Can an external device prevent dorsal displacement of the soft palate during strenuous exercise?

The research revolved around studying the effect of an external device (laryngohyoid support) on preventing the dorsal displacement of the soft palate in horses during rigorous exercise. The researchers found that this non-invasive device, which positions the larynx, effectively prevented this common equine condition, especially notable when the soft palate displacement was induced by muscle resection.

Research Methodology

• The researchers used ten horses for this study, exercising them on a high-speed treadmill under four different conditions: control (without any modifications); with the external laryngohyoid support device; after bilateral resection of thyrohyoid muscles; and after muscle resection with the external device employed.
• Two trials were conducted randomly for each of the four conditions: in Trial 1 videoendoscopic images of the upper airway, pharyngeal and tracheal static pressures, and arterial blood gases were collected. Trial 2 included airflow measurement with static pressure and upper airway impedance calculation.

Findings and Results

• Under control conditions, without any alterations, none of the horses developed dorsal displacement of the soft palate (DDSP).
• The laryngohyoid support (LHS) device didn’t have a significant effect on airway impedance or respiratory frequency, nor on arterial oxygen (PO2) and carbon dioxide (PCO2) levels.
• However, when thyrohyoid muscles were resected, 70% of the horses developed DDSP during the exercise. Using the LHS device in these horses, none showed signs of DDSP.
• Moreover, when the horses that had undergone muscle resection wore the LHS device during the workout, significant improvements were registered in inspiratory and expiratory flow and impedance.

Conclusions and Further Work

• The study concludes that the LHS device was able to prevent dorsal displacement of the soft palate—specifically when the condition was experimentally induced through thyrohyoid muscle resection—probably by fixing the larynx in a more rostral and dorsal position.
• Since the application was only tested under experimental conditions, the researchers suggest that field studies need to be conducted to fully determine the effectiveness of the LHS on horses with naturally occurring DDSP.