Dynamic evaluation of the equine upper respiratory tract.

Abstract: Each case of suboptimal equine athletic performance should be evaluated in a comprehensive manner, including physical examination; clinical pathologic analysis; and evaluation of the neurologic system, the musculoskeletal system, and the upper and lower respiratory system. A vital part of this examination is the clinical evaluation of dynamic upper respiratory tract function of the horse during treadmill exercise, which allows the observation of upper respiratory tract function during conditions simulating competitive racing. It generally is agreed that the endoscopic identification of an upper respiratory tract abnormality in the resting horse does not necessarily indicate a clinical problem. It is equally certain that the absence of an upper respiratory abnormality at rest does not rule out the presence of an intermittent obstruction during strenuous exercise. Although many upper respiratory abnormalities may be diagnosed at rest (specifically, most cases of continual epiglottic entrapment and total laryngeal paralysis) the diagnosis of intermittent DDSP, intermittent EE, and some cases of idiopathic laryngeal neuropathy necessitates the observation of the upper respiratory tract during strenuous exercise. This diagnostic technique allows absolute documentation of whether upper airway dysfunction is a contributing factor to inadequate athletic performance in each individual horse. In the decade to come, it is clear that the evaluation of potential upper respiratory tract dysfunction as a cause of exercise intolerance should be performed before specific recommendations are made for treatment in each equine athlete. In many cases, this evaluation has circumvented the unnecessary attempt at correction of suspected but nonexistent respiratory dysfunction. Thus, these horses benefit from a continuation of a comprehensive performance evaluation, enabling an elucidation of the true cause of inadequate performance. The routine use of this diagnostic technique at Tufts University School of Veterinary Medicine's Equine Sports Medicine Center has greatly expanded the documentation of the diversity of upper respiratory dysfunctions that can occur. It also has enabled a precise description of the anatomic abnormalities resulting in each case of upper airway obstruction. In addition, this new knowledge has made us cautious regarding conventional treatment regimens and allowed the capability to individualize attempts at surgical and managemental correction of each dysfunction to optimize the success of the treatment for each horse.