Evaluation of upper respiratory tract function during strenuous exercise in racehorses

Area of Science:

• Equine Sports Medicine
• Veterinary Internal Medicine
• Equine Upper Respiratory Tract Anatomy

Background:

• Poor performance in racehorses can stem from various factors.
• Upper respiratory tract (URT) dysfunction is a potential, yet often undiagnosed, cause of reduced athletic ability.
• Endoscopic evaluation during exercise is crucial for diagnosing dynamic URT obstructions.

Purpose of the Study:

• To investigate the prevalence and types of upper respiratory tract obstructions in poor-performing racehorses.
• To correlate endoscopic findings with exercise-induced performance deficits.
• To document the dynamic functional anatomy of diagnosed URT abnormalities.

Main Methods:

• Forty-six racehorses with a history of poor performance were evaluated.
• High-speed treadmill exercise endoscopy was used to assess laryngeal and pharyngeal function.
• Functional abnormalities were diagnosed and categorized based on endoscopic findings.

Main Results:

• Ten of the 46 horses (22%) exhibited functional upper respiratory tract abnormalities.
• Diagnoses included persistent dorsal displacement of the soft palate (4 horses), left laryngeal hemiplegia (5 horses), and epiglottic entrapment (1 horse).
• Thirty-two horses showed resting left laryngeal hemiparesis without exercise-induced impairment.

Conclusions:

• Upper respiratory tract obstruction is a significant cause of poor performance in a subset of racehorses.
• Dynamic endoscopic evaluation is essential for accurate diagnosis of exercise-induced URT dysfunction.
• Specific conditions like soft palate displacement and laryngeal hemiplegia require targeted management strategies.