Dynamic tracheal collapse as a cause of exercise intolerance in a Thoroughbred

Tracheal collapse in large animals occurs most commonly as a result of dire ct trauma. Tracheal collapse can limit athletic function by increasing airway impedanc e and turbulence, thereby increasing the work of breathing. When the cause of exercise intolerance cannot be determined in horses from endoscopic evaluation of the nasopharyrnx during rest and exercise, trachea l videoendoscopy should be performed during exercise.