Pharyngeal diameter in various head and neck positions during exercise in sport horses
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METHODOLOGY ARTICLE
Open Access
Pharyngeal diameter in various head and neck positions during exercise in sport horses Li-mei Go1*†, Ann Kristin Barton1,2† and Bernhard Ohnesorge1
Abstract Background: In equine athletes, dynamic stenotic disorders of the upper airways are often the cause for abnormal respiratory noises and/or poor performance. There are hypotheses, that head and neck flexion may influence the morphology and function of the upper airway and thus could even induce or deteriorate disorders of the upper respiratory tract. Especially the pharynx, without osseous or cartilaginous support is prone to changes in pressure and airflow during exercise. The objective of this study was to develop a method for measuring the pharyngeal diameter in horses during exercise, in order to analyse whether a change of head-neck position may have an impact on the pharyngeal diameter. Results: Under the assumption that the width of the epiglottis remains constant in healthy horses, the newly developed method for calculating the pharyngeal diameter in horses during exercise is unsusceptible against changes of the viewing-angle and distance between the endoscope and the structures, which are to be assessed. The quotient of the width of the epiglottis and the perpendicular from a fixed point on the dorsal pharynx to the epiglottis could be used to determine the pharyngeal diameter. The percentage change of this quotient (pharynx-epiglottis-ratio; PE-ratio) in the unrestrained head-neck position against the reference position was significantly larger than that of any other combination of the head-neck positions investigated. A relation between the percentage change in PE-ratio and the degree of head and neck flexion could not be confirmed. Conclusions: It could be shown, that the pharyngeal diameter is reduced through the contact position implemented by the rider in comparison to the unrestrained head and neck position. An alteration of the pharyngeal diameter depending on the degree of head and neck flexion (represented by ground and withers angle) could not be confirmed. Keywords: Horse, Equine pharynx, Head and neck position, Pharyngeal diameter, Upper respiratory tract
Background Dynamic stenosis of the upper airways occurs when the soft tissue of the upper airways can no longer withstand the high changes in pressure during exercise and structures of the nasopharynx or the larynx collapse into the lumen, thus leading to airflow obstruction [1,2]. Due to its musculomembraneous structure without osseous or cartilaginous support, the pharynx in particular is prone to changes in pressure and airflow during exercise [3]. Various studies have proven that dynamic stenotic disorders of the upper airways can only be reliably * Correspondence: [email protected] † Equal contributors 1 Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, Hannover D-30559, Germany Full list of author information is available at the end of the article
diagnosed during exercise [2,4-6]. Next to endoscopy on the high-
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