The revolution of overground respiratory video-endoscopy in exercising horses

Abstract

Event Abstract Back to Event The revolution of overground respiratory video-endoscopy in exercising horses Emmanuelle Van Erck1* 1 Internal Medicine Specialist, Equine Sports Medicine Practice, Belgium ABSTRACT Whatever the equestrian discipline, age or breed, the respiratory system represents the main limiting factor to exercise in the healthy horse. Respiratory diseases are the second most common cause of wastage in sport horses and racehorses. The upper airways (UA) are involved in the high prevalence of respiratory problems as a cause of poor performances. The advent of overground endoscopes has revolutionized our diagnosis of UA disorders in practice: we can now recreate “real-life” conditions and observe UA function in situations similar to work or competition. We can also account for important factors that interfere with upper airway stability or patency during work such as rider, equitation and tack. Whatever the clinical signs of UA dysfunction we observe during exercise, these are linked to a primary cause: identifying that underlying cause is of paramount importance to propose an adapted treatment be it medical or surgical. Missing the proper diagnosis inevitably leads to poor therapeutic success rate. A few elements of physiology To provide the lowest resistance due to inertance, friction and turbulence, the horse's upper airway should ideally have been be short, large, straight and rigid. However, they are long, narrowed in some critical areas such as the larynx, bended and compliant in others such as the pharynx. The pharyngeal and laryngeal sections of the UA is made of soft tissue and only sustained by muscles or mobile cartilages, making them highly susceptible to dynamic collapse when submitted to important transmural pressures, such as those physiologically encountered during exercise. Any abnormality that would reduce the airway section would be a potential factor of impaired ventilation and consequently impaired performance. Complex obstructions, where more than one structure collapses into the airway, or combinations of upper and lower airway disorders occur frequently. Multiple abnormalities will more commonly be associated with significant gas exchange impairment than single disorders. Dynamic UA obstruction is a common cause of respiratory noise during exercise and may lead to poor performance in equine athletes. The noise generated by an obstruction in the airway, be it functionally disabling or not, is often of concern to the horse’s rider, can be judged as deleterious in competition and decrease the commercial value of the horse. Reduction or sub-obstructions of the UA are mainly caused by functional, inflammatory or infectious problems. Diagnosis of UA problems A clinical exam of the UA requires a thorough evaluation of the entire horse. Any UA disorder can be associated to other clinical problems such as orthopedic issues, lower airway diseases or even cardiac problems. Observation of the horse in usual working conditions is of paramount importance if the horse is involved in racing or sports. This allows to elicit symptoms that would remain unobservable at rest (respiratory noise, defensive behavior, cough,…). In some cases of UA obstruction, the horse can fight against the riders aids, become nervous and difficult to handle and these can be the only apparent symptoms as UA is not necessarily associated to noise. Videoendoscopy during exercise is considered to be the “gold standard” for making a definitive diagnosis of dynamic upper airway collapse in horses, where findings at rest are frequently unreliable or absent. Although the grading of laryngeal function at rest can help to predict the degree of laryngeal obstruction observed during exercise, cases relating to palatal instability, dorsal displacement of the soft palate or pharyngeal collapse do not correlate with resting observations. Exercising endoscopy was traditionally performed on a high-speed treadmill. The recent advent of overground endoscopes has allowed the evaluation of upper airway mechanical behavior in normal exercising conditions. The technique has already been used to evaluate racehorses at the track, as well as ridden sport horses. Ridden examination is of particular importance, as equitation-related maneuvers or movements are a factor in the development of dynamic airway instability. Head flexion has been recognized as a factor contributing to the decrease of laryngeal diameter and the subsequent increase in UA resistance. Rider equitation and head flexion have a combined effects of on upper airway morphology and aggravate UA dynamic obstruction. It is important to note that whilst videoendoscopy enables visualisation of any dynamic airway collapse, it does not enable us to directly quantify the functional effects of an obstruction. Inclusion of a video-endoscopy to a simple standardized exercise test can be a means of evaluating the impact of the UA problem. The predisposing factors to equine UA disorders Horses are particularly prone to developing dynamic upper airway collapse because they are obligate nasal breathers. They cannot avoid the high negative pressures associated with nasal breathing and switch to oral breathing, as other species do during exercise. The equine UA are highly collapsible, especially in the nasopharyngeal region, which is not supported by osseous or cartilagenous structures. The nasopharynx relies solely on local muscular activity to maintain stability and patency. The dramatic variations in airway flow and transmural pressures that are encountered during intense exertion promote instability and potential secondary dynamic obstruction of the UA. Not all UA obstructive conditions have the same impact on respiratory function but they commonly create an increase in respiratory resistance, which may result in either reduced airflow or an increase in the trans-upper airway pressures required to maintain airflow. This increase in airway resistance will lead to an increase in respiratory workload, and where airflow is reduced the resulting hypoventilation may lead to decreased oxygen consumption, increased blood lactate concentration and exacerbation of arterial hypoxaemia and hypercapnia. Certainly a number of factors are implicated in the development of dynamic UA collapse in an individual horse. In many cases, it is linked to the type of exercise and its intensity, with many forms of UA collapse only occurring during strenuous work: inspiratory pressures become more negative as speed increases, fatigue of the respiratory musculature may also play a role. Hence the type of exercise test performed will have an impact on the ability to make a definitive diagnosis of dynamic UA collapse and it is necessary to recreate the work effort encountered in those circumstances. This may involve asking the usual rider to perform the test, make the horse go over jumps or run next to other horses. Other equitation factors may also be implicated in the development of dynamic UA collapse. These factors are particularly important in pleasure or sport horses, where dynamic airway collapse appears to commonly occur at lower exercise intensities than in racehorses. We found that pharyngeal collapse was more readily diagnosed in warmbloods during overground endoscopy compared with treadmill endoscopy. This is likely due to the fact that riding factors, including increased tension in the reins and head flexion, are frequently an important predisposing factor in the development of dynamic airway collapse these horses. Changes in poll flexion are easier to recreate during ridden exercise, although it is possible to induce changes in place the head in a flexed position during treadmill exercise. Changes in head and neck position have a significant effect on pharyngeal diameter, with the smallest diameter found when in a dorsal flexed position. Correspondingly, increased poll flexion leads to an increase in respiratory resistance and inspiratory pressures and results in decreased inspiratory flows. In addition, the flexed position increases the compliance of the upper airway walls and promotes the bulging of soft tissues within the upper airways. Upper airway instability is markedly affected by equitation and rider interaction. In a recent study, we looked at the effects of riding and head flexion on upper airway function, 90% and 81% of the horses developed or showed an aggravation in the severity of upper airway obstructive disorders with head flexion and rider intervention, respectively. In dressage horses, usually worked with a more acute head-neck angle, head flexion and riding had a more significant influence on the development of upper airway obstruction than in showjumpers (positive predictive value (PPV) for head flexion = 86% vs 65%; PPV for other riding maneuvers = 83% vs 57%). There was a significant association between rider intervention and exercising with increased head flexion for the detection of all dynamic upper airway obstructive conditions, except dorsal displacement of the soft palate (DDSP). However it was recently reported that DDSP in racing Standardbreds could occur in association with the driver grabbing a strong hold of the lines. Underlying airway inflammation has been suggested as a possible etiology or predisposing factor to UA obstruction. Pharyngeal instability, under the form of palatal instability or nasopharyngeal collapse, was significantly affected by the presence of upper (pharyngeal) or lower airway inflammation. The pathophysiology of nasopharyngeal collapse is not fully understood but has been associated to neuromuscular dysfunction of the upper airways. Inflammatory conditions such as pharyngeal lymphoid hyperplasia could result in nasopharyngeal instability and possibly displacement of the soft palate. Pharyngeal collapse has been reported to be most commonly associated with blood gas abnormalities in racehorses, either when occurring in isolation or in combination with other forms of UA collapse. In Warmblood showjumpers or dressage horses, nasopharyngeal instability has been associated with decrease in performances. The pathophysiology of DDSP, palatal instability and of other forms of nasopharyngeal collapse, although not fully elucidated, is generally believed to involve neuromuscular dysfunction of the upper airways. The integrity of the nerves and muscles involved in maintaining UA stability should be systematically assessed. This includes evaluating presence of infection or inflammation in the UA, including guttural pouches and lower airways, as well as any mechanical element (internal or external) that could interfere with correct UA function. Use of specific tack needs to be discussed and eventually tested with the rider. Changing the bit or allowing the horse to work in a different position is helpful to evaluate the underlying mechanisms behind the UA disorder. Pain is also an important element to evaluate. Pain can induce changes in behaviour and breathing pattern and promote changes in UA stability. AUTHOR BIOGRAPHY Emmanuelle graduated in 1996 from the French Veterinary School of Maisons-Alfort. She obtained a PhD on respiratory function testing in horses at the University of Liège (Belgium). After working two years in internal medicine at the equine clinic at the veterinary school of Lyon (France), she returned to the Equine Sports Medicine Centre in Liège in 2000. She specialized in the investigation of performance and poor performance in equine athletes of all disciplines, from racing Thoroughbreds to elite endurance horses. From 2006, she contributed to developing the equine sports medicine unit in the CIRALE in Normandy (France) where she consulted as senior clinician. In January 2010, she developed her own ambulatory referral practice ‘Equine Sports Medicine Practice’, based in Belgium. ESMP offers specialized service in equine internal and sports medicine throughout Europe. The Royal Belgian Federation of Equestrian Sports has appointed her as team veterinarian in 2015. Emmanuelle is a diplomate of the European College of Equine Internal Medicine (ECEIM) and a veterinary expert for the FEI. She is author or co-author of over 50 peer-reviewed scientific articles and regularly lectures at international conferences. She was awarded the BEVA Trust Peter D Rossdale Open Award for her paper entitled "Dynamic respiratory videoendoscopy in ridden sport horses: Effect of head flexion, riding and airway inflammation in 129 cases", published in Equine Veterinary Journal, 2011. Keywords: Endoscopy, Internal Medicine, Respiratory, Veterinary, Equine Conference: First and Second Conference on Current Veterinary Practices, Meldert-Lummen and Evergem, Belgium, 5 Mar - 26 Mar, 2016. Presentation Type: Oral Presentation Topic: Current Veterinary Practices Citation: Van Erck E (2016). The revolution of overground respiratory video-endoscopy in exercising horses. Front. Vet. Sci. Conference Abstract: First and Second Conference on Current Veterinary Practices. doi: 10.3389/conf.FVETS.2016.01.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Jan 2016; Published Online: 29 Jan 2016. * Correspondence: DVM, PhD. Emmanuelle Van Erck, Internal Medicine Specialist, Equine Sports Medicine Practice, Waterloo, 1410, Belgium, evanerck@esmp.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Emmanuelle Van Erck Google Emmanuelle Van Erck Google Scholar Emmanuelle Van Erck PubMed Emmanuelle Van Erck Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.