horses, no obvious abnormalities were identified at rest. Enforced poll flexion was found to be a contributing factor in 24% of cases. Conclusions: Dynamic obstructions of the URT were a common cause of poor performance and/or abnormal respiratory noise in sport horses referred for investigation of performance problems. Potential relevance: This study highlights the importance of videoendoscopic evaluation of the URT during exercise in horses utilised for equestrian sports where exercise during competition is submaximal in nature.