Dynamic obstructions of the equine upper respiratory tract. Part 1: observations during high-speed treadmill endoscopy of 600 Thoroughbred racehorses.
Authors: Lane J G, Bladon B, Little D R M, Naylor J R J, Franklin S H
Journal: Equine veterinary journal
Summary
# Editorial Summary Lane *et al.'s* landmark 2006 study examined high-speed treadmill endoscopy recordings from 600 Thoroughbred racehorses to characterise the prevalence and patterns of dynamic upper airway obstruction, a leading cause of poor racing performance. Dynamic collapse of the pharynx or larynx was identified in 471 horses (78.5%), with dorsal displacement of the soft palate (DDSP) and palatal instability accounting for 50% and 33% of cases respectively; crucially, complex obstructions involving multiple collapsing structures were present in 30% of affected horses. Age emerged as a significant risk factor, with younger horses predominantly experiencing DDSP whilst older horses showed increased susceptibility to laryngeal collapse, though no gender or racing format associations were evident. The finding that palatal instability and DDSP likely represent different expressions of the same nasopharyngeal malfunction challenges treatment approaches targeting isolated lesions, suggesting that managing dynamic obstruction in poor performers requires comprehensive airway assessment rather than addressing single structural faults. For practitioners, these results underscore the importance of exercise endoscopy in performance horses and indicate that single-intervention treatments may prove inadequate when multiple dynamic obstructions coexist—a clinical reality in nearly one-third of cases.
Read the full abstract on PubMed
Practical Takeaways
- •Dynamic airway obstructions are extremely common in racehorses in training; poor performance should prompt upper respiratory investigation with high-speed treadmill endoscopy rather than assumptions about other causes
- •Complex obstructions affecting multiple airway structures are frequent (30% of cases), meaning single-structure treatments may fail—diagnostic video-endoscopy should be thorough and treatments may need to address multiple sites
- •Age-related patterns exist: suspect DDSP in younger horses and laryngeal collapse in older horses, allowing targeted clinical focus based on horse demographics
Key Findings
- •Dynamic collapse of the upper respiratory tract was confirmed in 471 of 600 Thoroughbreds (78.5%), with DDSP (50%) and palatal instability (33%) being most common
- •Complex forms of dynamic collapse involving multiple structures occurred in 30% of horses with upper respiratory obstructions
- •Younger horses showed significantly increased risk of DDSP while older horses were at greater risk of laryngeal collapse
- •No association was found between gender or racing format and prevalence of these dynamic obstructions