Horses of all ages presented for investigation of poor performance require a thorough clinical investigation of the lower airways. The collection of both TW and BAL samples is indicated in order to confirm a diagnosis of IAD.

Care should be taken in interpreting negative findings during both procedures, but particularly during overground endoscopy if racing conditions have not been appropriately replicated.

Summary Dynamic upper respiratory tract (URT) obstructions occur commonly in the equine athlete. During the past 25 years, veterinary diagnostic capabilities have improved greatly with the ability to perform endoscopy during exercise and thus to visualise upper airway function during various types of exercise. After correctly reproducing and diagnosing an URT obstruction, the veterinary surgeon must consider the functional significance of the endoscopic findings for that individual athlete. This is the third paper in this series and focuses on the diagnosis of URT obstructions, their relationship to the exercise test and their functional significance.

Summary In the last decade there have been significant technological advances and increases in the availability of portable diagnostic equipment for use in the assessment of athletic performance. The design and application of appropriate exercise tests are critical factors for the diagnosis of conditions affecting equine performance and it is therefore necessary for veterinary surgeons using such equipment to develop an understanding of appropriate exercise testing methods. This is the first in a series of three papers covering exercise testing in the equine athlete, interpretation of heart rate and rhythm during exercise and interpretation of dynamic upper respiratory tract function. In this first paper, both performance and clinical exercise testing in the equine athlete are reviewed.

Dynamic collapse of the upper respiratory tract (URT) is a common cause of poor performance in horses. These conditions occur predominantly during strenuous exercise when the URT is unable to maintain dilation in the face of high inspiratory pressures. In most cases, these disorders cannot be accurately diagnosed during a resting endoscopic examination. To date, a definitive diagnosis of dynamic URT obstructions has been possible only by performing an endoscopic examination during high-speed treadmill exercise. However, recent technological advances now enable URT endoscopy to be performed while the horse is exercising in its normal environment.