Any factors that increase negative pressure in the upper respiratory tract (URT) can influence its mechanics. The aim of this report was to describe the results of URT diagnostic evaluation with overground endoscopy in sport and pleasure horses. The URT and plasma lactate levels were evaluated during rest and during overground endoscopic examination in 19 cases. Horses performed their normal training session. When history and clinical examination suggested a lower airway obstruction, we performed bronchoalveolar lavage. Dorsal displacement of the soft palate (DDSP) was diagnosed in 8 of 19 horses, which might have developed secondary to URT or lower respiratory tract inflammation or obstruction. DDSP was also detected at rest in four cases. Laryngeal hemiplegia (LHP) was diagnosed in 15 of 19 horses, 11 of which were complex cases with other types of URT obstructions. Severe pharyngeal collapse (PHC), suspected already at rest, was visible in two cases during exercise. In contrast, PHC diagnosed with nasal occlusion at rest in two cases was fully compensated under the rider. Plasma lactate levels significantly decreased during exercise. All DDSP cases were suspected to be of inflammatory or obstructive origin, which is different from findings in racehorses, where extrinsic causes are more common. Resting endoscopic examinations were sensitive in cases of obstructive origin. LHP and PHC could not be predicted on the basis of findings at rest, and increased neuromuscular activity during exercise could compensate for the problem in less severe cases. Decreased levels of lactate could be explained by the increased clearance during exercise.
- Dynamic upper respiratory tract obstruction
- Lower airway obstruction
- Overground endoscopy
- Sport horses
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