Use of Dynamic Endoscopy in the Investigation of Poor Performance in the Horse

The most frequently reported consequences of obstruction of the upper respiratory tract in the equine athlete are poor performance and abnormal respiratory noise. Diagnosing the cause of such non-specific clinical signs presents a challenge. Resting endoscopy often has limited value in determining the cause of upper respiratory tract obstruction since it is unable to accurately predict dynamic findings. The frequency of complex combinations of upper respiratory tract conditions further highlights the importance of dynamic respiratory tract evaluation. Until recently, this was best performed using a high-speed treadmill, an approach which also allows blood gas analysis, electrocardiography and even exercising ultrasonography in cases of poor performance. High speed treadmill endoscopy (HSTE) has widely been accepted as the ‘gold standard’ for diagnosis of diseases of the upper portion of the respiratory tract (URT) in horses, although it does not accurately emulate conditions during ridden exercise. The lack of rider and tack, difference in surface, speed, incline and environment, potential difference in head position and lack of other horses may mean that treadmill endoscopy will not result in certain URT pathology that would be seen in normal training conditions. Comparison of the treadmill and field exercise in a number of horses highlighted differences in heart rate, blood lactate and stride frequency and length. In addition to the uncertainty of the diagnostic accuracy of the HSTE technique, it has not been widely accepted by horse owners and trainers in some areas. […]