Inspiratory and expiratory tracheal pressures during high-intensity exercise in harness racehorses.
Authors: Vermedal Hanna, Hellings Ingunn Risnes, Fretheim-Kelly Zoe Louise, Fintl Constanze, Olsen Hanna Margrethe Berg, Strand Eric
Journal: Equine veterinary journal
Summary
# Editorial Summary Upper respiratory tract (URT) disorders significantly impact harness racing performance, yet quantifying their severity requires objective measurement tools beyond visual endoscopic assessment. Vermedal and colleagues measured inspiratory and expiratory tracheal pressures in 76 clinically normal Standardbred and Norwegian-Swedish coldblood trotters during a standardised treadmill protocol alternating between free head carriage and poll flexion, establishing reference values against which pathological obstruction can be compared. Inspiratory pressures became substantially more negative with exercise progression (ranging from -21.8 cmH₂O at walk to -34.9 cmH₂O at peak intensity), whilst expiratory pressures remained remarkably stable at approximately 11.5-12.5 cmH₂O throughout; notably, poll flexion reduced inspiratory pressures by a further 3.5 cmH₂O compared with free head carriage, a finding with considerable implications for training and ridden work. These reference values now provide practitioners—veterinarians, physiotherapists and coaches—with objective baseline data to interpret pressure measurements in horses presenting with suspected dynamic URT collapse or other obstructive pathologies identified during ridden or driven endoscopy. Future clinical application of these standards should enhance diagnostic precision and potentially guide evidence-based management decisions regarding training modifications, surgical interventions or head-neck positioning strategies.
Read the full abstract on PubMed
Practical Takeaways
- •Reference values for normal tracheal pressures during high-speed exercise now provide objective benchmarks to quantify the severity of upper airway obstruction in affected racehorses
- •Poll flexion during exercise significantly increases negative inspiratory pressures, which may exacerbate upper airway collapse in horses predisposed to dynamic obstruction — consider head/neck position in training and racing
- •Stable expiratory pressures across exercise intensities suggest inspiratory dysfunction dominates in exercise-related upper airway problems, helping focus diagnostic and therapeutic attention on inspiratory mechanics
Key Findings
- •Peak inspiratory tracheal pressures ranged from -21.8 cmH2O at rest to -34.9 and -34.3 cmH2O at peak exercise phases, becoming significantly more negative with exercise progression (p<0.001)
- •Inspiratory pressures were 3.5 cmH2O significantly lower (more negative) during poll flexion versus free head carriage (95% CI: -4.0 to -3.0, p<0.001)
- •Expiratory tracheal pressures remained stable across all exercise phases (11.5-12.5 cmH2O) with no significant changes
- •Respiratory rate stabilized between 89.6-90.8 breaths/minute from phase 3 onward with no significant breed differences between Standardbreds and Norwegian-Swedish coldblooded trotters