HESTEFORSK Larynx funksjon hos Norsk og Svensk kaldblodstraver - årsaksforhold for dynamisk larynx kollaps assosiert med nakkefleksjon

The horse is an obligate nasal breather, incapable of efficient air transport through the oral cavity. Sporting horses require up to 1500 liters of air/ minute during heavy exercise all of which passes through the nostrils, nasal passageways and nasophar ynx before entering the larynx and thereafter the lower airways. This rapid transport of large amounts of air during inspiration and expiration results in large pressure fluctuations that place certain regions of the upper airway under considerable stres s. A number of different upper respiratory tract abnormalities have been documented in resting and exercising horses The first review of this particular disorder was published by us in 2004 in the British journal -Equine Veterinary Education. The autho r of this application has also presented our clinical and updated scientific findings regarding this disorder as invited speaker at several recent international Congresses. A soon to be submitted retrospective study from our clinic in Oslo demonstrates t hat this is the most common upper airway abnormality in Coldblooded Trotters. Our current working hypothesis is that the entire laryngeal region is compressed during high poll flexion due to extraluminal forces. Our impression is that the larynx is lo cated further rostrally in some Coldblooded trotters than in many warm and hot blooded breeds, and this in combination with a relatively narrow intermandibular space in affected individuals leads to inward compression of the arytenoids cartilages during p oll flexion resulting in collapse of the vocal folds and other laryngeal structures. Horses that perform in a position of high poll flexion seem especially predisposed to this disorder. We have documented in Norway several horses which have collapsed o n the racetrack during races due to this disorder. This is obviously an animal welfare problem for the affected individuals, and a potential image problem for horseracing in Scandinavia.