Dynamic respiratory endoscopy in 67 Thoroughbred racehorses training under normal ridden exercise conditions

Reasons for performing study: There are potential advantages to imaging the upper portion of the respiratory tract (URT) of horses during ridden exercise. With the advent of a wireless endoscope, this is now possible. However, there has been no detailed validation of the technique and findings have not been compared to ridden speed. Objectives: To assess the combined use of a Dynamic Respiratory Scope (DRS) and global positioning system (GPS) receiver for examining the URT of a group of Thoroughbred racehorses randomly selected from a single flat racehorse training establishment. Methods: Horses were selected randomly from a population of Thoroughbred horses in training at the same training yard. Endoscopic images of the URT were recorded during a ridden exercise test on an ‘all‐weather‐gallop’ and were reviewed post testing. Speed was measured using a wrist mounted GPS receiver. Results: A total of 67 (34%) of the 195 horses in training were examined. Endoscopic findings included: normal URT function (44 cases); dorsal displacement of the soft palate (DDSP) (13 cases); laryngeal asymmetry (4 cases); and axial deviation of the aryepiglottic folds (3 cases). Maximum speed obtained by individual horses ranged from 41.8–56.3 km/h. Ridden speed was variably affected by DDSP. Conclusions: The DRS provides a safe effective system for imaging the equine URT during ridden exercise at speed. The abnormalities of the URT identified were similar to those observed during treadmill endoscopy studies reported in the literature. The effect of URT abnormalities on ridden speed requires further investigation. Potential relevance: This technique can be used to diagnose common causes of URT associated with poor performance in horses during normal training. This has substantial implications for future clinical diagnosis and treatment of URT pathology.     

Dynamic respiratory endoscopy of Standardbred racehorses during qualifying races

Reason for performing study: Examination of the equine upper airway during racing has not previously been documented. Objective: To describe the feasibility and appearance of the upper airways by overground respiratory endoscopic examination during racing conditions. Methods: Overground videoendoscopic examinations were performed on 46 Standardbred racehorses during qualifying races. Examined horses' speeds were recorded throughout the race with a portable GPS device. Results: The procedure did not interfere with performance as there were no significant differences in race times between races in which horses were examined with the endoscope in place and prior unexamined races. Airway obstructions during or after the race were documented in 21 horses. Most previously reported causes of upper airway obstruction were observed; surprisingly bilateral ventro‐medial arytenoid displacement (VMAD; n = 5) was seen during exercise as frequently as dorsal displacement of the soft palate (DDSP). Although DDSP (n = 10) was the most common diagnosis made, many displacements (n = 5) occurred after the race. Horses that demonstrated DDSP after the race had slower speeds than unaffected horses during the race. Conclusions: Racing endoscopy permits the diagnosis of upper airway obstructions without affecting performance. The occurrence of DDSP immediately after exercise may be clinically relevant. During racing VMAD may be an important anomaly. Potential relevance: Racing endoscopy could be used to correlate the sensitivity of diagnostic endoscopy during race‐training or treadmill examination. The pathogenesis and significance of VMAD deserves further investigation.     

Dynamic respiratory endoscopy without a treadmill: Initial experiences

There are potential advantages to imaging the upper portion of the respiratory tract (URT) of horses during ridden exercise within their normal environment. With the advent of a wireless endoscope, this is now possible. The following article describes initial experiences using the dynamic respiratory endoscope (DRS) on horses presented for the investigation of poor performance or abnormal respiratory noise and suggests that this technique can be used to diagnose common causes of URT associated with poor performance in horses during normal training. This has substantial implications for future clinical diagnosis, treatment of URT pathology and equine welfare.     

Assessment of dynamic upper respiratory tract function in the equine athlete

Dynamic upper respiratory tract (URT) obstructions occur commonly in the equine athlete. During the past 25 years, veterinary diagnostic capabilities have improved greatly with the ability to perform endoscopy during exercise and thus to visualise upper airway function during various types of exercise. After correctly reproducing and diagnosing an URT obstruction, the veterinary surgeon must consider the functional significance of the endoscopic findings for that individual athlete. This is the third paper in this series and focuses on the diagnosis of URT obstructions, their relationship to the exercise test and their functional significance.     

Exercising videoendoscopic evaluation of 7 horses with abnormal respiratory noise and poor performance following partial arytenoidectomy

Exercising upper airway endoscopic evaluation was performed in 7 horses with a history of poor performance after partial arytenoidectomy. Treadmill endoscopy revealed axial deviation of the ipsilateral aryepiglottic fold in all horses. Dynamic collapse of one or more additional upper airway structures was also observed. In 4 horses, laser resection of soft tissue structures that obstructed the upper airway was performed. After laser surgery, 3 horses raced and one performed adequately as a riding horse. Of the remaining 3 horses, 2 raced at a lower class and one performed adequately as a riding horse. In this population of horses, dynamic endoscopy of the upper airway was critical for case management. Based on our observations, horses post arytenoidectomy can have dynamic collapse of the ipsilateral aryepiglottic fold and laser resection of the fold may help resolve the performance problem.     

Exercising upper respiratory videoendoscopic evaluation of 100 nonracing performance horses with abnormal respiratory noise and/or poor performance

Reasons for performing study: Although well documented in racehorses, there is paucity in the literature regarding the prevalence of dynamic upper airway abnormalities in nonracing performance horses. Objective: To describe upper airway function of nonracing performance horses with abnormal respiratory noise and/or poor performance via exercising upper airway videoendoscopy. Methods: Medical records of nonracing performance horses admitted for exercising evaluation with a chief complaint of abnormal respiratory noise and/or poor performance were reviewed. All horses had video recordings of resting and exercising upper airway endoscopy. Relationships between horse demographics, resting endoscopic findings, treadmill intensity and implementation of head and neck flexion during exercise with exercising endoscopic findings were examined. Results: Dynamic upper airway obstructions were observed in 72% of examinations. Head and neck flexion was necessary to obtain a diagnosis in 21 horses. Pharyngeal wall collapse was the most prevalent upper airway abnormality, observed in 31% of the examinations. Complex abnormalities were noted in 27% of the examinations. Resting laryngeal dysfunction was significantly associated with dynamic arytenoid collapse and the odds of detecting intermittent dorsal displacement of the soft palate (DDSP) during exercise in horses with resting DDSP was only 7.7%. Exercising endoscopic observations were different from the resting observations in 54% of examinations. Conclusions: Dynamic upper airway obstructions were common in nonracing performance horses with respiratory noise and/or poor performance. Resting endoscopy was only helpful in determining exercising abnormalities with recurrent laryngeal neuropathy. Potential relevance: This study emphasises the importance of exercising endoscopic evaluation in nonracing performance horses with abnormal respiratory noise and/or poor performance for accurate assessment of dynamic upper airway function.     

Equitation and exercise factors affecting dynamic upper respiratory tract function: A review illustrated by case reports

The importance of undertaking appropriate exercise tests for the diagnosis of dynamic upper respiratory tract (URT) obstructions has been previously documented. Dynamic URT collapse is usually most severe during peak exercise; however, there are occasions when an URT collapse appears more severe during the immediate recovery period. In addition, equitation factors such as head and neck flexion and factors relating to the bit and bridle may induce or exacerbate dynamic URT collapse. The purpose of this paper was to review the literature and 5 cases within the authors' experience have also been included.     

Lower respiratory tract disease in Thoroughbred racehorses: analysis of endoscopic data from a UK training yard

REASON FOR PERFORMING STUDY: There has been much research directed at potential causative agents and the epidemiology of lower respiratory tract disease (LRTD), but few reports of the clinical progression and outcome. OBJECTIVES: To define clinical features of LRTD in racehorses, including association with age and average duration of disease, through the analysis of endoscopic data. METHODS: A retrospective analysis of records from a single training yard of endoscopic examinations undertaken over a 2-year period was performed. Horses were subjected to regular endoscopic examination for a variety of reasons, and all horses placed on antibiotic therapy for lower respiratory tract disease were rescoped following treatment. Data analysed included a 0-8 tracheal mucus score based on visible endoscopic mucus and gross tracheal lavage turbidity, as well as age and treatment duration and type. RESULTS: A total of 522 endoscopic examinations undertaken on 123 horses and tracking 169 episodes of lower respiratory tract disease were recorded. Mean duration of disease episode was 15.5 days (median = 11 days, range = 4-61 days). Horses age 2 years were significantly more likely than those age > or=3 years to have at least one episode of respiratory disease (P<0.001). There was a direct association between initial tracheal mucus score and rescope score after treatment. CONCLUSIONS: Lower respiratory tract disease was more common in 2-year-olds than in older horses. Affected horses had endoscopic evidence of increased tracheal mucus accumulation for an average of 15.5 days per episode, a considerably shorter period than that suggested by previous studies. POTENTIAL RELEVANCE: Endoscopic examinations permit longitudinal tracking of lower respiratory tract disease in Thoroughbred racehorses. A prolonged duration of disease, sometimes extending for months, can be expected in a small proportion of cases, some of which appear to be refractory to treatment. There is a clear need for evidence-based analysis of treatment regimes to assist clinicians in decision making when managing disease in both individual and group situations.     

Standardised exercise testing in 17 reining horses: Musculoskeletal,respiratory, cardiac and clinicopathological findings

Exercise testing can be useful to evaluate poor performance, as a preventative medicine tool, and in the assessment of training progression. A comprehensive exercise testing protocol that simultaneously evaluates common causes of poor performance has not been described in reining horses. The objective of this study was to describe the results of a standardised exercise testing protocol in reining horses. Seventeen reining horses that were part of a western performance intercollegiate team and had met the trainer's expectations during the athletic season were evaluated using a comprehensive standardised exercise test. Systems assessed included musculoskeletal system, upper respiratory tract, lower respiratory tract and cardiovascular system. These systems were assessed by means of historical questionnaires, general physical examinations, subjective lameness examinations, gait analysis using digital body mounted inertial sensors, resting and dynamic upper airway endoscopy, bronchoalveolar lavage fluid cytology, echocardiograms, resting and exercising electrocardiography, and laboratory tests (packed cell volume, lactate, creatine kinase and serum amyloid A). Subclinical abnormalities were detected frequently. The musculoskeletal system was the most commonly affected system, but cardiovascular and upper and lower airway abnormalities were also detected in some horses. These results suggest that exercise tests may be useful to detect subclinical abnormalities in horses used for reining. Further evaluation of both normally and poorly performing horses is necessary to determine if exercise testing can improve the health, performance and welfare of horses used for reining.     

Etiologic and epidemiologic analysis of bacterial infectious upper respiratory disease in Thoroughbred horses at the Seoul Race Park

Infectious upper respiratory disease (IURD) of Thoroughbred racehorses has been a frequent problem (29.6% of incidence) at the Seoul Race Park (Korea). Risk factors for IURD include the season with a high transfer rate (summer and fall), the stabling period (≤ 3 months), and age (2 to 3 years old), suggesting that the movement and new environment may have depressed the immune system of the horses and decreased their ability to respond properly to pathogens. The bacterial strains (n = 98) isolated from IURD horses included Pseudomonas spp., Escherichia coli, Staphylococcus spp., Streptococcus equi subsp. equi and zooepidemicus.     

Cohort study examining long‐term respiratory health,career duration and racing performance in racehorses that undergo left‐sided prosthetic laryngoplasty and ventriculocordectomy surgery for treatment of left‐sided laryngeal hemiplegia

Reasons for performing study: The risk of respiratory conditions, such as inflammatory airway disease (IAD) and exercise‐induced pulmonary haemorrhage (EIPH), are thought to be higher in racehorses that undergo prosthetic laryngoplasty with ventriculocordectomy (PLVC) surgery to treat left‐sided laryngeal hemiplegia (LLH) than in racehorses with normal laryngeal function. However, this has not been investigated formally owing to the difficulty of obtaining reliable follow‐up data. Objectives: To determine the incidence of respiratory conditions (IAD and EIPH), duration of racing career, number of starts and number of starts for which stakes money was earned in racehorses that had undergone PLVC surgery to treat LLH, compared with racehorses that did not have LLH or undergo any laryngeal surgery. Methods: A retrospective cohort study design was used, with surgical, clinical and race data of Thoroughbred racehorses obtained from the time of importation until retirement. The surgical cohort consisted of racehorses that had undergone PLVC for LLH and met specific inclusion criteria. Every surgical case was matched, according to trainer, year of import into Hong Kong and pre‐import international handicap rating, to 2 unexposed racehorses. Results: Respiratory conditions, such as excessive tracheal mucus and epistaxis due to severe EIPH, were significantly increased in the surgical cohort, compared with the matched unexposed cohort (P values <0.001 and <0.004, respectively). Racing career duration in the surgical cohort was significantly shorter than in the unexposed cohort, which was primarily due to retirement because of epistaxis. The number of race starts was fewer in the surgical than in the unexposed cohort after surgery/matching, but the number of starts for which stakes money was earned was not significantly different. Conclusions and potential relevance: Owners and trainers should be advised that racehorses with LLH that undergo PLVC surgery are at an increased risk of respiratory conditions (IAD and severe EIPH), which is likely to shorten their racing career compared to racehorses with normal laryngeal function. Racing performance in terms of race starts was significantly less in racehorses that had undergone PLVC surgery; however, the number of starts for which stakes money was earned was similar to those racehorses that were unexposed.