Effect of poll flexion and dynamic laryngeal collapse on tracheal pressure in Norwegian Coldblooded Trotter racehorses.
Authors: Strand E, Fjordbakk C T, Holcombe S J, Risberg A, Chalmers H J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Poll Flexion and Dynamic Laryngeal Collapse in Norwegian Coldblooded Trotters Dynamic laryngeal collapse (DLC) associated with poll flexion represents a significant but previously under-recognised upper airway obstruction in racing Norwegian Coldblooded Trotters, with direct mechanical consequences for airflow dynamics. Researchers measured tracheal pressure changes during treadmill exercise in five elite and six DLC-affected horses, alternating between free head carriage and induced poll flexion at racing intensities (heart rates >200 bpm), whilst simultaneously performing videoendoscopy. Affected horses demonstrated substantially more negative peak inspiratory tracheal pressures during flexed poll positions compared to elite horses (P = 0.0015), indicating greater resistance to airflow, whilst head position significantly influenced pressure measurements across both groups (P < 0.0001). The findings establish poll flexion as a clear mechanical trigger for DLC, rather than merely an associated finding, with the obstructive effect severe enough to compromise performance. For practitioners, this has important implications: assessment of upper airway function in underperforming trotters should include evaluation under various head positions, not just neutral carriage, and training or ridden work that enforces excessive poll flexion may exacerbate airway obstruction in predisposed individuals.
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Practical Takeaways
- •Poll flexion during racing significantly worsens airway obstruction in affected horses; training methods and head carriage control should be evaluated in underperforming trotters
- •Dynamic laryngeal collapse may be a previously unrecognized cause of poor racing performance in Norwegian Coldblooded Trotters; consider videoendoscopy with tracheal pressure measurement during exercise testing
- •Head position management during training and competition may be a non-invasive intervention strategy worth exploring for affected horses
Key Findings
- •Peak inspiratory tracheal pressures were significantly more negative in horses with DLC compared to elite horses (P = 0.0015) during poll flexion exercise
- •Head position significantly affected peak inspiratory pressure in both affected and elite horses (P < 0.0001)
- •Poll flexion significantly increased negative tracheal pressures in all horses, with greater magnitudes in DLC-affected horses
- •DLC in Norwegian Coldblooded Trotters is a severe obstructive upper respiratory disorder induced by poll flexion during high-intensity exercise