Measurement of upper airway pressures in exercising horses with dorsal displacement of the soft palate.

The research paper investigates if abnormal airway pressures contribute to the development of Dorsal Displacement of the Soft Palate (DDSP) in exercising horses. Using videoendoscopy and pressure measurements, the researchers assessed the correlation between nasopharyngeal morphology and tracheal and pharyngeal pressures in horses.

Research Method

• The study involved 14 healthy horses and 19 horses with intermittent DDSP.
• Using videoendoscopy and pressure measurements in their trachea and pharynx, the researchers measured the horses while they were exercising.
• The pressure signals were overlaid on the videoendoscopy footage. Both sets of data were recorded for later slow-motion analysis, which would allow identifying the exact occurrence of displacement in the respiratory cycle.
• The horses participated in an 8-minute high-speed trial, which peaked at 14 meters per second.

Findings

• Horses with DDSP did not exhibit excessively negative inspiratory pressures during exercise, as compared to healthy horses.
• Among the horses with DDSP, 8 displaced their soft palate during inspiration, 4 during expiration, and 7 by swallowing.
• The moment of palate displacement varied among horses – some displaced at the start of exercise, some at peak speed, and some when slowing down.
• The size of the epiglottis in horses with DDSP was normal, suggesting that epiglottic hypoplasia was not a cause of DDSP during exercise.
• After palate displacement, there was a significant alteration in airway pressures. Inspiratory pressures in pharyngeal and tracheal became less negative, while the pharyngeal expiratory pressure became less positive and the tracheal more positive, indicating a decrease in airflow and an increase in expiratory resistance in the upper airway.

This study shows that DDSP in exercising horses does not seem to be caused by excessively negative inspiratory pressures, and once displacement occurs, it leads to significant changes in airway pressures.