Retrospective study investigating causes of abnormal respiratory noise in horses following prosthetic laryngoplasty.

Reasons for performing the study: To investigate causes of respiratory noises in horses following prosthetic laryngoplasty (with or without a ventriculocordectomy) and to examine potential associations between degree of arytenoid abduction and the presence of other upper respiratory tract (URT) abnormalities, including right-sided collapse.

Methods: Clinical records and dynamic videoendoscopic recordings were examined from horses presented between 1995 and 2010 for investigation of respiratory noise during exercise, following a prosthetic laryngoplasty (+/- a ventriculocordectomy). Relationships between the degree of left arytenoid cartilage abduction and the presence of other URT disorders were investigated.

Results: Thirty horses matched the inclusion criteria. All horses had previously undergone a prosthetic laryngoplasty in different hospitals and in 63% (19/30) of these horses a left-sided ventriculocordectomy had also been performed. The majority of cases (87%) had multiple respiratory abnormalities and only 13% had a single URT disorder. Palatal dysfunction was the most common diagnosis (83%), followed by axial deviation of the aryepiglottic folds (60%) and vocal cord collapse (43%). The right arytenoid cartilage was fully abducted in all cases and no statistically significant correlation between the degree of left arytenoid abduction and any other URT disorders was detected.

Conclusions: Multiple forms of dynamic URT disorders were diagnosed in horses that presented with abnormal respiratory noise following laryngoplasty. There was no association between degree of left arytenoid abduction and other URT abnormalities. Furthermore, horses with suboptimal left arytenoid cartilage abduction were not predisposed to right-sided laryngeal collapse.

Clinical relevance: Our results demonstrate the fundamental role of dynamic endoscopy in correctly diagnosing dynamic airway collapse in horses that have undergone surgical treatment of the upper respiratory tract.