Complete upper airway collapse and apnoea during tethered swimming in horses.

BACKGROUND: There is limited knowledge of the breathing strategy and impact on the patency of the upper respiratory tract (URT) in swimming horses. OBJECTIVES: To describe the respiratory responses and endoscopic appearance of the URT during tethered swimming in horses. STUDY DESIGN: Prospective descriptive study. METHODS: Ten race-fit horses, with no history of URT obstruction, were examined during tethered swimming. Endoscopic examination, heart rate, sound recordings and above and below water video recordings were obtained. Plasma lactate concentration was measured before and 5 min after swimming and tracheal endoscopy was performed 30 min after exercise to assess for presence of blood or mucus. Four horses also underwent endoscopy during exercise on the track. RESULTS: Mean (±s.d.) breathing frequency was 28 ± 5 breaths/min during swimming, with a brief inspiration (mean ± s.d. TI  = 0.51 ± 0.08 s), followed by a period of apnoea (1.59 ± 0.53 s) and then a short, forced expiration (TE  = 0.42 ± 0.5 s). During apnoea all horses exhibited complete collapse of the URT including closure of the external nares, nasopharynx and rima glottidis (with bilateral adduction of the arytenoid cartilages and vocal folds) and, in two horses, epiglottic retroversion. No horses had URT collapse during overground exercise. Locomotor-respiratory coupling was not observed during swimming. Median (IQR) plasma lactate post swim was 4.71 mmol/L (2.08-8.09 mmol/L) vs 0.68 mmol/L (0.65-0.71 mmol/L) preswim. Post swim endoscopy revealed grade 1 exercise-induced pulmonary haemorrhage (EIPH) in 2 horses. Median mucus grade was 1 (range 0-3). MAIN LIMITATIONS: Overground endoscopy was not performed in all horses. CONCLUSIONS: Horses experienced complete URT collapse associated with post inspiratory apnoea when swimming. The reason for this is unknown but may be to aid buoyancy or associated with the mammalian dive response - a survival reflex to preserve oxygen stores and prevent water entering the lungs.

Impact of pharyngeal endoscopic tip placement and water flushing interval on upper respiratory tract disorders in horses undergoing overground endoscopy.

BACKGROUND: Endoscopic tip placement in the pharynx and water flushing interval (FI) may affect exercising upper respiratory tract (URT) endoscopic results. OBJECTIVES: To determine associations between the endoscopic tip position in the pharynx and automated FI with overground endoscopic (OGE) results. STUDY DESIGN: Randomised balanced 2X5 factorial design. METHODS: A total of n = 200 horses undergoing OGE were randomly assigned into 10 groups (n = 20/group) of different automated endoscopic FIs (no flushing, 60, 120, 180, 240 s) with the endoscope tip positioned either rostrally (position A) or caudally (position B) in the pharynx. Endoscopic videos were analysed and all URT abnormalities graded using published scales. Disorders with ≤10% prevalence were excluded from the final analysis with only arytenoid asymmetry at exercise (AAex), vocal fold collapse (VFC), palatal dysfunction (PD) and medial deviation of the aryepiglottic folds (MDAF) included. The association of endoscope position and FI with URT disorders was assessed using ordinal regression models with P≤0.05 significant. RESULTS: Endoscope tip positioning was significantly associated with PD grading (P = 0.002), with 63/100 horses diagnosed with PD in position A and 45/100 in position B. No other significant direct associations between URT disease and endoscope tip position were identified, although interactions between exercise velocity and endoscope position affected MDAF grade. FI was not directly associated with alterations in disorder grading, although interactions between exercise velocity and FI appeared to affect MDAF grade. MAIN LIMITATIONS: The same horse was not evaluated under each test condition potentially resulting in sample bias. Interactions between disorders were not evaluated. The sample size was insufficient to conclusively explore relationships between all factors and disorder grading. CONCLUSIONS: Position of the endoscope tip within the pharynx appears to affect grading of PD during OGE examination. Exercise velocity may affect MDAF grade through interactions with endoscope position and FI.

Serial evaluation of resting and exercising overground endoscopic examination results in young Thoroughbreds with no treatment intervention.

BACKGROUND: We hypothesised that grade/appearance for upper respiratory tract (URT) disorders identified at the first overground endoscopy (OGE) examination would vary at subsequent examinations. OBJECTIVES: To compare OGE examinations from horses evaluated on at least two occasions under similar exercise conditions without treatment intervention. STUDY DESIGN: Retrospective cohort. METHODS: Pre-exercise and exercising OGE recordings from Thoroughbred horses undergoing multiple examinations under similar exercise conditions were reviewed, with the first two recordings for each horse statistically evaluated. Paired Wilcoxon signed-rank tests were used to assess differences in exercise and physiological parameters between examinations. Z-tests were used to assess the proportion of changes in URT disorder grade/appearance between examinations. A McNemar's test was used to compare the proportion of horses with each disorder at each examination. Test-retest reliability across examinations was assessed using Spearman's ρ, and ordered logistic regression used to explore temporal effects on repeatability. Lattice plots were constructed to view variability in disorders over time. RESULTS: Seventy-eight horses (median age 2.4 years) with 195 resting endoscopic examinations including 72/78 horses with 179 pre-exercise and exercising OGE examinations were evaluated. Median time between examinations was 226.5 days with no differences between exercise and physiological parameters. Grades significantly varied between examinations for all disorders, and in particular for palatal instability (PI) and epiglottic grade at rest. A temporal link between examination interval and disorder grade change was identified for PI and resting arytenoid asymmetry. MAIN LIMITATIONS: OGE re-examinations within a shorter, more consistent time-frame would allow determination of intrahorse variability. The sample size was inadequate to conclusively establish temporal links between disorders and time between examinations. CONCLUSIONS: Variability for most URT abnormalities identified with OGE should be considered when making therapeutic decisions based on a single examination and may partially explain development of additional URT conditions after surgical intervention. The Summary is available in Portuguese - see Supporting Information.

Overground endoscopy in 311 Thoroughbred racehorses: findings and correlation to resting laryngeal function.

OBJECTIVE: To review a large number of equine overground endoscopy (OGE) examinations to determine the incidence of dynamic upper airway obstructions (DUAO); correlations were explored with laryngeal endoscopy findings at rest and abnormal exercising respiratory noise. METHODS: Retrospective analysis of horses presenting for OGE because of perceived poor performance and/or history of abnormal exercising respiratory noise between 2010 and 2014. Signalment, history and examination findings during resting laryngeal endoscopy and OGE were reviewed. RESULTS: Of the total examinations, 311 were reviewed. One or more DUAO were found in 249/311 horses. From 210 males (colts and geldings), 121 had arytenoid cartilage collapse (ACC) and 111 had vocal fold collapse (VFC). From 101 females, 25 had intermittent dorsal displacement of the soft palate (DDSP). Resting laryngeal function grade 4 was found in 121/311 of the study population and 92/210 of males. An association was found between horses with lower resting arytenoid abduction ability to dynamic ACC and higher resting arytenoid abduction ability with DDSP. Abnormal exercising respiratory noise was positively associated with the presence of DUAO. CONCLUSIONS: Multiple DUAO in association with abnormal exercising respiratory noise was a common finding in horses examined for poor performance. This study highlights the importance of OGE in accurately diagnosing the nature of DUAO associated with poor performance.

Intra- and interobserver reliability estimates for identification and grading of upper respiratory tract abnormalities recorded in horses at rest and during overground endoscopy.

BACKGROUND: Previous studies support good intra- and interobserver agreements for endoscopic evaluation of various upper respiratory tract (URT) diseases in horses. However, these studies mainly assessed resting endoscopic examination videos and/or focussed on a single URT abnormality. OBJECTIVES: To estimate intra- and interobserver agreement for identification and grading of all URT abnormalities from resting and overground endoscopy (OGE) videos of Thoroughbreds. STUDY DESIGN: Blinded, fully crossed design. METHODS: Resting and OGE URT videos for n = 43 Thoroughbreds were retrospectively chosen based on identification of common URT disorders. The videos were randomly evaluated in duplicate by 4 raters blinded to all information including prior URT disorder(s) diagnosis. Abnormalities were graded using well-described ordinal scales. Intra- and interobserver agreements were estimated using Cohen's weighted κ and Krippendorff's α, respectively. RESULTS: Intraobserver agreement was perfect/nearly perfect for arytenoid symmetry at exercise, epiglottic entrapment and epiglottic retroversion, substantial for arytenoid asymmetry at rest, palatal dysfunction (PD), medial deviation of the aryepiglottic folds (MDAF), pharyngeal mucus and epiglottic grade at exercise and moderate for vocal fold collapse (VFC), ventromedial luxation of the apex of the corniculate process of the arytenoid (VLAC), nasopharyngeal collapse (NPC) and epiglottic grade at rest. Interobserver agreement was substantial for arytenoid symmetry at exercise and PD and moderate for arytenoid asymmetry at rest, MDAF, VLAC and epiglottic entrapment. It was only fair for VFC, epiglottic grade at exercise, epiglottic retroversion, pharyngeal mucus and NPC and poor for epiglottic grade at rest. MAIN LIMITATIONS: Sample size was insufficient to allow assessment of the effect of one abnormality on the grading of another abnormality. CONCLUSIONS: Observers were consistent in grading URT disorders. However, significant disparity in grading existed between observers for some conditions affecting reliability.

Dynamic upper respiratory abnormalities in Thoroughbred racehorses in South Africa.

Upper airway endoscopy at rest has been the diagnostic method of choice for equine upper respiratory tract (URT) conditions. Development of high-speed treadmill endoscopy improved the sensitivity of URT endoscopy by allowing observation of the horse's nasopharynx and larynx during exercise. However, treadmill exercise may not always accurately represent the horse's normal exercise as track surface, rider, tack and environmental variables are altered. Recently, the development of dynamic overground endoscopy (DOE) has addressed some of these shortcomings. A retrospective study was undertaken to describe the URT abnormalities detected during DOE in racehorses presenting with poor performance and/or abnormal respiratory noise. Patient records of Thoroughbred racehorses undergoing DOE from November 2011 to August 2012 were reviewed. Data collected included signalment, primary complaint, distance exercised, maximum speed and dynamic airway abnormalities detected. Fifty-two horses underwent DOE for investigation of poor performance and/or abnormal respiratory noise. The main abnormalities detected included axial deviation of the aryepiglottic folds (40%), vocal cord collapse (35%), abnormal arytenoid function (33%) and dorsal displacement of the soft palate (25%). A total of 40 horses were diagnosed with one or more abnormalities of the URT (77%). Fifteen horses (29%) had a single abnormality and 25 horses (48%) had multiple abnormalities. This study showed that DOE is a useful technique for investigating dynamic disorders of the URT in racehorses in South Africa. The total number and type of dynamic pathological conditions were comparable with those identified in similar populations in other geographical locations.

Comparison of dynamic and resting endoscopy of the upper portion of the respiratory tract in 57 Thoroughbred yearlings.

REASONS FOR PERFORMING THE STUDY: Endoscopic examination of Thoroughbred (TB) yearlings is performed routinely to determine the suitability of horses for racing and to ensure that the conditions of sale are satisfied. However, previous research has demonstrated that resting endoscopic examination can be inaccurate in the diagnosis of functional pathology of the upper portion of the respiratory tract (URT). OBJECTIVES: To investigate the feasibility of performing dynamic overground endoscopy in a group of TB yearlings and to compare the results of resting and dynamic endoscopic examination of the URT. STUDY DESIGN: Prospective cohort study. METHODS: Resting (pre- and post exercise) and exercising endoscopy was performed on 57 TB yearlings at a single training yard. Observed abnormalities were recorded and graded. The results of resting and dynamic examination were compared. RESULTS: Dynamic overground endoscopy was well tolerated and was performed with few complications. Laryngeal asymmetry (29 cases) was the most common abnormality identified at rest, while intermittent dorsal displacement of the soft palate (IDDSP; 19 cases) was the most common at exercise. Significant variation in laryngeal function and variation in the occurrence of IDDSP was noted between examinations. Other potentially significant pathology that was not noted at rest but was present during exercise included collapse of the apex of the corniculate process, pharyngeal collapse and cricotracheal ligament collapse. The occurrence of IDDSP at exercise was significantly associated with epiglottic structure grade>2 and a recent history of respiratory tract infection. CONCLUSIONS: Dynamic overground endoscopy is safe and potentially useful when assessing URT function in TB yearlings. Significant variations in the results of endoscopy at rest and during exercise were identified, which indicate that resting endoscopy may not be sufficient to predict the occurrence of pathology during exercise. POTENTIAL RELEVANCE: Dynamic overground endoscopic examination could be considered a suitable means of assessing URT function in TB yearlings and may provide additional pertinent information to that obtained during standard resting examination.

Brachycephalic airway syndrome: management.

Brachycephalic airway syndrome (BAS) is a group of primary and secondary abnormalities that result in upper airway obstruction. Several of these abnormalities can be addressed medically and/or surgically to improve quality of life. This article reviews potential complications, anesthetic considerations, recovery strategies, and outcomes associated with medical and surgical management of BAS.

Complex dynamic upper airway collapse: associations between abnormalities in 99 harness racehorses with one or more dynamic disorders.

REASONS FOR PERFORMING STUDY: Many horses demonstrate dynamic collapse of more than one upper respiratory tract (URT) structure during high-speed treadmill videoendoscopy (HSTV). OBJECTIVES: To report the frequency of complex dynamic URT collapse in harness racehorses and determine if an association exists between occurrence of certain disorders. METHODS: Retrospective study of 99 Standardbreds and Coldblooded trotters that had one or more dynamic URT disorders identified during HSTV between 1998 and 2006. The horses underwent HSTV using a protocol that included periods of free head carriage and poll flexion until fully fatigued. Dynamic abnormalities were classified as: dynamic laryngeal collapse (DLC) associated with poll flexion; axial deviation of the aryepiglottic folds (ADAF); dynamically flaccid epiglottis (FE); caudal palatal instability (PI); intermittent dorsal displacement of the soft palate (iDDSP); pharyngeal collapse (PC); alar fold collapse (AFC) and nasal flutter (NF). Cluster analysis and Fisher's exact test was performed between groups. Significance was set at P<0.05. RESULTS: The overall incidence of complex dynamic URT collapse was 69.7%. Axial deviation of the aryepiglottic folds was significantly associated with PI (P<0.0001) and FE (P<0.0001); iDDSP was significantly associated with PI (P = 0.004) only. Dynamic laryngeal collapse associated with poll flexion was significantly associated with FE (P = 0.002). Cluster analysis confirmed strong associations between the above diagnosis groups and weaker associations between others. CONCLUSION: Caudal PI seems to result in 2 diagnosis groupings: one that leads to ADAF and the other to iDDSP. Dynamic collapse of the margins of the epiglottis was a common finding in this study strongly associated with DLC, PI and ADAF. POTENTIAL CLINICAL RELEVANCE: The associations between certain dynamic diagnoses identified in this study seems best explained as due to local anatomic and functional weaknesses that influence other structures through the Bernouilli principle, rather than being due to a generalised neurological disorder.

Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998-2006).

REASONS FOR PERFORMING STUDY: Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds. OBJECTIVES: To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders. METHODS: Retrospective study of 88 Norwegian Coldblooded Trotters (NCT) and 97 SBs referred to this hospital for URT evaluation between 1998 and 2006. Case records of all horses diagnosed with an URT disorder during resting endoscopy, and all horses undergoing high-speed treadmill videoendoscopy (HSTV) with one or more periods of induced poll flexion were evaluated. The relative prevalence of URT disorders between the 2 breeds was analysed using a Fisher's exact test. RESULTS: There was a significant (P<0.05) breed predisposition regarding 6 URT disorders. Bilateral dynamic laryngeal collapse associated with poll flexion and flaccid epiglottis was significantly more frequent in the NCT. Alar fold collapse and nasopharyngeal collapse were significantly more frequent in SBs. Epiglottic entrapment and nasal flutter were only diagnosed in the SBs. Dynamic disorders were more common than resting disorders in both breeds. CONCLUSION: URT obstructive disorders (dynamic laryngeal collapse associated with poll flexion, flaccid epiglottis, pharyngeal collapse, alar fold collapse, nasal flutter and epiglottic entrapment) are breed related, indicating an anatomic or functional cause. Periods of induced poll flexion during HSTV was essential to declare harness racehorses free of URT disorders. POTENTIAL RELEVANCE: Further anatomic or physiological studies comparing these breeds could potentially provide insight into the pathogenesis of certain URT obstructive disorders. Induced poll flexion should be included in routine HSTV examinations of all harness racehorses.

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.

Dynamic respiratory endoscopy without treadmill in 68 performance Standardbred, Thoroughbred and saddle horses under natural training conditions.

REASONS FOR PERFORMING STUDY: High speed treadmill endoscopy provides a true assessment and diagnosis of the dynamic obstructions of the upper equine respiratory tract (DO-URT). However, treadmills do not always allow reproduction of the exact conditions of dynamic collapse of the URT. The availability of on-board endoscopes, which could be used without a treadmill, would make exercising endoscopy readily available to more equine practices. OBJECTIVES: To develop and validate an innovative endoscope which could be used for the examination of the URT at exercise in ridden and harnessed sport horses performing in natural conditions. METHODS: Authors worked closely with engineers of a company manufacturing veterinary endoscopes. Over a 2-year period several prototypes were tested on more than 20 cooperative horses performing either in trot, gallop, jumping or endurance. The final Dynamic Respiratory Scope (DRS) allows real-time visualisation of the URT and video recordings for post test reviewing and archiving. The DRS was then tested in 2 equine livery yards. Performance horses presented for investigation of abnormal respiratory noises at exercise and/or poor performance were subjected to exercising endoscopy. Endoscopic images of the URT were recorded and video recordings of the URT were reviewed post test. RESULTS: A total of 68 horses were examined: 39 harnessed Standardbred and 29 mounted horses (16 Thoroughbred and 13 saddle horses). Of these, 44 were diagnosed with a URT abnormality. Good quality videos were obtained even at maximum speed in all cases. The innovative insertion tube provided very stable images compared to those obtained with flexible video endoscopes on treadmills. CONCLUSIONS: This study validates the safety and the reliability of the DRS for imaging the equine URT during natural exercising conditions. POTENTIAL RELEVANCE: Most common causes of DO-URT can be diagnosed easily during any type of performance without a treadmill and the DRS offers a great potential for further URT clinical research.

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.

Efficacy of thermal cautery for intermittent dorsal displacement of the soft palate as compared to conservatively treated horses: results from 78 treadmill diagnosed horses.

REASONS FOR PERFORMING STUDY: Previously, objective comparisons of surgical procedures to relieve dorsal displacement of the soft palate (DDSP) have been limited by the presumptive basis of the diagnostic measures applied. OBJECTIVES: To assess and compare the efficacy of thermal cautery surgery to conservatively treated controls in racehorses definitively diagnosed with idiopathic intermittent DDSP. HYPOTHESIS: Both conservative and surgical treatments have a beneficial result on racing performance in racehorses affected with DDSP. METHODS: Race records were obtained for Thoroughbred racehorses definitively diagnosed with DDSP using high-speed treadmill endoscopy. Racing performance was assessed based on prize money won. RESULTS: Forty-eight horses that underwent thermal cautery and 30 conservatively treated controls were included. Pretreatment earnings significantly decreased in the race immediately prior to diagnosis. A high proportion of previously raced horses returned to racing after both treatments (90-96%). Intrahorse comparison of earnings in 3 races pre- vs. post treatment showed that 53% of conservatively treated horses and 36% of the thermal cautery group had improved performance. Although the difference between these 2 groups may be interpreted as being clinically significant, it was not statistically significant. CONCLUSIONS AND POTENTIAL RELEVANCE: A higher percentage of conservatively treated controls had improved individual performance compared to horses treated with thermal cautery. Thermal cautery appears less effective than other previously published surgical treatments for DDSP. Comparison of the 2 treatment methods should be interpreted cautiously because treatments were not randomised, resulting in baseline variability between groups.

Ultrasonographic assessment of laryngohyoid position as a predictor of dorsal displacement of the soft palate in horses.

Dorsal displacement of the soft palate is an important cause of poor performance in racehorses, yet its etiology is not fully understood. Diagnosis requires treadmill videoendoscopy, which is not widely available. The relationship of the larynx, the hyoid apparatus, and the remainder of the skull may be important in predisposing horses to dorsal displacement of the soft palate. We hypothesized that this relationship could be accurately assessed in unsedated horses through ultrasonographic examination. Fifty-six racehorses presented for evaluation of poor performance were subjected to treadmill videoendoscopy and resting ultrasonography. Using ultrasound-assisted percutaneous measures of laryngo-hyoid position, the relationship between selected anatomic structures and the occurrence of dorsal displacement of the soft palate was evaluated. A significant relationship was found between the depth of the basihyoid bone at rest and the occurrence of dorsal displacement of the soft palate at exercise (P = 0.03). Other measures of laryngohyoid position were not found to be associated with dorsal displacement of the soft palate. Thus, there is an association between the occurrence of dorsal displacement of the soft palate at exercise and the resting position of the basihyoid bone, whereby on average a more ventral location of the basihyoid bone is present in horses with dorsal displacement of the soft palate. The pathophysiologic implications of this finding are not fully understood but, based on our findings, ultrasound examination is of value in assisting in the diagnosis of dorsal displacement of the soft palate.

Racing performance following the laryngeal tie-forward procedure: a case-controlled study.

REASONS FOR PERFORMING STUDY: The laryngeal tie-forward procedure (LTFP) is becoming widely used for correction of dorsal displacement of the soft palate (DDSP) despite the absence of an evidence-based assessment of its efficacy. HYPOTHESES: The LTFP returns racing performance to preoperative baseline levels and to that of matched controls; and post operative laryngohyoid position is associated with post operative performance. DESIGN AND POPULATION: Case-controlled study of racehorses undergoing a LTFP for dorsal displacement of the soft palate at Cornell University between October 2002 and June 2007. METHODS: The presence of at least one post operative start and race earnings ($) were used as outcome variables. Controls were matched by age, breed and sex from the third race prior to surgery. A novel radiographic reference system was used to determine laryngohyoid position pre- and post operatively. Data for definitively and presumptively diagnosed cases were analysed separately. RESULTS: During the study interval, 263 racehorses presented, of which 106 were included in the study; 36 had a definitive diagnosis of DDSP and 70 a presumptive diagnosis. Treated horses were equally likely to race post operatively as controls in the equivalent race. Treated horses had significantly lower earnings in the race before surgery than matched controls. The procedure moved the basihyoid bone dorsally and caudally and the larynx dorsally and rostrally. A more dorsal post operative basihyoid position and more dorsal and less rostral laryngeal position were associated with an increased probability of racing post operatively. CONCLUSIONS: Horses undergoing a LTFP are as likely to race post operatively as matched controls. The procedure restores race earnings to preoperative baseline levels and to those of matched controls. POTENTIAL RELEVANCE: This study provides strong evidence supporting the use of the LTFP in racehorses. Further work is needed to determine the relationship between laryngohyoid conformation and nasopharyngeal stability in horses.

The use of race winnings, ratings and a performance index to assess the effect of thermocautery of the soft palate for treatment of horses with suspected intermittent dorsal displacement. A case-control study in 110 racing Thoroughbreds.

REASONS FOR PERFORMING THE STUDY: There have been no reports of the efficacy of thermocautery of the soft palate (TSP) assessed objectively as a treatment of intermittent dorsal displacement of the soft palate (DDSP). OBJECTIVE: To compare: racing performance of horses that underwent thermocautery of the soft palate with matched controls; and 'Racing Post ratings' (RPR) with prize money won (RE) and a performance index (PI) for each of the horses in the study. HYPOTHESIS: Thermocautery of the soft palate has no beneficial effect on racing performance and the 3 measures of performance are significantly related. METHODS: The inclusion criteria were fulfilled by 110 horses and each was matched with 2 controls. Changes in performance were compared statistically. RPR, RE and PI were analysed using a regression model. RESULTS: The percentage of horses that improved in performance following the procedure was 28-51% for the 3 measures of performance, compared to 21-53% for the matched controls. There was no significant effect of the procedure on the changes in RPR or RE. There was a significant effect of the procedure on the change in PI (P=0.015) with more treated horses achieving an improved PI and fewer acquiring a worse PI than matched control horses. The measures of performance showed significant correlation. CONCLUSIONS: Thermocautery of the soft palate alone may not be the most efficacious treatment of DDSP. POTENTIAL RELEVANCE: Production of a reliable measure of racehorse performance may be possible.

Surgery of the upper respiratory system.

Surgery of the respiratory tract often is considered a last resort. However, these surgeries can be performed successfully, allowing for preservation of genetics and productivity. This article discusses surgery of the upper respiratory system. Aspects of physical, radiographic, endoscopic, and ultrasonographic examination are explored. Conditions of the nares, paranasal sinuses, nasopharynx, palate, nasolacrimal duct, pharynx, and larynx are covered.

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.

Effect of head position on radiographic assessment of laryngeal tie-forward procedure in horses.

OBJECTIVE: To assess the effect of head position on relative position of the larynx and hyoid apparatus in horses with palatal dysfunction, and to define a standard position for radiographic assessment of laryngeal tie-forward. STUDY DESIGN: Prospective clinical study. ANIMALS: Adult horses (n=9) with palatal dysfunction. METHODS: Left lateral radiographs of the larynx were obtained pre and postoperatively for 3 different head positions (flexed=90 degrees ; neutral=100 degrees ; extended=115 degrees ). Distance between thyrohyoid bone and thyroid cartilage was measured. Data were analyzed to investigate differences between head positions, and to compare differences between pre- and postoperative measurements. RESULTS: Head position had a significant effect on relative position of the larynx and hyoid apparatus preoperatively. There was no significant difference in postoperative measurements of the 3 head positions. A significant difference between pre- and postoperative measurements was found with the head in the neutral or extended position whereas there were no significant differences between pre- and postoperative measurements using the flexed position. CONCLUSIONS: Head position affects the relationship between the hyoid apparatus and larynx preoperatively, with greatest distance occurring when the head is extended. In a flexed position, it is not possible to ascertain whether laryngeal position has changed postoperatively. CLINICAL RELEVANCE: A standardized head position is necessary when assessing the laryngeal tie-forward procedure radiographically. An extended head position is most useful for this assessment.