Correlation of resting and exercising endoscopic findings for horses with dynamic laryngeal collapse and palatal dysfunction.
Authors: Barakzai S Z, Dixon P M
Journal: Equine veterinary journal
Summary
# Editorial Summary Barakzai & Dixon (2011) reviewed high-speed treadmill endoscopy (HSTE) records from 281 horses examined over a decade to establish whether resting endoscopic findings could predict dynamic airway dysfunction during exercise. Using the Havemeyer grading system, they found a moderate but significant correlation between resting laryngeal grades (1–4) and exercising function (ρ=0.53, P<0.001), with subgrades of grade 3 laryngeal collapse also showing meaningful correlation to exercise-induced changes (ρ=0.43, P=0.0017). Dorsal displacement of the soft palate (DDSP) observed at rest was substantially more common in horses that subsequently developed DDSP during HSTE (relative risk 4.1), though the sensitivity of resting DDSP as a diagnostic test was modest at 25.5% with high specificity of 95.1%. For practitioners, these findings validate the Havemeyer system's reliability at rest and confirm that horses with spontaneous resting DDSP are genuinely at elevated risk of palatal dysfunction during exercise; however, the low sensitivity means many horses developing exercise-induced DDSP will not show signs at rest, underscoring the continued importance of HSTE for horses with suspected dynamic upper airway obstruction despite unremarkable resting examination.
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Practical Takeaways
- •Resting endoscopic examination of laryngeal grade can help predict exercising laryngeal function, supporting its use in clinical diagnosis and pre-purchase evaluations
- •Absence of DDSP at rest has good negative predictive value (0.83) for ruling out exercise-induced DDSP, but presence at rest does not reliably predict exercise DDSP due to low sensitivity
- •High-speed treadmill endoscopy remains important for definitive diagnosis of dynamic palatal and laryngeal dysfunction, as resting exams miss approximately 75% of exercise-induced DDSP cases
Key Findings
- •Significant correlation exists between resting and exercising laryngeal function grades (ρ=0.53, P<0.001) using the Havemeyer grading system
- •DDSP observed at rest was 4.1 times more likely in horses that developed DDSP during exercise (P<0.001)
- •Resting endoscopy for DDSP has 25.5% sensitivity and 95.1% specificity as a predictor of exercise-induced DDSP
- •The Havemeyer system is validated for grading laryngeal function in resting horses and correlates with dynamic exercise findings