RESUMO
BACKGROUND: There is contradictory evidence on the potential benefits of tongue ties on upper airway function and their efficacy in inhibiting intermittent dorsal displacement of the soft palate (DDSP) in racehorses. OBJECTIVES: To test the hypothesis that tongue ties increase the pharyngeal diameter and decrease the occurrence of dynamic airway obstruction in racehorses. STUDY DESIGN: Prospective, crossover blinded clinical study. METHODS: Data of 22 Thoroughbred and 8 Standardbred racehorses examined using overground endoscopy under full-intensity exercise on training racetracks with and without fixation of the tongue by use of tongue ties were analysed. Equivalent exercise intensity was ensured by measuring heart rate (bpm), speed (GPS) and venous lactate. Pharyngeal diameter was expressed as pharyngeal-epiglottis (PE) ratios and laryngeal abduction accordingly as laryngeal-median-ratios. Data were analysed using multivariable repeated-measurements ANOVA. RESULTS: The PE ratio increased significantly from 1.11 ± 0.19 to 1.28 ± 0.30 in all horses between rest and full-intensity exercise (p < 0.01). Multi-variable analysis revealed that this effect decreased significantly by the application of tongue ties (1.15 ± 0.27, p < 0.01). Tongue ties did not influence maximum laryngeal width (p = 0.09) and area (p = 0.2) significantly. DDSP was found in 4 of 30 examinations with tongue tie and in 1 of 30 examinations without tongue tie. MAIN LIMITATIONS: The study population was not randomly chosen and was heterogeneous. Few horses had a respiratory noise and the prevalence of upper respiratory tract disorders was too low for statistical comparison of the rate of DDSP with and without tongue ties. CONCLUSIONS: A positive effect of tongue ties on pharyngeal or laryngeal diameters was not found in this study. Therefore, the results of this study do not support the use of tongue ties to enhance upper airway function.