Kate J Allen

Comparisons of overground endoscopy and treadmill endoscopy in UK Thoroughbred racehorses

REASONS FOR PERFORMING STUDY To date there is no information on the comparison of the more recently documented technique of performing endoscopy during ridden exercise in the field, with the more traditional method of endoscopy during high-speed treadmill exercise. OBJECTIVES To compare the results of upper respiratory tract endoscopy in UK Thoroughbred racehorses performed during ridden exercise in the field with those obtained during exercise on the treadmill. METHODS A direct comparison was undertaken in 4 horses whereby both procedures were performed in the same horse within 10 days of each other. An indirect comparison was also undertaken whereby the results of overground endoscopy performed in 50 racehorses was compared to the results obtained during treadmill endoscopy in a further 50 racehorses. Horses were matched for age, gender, use (National Hunt vs. Flat) and presenting complaint (abnormal respiratory noise vs. poor performance). RESULTS Dorsal displacement of the soft palate was diagnosed less frequently during overground endoscopy than during treadmill endoscopy. There was no significant difference in the diagnosis of dynamic laryngeal collapse between the 2 techniques. The treadmill exercise test was performed over longer distances at higher inclines, albeit at lower speeds than the overground test. In contrast to the treadmill test, the overground test was frequently performed in intervals. CONCLUSIONS The results of both the direct and indirect comparisons suggest that dorsal displacement of the soft palate is diagnosed less often during overground endoscopy than during treadmill endoscopy. Strenuous exercise tests may be more easily performed on a treadmill than by performing multiple exercise intervals in the field. POTENTIAL RELEVANCE Care should be taken in interpreting negative findings during both procedures, but particularly during overground endoscopy if racing conditions have not been appropriately replicated.

Clinical trials using a telemetric endoscope for use during over-ground exercise : A preliminary study

Dynamic collapse of the upper respiratory tract (URT) is a common cause of poor performance in horses. These conditions occur predominantly during strenuous exercise when the URT is unable to maintain dilation in the face of high inspiratory pressures. In most cases, these disorders cannot be accurately diagnosed during a resting endoscopic examination. To date, a definitive diagnosis of dynamic URT obstructions has been possible only by performing an endoscopic examination during high-speed treadmill exercise. However, recent technological advances now enable URT endoscopy to be performed while the horse is exercising in its normal environment.

Assessment of the exercise tests used during overground endoscopy in UK Thoroughbred racehorses and how these may affect the diagnosis of dynamic upper respiratory tract obstructions

REASONS FOR PERFORMING STUDY Overground endoscopy is being performed with increasing frequency in the UK. A previous study has shown that the type of exercise test may affect the diagnosis of upper respiratory tract (URT) obstructions. The successful clinical application of overground endoscopy systems requires understanding of appropriate field exercise testing protocols. OBJECTIVES The aim of this study was to report the exercise test parameters used during overground endoscopy in UK Thoroughbred racehorses and to investigate potential effects of these on the diagnosis of URT obstructions. METHODS The exercise test parameters used and the endoscopic observations of the URT during exercise were recorded for 140 Thoroughbred racehorses referred for the investigation of abnormal respiratory noise and/or poor athletic performance. RESULTS The exercise test parameters varied widely between horses. The presenting complaint was easiest to reproduce in horses with a history of abnormal noise in training and hardest to reproduce in those referred for investigation of poor performance with no abnormal noise. No associations between the presence or not of an URT obstruction and exercise test parameters was identified. For horses referred for abnormal noise during racing DDSP was more likely to be observed when longer distances were performed. CONCLUSIONS It is difficult to standardise exercise tests in the field when multiple premises are used and when training gallops differ markedly to racecourses. It was not possible to establish exercise test protocols which should be used for all Thoroughbred racehorses. Therefore, at present the best advice for horses which make abnormal noise during a race or have poor race performance, can only be to replicate race conditions as closely as possible. For horses that race over longer distances this will require the use of a circular gallops (e.g. racecourse) if only short gallops are available at the trainers premises.

A systematic review of the efficacy of interventions for dynamic intermittent dorsal displacement of the soft palate.

There are numerous treatments for correction of dorsal displacement of the soft palate (DDSP). However, the efficacy of these treatments is controversial and there is little consensus on how best to treat this condition. The aims of this study were to systematically review the literature and to assess the evidence on the clinical effects of interventions for dynamic intermittent DDSP. A secondary objective was to assess whether factors relating to study quality affected reported success rates. Twenty-three studies were included, covering a wide number of interventions but also differing widely is terms of study design, sample size, method of diagnosis, outcome measure and the number lost to follow-up. The assessment of adverse effects was severely limited because of lack of reporting. The way in which success is measured appears to have a great effect on the reported results. Research synthesis has been severely limited because of the heterogeneity in the included studies. The low level of evidence makes it difficult to draw firm conclusions as to the efficacy of procedures for DDSP. Hence it is currently not possible to determine which procedure is the most appropriate. This systematic review highlights the difficulties of studying palatal dysfunction and suggests areas where improvements can be made in future studies.

Poor performance associated with equine gastric ulceration syndrome in four Thoroughbred racehorses

Summary Equine gastric ulceration syndrome (EGUS) is commonly recognised in Thoroughbred racehorses. Although EGUS has previously been associated with reduced athletic performance, no objective studies have been reported. This case report describes 4 racehorses referred for investigation of poor athletic performance where EGUS was the only abnormal finding during a thorough investigation of all body systems. All horses showed considerable improvement in performance following treatment with omeprazole. Therefore, this is the first report in which evidence is presented suggesting a direct link between EGUS and decreased performance, other causes of poor performance having been excluded.

Investigation of the incidence and type of injuries associated with high-speed treadmill exercise testing

REASONS FOR PERFORMING STUDY During the past 20 years, treadmill exercise testing has played an important role in both the study of equine exercise physiology and the investigation of poor athletic performance. However, it has been suggested that some trainers and veterinarians may be reluctant to refer horses for treadmill exercise testing because of fears that horses may be at increased risk of musculoskeletal injury during treadmill exercise. OBJECTIVE To investigate the incidence and types of injuries sustained by horses undergoing treadmill exercise. METHODS Data were collated from 9 centres in the UK, France and Belgium, and the prevalence and types of injury were established. RESULTS A total of 2305 records were reviewed, with 2258 horses performing treadmill exercise. There was an overall injury rate of 5.4%. However, the majority of injuries sustained were minor in nature (4.7%). Only 13 horses (0.6%) sustained major injuries in association with treadmill exercise. These included 5 cases of severe exercise-induced myopathy, 4 fractures (of which 1 was catastrophic), 2 tendon injuries, 1 case with undiagnosed severe lameness and 1 with marked exacerbation of a previously diagnosed lameness. Two other major incidents were reported but were not directly associated with treadmill exercise (one had iliac thrombosis and one collapsed and died as a result of a pulmonary embolism). CONCLUSIONS This study confirms that the majority of horses undergo treadmill exercise without incident. The majority of injuries that did occur were minor in nature and the incidence of major injuries was similar to that reported during competition elsewhere. POTENTIAL RELEVANCE Treadmill exercise is a safe procedure and does not appear to pose an increased risk of injury in comparison with overground exercise.

Characteristics of palatal instability in Thoroughbred racehorses and their association with the development of dorsal displacement of the soft palate.

REASON FOR PERFORMING STUDY Two forms of dynamic upper respiratory tract obstruction affecting racehorses that involve the soft palate have been described: palatal instability (PI) and dorsal displacement of the soft palate (DDSP). Observation of DDSP is straightforward in that it is an all or nothing event, whereas observation of PI is subjective and interpretation may vary between clinicians. OBJECTIVES The aim of this study was to attempt to characterise PI and to investigate endoscopic features that precede DDSP. METHODS A retrospective study on the endoscopic observations of Thoroughbred racehorses referred for high-speed treadmill endoscopy was performed. Endoscopic observations were reviewed during the last 10 s of the exercise test or the last 10 s prior to DDSP. The degree of axial deviation of the aryepiglottic folds (ADAF), the conformation of the epiglottis, the conformation of the soft palate and the amount of obstruction of the rima glottidis by the soft palate (i.e. soft palate stability) were assessed. RESULTS A total of 72 horses were included in this study, of which 7 showed no evidence of PI. Of the 65 horses with PI, 30 (46%) developed DDSP. There were significant associations between the stability of the soft palate, epiglottic conformation and ADAF. Furthermore, development of DDSP was associated with increased severity of PI and ADAF and with changes in epiglottic conformation. CONCLUSIONS This study has characterised the endoscopic features associated with PI and identified certain characteristics that precede DDSP. POTENTIAL RELEVANCE These observations may assist veterinary surgeons in recognising PI and the prodromal signs of DDSP.

The effect of palatal dysfunction on measures of ventilation and gas exchange in thoroughbred racehorses during high-intensity exercise

REASON FOR PERFORMING STUDY The effect of palatal instability (PI) on measures of ventilation and gas exchange is not well understood. OBJECTIVES To assess to what degree different severities of naturally occurring palatal dysfunction affect ventilation and gas exchange during strenuous exercise. METHODS A retrospective study was performed using data collected from 40 Thoroughbred racehorses diagnosed with naturally occurring dynamic palatal dysfunction during high speed treadmill exercise. Upper airway videoendoscopic recordings were made concurrently with measurements of ventilation and gas exchange. Three categories of soft palate dysfunction were formed: mild palatal instability; moderate to severe palatal instability; and dorsal displacement of the soft palate (DDSP). Minute ventilation, tidal volume, breathing frequency, end-tidal carbon dioxide and oxygen concentrations, oxygen consumption and carbon dioxide production were calculated during the last 10 s of the exercise test, when airway obstruction was at its worst. RESULTS There was a trend for minute ventilation, tidal volume, oxygen consumption and carbon dioxide production to decrease with increasing degree of palatal dysfunction, although statistically significant differences were only seen with DDSP. End-tidal carbon dioxide increased and end-tidal oxygen decreased with increasing obstruction, with both parameters showing significant differences between mild PI and moderate to severe PI. CONCLUSIONS The results suggest that PI has a negative effect on certain respiratory parameters, although this is not as great as that associated with DDSP. POTENTIAL RELEVANCE Palatal instability may be detrimental to athletic performance even when progression to DDSP does not occur.

RAO and IAD: respiratory disease in horses revisited

RESPIRATORY disease continues to be a major problem for horse owners and trainers worldwide. Lower airway inflammation is now recognised in a range of animals, from aged ponies to young racehorses. This article discusses recent developments in the definitions and understanding of recurrent airway obstruction (RAO) and inflammatory airway disease (IAD). For both conditions, it describes the clinical signs, diagnosis and treatment. A more comprehensive discussion of therapeutic options was provided in an earlier article in In Practice (Durham 2001).

The Prevalence of Abnormal Breathing Patterns During Exercise and Associations with Dynamic Upper Respiratory Tract Obstructions

REASONS FOR PERFORMING STUDY There is very limited published information on the prevalence and significance of abnormal breathing patterns adopted during canter/gallop. OBJECTIVES The aim of this study was to report the prevalence of abnormal breathing patterns during canter/gallop and to investigate whether these may be associated with dynamic upper respiratory tract (URT) obstructions. STUDY DESIGN Retrospective analysis of clinical records. METHODS Simultaneous audio and URT videoendoscopy recordings from 365 horses referred for treadmill evaluation were analysed. RESULTS Thirty percent of horses had an abnormal breathing pattern at canter or gallop, of which 23% had a 2:1 breathing pattern (i.e. one breath is taken over two strides). The prevalence of abnormal breathing patterns was higher at low canter speeds than during strenuous exercise. There was a significant association between breathing pattern during strenuous exercise and the presence of an URT obstruction. CONCLUSIONS This study suggests that abnormal breathing patterns during canter and gallop may be associated with dynamic URT obstructions; therefore, horses identified by owners or veterinary surgeons to have an abnormal breathing pattern during exercise, in particular a 2:1 breathing pattern, may warrant investigations for diagnosis of respiratory tract disease.