Poor performance secondary to airway obstruction in horses

Abstract

Upper respiratory tract (URT) obstructions are a common cause of poor performance in both racehorses and sport horses. The URT experiences changes in pressure throughout the different phases of respiration. During inspiration, when the diaphragm contracts, negative pressure develops in the upper and the lower respiratory tract, which is further increased during strenuous exercise and may exacerbate disorders of the URT. Whilst some disorders may be detected by endoscopy at rest, many are only seen during exercise and are referred to as dynamic disorders of the URT. Any of the factors that increase negative pressure in the URT – e.g. poll flexion, increased pressure in the lower respiratory tract or multiple obstructions – or constitutional changes can markedly influence URT mechanics. This study was undertaken to describe the URT abnormalities detected during dynamic overground endoscopy in competitive and pleasure horses presenting with poor performance, abnormal respiratory noise and/or coughing. Following a clinical examination and recording the medical history, the upper airway was evaluated during rest and OE in 9 cases. The horses performed their normal training session. When the history and clinical examination suggested a lower airway obstruction, a broncho-alveolar lavage was performed. When URT inflammation was suspected a bacteriological sample was taken from the trachea.