A frequent problem with horses is respiratory noise during exercise. The horse must breath through his nostrils to accommodate exercise and is unable to switch from nasal to mouth breathing to decrease the work of breathing, particularly during inspiration. The horse relies on muscles in the pharynx and associated structures to dilate and stabilize the airway during intense exercise. A dysfunction of these tissues can result in noises that vary from grunts to wheezes to whistles but occur rhythmically with breathing. The most common abnormalities found are:

• laryngeal dysfunction
• dorsal displacement of the soft palate
• epiglottic entrapment
• epiglottic flutter
• aryepiglottic fold flutter (axial deviation of the aryepiglottic folds)
• pharyngeal collapse
• arytenoiditis
• vocal cord flutter
• false nostril noise
• pharyngeal lymphoid hyperplasia
• soft palate hemorrhage
• positional arytenoid collapse

The noises starts during exercise because of the increase volume of air being moved with each breath. If severe, the problem may interfere with the horses ability to work. It is estimated that 14% of horses with exercise intolerance have upper airway disorders. This article deals with the differential diagnosis and treatment of upper respiratory noise and associated exercise intolerance.