Equine Upper Airway Obstruction Diagnosis PDF

EQUINE UPPER AIRWAY OBSTRUCTION: Diagnosis Samantha Franklin BVSc, PhD, DACVSMR, MANZCVS, FRCVS Specialist in Equine Sports Medicine Recommended reading Equine clinical medicine, surgery & reproduction – Munroe & Weese, chapter 3.2. Additional reading: Equine Sports Medicin...

EQUINE UPPER AIRWAY OBSTRUCTION: Diagnosis Samantha Franklin BVSc, PhD, DACVSMR, MANZCVS, FRCVS Specialist in Equine Sports Medicine Recommended reading Equine clinical medicine, surgery & reproduction – Munroe & Weese, chapter 3.2. Additional reading: Equine Sports Medicine & Surgery – Hinchcliff, Kaneps & Geor. Chapters 25 & 26. Equine Surgery - Auer & Stick, Chapters 41 – 45. Handbook of veterinary endoscopy – Barakzai. Learning objectives Review the functional anatomy of the equine upper respiratory tract (URT) and explain why it is prone to collapse / obstruction. Describe the clinical signs associated with URT obstruction. Discuss which methods are appropriate for making a diagnosis of dynamic URT obstruction. Describe the common forms of URT obstruction in the horse and discuss their aetiopathogenesis.  Upper airway obstruction / collapse Static vs dynamic obstructions. Dynamic airway collapse occurs when structures within the URT collapse into the airway, during exercise, resulting in obstruction to airflow. Often not apparent during resting examination. Areas prone to collapse: nostrils nasopharynx (walls, roof, floor) larynx Commonly see collapse of multiple structures.  Dynamic airway collapse Predominantly occurs during strenuous exercise A common cause of poor performance in racehorses. Dynamic airway collapse Also occurs in lsport horses during submaximal exercise frequently associated with poll flexion Signs of upper airway obstruction Abnormal respiratory sounds (during exercise) Exercise intolerance Respiratory distress Nasal discharge Cough Investigation of upper airway obstruction Endoscopic examination Resting Exercising Additional investigations may include: Ultrasonography Radiography MRI Resting endoscopic examination: Resting endoscopic examination of the larynx Ideally performed un-sedated NB. Positioning artefact. Assessment of laryngeal function: Nasal occlusion Elicit swallowing ? Slap test (thoracolaryngeal reflex) Grading of laryngeal function at rest – Havemeyer, 2003 Grade I: All arytenoid cartilage movements are synchronous and symmetrical. Full abduction can be achieved and maintained. Grade II: Arytenoid cartilage movements are asynchronous and / or asymmetric at times but full abduction can be achieved and maintained. II.1 Transient asynchrony, flutter or delayed movements. II.2 Asymmetry much of the time due to reduced mobility of arytenoid and vocal fold but occasions (after swallowing / nostril occlusion) when full symmetrical abduction is achieved and maintained. Grade III: Arytenoid cartilage movements are asynchronous and / or asymmetric. Full abduction cannot be achieved and maintained. III.1 Asymmetry much of the time due to reduced mobility of arytenoid and vocal fold but occasions when full symmetrical abduction is achieved but not maintained. III.2 Obvious arytenoid abductor deficit and arytenoid asymmetry. Full abduction is never achieved. III.3 Marked but not total arytenoid abductor deficit and asymmetry with little arytenoid movement. Full abduction is never achieved. Grade IV: Complete immobility of the arytenoid and vocal fold. How useful is resting endoscopy? 18 EQUINE VETERINARY JOURNAL Equine vet. J. (2011) 43 (1) 18-23 doi: 10.1111/j.2042-3306.2010.00108.x Correlation of resting and exercising endoscopic findings for horses with dynamic laryngeal collapse and palatal dysfunction S. Z. BARAKZAI* and P. M. DIXON Division of Veterinary Clinical Science, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, UK. Keywords: horse; DDSP; treadmill; endoscopy; larynx; pharynx Significant correlation between grade of laryngeal function at rest & exercise Summary that are apparent at rest and secondly, to use the appearance and function. Reasons for performing study: To correlate resting and function of the larynx or nasopharynx at rest as predictors for their function during exercise. exercising endoscopic grades of laryngeal function in horses In particular, resting laryngeal function grading systems are undergoing high-speed treadmill endoscopy (HSTE) using the used to make an informed prediction of the likelihood of dynamic (sensitivity = 77%, specificity = 88%; +ve predictive value = 69%) Havemeyer grading system. To correlate dorsal displacement of the soft palate (DDSP) seen at rest with palatal function laryngeal collapse occurring during exercise. Several grading systems for laryngeal function at rest have previously been during exercise. described in the literature (Hackett et al. 1991; Lane 1993; Dixon Methods: Records of horses that underwent HSTE examination et al. 2001), of which the 4- and 5-grade systems have been (1999–2009) were reviewed. Resting laryngeal function score correlated to exercising laryngeal function in a number of studies and other abnormalities noted on resting endoscopy were (Hackett et al. 1991; Hammer et al. 1998; Martin et al. 2000; recorded as were results of HSTE. Results of resting and Lane et al. 2006b). In 2003, a consensus system of endoscopic DDSP at rest occurred more commonly in horses with DDSP during exercise exercising endoscopic findings were correlated. Results: 281 horses underwent HSTE. There was significant laryngeal grading (the ‘Havemeyer’ system) was developed by an international panel of specialists (Robinson 2004). The Havemeyer but specificity was low and +ve predictive value was only 57%. correlation between grade of laryngeal function at rest (grades 1–4) and exercise (r = 0.53, P50% Fig 3: Symmetrical defect, extending several cm rostral to the level of of soft palate length), or not specified (n = 2, rostral aspect of defect pouch ostia and continuing rostrally (out of sight in this photogra Laryngeal hemiplegia (grade 4 RLN) not visible in photographs). Three horses had concurrent epiglottic extended). entrapment. One yearling Clydesdale had a granuloma on the nasal aspect of its soft palate and epiglottic hypoplasia. Exercising endoscopic examination was performed in one Twelve of 15 horses had nasopharyngeal and/or laryngeal contamination Thoroughbred racehorse that was presented because of with food but the timing of feeding in association with endoscopic respiratory noise during exercise, using a telemetric o examination was not recorded in the majority of cases. The results of endoscope (Dynamic Respiratory Scope)a. Resting endoscopy s tracheal endoscopy was recorded in only 12 horses and 11 of these had horse to have an extensive palatal defect and concurren variable amounts of food material, saliva and mucopus within the tracheal entrapment. Endoscopy of the larynx and nasopharynx durin Arytenoid chondritis lumen, with the remaining horse having mucopurulent respiratory (Item S1) was often obscured by considerable volumes of saliva secretions in the trachea. Two horses underwent broncho-alveolar lavage from the oropharynx. The left and right portions of the soft pal (BAL) and had normal BAL fluid cytology (170 cm) horses are Neurogenic atrophy of Horse 1To determineHorse Objective: whether2 RLN should be classified Horse 3 as a in the order of 250 cm long, making them the longest nerves in the mono- or polyneuropathy. horse. They course from the brainstem around the great thoracic Methods: Multiple long peripheral nerves and their vessels before turning cranially to innervate portions of the associated musculature innervated muscles were examined systematically in oesophagus and larynx. The left recurrent laryngeal nerve is about 3 clinically affected RLN horses 30 cm longer than the right nerve in mature Thoroughbreds Results: Severe lesions were evident in the left as well as right because it loops around the aorta, rather than the more cranially recurrent laryngeal nerves in all horses, both distally and, in placed right subclavian artery. (adductor and abductors). one case, also proximally. No primary axonal lesions were Fig 1: Recurrent evident inlaryngeal segments (upper row), innervated nerve lesions. other nerves Compared nor were to proximal changes found in nerve all horses show a significant (P