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Dynamic obstructions of the equine upper respiratory tract. Part 1: Observations during high-speed treadmill endoscopy of 600 Thoroughbred racehorses
Equine Veterinary Journal
Abstract
To review the prevalence of single and complex forms of dynamic airway obstructions within a large group of Thoroughbred horses in training referred for investigation of poor performance.
Video-endoscopic recordings of the upper respiratory tract made during a standardised treadmill exercise test of 600 Thoroughbred racehorses were reviewed and analysed in real time and slow motion to identify dynamic collapse by the tissues bordering onto the pharyngeal and laryngeal airways.
Dynamic collapse within the nasopharynx or larynx was confirmed in 471 of the 600 horses. Dorsal displacement of the soft palate (DDSP; 50%) and palatal instability (33%) were the disorders most frequently identified. It was concluded that deglutition is not a significant event in the triggering of DDSP. Complex forms of dynamic collapse were present in 30% of the horses with upper respiratory tract obstructions. A significant influence of age on the prevalence of DDSP and dynamic laryngeal collapse was identified. There was an increased risk of DDSP in younger horses, and of laryngeal collapse in older horses. No association with gender or format of racing was identified.
Palatal instability and DDSP comprised the most frequently encountered forms of dynamic collapse within the upper respiratory tract of the Thoroughbred racehorses in this study and are probably expressions of the same nasopharyngeal malfunction. Complex obstructions, i.e. where more than one structure collapses into the airway, occur frequently and therefore treatments that address solitary disorders may often be unsuccessful. Younger horses were found to be at greater risk of sustaining DDSP while older horses seemed more at risk to vocal cord collapse but not to collapse of the arytenoid cartilage itself.
... On the other hand, guttural pouch disease can lead to neuropathy of the cranial nerves that are closely associated with them which can cause 'true' nasopharyngeal collapse. Nasopharyngeal collapse has been identified in high-performance sport horses, 9,16 Standardbred racehorses 8,42 and Thoroughbred racehorses 39,43 ; this possibly reflects the population of horses likely to be referred for treadmill examinations. In one study, the prevalence of disease was higher in sport horses compared to Thoroughbred racehorses referred to the same facility. ...
... In one study, the prevalence of disease was higher in sport horses compared to Thoroughbred racehorses referred to the same facility. 39 This may be because racehorses may have generally increased conditioning of the upper airway musculature due to their intensive training regime. Additionally, NPC can be exacerbated with ventro-flexion of the neck (i.e., poll flexion), thus the disease may be over-represented in sport-horses compared to Thoroughbreds. ...
... 2 10 | SCOPE FOR FURTHER RESEARCH Nasopharyngeal collapse affects up one quarter of high-performance equine athletes presenting for poor performance. [1][2][3]16,22,[38][39][40][41] With no definitive treatment option available, a diagnosis of NPC can prematurely end competitive careers and lead to a high turnover rate with substantial economic loss within the racing and elite-level equine performance industries. 2,4,[6][7][8][9] Compared to other dynamic URT disorders, the amount of literature on NPC is scarce. ...
Dynamic nasopharyngeal collapse (NPC) is an obstructive upper airway disease that affects mainly the inspiratory phase of respiration in horses undergoing strenuous exercise. It occurs when the neuromuscular activity of the nasopharynx is overwhelmed by the intense negative pressures generated during exercise. This leads to collapse of at least one of the four components of the nasopharynx which is comprised of the two lateral walls, the dorsal roof and the ventral soft palate. As a result, the airway diameter and thus airflow become compromised. Even small changes in the airway diameter produces profound increases in negative inspiratory pressure, perpetuating the cycle of collapse. Compared to other dynamic upper respiratory tract disorders, the amount of literature on NPC as a disease entity is limited. The exact pathophysiology of NPC is unknown; however, it impacts up to one quarter of high‐performance equine athletes presenting for poor performance. There is currently no definitive treatment for this severely performance‐limiting condition. Thus, the prognosis for future athletic prognosis is guarded, with most horses being retired from racing or athletic use in general. Further research is warranted in this field to reduce the impact of disease and in turn, reduce the turnover rate and economic loss by enhancing the career longevity of elite equine athletes diagnosed with NPC.
... Moreover, the nasopharyngeal region is not supported by osseous or cartilaginous structures and relies only on muscle activity to maintain its stability [1,2]: therefore, during exercise, when airflow turbulence and negative pressures occur at the floor of the nasopharynx and within the larynx, these structures may collapse, and horses may develop different forms of dynamic upper airway obstruction (DUAO) [3]. As a consequence, respiratory function and gas exchanges at the alveolar-capillary level may be impaired, determining poor athletic performance, especially in racehorses working at supramaximal exercise [4][5][6][7]. ...
... Among reports including both Standardbreds and Thoroughbreds diagnosed by HSTE, DUAO prevalence varies from 22.6% [48] to 65% [22]. Interestingly, the highest frequencies have been reported by studies only including Thoroughbred racehorses, with percentages ranging from 72.6% to 80.1% [5,[49][50][51]; similarly, in our study 75% of the Thoroughbred patients showed DUAO during HSTE, which was significantly more frequent than in Standardbreds (50.32%), suggesting a breed predisposition. However, in our population, most Standardbreds were referred for poor performance, while Thoroughbreds were more often referred for abnormal respiratory noises during exercise, with a consequent higher probability of being diagnosed with DUAO; this could have biased the results of our study. ...
... In our study, the Thoroughbreds more commonly showed upper respiratory tract alterations at rest; it must be noticed that the Thoroughbreds were younger than the Standardbreds, probably due to the shorter racing career, and that alterations at rest were more frequently observed in younger horses. Some authors suggest that young age may predispose horses to the development of DUAO [5,9] and that affected horses could spontaneously resolve this condition over time [10]; in fact, it has been hypothesized that increased palatal musculature in older horses may improve muscular activity and provide a better resistance against collapsing forces [5]. In contrast, other reports found no association between age and DUAO [11] or even a higher susceptibility in older horses [54]. ...
Dynamic upper airway obstructions (DUAO) are common in racehorses, but their pathogenetic mechanisms have not been completely clarified yet. Multiple studies suggest that alterations of the pharyngo-laryngeal region visible at resting endoscopy may be predictive of the onset of DUAO, and the development of DUAO may be associated with pharyngeal lymphoid hyperplasia (PLH), lower airway inflammation (LAI) and exercise-induced pulmonary hemorrhage (EIPH). The present study aims to investigate the possible relationship between the findings of a complete resting evaluation of the upper and lower airways and DUAO. In this retrospective study, 360 racehorses (Standardbreds and Thoroughbreds) referred for poor performance or abnormal respiratory noises were enrolled and underwent a diagnostic protocol including resting and high-speed treadmill endoscopy, cytological examination of the bronchoalveolar lavage fluid and radiographic assessment of the epiglottis length. In this population, epiglottis flaccidity was associated with dorsal displacement of the soft palate, while no relationship was detected between DUAO and epiglottis length. No associations were detected between DUAO and PLH, LAI or EIPH. In conclusion, it is likely that epiglottis plays a role in upper airway stability, while airways inflammation does not seem to be involved in the pathogenesis of DUAO.
... In accordance with our findings, the majority of studies about racehorses report DDSP as the most common DUAO detected at exercise endoscopy. [2][3][4]33,41,42 High frequencies of NPC have been reported by other authors, 3,12 although this dynamic obstruction is more common in nonracing sport horses, due to the influence of head and neck position required in some athletic disciplines. 41,42 Even though MDAF was the third most common DUAO among our patients, it was rarely diagnosed alone; in most cases, it was associated either with DDSP, NPC, EE, or both DDSP and NPC. ...
... This observation has been reported by several studies, suggesting that MDAF may represent either a cause or a consequence of other DUAOs. 2,4,12,41,43,44 Other associations observed in our study included DDSP and NPC, and DDSP and EE, which have also been observed by previous studies. 2 The low prevalence of DLC observed among our patients may be surprising, as other authors reported higher frequencies 3,41 ; however, another study 12 reported a very low incidence. ...
... Moreover, horses with obvious laryngeal asymmetry at rest are less likely to be referred for treadmill endoscopy by equine practitioners in the field; furthermore, horses in our study were young (median age, 3 years old) and RLN is known to be a progressive condition that becomes more severe in older horses. 4 The low prevalence of EE and ER observed in our horses was consistent with previous studies. 3,42,45 In the present study, we did not consider horses with palatal instability, which has been described by different authors as the dorsoventral billowing of the caudal part of the soft palate. ...
OBJECTIVE
To evaluate the association between the severity of dynamic upper airway obstruction (DUAO) and selected fitness parameters in Standardbred racehorses measured by treadmill test.
ANIMALS
191 Standardbred racehorses that underwent a standardized diagnostic protocol for poor performance evaluation between 2002 and 2021 at the Veterinary Teaching Hospital, University of Milan.
PROCEDURES
Horses underwent a diagnostic protocol including clinical examination, lameness evaluation, laboratory analyses, ECG, resting upper airway endoscopy, metabolic incremental treadmill test, high-speed treadmill endoscopy, postexercise tracheobronchoscopy, and bronchoalveolar lavage fluid cytology. On the basis of findings of the high-speed treadmill endoscopy, horses were divided into the following groups: no DUAO, mild DUAO (medial deviation of the aryepiglottic folds or epiglottic entrapment), severe DUAO (dorsal displacement of the soft palate, nasopharyngeal collapse, dynamic laryngeal collapse, or epiglottic retroversion), and multiple DUAOs (different forms of DUAO occurring concomitantly). Fitness parameters, measured by incremental treadmill test, included speed at a heart rate of 200 bpm (V200), speed and heart rate at a lactate concentration of 4 mmol/L (VLa4, HRLa4), peak lactate, maximum speed, maximum hematocrit, and minimum pH. Data were compared between groups by use of descriptive and statistical analyses.
RESULTS
Horses affected by severe or multiple DUAOs showed lower V200 and VLa4, compared to the no-DUAO group; horses with multiple DUAOs also had higher peak lactate concentrations compared to horses without DUAOs.
CLINICAL RELEVANCE
While mild forms of DUAO do not affect athletic capacity, severe forms of DUAO and multiple DUAOs may lead to reduced fitness in Standardbred racehorses by impairing aerobic capacity.
... Intermittent dorsal displacement of the soft palate (IDDSP) is a multifactorial disease occurring in 10-20% of racehorses (1)(2)(3)(4)(5)(6)(7) and 28% of competing draft horses (8). Females and young horses (2-4 years old) have been reported to be more affected than male and older horses (9). ...
... The LTFB procedure was performed in a manner similar to the technique described by Rossignol et al. (27). Using this technique, USP No. 5 polyester suture 2 was threaded through the eyelet of the suture-button (2 mm thick rounded plate with 2, 1.5 mm diameter holes), and the free ends of the sutures were inserted through the eye of a ½-circle, trocar-point needle 4 . The needle was passed once through the caudoventral margin of the right or left lamina of the thyroid cartilage in a manner similar to that described using the LTF, and by applying tension to the suture, the button became seated firmly on the ventral aspect of the caudal edge of the thyroid cartilage (Figure 4). 4 Richard-Allan, cat. ...
... The needle was passed once through the caudoventral margin of the right or left lamina of the thyroid cartilage in a manner similar to that described using the LTF, and by applying tension to the suture, the button became seated firmly on the ventral aspect of the caudal edge of the thyroid cartilage (Figure 4). 4 Richard-Allan, cat. no. ...
Rostral laryngeal advancement, also known as laryngeal tie-forward, is used to treat horses for intermittent dorsal displacement of the soft palate and has a morbidity rate of about 6%. We hypothesized that a novel laryngeal clamp would prevent morbidity associated with the sutures tearing through the thyroid cartilage. Larynges (n = 35 horses) were used for ex vivo testing. For uniaxial testing, 15 equine larynges were tested in one of three laryngeal tie-forward constructs [standard laryngeal tie-forward; modified laryngeal tie-forward using a suture-button; and modified laryngeal tie-forward using a laryngeal clamp]. For biaxial testing, 20 larynges were tested in one of two treatment groups: laryngeal tie-forward and laryngeal tie-forward using a laryngeal clamp. Constructs were tested in single cycle-to-failure. Statistical analyses were performed using ANOVA for uniaxial testing and t-tests for biaxial testing. The laryngeal tie-forward using a laryngeal clamp construct was superior to laryngeal tie-forward and laryngeal tie-forward using a suture-button constructs in resistance to pullout in uniaxial testing. The laryngeal tie-forward using a laryngeal clamp presented a significantly different method of failure than the standard laryngeal tie-forward in the biaxial testing. Failure modes for each construct were primarily by suture failure at the clamp (laryngeal tie-forward using a laryngeal clamp), suture pullout through the thyroid cartilage, or, less commonly, tearing of the cricothyroid ligament (laryngeal tie-forward). In uniaxial testing, the laryngeal tie-forward using a laryngeal clamp failed most commonly due to tearing of the cricothyroid ligament, whereas the standard laryngeal tie-forward and the laryngeal tie-forward using a suture-button failed due to the tearing of the cartilage. The laryngeal clamps provided greater stiffness, load at yield, and tensile stress at yield than did the standard construct. Laryngeal clamps may offer an alternative to standard methods of anchoring the thyroid cartilage when performing the laryngeal tie-forward procedure. Further testing and clinical trials are needed to elucidate the utility of the laryngeal tie-forward using a laryngeal clamp.
... Human medicine recently agreed upon the phrase Exercise Induced Laryngeal Obstruction (EILO) (Christensen et al., 2015;Halvorsen et al., 2017) to describe the phenomenon that in equines is usually referred to as dynamic obstruction of the upper respiratory tract (Lane et al., 2006a). These conditions represent comparable sets of disorders characterized by the larynx appearing normal at rest, with abnormalities seemingly induced by the increased ventilatory demands during ongoing exercise, and thereafter quickly resolving with cessation of exercise. ...
... In both equines and humans, the common presenting complaint is reduced exercise tolerance occurring secondary to dyspnea, which is typically characterized by inspiratory stridor that worsens as exercise intensity increases and resolves within a few minutes of cessation of exercise (Newman et al., 1995;Beard, 1996;Rundell and Spiering, 2003;Lane et al., 2006a). In humans, panic reactions occasionally occur as a response to breathlessness . ...
... Similarly, symptoms of dynamic obstruction of the upper respiratory tract in equines often present around 2-3 years of age, as performance expectations increase (Lane et al., 2006a). Trainers report the horse not exerting itself as fully as before, abnormal respiratory noise at higher exercise intensities, and poorer race performance in terms of placings and earnings (Beard, 1996). ...
Dynamic obstructions of the larynx are a set of disorders that occur during exercise in equines and humans. There are a number of similarities in presentation, diagnosis, pathophysiology and treatment. Both equines and humans present with exercise intolerance secondary to dyspnea. During laryngoscopy at rest, the larynx appears to function normally. Abnormalities are only revealed during laryngoscopy at exercise, seemingly triggered by increased ventilatory demands, and quickly resolve after cessation of exercise. Lower airway disease (asthma being the most prevalent condition), cardiac disease and lack of fitness are the major differentials in both species. Laryngoscopic examination during exercise should be performed from rest to peak exertion to allow for a comprehensive diagnosis, including where the airway collapse begins, and thereafter how it progresses. Dynamic disorders with most visual similarity between humans and equines are: aryepiglottic fold collapse (both species); equine dynamic laryngeal collapse (DLC) relative to some forms of human combined supraglottic/glottic collapse; and epiglottic retroversion (both species). Quantitative grading techniques, such as airway pressure measurement, that have proven effective in veterinary research are currently being piloted in human studies. Conditions that appear visually similar are treated in comparable ways. The similarities of anatomy and certain types of dynamic collapse would suggest that the equine larynx provides a good model for human upper respiratory tract obstruction during exercise. Thus, close collaboration between veterinarians and medical personal may lead to further advancements in understanding pathophysiologic processes, and enhance the development of improved diagnostic tests and treatments that will benefit both species.
... 1,[3][4][5][6] Soft palate cautery (SPC), another treatment for PD, does not appear to produce similar results, 7,8 but SPC is often combined with LTF, particularly in Europe. [9][10][11] Exercise endoscopy is considered essential for a definitive diagnosis of PD [12][13][14][15][16] because endoscopy at rest has been associated with an 85% rate of false negative findings. 12 Horses with a presumptive diagnosis of DDSP have been included in previous studies, potentially affecting reported success rates. ...
... [9][10][11] Exercise endoscopy is considered essential for a definitive diagnosis of PD [12][13][14][15][16] because endoscopy at rest has been associated with an 85% rate of false negative findings. 12 Horses with a presumptive diagnosis of DDSP have been included in previous studies, potentially affecting reported success rates. 4,6 National Hunt thoroughbred (NH) racehorses run substantially longer distances (3.2-7.2 km) compared with horses engaged in flat racing (1.0-2.4 km). ...
... Group C was created because the association between iDDSP and PI is well recognized. 2,12,14,29 Allen and Franklin 29 found that 46% of horses with PI developed DDSP. Because OGE was performed only over a distance of 3.2 kilometers, it may be possible that some horses with PI may have developed iDDSP when fatigued. ...
Objective:
To assess racing performance of National Hunt thoroughbred (NH) racehorses with a definite diagnosis of palatal dysfunction treated with a laryngeal tie-forward procedure (LTF) and soft palate cautery (SPC) with or without transendoscopic laser excision of the aryepiglottic folds (TLEAF) and to determine correlation between performance measures.
Study design:
Retrospective cohort study.
Animals:
National Hunt racehorses treated with LTF, SPC ± TLEAF (n = 44) and nonaffected controls (n = 88).
Methods:
Performance was evaluated by using Racing Post ratings (RPR), race earnings (RE), and performance index (PIndex). Affected horses were compared with nonaffected horses. The effect of TLEAF and correlations between measures were analyzed.
Results:
Racing Post rating, RE and PIndex improved by 50%, 26%, and 12% in treated, and by 50%, 39%, and 24% in control horses, respectively, when measurements were evaluated for the median of three presurgical and postsurgical races. Lower postsurgical performance was detected when five postsurgical races were compared with two presurgical races (P ≤ .03). The number of postsurgical earnings rated at zero was greater in treated horses than in control horses (P < .05). Race earnings and RPR correlated more strongly (r = 0.634-0.796) than PIndex and other measures (r = 0.378-0.692).
Conclusion:
Postsurgical performance of NH racehorses with palatal dysfunction after LTF and SPC ± TLEAF was decreased compared with unaffected controls. The negative effect of TLEAF on performance was detected.
Clinical significance:
Although LTF is widely performed in NH racehorses, it may not be the most efficient treatment for palatal dysfunction.
... Both soft palate caudal portion motility and position were assessed, as summarized in Table 2. Palatal instability (PI) was identified when dorsoventral billowing movements of the caudal portion of the soft palate were observed, causing epiglottis flattening ( Figure 1C). Dorsal displacement of the soft palate (DDSP) was diagnosed when the caudal border of the soft palate displaced above the epiglottis, preventing its visualization and obstructing the rima glottis ( Figure 1D) [36,37]. Horses having no signs of palatal disorders were assigned the score 0, and horses showing signs of solely palatal instability or solely palatal displacement were assigned the score 1. ...
... It has been suggested that PI always precedes the development of DDSP [36,37], suggesting that PI may represent a preliminary stage of DDSP. This is in agreement with our study, where all of the horses showing DDSP were concomitantly affected by PI. ...
According to the “unified or united airway disease” theory, diseases in the upper and lower airways frequently co-occur because they represent a single morphological and functional unit. Palatal disorders (PDs) and severe equine asthma (SEA) are frequent diseases that, respectively, affect upper and lower equine airways; however, clinical studies focusing on the co-occurrence of PDs and SEA are limited. The present study investigated the prevalence of PDs in horses affected by SEA, and whether prevalence decreased after SEA treatment. Forty-six privately owned horses affected by SEA in exacerbation were included. For each horse, the severity of the asthma clinical signs was assessed using a previously described scoring system, and the co-occurrence of palatal disorders was investigated using overground endoscopy, before and after treatment for SEA. Before treatment (in exacerbation), 67.4% of SEA-affected horses showed evidence of PDs, including 39.1% showing evidence of palatal instability (PI) and 28.3% of dorsal displacement of the soft palate (DDSP). Airway inflammation (neutrophil percentage in the tracheal wash and bronchoalveolar lavage fluid) was worse in horses with co-occurring PDs. After treatment (in remission), no horses showed evidence of PI, while DDSP was diagnosed in 8.7% of horses. These findings suggest that palatal disorders respond to asthma treatment, supporting the hypothesis that both diseases could be manifestation of a common underlying disorder.
... Intermittent dorsal displacement of the soft palate (iDDSP) is the most commonly reported exercise-induced upper respiratory tract (URT) disorder encountered in racehorses. [1][2][3][4][5][6] The reported prevalence of iDDSP in harness racehorses presenting for exercising URT endoscopy is 25% and 29% for Norwegian-Swedish Coldblooded Trotters (NSCT) and Standardbreds, respectively, 1 and up to 50% for Thoroughbreds with confirmed URT obstruction. 2 The prevalence appears lower for harness racehorses than for Thoroughbreds; however, harness racehorses appear to have a greater array of URT disorders potentially due to conformational phenotypes and to the high head and neck position induced by the overcheck used in harness racing. 1 The current most widely used surgical treatment for iDDSP in racehorses is the laryngeal tie-forward (LTF) procedure, although there are conflicting results from clinical studies regarding the outcome. ...
... [1][2][3][4][5][6] The reported prevalence of iDDSP in harness racehorses presenting for exercising URT endoscopy is 25% and 29% for Norwegian-Swedish Coldblooded Trotters (NSCT) and Standardbreds, respectively, 1 and up to 50% for Thoroughbreds with confirmed URT obstruction. 2 The prevalence appears lower for harness racehorses than for Thoroughbreds; however, harness racehorses appear to have a greater array of URT disorders potentially due to conformational phenotypes and to the high head and neck position induced by the overcheck used in harness racing. 1 The current most widely used surgical treatment for iDDSP in racehorses is the laryngeal tie-forward (LTF) procedure, although there are conflicting results from clinical studies regarding the outcome. Studies on racing performance after LTF have shown a wide range of success rates from 9%-46% in one study 7 to 80%-82% in another, 8 whereas other studies have demonstrated no difference when compared with controls or horses treated with staphylectomy. ...
Background
The laryngeal tie‐forward (LTF) procedure is commonly used to treat intermittent dorsal displacement of the soft palate (iDDSP). There is a wide range in reported efficacy of treating horses with and without a definitive diagnosis of iDDSP.
Objectives
To evaluate the racing performance of harness racehorses in which iDDSP had been definitely diagnosed and treated solely with the LTF procedure.
Study design
Retrospective case series.
Methods
Ninety‐five harness racehorses were treated with LTF for confirmed iDDSP. A definite diagnosis of iDDSP was made with high‐speed treadmill or overground endoscopy. Upper respiratory tract (URT) disorders, short‐term complications, and horses returning for recurrence of URT problems were recorded. Performance before and after LTF was assessed by reviewing career race records and comparing performance index (PI), and racing speed marks from the baseline, preoperative, and postoperative periods. The effect of basihyoid‐cricoid (BC) net distance shortened on racing performance was assessed.
Results
Postoperatively, PI increased in 36/54 (67%, 95% CI 54%‐79%) of experienced racehorses, and 44/67 (66%, 54%‐77%) established or improved their racing speed mark relative to the preoperative period. As a group, PI decreased by a mean (SE) of 0.9 (0.17) points (P < .001) prior to diagnosis/surgery. Postoperatively, PI increased by 0.5 (0.16) points (P = .003), and racing speed improved by 0.83 (0.22) s (P < .001). Twenty‐five percent (17%‐34%) and 49% (39%‐60%) of horses did not demonstrate a decline in PI and racing speed prior to diagnosis, respectively. Net BC distance shortening did not affect performance postoperatively. Twenty of 95 horses (21%, 13%‐29%) had confirmed recurrence of iDDSP 46‐708 days postoperatively.
Main limitations
Not all horses were evaluated with exercising endoscopy postoperatively. Racehorses inevitably develop other racing‐related problems which confound studies of this nature.
Conclusions
This study provides scientific support for the use of LTF to treat iDDSP in harness racehorses although iDDSP seems to affect harness racehorses differently as individuals.
... The horse is an obligate nasal breather, where the caudal free border of the soft palate seals the nasopharynx ventrally to the epiglottis [2]; any perturbation of this normal anatomical relationship causes increased airflow turbulence and respiratory impedance [3]. A specific condition whereby the free caudal border of the soft palate moves dorsal to the epiglottis during exercise, named intermittent Dorsal Displacement of the Soft Palate (DDSP), has been recognized as a common cause of airway obstruction in racehorses with a reported prevalence of 10-20% in horses with poor performance [4][5][6][7]. ...
... The other two horses had palatal instability but no episodes of palatal displacement after instrumentation. As previous studies suggested that palatal instability (PI) and DDSP are manifestations of the same condition, and PI represents the preliminary stage of a disorder that may progress to DDSP, as part of a syndrome named palatal dysfunction [5,31,32], we decided to maintain the four horses within the original group identified at the time of enrollment (DDSP). ...
Exercise induced intermittent dorsal displacement of the soft palate (DDSP) is a common cause of airway obstruction and poor performance in racehorses. The definite etiology is still unclear, but through an experimental model, a role in the development of this condition was identified in the dysfunction of the thyro-hyoid muscles. The present study aimed to elucidate the nature of this dysfunction by investigating the spontaneous response to exercise of the thyro-hyoid muscles in racehorses with naturally occurring DDSP. Intramuscular electrodes were implanted in the thyro-hyoid muscles of nine racehorses, and connected to a telemetric unit for electromyographic monitoring implanted subcutaneously. The horses were recruited based on upper airway function evaluated through wireless endoscopy during exercise. Five horses, with normal function, were used as control; four horses were diagnosed as DDSP-affected horses based on repeated episodes of intermittent dorsal displacement of the soft palate. The electromyographic activity of the thyro-hyoid muscles recorded during incremental exercise tests on a high-speed treadmill was analyzed to measure the mean electrical activity and the median frequency of the power spectrum, thereafter subjected to wavelet decomposition. The affected horses had palatal instability with displacement on repeated exams prior to surgical implantation. Although palatal instability persisted after surgery, only two of these horses displaced the palate after instrumentation. The electromyographic traces from this group of four horses showed, at highest exercise intensity, a decrease in mean electrical activity and median power frequency, with progressive decrease in the contribution of the high frequency wavelets, consistent with development of thyro-hyoid muscle fatigue. The results of this study identified fatigue as the main factor leading to exercise induced palatal instability and DDSP in a group of racehorses. Further studies are required to evaluate the fiber type composition and metabolic characteristics of the thyro-hyoid muscles that could predispose to fatigue.
... The displacement can usually be selfcorrected by the animal through swallowing or readjusting the head position; however, it can occur several times during a single training session or race causing interruptions to normal breathing and, consequently, a significant decrease in performance. Overall, DDSP is estimated to occur in 10-40% of competitive horses, especially Thoroughbreds and Standardbred racehorses [2][3][4][5][6][7][8]. Clinical symptoms consist of a loud gurgling or snoring noise, fluttering of the cheeks as air is diverted beneath the palate, exercise intolerance, or commonly described by trainers as "choking down" Figure 1: Wind tunnel apparatus. ...
... Conservative treatments include tongue-tying during exercise, various types of bits, or the Cornell Collar. When conservative treatments fail, more invasive surgical procedures are completed, including the laryngeal tie-forward procedure, laser staphylectomy, myectomy, palatal sclerotherapy, or a combination of different procedures, which have a reported 58-78% clinical success rate [2][3][4][5][6][7][8][9] but without a consensus treatment of choice [10]. With some similarities, snoring is a condition that affects people of all ages, including 48% of men and 34% of women [11][12][13]. ...
The mechanical properties of the soft palate can be associated with breathing abnormalities. Dorsal displacement of the soft palate (DDSP) is a naturally occurring equine soft palate disorder caused by displacement of the caudal edge of the soft palate. Snoring and a more serious, sometimes life-threatening, condition called obstructive sleep apnea (OSA) are forms of sleep-related breathing disorders in humans which may involve the soft palate. The goal of this study was to investigate the effect of injecting the protein crosslinker genipin into the soft palate to modify its mechanical properties for the treatment of equine DDSP with potential implications for the treatment of snoring and OSA in humans. Ex vivo experiments consisted of mechanical testing and a wind tunnel study to examine the effect of genipin on the mechanical properties, displacement, and vibration of equine soft palates. A pilot in vivo study was completed using DDSP and control horses to test the safety and effectiveness of injecting a genipin reagent into the soft palate. The wind tunnel testing demonstrated a greater than 50% decrease in transient deformation and a greater than 33% decrease in steady-state vibrations for all doses of genipin tested. Ultimate tensile stress, yield stress, and Young’s modulus were higher in the genipin-treated distal soft palate specimens by 52%, 53%, and 63%, respectively. The pilot in vivo study showed a reduction of snoring loudness in all DDSP horses and elimination of DDSP in at least one of three horses. The difficulty of using a 1-meter-long endoscopic injection needle contributed to a consistent overinjection of the equine soft palates, causing excessive stretching (pillowing) and related degradation of the tissue. These ex vivo and in vivo results demonstrated reduced vibration amplitude and flaccidity and increased strength of genipin-treated soft palates, suggesting that genipin crosslinking could become an effective and safe treatment for soft palate related breathing abnormalities.
... Ten minutes of exercise endoscopy during the standardized riding protocol (trot and canter) was evaluated by two examiners (internal F I G U R E 2 Endoscopic parameters evaluated in this study: (a) swallowing (in counts), (b) secretion (in grades-amount and type, grade 2/4 pictured), (c) pharyngeal collapse (in grades, grade 4/4 pictured) (Boyle et al., 2006), (d) full adduction of the arytenoid cartilages (in counts) , (e) axial deviation of the aryepiglottic folds (ADAF; in counts) , and (f) dorsal displacement of the soft palate (DDSP; in counts) . Definitions of pharyngeal abnormalities based on Boyle et al. (2006) and Lane et al. (2006). ...
Background/Objectives
The public perception relating to the welfare of horses involved with equestrian sports is associated with training methods used and the presentation of horses at events. In this context, very tight nosebands, which are intended to prevent the horse from opening its mouth, also attract a lot of attention. Various studies have evaluated the impact of tight nosebands on stress parameters, whereas the effect of tight nosebands on upper airway function is unknown. Therefore, the aim of the study was to use overground endoscopy to evaluate changes in pharyngeal and laryngeal function when a tight noseband is fitted. Moreover, the ridden horse pain ethogram (RHpE) was applied to investigate signs of discomfort (Dyson et al., 2018).
Study design
A randomized, blinded, and prospective study was performed.
Methods
Sixteen warmblood horses consisting of twelve mares and four geldings with a mean age of 11.63 ± 3.53 years were ridden on 2 consecutive days with either loose or tight nosebands (two fingers or no space between bridge of the nose and noseband, respectively) and inserted endoscope in a random order. Videos were taken in a riding arena during a standardized exercise protocol involving beginner level tasks for 30 min in all gaits. For video analysis, freeze frames were prepared and analyzed at the beginning of the expiration phase. Pharyngeal diameter was measured using the pharynx‐epiglottis ratio. Other findings (swallowing, pharyngeal collapse, soft palate movements, and secretion) were also evaluated. Moreover, the RHpE was applied. Descriptive statistics and generalized linear mixed effects models were used. Results with a p‐value < 0.05 were considered statistically significant.
Results
While the pharynx‐epiglottis ratio did not change significantly in horses ridden with loose versus tight nosebands, there was an increase in mean grade and total counts of parameters assessed in the pharyngeal region, for example, grade of secretion (1.5 [±SD 0.89] vs. 3.13 [±SD 0.96]; p = 0.0001), axial deviation of the aryepiglottic folds (0.29 [±SD 0.73] vs. 1.33 [±SD 1.44]; p = 0.01), and pharyngeal collapse (0.69 [±SD 0.87] vs. 1.88 [±SD 1.54]; p = 0.005) in horses ridden with tight nosebands. There was no RHpE score above 8 indicating musculoskeletal pain, but the RHpE scores were significantly higher in horses ridden with tight nosebands (p < 0.001).
Main limitations
Video quality was limited when horses showed large amounts of secretion. Another limitation was the small number of horses.
Conclusions
Results add to the evidence obtained in other studies that tight nosebands do not only cause adverse reactions based on the RHpE score such as head behind the vertical or intense staring but also contribute to changes in the pharyngeal region, such as increased secretion and collapse of pharyngeal structures. This may provide further support for future decisions regarding regulations on nosebands.
... A modified C1/C2 nerve transplantation technique improved exercising laryngeal function grade in 8/14 horses with clinical signs of RLN, however we are not aware of any reports detailing the success rates of reinnervation techniques on subclinical cases of RLN.Interestingly, there were more instances of DDSP in the PL group compared with the unknown outcome group. There is some clinical evidence that DDSP can co-exist with RLN,46 however it was not considered to be a confounder in this study as it was not deemed to be causally associated with both the exposure and outcome. From our observations, increased duration of the endoscopic examination and increased laryngeal stimulation appeared to increase the frequency of DDSP, however no statistical analysis was performed between groups. ...
Background
Yearling laryngeal function (YLF) is frequently assessed at the time of sale and the outcomes of these assessments can have significant economic implications. The YLF of horses that subsequently underwent a prosthetic laryngoplasty (PL) is unknown.
Objectives
We hypothesised horses with YLF ≥grade II.2 would be at increased risk of requiring PL, compared with YLF <grade II.2.
Study design
Case–control.
Methods
There were 150 PL cases from 2019 to 2021 with an available yearling post‐sale videoendoscopic examination and 600 controls. Two observers unaware of the outcome graded YLF using the Havemeyer system. The risk of PL for each YLF grade was calculated using multivariable conditional logistic regression.
Results
The proportions of each YLF grade in the control group and PL group, respectively, were grade I: 25.8% and 13.3%, grade II.1: 54.3% and 35.3%, grade II.2: 16.7% and 26%, grade III.1: 3% and 20.7%, grade III.2: 0.2% and 3.3%, grade III.3: 0% and 0.7%, grade IV: 0% and 0.7%. The odds ratio (OR, 95% confidence interval) of requiring PL compared with the referent grade I were: grade II.1: 1.2 (0.7, 2.2, p = 0.5), grade II.2: 3.4 (1.8, 6.1, p < 0.001), grade III.1: 13.8 (6.0, 31.6, p < 0.001), grade III.2: 55.5 (10.3, 299.2, p < 0.001), grade III.3: 2930,000 (398173.7, 21 600,000, p < 0.001), grade IV: 26300,000 (3 420 000, 202 000 000, p < 0.001). Yearling LF ≥grade II.2 had an OR of 4.61 (3.0, 7.1, p < 0.001) compared with <grade II.2; YLF ≥grade III.1 had an OR of 10.7 (5.6, 20.4, p < 0.001) compared with <grade III.1.
Main limitations
Lack of performance data to compare the PL and control groups. The control group was not ‘disease‐free’ and may have developed disease and been retired or undergone surgery elsewhere.
Conclusions
Three‐quarters of the PL group had ≤grade II.2 YLF, demonstrating deterioration in LF post‐sale was common. The risk of requiring PL increased from YLF grade II.2 upwards.
... Recurrent laryngeal neuropathy (RLN) is a common cause of upper respiratory tract obstruction and when severe is always associated with either ipsilateral or bilateral vocal cord collapse (VCC). 1 In RLN-affected horses with exercising grade C or D arytenoid function 2 , dynamic collapse of an unstable left arytenoid cartilage and VCC during inspiration are the cause of marked airflow obstruction, decreased athletic performance and noise. [3][4][5][6] Bilateral ventriculocordectomy (VeC) via laryngotomy or unilateral VeC via transendoscopic laser have been shown to reduce respiratory sound levels in experimental and clinical cases of severely affected RLN horses. ...
Background: There is no objective information reporting the effect of unilateral laser ventriculocordectomy (VeC) on arytenoid abduction or stability. Objectives: To evaluate arytenoid stability and abduction in horses with severe recurrent laryngeal neuropathy (RLN) before and after unilateral laser VeC. Study design : Prospective study in clinically affected client-owned horses. Methods: Sample size calculations indicated ≥7 horses were required. Horses with grade C or D exercising laryngeal function that underwent unilateral laser VeC were included. Exercising endoscopy was performed before and ≥6 weeks after left-sided laser VeC. Arytenoid stability at maximal exercise was calculated by measuring the left-to-right quotient angle ratio (LRQ) of the corniculate processes at the points of maximal arytenoid abduction (expiration) and maximal arytenoid collapse (inspiration). For each horse, means of measurements obtained for four breaths pre- and post-operatively were used for statistical analysis. Results: Eight horses were included: 5 grade C and 3 grade D laryngeal function. The difference in LRQ between inspiration and expiration was lower post-operatively (median 0.039; interquartile range [IQR] 0.032-0.047) compared to pre-operatively (median 0.158; IQR 0.083-0.249; p=0.01) confirming the left arytenoid was more stable following unilateral laser VeC. The degree of improvement was significantly greater for grade D horses compared to grade C horses (p=0.04). The LRQ measured on maximal abduction was also lower post-operatively (median 0.467; IQR 0.444-0.506) compared to pre-operatively (median 0.578; IQR 0.554-0.655; p=0.02) indicating the left arytenoid was less abducted following surgery. Main study limitations: The sample size was small, no racehorses were included and post-operative assessment was conducted at a variable time after surgery. Conclusion: Unilateral laser VeC in grade C and D RLN-affected horses results in slightly reduced left arytenoid abduction but increased arytenoid stability.
... Recurrent laryngeal neuropathy (RLN) is a common cause of upper respiratory tract obstruction and when severe is always associated with either ipsilateral or bilateral vocal cord collapse (VCC). 1 In RLN-affected horses with exercising grade C or D arytenoid function, 2 dynamic collapse of an unstable left arytenoid cartilage and VCC during inspiration are the cause of marked airflow obstruction, decreased athletic performance and noise. [3][4][5][6] Bilateral ventriculocordectomy (VeC) via laryngotomy or unilateral VeC via transendoscopic laser have been shown to reduce respiratory sound levels in experimental and clinical cases of severely affected RLN horses. ...
Background
There is no objective information reporting the effect of unilateral laser ventriculocordectomy (VeC) on arytenoid abduction or stability.
Objectives
To evaluate arytenoid stability and abduction in horses with severe recurrent laryngeal neuropathy (RLN) before and after unilateral laser VeC.
Study design
Prospective cohort.
Methods
Eight horses with grade C or D exercising laryngeal function that underwent unilateral laser VeC were included. Exercising endoscopy was performed before and ≥6 weeks after left‐sided laser VeC. Arytenoid stability at maximal exercise was calculated by measuring the left‐to‐right quotient angle ratio (LRQ) of the corniculate processes at the points of maximal arytenoid abduction (expiration) and maximal arytenoid collapse (inspiration). For each horse, means of measurements obtained for four breaths pre‐ and post‐operatively were used for statistical analysis.
Results
The difference in LRQ between inspiration and expiration was lower post‐operatively (median 0.039; interquartile range [IQR] 0.032–0.047) compared with pre‐operatively (median 0.158; IQR 0.083–0.249; p = 0.01) confirming the left arytenoid was more stable following unilateral laser VeC. The degree of improvement was significantly greater for grade D horses compared with grade C horses (p = 0.04). The LRQ measured on maximal abduction was also lower post‐operatively (median 0.467; IQR 0.444–0.506) compared with pre‐operatively (median 0.578; IQR 0.554–0.655; p = 0.02) indicating the left arytenoid was less abducted following surgery.
Main limitations
The sample size was small, no racehorses were included and post‐operative assessment was conducted at a variable time after surgery.
Conclusion
Unilateral laser VeC in grade C and D RLN‐affected horses results in slightly reduced left arytenoid abduction but increased arytenoid stability.
... Exercise-related upper respiratory tract (URT) disorders are a common cause of poor performance and abnormal respiratory noise at exercise in sport horses and racehorses (Davidson et al., 2011;Kannegieter & Dore, 1995;Lane et al., 2006;Morris & Seeherman, 1991;. The literature suggests a breed, gait and sporting discipline difference in the prevalence (Kannegieter & Dore, 1995;Tan et al., 2005) and predisposition to different forms of URT disorders. ...
Background
Horses exercised ‘onto the bit’ with periods of induced poll flexion can demonstrate a unique array of upper respiratory tract (URT) disorders.
Objectives
To describe a previously unreported exercise‐related disorder of the epiglottis associated with poll flexion in harness racehorses.
Study design
Retrospective observational study.
Methods
Medical records of all harness racehorses that presented for exercising URT endoscopy between 2005 and 2022 were reviewed. These horses were exercised on a high‐speed treadmill using a previously standardised protocol with alternating 1‐min phases of free head carriage (no rein tension on the bit) and poll flexion (driven onto the bit with long reins) until they could no longer maintain the trotting gait.
Results
Seven Standardbreds and 11 Norwegian‐Swedish Coldblooded trotters were diagnosed with unilateral or bilateral compression of the epiglottis during exercise in poll flexion. These horses demonstrated progression of this disorder during the phases of induced poll flexion and showed no signs of epiglottic compression during phases exercised with free head carriage.
Main limitations
Retrospective nature of study and limited sample size due to low prevalence.
Conclusions
Exercise‐related compression of the base of the epiglottis is a URT disorder only evident videoendoscopically when horses are driven onto the bit leading to poll flexion. It is most often seen in association with dynamic laryngeal collapse but can also be witnessed as a solitary disorder. Videoendoscopically, it appears that the compression is initiated by the rostral advancement of the larynx and hyoid apparatus within a progressively narrowing intermandibular space during poll flexion. Visually, this leads to local inward compression of the lateral nasopharyngeal walls and base of the epiglottis. Further studies are ongoing to confirm this hypothesis and to objectively quantify the degree of URT obstruction caused by this conformational narrowing of the epiglottis during poll flexion.
... Exercise-induced upper respiratory tract (URT) disorders are a common cause of poor performance and abnormal respiratory noise at exercise in sport horses and racehorses (Morris & Seeherman 1991;Kannegieter & Dore 1995;Lane et al. 2006;Davidson et al. 2011;. The literature suggests a breed, gait and sporting discipline difference in the prevalence (Kannegieter & Dore 1995;Tan et al. 2005;) and predisposition to different forms of URT disorders. ...
Background: Horses exercised “onto the bit” with periods of induced poll flexion can demonstrate a unique array of upper respiratory tract (URT) disorders. Objectives: To describe a previously unreported exercise-induced disorder of the epiglottis associated with poll flexion in harness racehorses. Study design: Retrospective observational study. Methods: Medical records of all harness racehorses that presented for exercising URT endoscopy between 2005 and 2022 were reviewed. These horses were exercised on a high-speed treadmill using a previously standardised protocol with alternating one-minute phases of free head carriage (no rein tension on the bit) and poll flexion (driven onto the bit with long reins) until they could no longer maintain the trotting gait. Results: Seven Standardbreds and 11 Norwegian-Swedish Coldblooded trotters were diagnosed with unilateral or bilateral compression of the epiglottis during exercise in poll flexion. These horses demonstrated progression of this disorder during the phases of induced poll flexion and showed no signs of epiglottic compression during phases exercised with free head carriage. Main limitations: Retrospective nature of study and limited sample size due to low prevalence. Conclusions: Exercise-induced compression of the base of the epiglottis is an URT disorder only evident videoendoscopically when horses are driven onto the bit leading to poll flexion. It is most often seen in association with dynamic laryngeal collapse but can also be witnessed as a solitary disorder. Videoendoscopically, it appears that the compression is initiated by the rostral advancement of the larynx and hyoid apparatus within a progressively narrowing intermandibular space during poll flexion. Visually this leads to local inward compression of the lateral nasopharyngeal walls and base of the epiglottis. Further studies are ongoing to confirm this hypothesis and to objectively quantify the degree of URT obstruction caused by this conformational narrowing of the epiglottis during poll flexion.
... The evaluation of upper respiratory tract dysfunctions as a cause of exercise intolerance has long been performed before specific recommendations are made for treatment in each equine athlete [27]. This phenomenon is referred to as dynamic obstruction of the upper respiratory tract in horses [28]. Not long ago, a comparative review was published reporting a similar situation identified more recently in human beings and classified as exercise-induced laryngeal obstruction (EILO) [29]. ...
Simple Summary
The impact of various degrees of poll hyperflexion on the welfare of ridden horses has previously been evaluated. The International Society for Equitation Science advised that lesser degrees of poll flexion should also be investigated. The aim of this study was to evaluate the effects of two degrees of poll flexion with a difference of only 15° on the respiratory system and behaviour of a horse during ridden exercise. Twenty high-level dressage and twenty show-jumping horses were ridden twice for 40 min 3 weeks apart, with the first ridden exercise at an 85° ground angle and the second at a 100° ground angle (the angle between the ground and the line from the forehead to the muzzle). Conflict behaviour was registered, as were manifestations of upper airway collapse, observed on an over-ground endoscopy. Arterial blood oxygen and lactate, pleural pressure, pharyngeal diameter, and heart and respiratory rates were evaluated. For both groups, at 100°, both conflict behaviours and upper airway abnormalities were seen more frequently, the intrathoracic pressure was higher, and the pharyngeal diameter was lower. At 85°, relaxation behaviours were more frequent. Compared to the first ridden exercise, the HR and RR were lower at the beginning of the second ridden exercise but higher at the end. The differences found here support the idea that an increase of just 15° in ridden poll flexion can have negative effects on the respiratory system and behaviour of a horse and therefore on its welfare.
Abstract
From previous studies, the International Society for Equitation Science has advised that further research be conducted on the physiological/psychological effects of less-exacerbated poll flexion angles. We aimed to evaluate the effects of two riding poll flexion positions with a difference of only 15° on the respiratory systems and behaviour of horses through an evaluation of dynamic airway collapse via over-ground endoscopy, the pharyngeal diameter, pleural pressure, arterial oxygenation and lactate, HR/RR, and the occurrence of conflict behaviours. Twenty high-level dressage and twenty show-jumping horses underwent a 40 min ridden test at a ground angle of 85°; 3 weeks later, they underwent a ridden test at a 100° ground angle (the angle between the ground and the line from the forehead to the muzzle) and in a cross-over design. Using a mixed model for repeated measures, Wilcoxon/Friedman tests were carried out according to the experimental design and/or error normality. For both groups, at 100°, conflict behaviours and upper airway tract abnormalities were significantly more frequent, and the pleural pressure was higher, and the pharyngeal diameter was lower. At 85°, relaxation behaviours were significantly more frequent. Lactate was significantly higher at 100° only in the dressage horses. Compared to the first test at 85°, the HR/RR were significantly lower at the beginning of the second test (at 100°) but higher at the end. The significant differences identified in these dressage and show-jumping horses support the idea that an increase of just 15° in riding poll flexion can have negative effects on the respiratory system and behaviour of a horse and therefore on its welfare.
... Obstructing or narrowing of any part of the upper respiratory tract is likely to cause the horse to experience breathlessness, which has been described as 'unpleasant respiratory effort', 'air hunger' or 'chest tightness' (Mellor and Beausoleil, 2017). There are three mechanisms through which the bit is thought to induce upper airway disturbance and contribute to breathlessness: breaking the airtight lip seal due to placement of the bit in the mouth and/or the mouth opening due to pain caused by the bit, retraction of the tongue to avoid pain caused by the bit, and flexion at the poll due to bit pressure resulting in a reduced jowl angle (Allen et al., 2011;Cook, 1999;Lane et al., 2006). ...
Using a bit to communicate with and control the horse while riding is one of the longest standing traditions in
horse riding. However, horses’ aversion to bits and high levels of bit-induced trauma have led some to question
whether this practice is commensurate with modern understanding of animal welfare. This study represents one
of the first attempts to compare horses ridden with and without a bit in terms of horse welfare, rider safety and
rider satisfaction. Australian recreational and sport horse riders (n = 399, 94.4% female; Mdn age=46.0 years)
from a range of riding disciplines were anonymously surveyed online. Only n = 20 (5.0%) participants reported
riding without a bit, however, this is likely consistent with the recreational horse-riding population, given riding
with a bit is mandated in most equestrian sports. A whole sample analysis and a case-matched analysis were
performed where cases were matched based on horse breed and age, discipline, and rider age. Whole sample
analyses found horses ridden without a bit have better relative welfare scores for management, and during riding
and handling compared to horses ridden with a bit (Mdn 13.0, IQR 2.0 and Mdn 11.0, IQR 5.0; Mdn 35.0, IQR 9.0
and Mdn 32.0, IQR 6.0; and Mdn 24.0, IQR 3.25 and Mdn 23.0 IQR 4.0 respectively, p < 0.05), but did not differ
in relation to health. Fewer ridden hyperreactive behaviours (bucking, spooking, rearing and bolting) were reported
for bitless horses compared with bitted horses (Mdn 0.0, IQR 1.0 and Mdn 1.0, IQR 4.0, respectively, p =
0.04), however, rider safety and perceived control were similar for both groups. Riders of bitless horses were
more satisfied than riders of bitted horses (Mdn 16.0, IQR 2.0 and Mdn 14.0, IQR 4.0, respectively, p = 0.01) and
reported better horse-rider partnerships (Mdn 4.0, IQR 0.0 and Mdn 3.0, IQR 1.0, respectively, p < 0.001). More
riders of bitless horses had knowledge of learning theory than riders of bitted horses (55.0% and 23.0%
respectively, p = 0.003). Results from the case-matched analysis were consistent with the whole sample results,
except for rider satisfaction and knowledge of learning theory which were not statistically significant. These
findings suggest that bitless riding is not related to reduced horse control or rider safety, but is related to greater
rider satisfaction and improved horse-rider partnership. Considering current challenges to the industry’s social
licence to operate due to poor horse welfare, increased adoption of bitless riding may present a valuable opportunity
to improve horse welfare.
... Among horses with dynamic upper respiratory tract (URT) collapse diagnosed using exercising endoscopy the reported prevalence of iDDSP is 10%-50%. [1][2][3][4][5] During iDDSP the seal between the oropharynx and nasopharynx is disrupted leading to turbulent, inefficient airflow. This diminishes the horse's athletic ability both during high intensity exercise such as racing, as well as lower intensity disciplines in more severe cases. ...
Objectives:
To investigate the feasibility and describe the clinical experience of performing laryngeal tie-forward (LTF) in standing horses unaffected (experimental) and affected (clinical) by intermittent dorsal displacement of the soft palate (iDDSP).
Study design:
Experimental study and case series.
Animals:
Five normal experimental controls and five client owned horses affected by iDDSP.
Methods:
Standing LTF was performed and evaluated in five experimental horses and five clinical cases diagnosed with iDDSP. Standing LTF was performed under endoscopic guidance with horses sedated and the surgical site desensitized with local anesthetic solution. Short term outcome was assessed using radiography, resting and (in clinical cases) dynamic upper respiratory tract (URT) endoscopy.
Results:
Standing LTF was well tolerated and completed in all horses. Radiographic assessment demonstrated that compared to preoperatively, the basihyoid bone and thyrohyoid-thyroid articulation were positioned dorsally (9.6 mm, p = .006 and 20.4 mm, p = .007, respectively) at 2 days postoperatively. During repeat dynamic URT endoscopy at 48 hours postoperatively, 3/5 horses showed resolution of iDDSP and 2/5 marked improvement. One horse experienced brief iDDSP associated with neck flexion which corrected after swallowing. The second achieved a greater speed and total distance prior to iDDSP.
Conclusions:
Standing LTF did not incur any major peri- or postoperative complications. The laryngohyoid apparatus was repositioned dorsally and in a small case series had a similar surgical effect on laryngeal position.
Clinical significance:
Standing LTF is feasible, mitigates the risk of general anesthesia related complications and reduces cost.
... DDSP is the most common dynamic obstruction in Thoroughbreds with a prevalence of 10%-20%. [25][26][27][28] This prevalence is comparable to our study population (4 of 38 horses). A higher prevalence might have been observed with more strenuous exercise. ...
Background
There is contradictory evidence on the potential benefits of tongue ties on upper airway function and their efficacy in inhibiting intermittent dorsal displacement of the soft palate (DDSP) in racehorses.
Objectives
To test the hypothesis that tongue ties increase the pharyngeal diameter and decrease the occurrence of dynamic airway obstruction in racehorses.
Study design
Prospective, crossover blinded clinical study.
Methods
Data of 22 Thoroughbred and 8 Standardbred racehorses examined using overground endoscopy under full‐intensity exercise on training racetracks with and without fixation of the tongue by use of tongue ties were analysed. Equivalent exercise intensity was ensured by measuring heart rate (bpm), speed (GPS) and venous lactate. Pharyngeal diameter was expressed as pharyngeal‐epiglottis (PE) ratios and laryngeal abduction accordingly as laryngeal‐median‐ratios. Data were analysed using multivariable repeated‐measurements ANOVA.
Results
The PE ratio increased significantly from 1.11 ± 0.19 to 1.28 ± 0.30 in all horses between rest and full‐intensity exercise (p < 0.01). Multi‐variable analysis revealed that this effect decreased significantly by the application of tongue ties (1.15 ± 0.27, p < 0.01). Tongue ties did not influence maximum laryngeal width (p = 0.09) and area (p = 0.2) significantly. DDSP was found in 4 of 30 examinations with tongue tie and in 1 of 30 examinations without tongue tie.
Main limitations
The study population was not randomly chosen and was heterogeneous. Few horses had a respiratory noise and the prevalence of upper respiratory tract disorders was too low for statistical comparison of the rate of DDSP with and without tongue ties.
Conclusions
A positive effect of tongue ties on pharyngeal or laryngeal diameters was not found in this study. Therefore, the results of this study do not support the use of tongue ties to enhance upper airway function.
... It is a common disorder, affecting 10%-20% of racehorses with poor performance Lane et al., 2006;Parente et al., 2002;Priest et al., 2012). ...
Background
Palatal dysfunction is a common cause of poor performance in racehorses. Although conservative management resolves just over 60% of cases, there is a requirement for further intervention in the residual 40% of cases that do not respond. It is proposed that a palatal stiffening technique that is simple to perform, safe, minimally invasive and enables a rapid return to exercise would be an acceptable first intervention. Genipin is a self‐polymerising molecule that bonds to collagen matrices increasing tissue strength, stiffness and resilience. A previous study demonstrated that implanted genipin increased palatal strength and its resistance to deformation and potentially was effective in decreasing likelihood of palatal dysfunction in horses.
Objectives
The objective of the study was to appraise the safety and feasibility of implanting genipin oligomers into the equine soft palate and to report on racehorse trainers' subjective assessment of its usefulness in management of palatal dysfunction.
Study design
Prospective, non‐randomised, pilot study.
Methods
Fifty Thoroughbred racehorses diagnosed with palatal dysfunction were implanted transendoscopically with genipin. The horses were monitored for adverse reactions during hospitalisation. A standard questionnaire provided to the horses' trainers was used to record additional adverse reactions and satisfaction with the animals' subsequent performance. Post‐treatment dynamic endoscopy was performed in a subgroup of animals.
Results
One horse developed adverse clinical signs of pyrexia and reduced appetite, which responded to treatment. Post‐procedural endoscopic examination revealed mild palatal abnormalities in 6 of 50 horses that showed no clinical signs. One horse had mild generalised oedema, four with mild focal swelling and one with a superficial mucosal ulceration at a single site of implantation of the soft palate. Following treatment, 76% of horses were reported to show clinical improvement by their trainers with 24% reported not to show improvement.
Main limitations
The study was not controlled, and outcome measures were mainly subjective.
Conclusions
The procedure was well tolerated, safe, minimally invasive and enabled a rapid return to exercise. Trainer reported improvement was comparable to previously reported palatoplasty procedures.
... U pper airway abnormalities such as laryngeal and palatal dysfunction are common causes of poor performance in racehorses. [1][2][3][4][5][6] These conditions result in dynamic airway obstruction, causing obstruction to airflow and reduced oxygen supply to the exercising muscles, ultimately leading to reduced athletic performance. [7][8][9][10][11][12] The identification of potential upper airway abnormalities that may affect future performance is an important consideration for prospective purchasers of racehorses. ...
Introduction:
Upper airway endoscopy of thoroughbred (TB) yearlings is commonly used in an attempt to predict laryngeal function (LF) and its impact on future race performance. The aim of this study was to determine if different grading systems and laryngeal grades were correlated with future performance.
Materials and methods:
Postsale endoscopic recordings were obtained from an Australian TB yearling sale during a four-year period from 2008 to 2011. Horses were included if they had a diagnostic postsale video endoscopic recording and raced within Australia. Recordings were graded using the Havemeyer system and subsequently recategorised according to the Lane scale and two condensed scales. Performance data were sourced from Racing Australia and comparisons were made between groups.
Results:
A total of 1244 horses met the inclusion criteria. There were no significant differences in sex or sales price between groups. There were no significant differences in the number of starts or wins between groups for any grading system. For the condensed Havemeyer scale, horses with intermediate LF were separated into two groups. Significant differences in earnings were found between 'normal' and 'abnormal' (P = 0.02) and 'intermediate-low' and 'abnormal' grades (P = 0.03). There were no significant differences between horses with 'intermediate-high' and 'abnormal' grades (P = 0.40). No significant differences were found between the two intermediate grades (P = 0.60) or between horses with normal LF and either 'intermediate-low' or 'intermediate-high' grades (P = 0.99).
Discussion:
Resting LF in Australian yearling TBs assessed using a condensed Havemeyer grading scale had some predictive value for future racing performance. This information should be considered when performing yearling endoscopic examinations.
... In addition, the mean age of the grade IV laryngeal function horses was younger than the grade III laryngeal function horses so they may is more than one structure that collapses into the airway. 26,27 The only variable found to influence postoperative earnings was preoperative racing. Horses that raced at least one time prior to surgery had higher mean postoperative earnings compared with horses that had not raced preoperatively. ...
Background
There is persistent concern among some trainers, owners and veterinarians regarding the effect of preoperative laryngeal function grade on the outcome of laryngoplasty and ventriculocordectomy (LPVC).
Objectives
To determine the effect of laryngeal function grade prior to LPVC on postoperative performance.
Study design
Retrospective case‐series.
Methods
Medical and race records of Thoroughbred racehorses diagnosed with recurrent laryngeal neuropathy (RLN) and treated with LPVC between 1998 and 2013 were reviewed. Horses were placed into three groups based on preoperative laryngeal function grade (grade III.1, grades III.2/III.3, and grade IV). The effect of preoperative laryngeal function grade on postoperative performance was determined by multivariable logistic regression, Cox proportional hazard model and multivariable linear regression analysis.
Results
In a multivariable logistic regression, grade III.2/III.3 horses had 1.88 times higher odds (95% CI = 1.03‐3.43) of racing after LPVC than grade IV (P = .04). A multivariable Cox's proportional hazard analysis controlling for race prior to surgery (P < .01) showed that likelihood of racing postoperatively was not different between grade III.1 and grade IV (P = .6), and although not statistically significant, there was a tendency for grades III.2/III.3 to be more likely to race postoperatively than horses with grade IV (P = .07). Kaplan–Meier survival analysis showed that grade IV horses took a longer time to race compared with grade III.1 and grade III.2/III.3. Laryngeal function grade did not influence the mean earnings per start.
Main limitations
The small number of horses in the grade III.1 group compared with the III.2/III.3 and IV groups influenced the effect of grade III.1 on outcome.
Conclusions
Laryngeal function grade may affect likelihood of racing after LPVC, but not earnings per start. Grade III. 2/III.3 horses were more likely to race postoperatively than grade IV horses, and grade IV horses took a longer time to first race after LPVC.
... Causes of such respiratory stress include anatomic position of the head and neck, infectious and non-infectious respiratory diseases, and traumatic and mechanical blockage. [40][41][42] For collars 6 and 7, the trachea was considered a critical point, as even at rest, close contact occurs between the collars and the skin. Due to their design, collars 1, 2, 4 and 5 do not contact the trachea region, so the trachea was not considered a critical point. ...
Background:
Working donkeys represent an important source of energy worldwide. Poor working conditions and equipment affect their ability to work. Poorly designed, ill-fitted harness causes inefficient transfer of power and leads to health and welfare issues. Using technology to assess different types of collars provides a better understanding of those that are most efficient for working donkeys.
Materials and methods:
Seven different collars were tested using pressure pads. Contact area, median, maximum and peak pressures were obtained for the whole collar and critical points. Eight donkeys pulled 20% and 40% of their body weight, using each collar, under controlled conditions.
Results:
Contact area and pressures vary between collars and effort, with design and expansion capacity of the collars playing a major role. Simple collars designed specifically for donkeys performed well, with full collars designed for horses also having good results. Due to reduced expansion capacity and contact in the critical points, the breast collars were the least effective.
Conclusion:
Design, appropriate padding and manufacturing materials and adjustment capacity are key features for good collars, and such parameters are of paramount importance in terms of health and welfare for working donkeys.
... In addition, HSTE technique, it has not been found it useful by horse owner and trainers because of the expense of equipment, personnel required, and time taken, and some horse injuries have been reported during the performing of HSTE [20]. ...
The purpose of the study was to find the source of complaints and to diagnose dynamic upper respiratory tract problems, which were derived from the horse owners, trainers, and jockeys, and to evaluate the overground endoscopic examination efficiency to determine the subclinical upper respiratory tract (URT) abnormalities, which were unable to diagnose with resting endoscopy. In the study, overground endoscopy has been used which nowadays there is a more useful and safe technique of performing endoscopy during ridden exercise in the natural field to diagnose dynamic upper respiratory tract (URT) abnormalities in comparison with the more traditional method of resting endoscopy. This study focused on 25 racehorses (Thoroughbred, n:22 and Arabian n: 3), which were admitted to Racehorse Hospital with complaints of fade abruptly and/or abnormal respiratory noise during the last meters of the race. All horses were examined for the complaints to be associated with systemic disorders and/or lameness, the racehorses with lameness and/or systemic disorders findings were excluded. Resting (post-exercise) and overground endoscopy by using Dr. Fritz® ETL-Equine Overground Endoscopy was performed on a polytrack racecourse in all racehorses. Observed abnormalities were recorded as simple and complex cases and the results of resting and dynamic examination were compared. It was concluded the overground endoscopic examination has a useful diagnostic value in determining the cause of abnormal respiratory noise and/or fade abruptly.
... This can lead to impaired athletic performance due to reduced oxygen supply to the exercising muscles [1]. Dorsal displacement of the soft palate is one of the most common forms of dynamic upper airway collapse affecting racehorses [4,5]. Studies have estimated that up to 20% of racehorses may be affected by the condition [6,7]. ...
This article reports on the results of a survey of racehorse trainers (n = 112) outlining the reasons for tongue-tie (TT) and noseband (NB) use by Thoroughbred trainers (TBTs) (n = 72) and Standardbred trainers (SBTs) (n = 40). The study also investigated the reported effectiveness of TTs and possible complications arising from their use. Tongue-tie use was reported by 62.5% (n = 70) of racehorse trainers. The reasons for TT use varied between TBTs and SBTs. For TBTs, the most common reason for TT use was to prevent or reduce airway obstruction (72.3%, n = 34), followed closely by to prevent or reduce airway noise (55.3%, n = 16). Standardbred trainers assigned equal importance for TT use [to prevent or reduce airway obstruction (69.6%, n = 16) and to prevent the horse from moving its tongue over the bit (69.6%, n = 16)]. Tongue-ties were considered significantly less effective at improving performance than at reducing airway obstruction and preventing the tongue from moving over the bit (t = −2.700, p = 0.0007). For respondents who used both TTs and NBs, there was a mild to moderate positive association between the reasons for using TTs and NBs. Of the 70 TT-using respondents, 51.4% (n = 36) recorded having encountered either a physical or behavioural complication due to TT use, with redness/bruising of the tongue (20.0%, n = 14) being the most common physical complication reported. Duration of use influenced the risk of observing complications. The likelihood of a respondent reporting a behavioural complication due to TT use increased with every minute of reported application and a nine-minute increment in application period doubled the odds of a respondent reporting a complication. Tightness was a risk factor for physical complications: Checking TT tightness by noting the tongue as not moving was associated Citation: Weller, D.; Franklin, S.; White, P.; Shea, G.; Fenner, K.; Wilson, B.; Wilkins, C.; McGreevy, P. The Reported Use of Tongue-Ties and Nosebands in Thoroughbred and Standardbred Horse Racing-A Pilot Study. Animals 2021, 11, 622.
... Both high-speed treadmill and overground endoscopy have proven superior for evaluation of dynamic obstructions of the upper airway when compared to resting endoscopy in the horse. Of these two diagnostic options, overground endoscopy has the added advantage of examining the horse in the same environment, equipment and performance conditions in which the clinical signs occurred (Tan et al. 2005;Lane et al. 2006a, b;Priest et al. 2012;Kelly et al. 2013;Davison et al. 2017;Fretheim-Kelly et al. 2019). Additional disadvantages of treadmill endoscopy include the requirements for specialty equipment, trained personnel and trucking of the horse into the hospital facilities for evaluation (Fretheim-Kelly et al. 2019). ...
A 3‐year‐old Standardbred trotting gelding presented to the Atlantic Veterinary College for diagnostic work‐up of poor performance and abnormal respiratory noise during exercise. Physical examination was unremarkable, and no significant findings were identified on standing endoscopic examination of the upper respiratory tract. Treadmill endoscopy was utilised for dynamic evaluation of the upper respiratory tract; a diagnosis of epiglottic retroversion was confirmed. The owner requested euthanasia of the gelding, and a post‐mortem evaluation was completed. Despite thorough gross and histological examination of the head and neck on post‐mortem examination, no evidence was identified to support the postulated aetiologies for epiglottic retroversion currently found in the literature. This case represents the first reported findings from a post‐mortem examination of a horse with epiglottic retroversion.
... This leads to an intermittent obstruction of the upper respiratory tract resulting in inspiratory stridor and dyspnea (Skerret et al., 2015). Similar conditions can be found in horses and humans (Woo, 1992;Parente et al., 1998;Lane et al., 2010;Terrón-Canedo and Franklin, 2013). The etiology of ER in dogs is still unknown (Skerret et al., 2015). ...
Epiglottic retroversion (ER) is an uncommon and poorly understood disorder of the upper respiratory tract in small breed dogs. In this retrospective study, perioperative characteristics, surgical technique, outcome, and complications in nine dogs that underwent surgical treatment for ER and/or concurrent upper respiratory tract disorders, were evaluated. The most frequently reported clinical symptoms were chronic intermittent inspiratory stridor (89%), exercise intolerance (78%), and dyspnea (67%). Concurrent respiratory disorders were highly prevalent (78%). Five dogs initially underwent a temporary epiglottopexy and two a permanent epiglottopexy. In two dogs, both suffering from concurrent laryngeal paralysis, only a unilateral cricoarytenoid lateralization was performed. After initial clinical improvement, temporary and permanent epiglottopexy eventually failed in 4/6 dogs (67%) that were available for follow-up, necessitating partial epiglottectomy as revision surgery. This resulted in a successful long-term outcome in 5/6 of these dogs (83%). In the dogs with primary ER or in cases where the presence of secondary ER led to significant respiratory symptoms, partial epiglottectomy as a primary surgical technique appeared to be a more permanent treatment option than epiglottopexy. Both dogs with surgically corrected concurrent laryngeal paralysis without epiglottopexy or epiglottectomy showed clinical improvement. This might indicate that, in case of secondary ER, positive results can be achieved after management of the underlying respiratory disorder.
... Palatal instability PI [7,8], dorsal displacement of the soft palate DDSP [9,10] and pharyngeal dysfunction PD [11,12] were some of these. The application of nosebands to reduce the impact of these dysfunctions was commonly mentioned in the literature with reference to thoroughbred and standardbred racehorses [10,13]. More recently it had been recognised that these issues were also a common cause of poor performance in sports horses [11,14]. ...
There had been mounting concern over the use of nosebands and in particular those regarded as being restrictive with the potential to cause stress to horses. It had been suggested that mouth opening during ridden exercise was primarily triggered by rider, tack, training or pain issues. At the same time the long held association between mouth opening and upper airways dysfunctions such as PI, DDSP and PD was being mostly ignored. It was therefore suggested that horses that were continually or intermittently attempting to open their mouths during ridden exercise should firstly undergo overground endoscopy to rule out upper airways issues, prior to exploring other potential causes. This particularly in light of more recent studies in sports horses as well as racehorses which had shown a high incidence of PI and DDSP in competition. If a dysfunction such as PI , DDSP or PD was diagnosed, then these issues should be addressed firstly. If successfully treated the need for tack such as a nosebands would be reassessed.
... 1,10 Intermittent dorsal displacement of the soft palate (iDDSP) is one of the most commonly reported obstructive dynamic upper respiratory tract (URT) disorders in racehorses. 3,11 The laryngeal tie-forward procedure (LTFP) is currently considered the best surgical treatment for iDDSP in horses 12 and offers a low rate of reported postoperative complications. 12,13 Dynamic laryngeal collapse associated with poll flexion, to the best of the authors' knowledge, has not been reported as a complication after the LTFP in horses. ...
Objective:
To report dynamic laryngeal collapse (DLC) associated with poll flexion as a potential complication of the laryngeal tie-forward procedure (LTFP) in harness racehorses.
Study design:
Short case series.
Animals:
Three harness racehorses.
Methods:
Preoperative and postoperative medical records of all harness racehorses that underwent the LTFP were reviewed, as were high-speed treadmill videoendoscopy recordings of 35 horses that returned for upper airway evaluation postoperatively.
Results:
One standardbred and two Norwegian coldblooded trotters in which dorsal displacement of the soft palate had been initially diagnosed were found to have bilateral arytenoid cartilage and vocal fold collapse associated with poll flexion after the LTFP. These three horses were otherwise clinically normal when exercised in free head carriage.
Conclusion:
Dynamic laryngeal collapse associated with poll flexion can occur as a complication after the LTFP in harness racehorses and should be considered as a differential in horses with persistence of airway problems after surgery.
Clinical significance:
Postoperative DLC may be underdiagnosed in harness racehorses because this complication is obvious only when horses are driven with bit and reins during high speed treadmill or overground videoendoscopy.
Background
Palatal dysfunction (PD), which encompasses palatal instability (PI) and intermittent dorsal displacement of the soft palate, is the most common performance‐limiting upper respiratory tract obstruction in young Thoroughbred racehorses. Soft palate thermocautery (SPT) performed under general anaesthesia is a routinely performed procedure for PD in some countries, but the procedure for and outcome of SPT performed under standing sedation has not been published.
Objectives
(1) To describe a technique for SPT performed under standing sedation; and (2) to assess post‐operative performance in horses compared to controls using the Racing Post rating (RPR), British Horseracing Authority official rating (OR), Performance Index and Earnings.
Study design
Retrospective case series.
Methods
Medical records were reviewed for all horses that had SPT performed under standing sedation following topical and local infusion of lidocaine hydrochloride into the rostral soft palate, and that were identified to have PI by overground endoscopy. Two matched controls were identified for each case. The median RPR, OR, Performance Index and Earnings for the three pre‐operative and three post‐operative races were compared.
Results
No significant differences were identified between the SPT (n = 23) and Control groups (n = 46) for baseline characteristics or outcomes.
Main limitations
Retrospective study design, small sample size.
Conclusions
No significant differences in racing performance were identified between horses that had SPT performed under standing sedation and controls.
Abstract
Objective: To assess a three-dimensional (3-D)-printed laryngeal clamp (LC) designed to enhance the anchoring of laryngeal prostheses at the cricoid cartilage
Study design: Ex vivo biomechanical study.
Sample population: A total of 22 equine larynges.
Methods: Two experimental groups included larynges with standard prosthetic laryngoplasty (PL; n = 10) and larynges with prosthetic laryngoplasty modified with laryngeal clamps (PLLC; n = 10). All constructs underwent 3000 cycles of tension loading and a single tension to failure. Recorded biomechanical parameters included maximum load, actuator displacement, and construct failure. Finite element analysis (FEA) was performed on one PL and one PLLC construct.
Results: The maximum load at single tension to failure was 183.7 ± 46.8 N for the PL construct and 292.7 ± 82.3 N for the PLLC construct (p = .003). Actuator displacement at 30 N was 1.7 ± 0.5 mm and 2.7 ± 0.7 mm for the PL and PLLC constructs, respectively (p = .011). The cause of PL constructs failure was mostly tearing through the cartilage whereas the PLLC constructs failed through fracture of the cricoid cartilage (p = .000). FEA revealed an 11-fold
reduction in the maximum equivalent plastic strain, a four-fold reduction in maximum compressive stress, and a two-fold increase in the volume of engaged cartilage in PLLC constructs.
Conclusion: The PLLC constructs demonstrated superior performance in biomechanical testing and FEA compared to standard PL constructs.
Clinical significance: The use of 3-D-printed laryngeal clamps may enhance the outcomes of laryngoplasty in horses. In vivo studies are necessary to determine the feasibility of performing laryngoplasty using the laryngeal clamp in horses.
Le pharynx est une structure musculaire qui doit s’adapter à des changements extrêmes en matière de pression inspiratoire/expiratoire ou de volumétrie lors de l’effort. Ceci est rendu possible par sa musculature intrinsèque et extrinsèque complexe. L’affection dynamique la plus fréquente est le déplacement dorsal intermittent du voile du palais (DDIVP), dont l’incidence est estimée entre 20 et 30 % chez les chevaux de course de 2 et 3 ans. Le traitement du DDIVP passe par des mesures conservatrices et un traitement médical avant qu’un traitement chirurgical ne soit proposé. Les autres affections pharyngées plus rares sont la fente palatine ou encore l’atrésie des choanes chez le poulain, ainsi que la cicatrice pharyngée ou les masses pharyngées chez l’adulte. Compte tenu du caractère congénital de l’atrésie des choanes ou de la fente palatine, les chevaux affectés doivent être exclus de la reproduction s’ils survivent au traitement chirurgical.
Objective:
To create a model of transient unilateral laryngeal paralysis (LP) that will allow the study of cricoarytenoideus dorsalis dysfunction and a method for quantification of varying degrees of LP in dogs.
Animals:
5 castrated male research Beagles.
Procedures:
Between January and February 2018, dogs were anesthetized and instrumented with a laryngeal mask airway and a flexible endoscope to record the rima glottidis. The left or right recurrent laryngeal nerve (RLn) was localized using ultrasonography and electrical stimulation, then conduction blockade was induced with perineural lidocaine. The normalized glottal gap area (NGGA) was measured before and every 15 minutes after the block. Inspired 10% carbon dioxide (CO2) was administered for 1 minute at each sampling time. The inspiratory increase in NGGA (total and each side) was measured at peak inspiration. The change in hemi-NGGA for the control side versus the anesthetized side was evaluated with a mixed-effect model.
Results:
During CO2 stimulation, the increase in inspiratory hemi-NGGA was consistently less (P < .001) for the treated side (-8% to 13%) versus the control side (49% to 82%). A compensatory increase (larger than at baseline) in the control hemi-NGGA was observed. The total NGGA remained unaffected.
Clinical relevance:
Unilateral local anesthesia of the RLn produced transient unilateral LP with a compensatory increase in the hemi-NGGA for the contralateral side. This model could facilitate the evaluation of respiratory dynamics, establishment of a grading system, and collection of other important information that is otherwise difficult to obtain in dogs with LP.
Exercise-induced upper airway collapse (UAC) probably occurs when the stabilising muscles of the upper airway are unable to withstand the dramatic changes in airflow and pressure that occurs during exercise. In racehorses, the mainstay of treatment is surgical intervention. In human athletes, exercise-induced laryngeal obstruction has been treated successfully with inspiratory muscle training (IMT). The aims of this study were: (1) to assess the feasibility of IMT in racehorses; and (2) describe the exercising endoscopy findings pre- and post-IMT in racehorses diagnosed with dynamic UAC. Horses undergoing IMT wore a mask with an attached threshold-valve to apply an additional load during inspiration, creating a training stimulus with the purpose of increasing upper airway muscle strength. Each horse underwent IMT once daily, while standing in the stable, 5-6 days/week for 10 weeks. Endoscopy recordings were analysed in a blinded manner using an objective grading scheme and subjective pairwise analysis.
Seventeen horses successfully completed the IMT protocol, with full information available for 10 horses. Objective grading analysis showed a lower grade of vocal fold collapse (6/9 horses), palatal instability (7/10 horses) and intermittent dorsal displacement of the soft palate (5/7 horses) post-IMT. Pairwise subjective analysis suggested better overall airway function post-IMT in 3/10 horses. The main limitations of this preliminary investigation were the low number of horses examined and lack of a control population. Further research is required to investigate the effects of IMT on upper airway muscle strength and to evaluate its efficacy for prevention and treatment of UAC.
Tongue‐ties (TTs) are used to aid control and aim to conservatively treat upper airway disorders in racehorses. However, welfare concerns have led to their use being banned in other equestrian disciplines. In the United Kingdom, TTs have been reported to be used in approximately 5% of starts. The frequency of their use elsewhere is unknown. The objectives of this retrospective single cohort study were to estimate the frequency of TT use within the Australian Thoroughbred (TB) racing industry, and to describe usage patterns. Data of all Australian TB horse races from 2010 to 2013 calendar years were collected by accessing the Racing Information Services Australia database. Frequency of TT use was calculated, and usage patterns were explored at the start, horse and trainer levels. Between 2010 and 2013, there were a total of 728,678 starts from 62,377 horses prepared by 4927 trainers and that raced on 1453 race dates across 402 venues. Tongue‐ties were used in 21.4% of starts; however, frequency varied according to location, race, trainer and horse. At the horse level, 32.2% wore a TT at least once and 7.6% wore it at every race on record. At the trainer level, 71.3% used TTs in at least one of their horses but only 1.4% used them systematically. The present study concludes that TT use in Australian TB racehorses, during the period 2010–2013, was common and considerably higher than previously reported in the United Kingdom. Most Australian trainers use the device and appear to adapt its usage according to individual horse and race factors.
Upper oesophageal sphincter aplasia and subsequent incompetence had been reported as one element of the fourth branchial arch defect syndrome and also as a possible sequelae to the placement of a laryngeal abductor prosthesis. Fourth branchial arch defects were thought to be uncommon and when diagnosed it was more often the cartilaginous abnormalities with associated arytenoid abductor incompetence that were discussed. As a consequence of introducing manual assessments of upper oesophageal sphincter tone to the oropharyngeal examination performed prior to palatoplasty procedures, it was determined that this presentation was more common than previously reported. In addition and as a result of pre and post operative examinations and history collection there appeared to be a possible association in some instances with cases of dorsal pharyngeal collapse and paradoxical sleep deprivation.
Respiratory function in the horse can be severely compromised by arytenoid chondritis, or arytenoid chondropathy, a pathologic condition leading to deformity and dysfunction of the affected cartilage. Current treatment in cases unresponsive to medical management is removal of the cartilage, which can improve the airway obstruction but predisposes the patient to other complications like tracheal penetration of oropharyngeal content and dynamic collapse of the now unsupported soft tissue lateral to the cartilage. A tissue engineering approach to reconstructing the arytenoid cartilage would represent a significant advantage in the management of arytenoid chondritis. In this study we explored if decellularized matrix could potentially be incorporated into the high motion environment of the arytenoid cartilages of horses. Equine arytenoid cartilages were decellularized and a portion of the resultant acellular scaffolds was implanted in a full thickness defect created in the arytenoids of eight horses. The implantation was performed bilaterally in each horse, with one side randomly selected to receive an implant seeded with autologous bone marrow-derived nucleated cells (BMNC). Arytenoids structure and function were monitored up to 4 months. In vivo assessments included laryngeal ultrasound, and laryngeal endoscopy at rest and during exercise on a high-speed treadmill. Histologic evaluation of the arytenoids was performed post-mortem. Implantation of the cartilaginous graft had no adverse effect on laryngeal respiratory function or swallowing, despite induction of a transient granuloma on the medial aspect of the arytenoids. Ultrasonographic monitoring detected a post-operative increase in the thickness and cross-sectional area of the arytenoid body that receded faster in the arytenoids not seeded with BMNC. The explanted tissue showed epithelialization of the mucosal surface, integration of the implant into the native arytenoid, with minimal adverse cellular reaction. Remodeling of the scaffold material was evident by 2 months after implantation. Pre-seeding the scaffold with BMNC increased the rate of scaffold degradation and incorporation. Replacement of arytenoid portion with a tissue engineered cartilaginous graft pre-seeded with BMNC is surgically feasible in the horse, well tolerated, results in appropriate integration within the native tissue, and prevented laryngeal tissue collapse during exercise.
Background
Bits have often been incriminated as a cause of upper respiratory tract obstruction in horses; however, no scientific studies are available to confirm or refute these allegations. Clinical signs of dynamic laryngeal collapse associated with poll flexion (DLC) are induced when susceptible horses are ridden or driven into the bit.
Objective
To determine whether use of Dr Cook's™ Bitless Bridle, instead of a conventional snaffle bit bridle, would reduce the severity of DLC in affected horses measured objectively using inspiratory tracheal pressures.
Study design
Intervention study using each horse as its own control in a block randomised order.
Methods
Nine Norwegian Swedish Coldblooded trotters previously diagnosed with DLC were exercised on two consecutive days using a standardised high‐speed treadmill protocol with either a conventional bridle with a snaffle bit, or Dr Cook's™ Bitless Bridle. Head and neck position, rein tension, inspiratory tracheal pressure measurements, and laryngeal videoendoscopy recordings were obtained. A heart rate greater than 200 bpm, and similar degrees of poll flexion/head height, had to be achieved in both bridles for the individual horse's data to be included for comparison.
Results
Seven horses’ data met the inclusion criteria. The change in mean inspiratory tracheal pressure between free and flexion phases in the bitless bridle (−15.2 ± 12.3 cmH2O) was significantly greater (P < .001) than in the snaffle bit bridle (−9.8 ± 7.9 cmH2O). Mean inspiratory pressure during the free phase was significantly (P < .001) more negative with the snaffle bit bridle (−32.3 ± 6.3 cmH2O), vs the bitless bridle (−28.5 ± 6.9 cmH2O). Mean pressures in flexion phase, snaffle bridle (−42.1 ± 10.8 cmH2O), vs bitless bridle (−43.7 ± 15.6 cmH2O) where not significantly different between bridles (P = .2).
Main limitation
Small sample size due to difficulty recruiting suitable clinical cases.
Conclusions
This study could not provide any clear evidence that the effect of a snaffle bit in a horse's mouth influences the development or severity of DLC. Instead, head and neck angles induced by rein tension seem to be the key event in provoking DLC in susceptible horses.
Flexion of the horse's head and neck during dressage riding reduces the pharyngeal lumen with the risk of increased upper airway resistance and upper airway obstructions. According to the Fédération Equestre Internationale, hyperflexion is achieved through force, whereas the position low-deep-round is nonforced. The objectives of this study were to evaluate (1) applied rein tension and (2) dynamic structural disorders in the upper airways in dressage horses in different gaits and different head-neck positions (HNPs). Overground endoscopy (OGE) and rein tension were evaluated in 13 clinically healthy and high-performance Warmblood dressage horses while being ridden in a standardized program comprised of four different gaits (halt, walk, trot, and canter) and in four HNPs (unrestrained, competition frame, hyperflexion, and low-deep-round). All included horses were able to achieve the desired HNPs. The HNP low-deep-round showed significantly lower rein tension than competition frame (P < .001) and hyperflexion (P < .001). An association was found between dynamic structural disorders in the upper airway tract evaluated by OGE and head-neck flexion, but this association was not linked to the degree of flexion. The HNP hyperflexion was neither associated with greater rein tension nor severe dynamic structural disorders than the HNP competition frame. This study confirms that low-deep-round is a nonforced position, in contrast to hyperflexion. Further studies are needed to evaluate whether dynamic structural disorders are a result of flexion or if the degree of flexion has an impact.
Dorsal displacement of the soft palate (DDSP) usually occurs in athletic adult horses. Congenital DDSP in foals secondary to the persistent frenulum of the epiglottis is rarely observed. The aim of this report was to describe a case of a seven-day-old female neonate Quarter Horse presenting dysphagia, milk reflux through the nostrils and mouth, and expiratory dyspnea since 4 days. Thoracic auscultation was indicative of aspiration pneumonia. Diagnosis of DDSP associated with local inflammation was made after endoscopic examination of upper respiratory tract. Radiographic examination was performed to rule out hypoplasia of the epiglottis. No clinical improvement was observed after anti-inflammatory treatment with flunixin meglumine. Oral endoscopy under general anesthesia revealed that the displacement of the soft palate was caused by a persistent frenulum of the epiglottis. Using a 30° rigid endoscope and a curved laparoscopic scissors, the frenulum was transected. After surgery, no dysphagia or dyspnea at rest was observed. However, discreet respiratory noise persisted during exercise for 5 days postoperatively. After discharge, the owner reported that the animal was completely normal during exercise. The animal is currently 3 years old and is developing a normal athletic performance. Persistent frenulum of the epiglottis should be considered while examining neonates with nasal milk reflux associated with expiratory dyspnea. This case report emphasizes the importance of the differential diagnosis for DDSP and for DDSP secondary to the persistent frenulum of the epiglottis in neonatal foals. It also underlines the importance of oral endoscopic examination for diagnosis.
With the advent of overground endoscopy, there is more scrutiny of equine airways than ever before. Possibly as a result of this trend, owners, trainers and breeders seem to have a greater awareness of equine breathing problems. As our understanding evolves in the veterinary sector, there is a need to keep abreast of new techniques and procedures as they become available. It can be difficult for practitioners performing intermittent examinations to gain confidence with equine upper respiratory tract endoscopic anatomy. This article provides a quick reference guide to the majority of conditions and post-operative procedures/abnormalities that the equne practitioner is likely to encounter.
The physiology of exercise and training is fascinating, and hundreds of interesting studies have given insight into its mechanisms. Exercise testing is a useful clinical tool that can help veterinarians assess poor performance, fitness, and performance potential and prevent injuries. The clinically applicable aspects of cardiovascular adaptions to training and exercise testing are highlighted in this review. Different exercise tests should be used to evaluate horses performing in different disciplines and levels. Exercise tests that simultaneously assess several body systems can be beneficial when assessing poor performance, because this is often a multifactorial problem with signs not detectable at rest.
Thesis (doctoral)--Massey University, 1984.
A clinical sports medicine evaluation was applied to 275 racehorses with a history of poor racing performance. The poor performance evaluation included a) general physical examination and basic laboratory screening; b) respiratory examination including auscultation, thoracic radiographs, ventilation-perfusion lung scintigraphy and upper airway endoscopy at rest and during maximal treadmill exercise c) examination of the musculoskeletal system including lameness examination, video gait analysis at high speed, post exercise serum chemistry to identify obvious as well as sub-clinical myopathies, high detail radiography and nuclear scintigraphy; d) cardiac examination including auscultation, electrocardiographic analysis during strenuous exercise and when indicated, echocardiography; and e) a standardised exercise stress test entailing the measurement of oxygen consumption, carbon dioxide production, venous blood lactate concentration and heart rate during sequentially increasing running speeds on the high speed treadmill. The choice of diagnostic methodologies utilised were tailored to each individual in order to determine most efficiently the abnormalities contributing to inadequate racing performance. The results of this clinical evaluation showed that 1) many of the diagnoses were subtle requiring the use of sophisticated diagnostic equipment including scintigraphy and dynamic evaluation of the horse exercising on the high speed treadmill and 2) 84 per cent of the horses were diagnosed as suffering from more than one problem leading to the supposition that inadequate athletic performance is often caused by a constellation of abnormalities requiring a comprehensive approach to diagnosing decreased athletic capability.
Endoscopy of the upper respiratory tract was performed in 100 horses during high speed treadmill exercise. Reasons for endoscopy were a history of an abnormal noise during exercise in 75 horses, poor performance in 17 horses and to evaluate the results of upper respiratory tract surgery in 8 horses.
Of the 75 horses with a history of an abnormal noise during exercise the cause was determined in 67 (89%). Endoscopic abnormalities were detected at rest in 40 of these 75 horses (53%). In these 40 horses, a similar diagnosis as to the cause of the abnormal noise was made at rest and during exercise on the treadmill in 19 cases, while in the remaining 21 the endoscopic findings during exercise varied from that seen at rest. This included 3 horses in which a diagnosis was made at rest but no abnormalities were detected during exercise. Some of the findings during treadmill endoscopy included laryngeal dysfunction, grades 3, 4 and 5 (22 cases), dorsal displacement of the soft palate (20), epiglottic entrapment (8), epiglottic flutter (4), aryepiglottic fold flutter (4), pharyngeal collapse (3), arytenoiditis (3), vocal cord flutter (3), false nostril noise (2), pharyngeal lymphoid hyperplasia (2), soft palate haemorrhage (1) and positional arytenoid collapse (1).
More than one abnormality was observed during exercise in 7 horses. A complete and correct diagnosis based on the resting endoscopy findings alone was made in 19 (25%) of these 75 cases.
In the 17 horses examined because of poor performance, no abnormalities were detected during treadmill endoscopy that were not evident at rest. None of these 17 horses presented with a history of an abnormal respiratory noise, although one, diagnosed as having grade 4 laryngeal function at rest and exercise, did make a characteristic inspiratory noise during treadmill exercise.
Eight horses were evaluated after surgery for correction of laryngeal hemiplegia, as the post‐operative performance or the amount of respiratory noise present was considered unsatisfactory. Of these, 3 were found to have a satisfactory airway during exercise and other reasons for poor performance were detected; 3 had insufficient abduction; and 2 had intermittent dorsal displacement of the soft palate.
Endoscopy of the upper respiratory tract was found to be a useful technique for evaluating the cause of abnormal respiratory noise in most cases. We concluded that treadmill endoscopy in horses presented for poor performance, without a history of an abnormal respiratory noise, was of little value. The technique, in conjunction with arterial blood gas measurements, was useful in determining the efficacy of surgical treatment of laryngeal hemiplegia.
To determine whether abnormal airway pressures have a role in development of dorsal displacement of the soft palate (DDSP), measurements of tracheal and pharyngeal pressures were correlated with nasopharyngeal morphology in exercising horses. Exercising videoendoscopy and measurement of tracheal and pharyngeal pressures were used in 14 clinically normal horses and 19 horses with intermittent DDSP. The pressure signals were superimposed on the videoendoscope image, and both images were saved simultaneously on a videocassette for slow motion analysis to determine the instant displacement occurred in the respiratory cycle. Horses were submitted to an escalating 8-minute high-speed test with a maximal speed of 14 m/s. Compared with clinically normal horses, horses with intermittent DDSP did not have excessively negative inspiratory pressures during exercise. Eight horses displaced the soft palate during inspiration, 4 horses displaced it during expiration, and 7 displaced it by swallowing. Some horses displaced the soft palate at the beginning of the exercise trial, before reaching maximal speed, some horses displaced it at the peak speed, and some horses displaced it when slowing down. Epiglottic size in horses with DDSP was within normal limits, ruling out epiglottic hypoplasia as a cause of DDSP during exercise. Airway pressures were significantly (P < 0.002) altered after DDSP. Pharyngeal and tracheal inspiratory pressures were less negative, whereas pharyngeal expiratory pressure became less positive and tracheal expiratory pressure became more positive after displacement, suggesting a decrease in airflow and an increase in expiratory resistance in the upper airway.
Six Dutch warmblood horses, ridden by an experienced rider, cantered 3320 m at a speed adapted to the individual horse's anaerobic threshold, under four different conditions: 1, on a firm shell track with the speed varying from 6.5 to 9.4 m/s; 2, on a horizontal treadmill at the same speeds and for the same duration as in test 1; 3, on a horizontal treadmill for the same duration as in tests 1 and 2, but at a 10 per cent higher speed; and 4, on a treadmill at the same speed and for the same duration as in test 1, but at an inclination of 1 to 2 per cent adjusted individually to obtain heart rates similar to those recorded in test 1. On the basis of the heart rates and plasma lactate concentrations, the workload of the horses was significantly greater in the normal exercise test (1) than in the first treadmill test (2). Increasing the speed of the test on the horizontal treadmill by 10 per cent (test 3) resulted in heart rates and plasma lactate concentrations similar to those recorded in test 1. Inclining the treadmill on the basis of the heart rates achieved in test 1 had a less consistent effect than increasing the speed, but imitated a normal exercise test better than the horizontal treadmill test 2.
To determine the effect of bilateral tenectomy of the tensor veli palatini muscle on soft palate and nasopharyngeal function in exercising horses.
5 Standardbreds.
Treadmill videoendoscopy was performed on 5 Standardbreds exercising at 50, 75, and 100% of the speed that produced maximum heart rate; tracheal and pharyngeal pressures were measured before and after surgery. Tenectomy of the tensor veli palatini muscle was performed bilaterally on each horse while under general anesthesia, using a transoral approach.
Peak inspiratory tracheal pressures were significantly (P = 0.016) more negative and there was a trend (P = 0.06) for peak pharyngeal inspiratory pressure to be less negative following bilateral tenectomy of the tensor veli palatini muscle, compared with preoperative values. The rostral half of the soft palate was unstable and collapsed dorsally into the nasopharynx during inspiration, causing partial obstruction of the nasopharynx. The caudal free margin of the soft palate remained ventral to the epiglottis, and dorsal displacement of the soft palate did not occur in any horse.
Bilateral tenectomy of the tensor veli palatini muscle did not cause dorsal displacement of the soft palate in horses while exercising at maximum heart rate, but resulted in collapse of the nasopharynx during inspiration.
Results of our study indicate that the tensor veli palatini muscle functions to support and dilate the nasopharynx during intense inspiratory efforts in horses by tensing the palatine aponeurosis.
To determine the effect of bilateral hypoglossal and and glossopharyngeal nerve block on epiglottic and soft palate position and tracheal and pharyngeal pressures in exercising horses.
5 Standardbreds.
Tracheal and pharyngeal pressures were measured in 5 Standardbreds exercising at the speed at which the horses achieved 50, 75, and 100% of maximal heart rate after bilateral hypoglossal and glossopharyngeal nerve block and without nerve block. Nerve block was achieved by injection of 1 to 2 ml of 2% mepivicaine hydrochloride between the glossopharyngeal and hypoglossal nerves, as they coursed through the medial compartment of the diverticulum of the auditory tube (guttural pouch), using videoendoscopic guidance and an injection apparatus.
Compared with control values, peak inspiratory tracheal pressure was significantly (P = 0.02) more negative, and peak pharyngeal inspiratory pressure was less negative (P = 0.004) after bilateral hypoglossal and glossopharyngeal nerve block. Respiratory frequency was significantly (P = 0.024) lower after nerve block, compared with control values. The epiglottis was unstable and retroflexed through the rima glottis during inspiration after bilateral hypoglossal and glossopharyngeal nerve block. Despite loss of contact between the epiglottis and the caudal free margin of the soft palate, dorsal displacement of the soft palate did not occur.
Loss of contact of the epiglottis with the soft palate did not affect soft palate position, suggesting that when the soft palate is normal, the epiglottis does not function as a support, holding the soft palate in a ventral position. Therefore, epiglottic dysfunction is not solely responsible for intermittent dorsal displacement of the soft palate in horses, and neuromuscular dysfunction involving the hyoepiglotticus muscle, geniohyoideus muscle, or the hypoglossal nerve may cause epiglottic retroflexion in horses.
To determine the effect of bilateral blockade of the pharyngeal branch of the vagus nerve on soft palate function in horses.
5 Standardbreds.
Peak tracheal inspiratory and expiratory pressures and airflow were measured while horses exercised at the speeds corresponding to 75 and 100% of the speed that resulted in maximal heart rate, with and without pharyngeal branch of the vagus nerve blockade. Respiratory frequency-to-stride frequency coupling ratio was measured by correlating foot fall measurements with respiratory frequency. The pharyngeal branch of the vagus nerve was blocked bilaterally as the nerve coursed through the auditory tube diverticulum (guttural pouch) across the longus capitus muscle.
Persistent, reversible dorsal displacement of the soft palate (DDSP) occurred in all horses after nerve blockade, and lasted from 1 to 3 hours; normal nasopharyngeal function returned within 3 hours. Compared with control values, peak expiratory tracheal pressure increased (P = 0.001), expiratory impedance increased (P = 0.007), and minute ventilation decreased (P = 0.04). Respiratory frequency-to-stride frequency coupling ratio decreased (P = 0.009) so that horses took 1 breath/stride without the nerve block and, approximately, 1 breath/2 strides with the block.
DDSP creates flow-limiting expiratory obstruction and may be caused by neuromuscular dysfunction involving the pharyngeal branch of the vagus nerve. It may alter performance by causing expiratory obstruction and by altering breathing strategy in horses.
A repeatable, reversible model of DDSP exists that allows further study of the disease. Dysfunction of the neuromuscular group, pharyngeal branch of the vagus nerve and palatinus and palatopharyngeus muscles, may be implicated in the pathogenesis of clinical DDSP.
Standardised exercise tests were performed at 2 different tracks and on an uninclined treadmill during the same week to determine the influence of exercise surface on different measured variables such as heart rate (HR), blood lactate concentration, packed cell volume, stride frequency, stride length, gait symmetry and regularity and on different derived physiological variables such as the speed at a HR of 200 beats/min (V200), the speed at a blood lactate concentration of 4 mmol/l (V4), the speed at a maximal HR (VHRmax). Five French Trotters, age 3 years, in training for 3 months prior to the test, performed 3 exercise tests on a training track (Test 1), a racetrack (Test 2) and an uninclined treadmill (Test 3). Test 1 utilised 3 steps each of 3 min at speeds of 490, 560 and 630 m/min. Tests 2 and 3 utilised the same speeds and a fourth step in which the horse was accelerated for 30 s to speed approaching maximal. No significant differences (P < 0.05) were found for the physiological and locomotor variables between the 2 tracks. In contrast, there was a significant difference (P < 0.05) for these variables between the tracks and the treadmill, horses showing lower heart rate and blood lactate response, reduced stride frequency and increased stride length and regularity on the uninclined treadmill. We concluded that this standardised exercise test was repeatable on various tracks even when the surface and geometry vary. In contrast, both physiological and locomotor variables were different when comparing the tracks with the uninclined treadmill.
To determine results for horses undergoing a high-speed treadmill examination, including videoendoscopy of the pharynx and larynx before and during exercise, echocardiography before and after exercise, and electrocardiography before, during, and after exercise, because of poor performance.
Retrospective study.
348 horses.
A definitive diagnosis was obtained for 256 (73.5%) horses. One hundred forty-eight horses had dynamic obstruction of the airway during exercise, 33 had clinically important cardiac arrhythmias alone, 22 had a combination of dynamic airway obstruction and clinically important cardiac arrhythmias, 19 had poor cardiac fractional shortening immediately after exercise, 10 had exertional rhabdomyolyis, 15 had clinically apparent lameness, and 9 had other disorders. Thirty-nine of the horses with dynamic obstruction of the airway during exercise had multiple airway abnormalities. Fifty-three horses also had subclinical myopathy
Results suggest that a complete evaluation, including a high-speed treadmill examination, should be conducted in horses with poor performance, regardless or whether horses do or do not have a history of abnormal respiratory noises and particularly if the horses have grade-II or -III left laryngeal hemiplegia.
To describe the clinical findings in 52 racehorses with axial deviation of the aryepiglottic folds (ADAF) and to report outcome in 33 of these horses after either rest or transendoscopic laser excision of aryepiglottic fold tissue.
Retrospective study. Animal or
Racehorses admitted for high-speed treadmill (HST) evaluation of poor performance.
Medical records and videotapes of resting and exercising videoendoscopic examinations were reviewed. Racing performance records and owner or trainer interviews, at least 1 year after HST examination, were used to compare results after either surgical management or rest in 33 horses with ADAF and no other upper-airway abnormalities.
ADAF occurred in 6% of horses evaluated for poor performance. No breed or gender predisposition existed, but horses with ADAF were younger than the overall population evaluated on the HST. Of 52 horses with ADAF, 19 horses had at least one other upper-airway abnormality. There was no apparent association between ADAF and other causes of dynamic upper-respiratory obstruction. Surgical correction was successfully performed in standing or anesthetized horses without complications. When ADAF was the only upper-airway obstruction, 75% of horses that had surgery and 50% of rested horses had objective improvement in performance. Owners and trainers also perceived greater improvement in performance in horses that had surgery.
Whereas surgical management of ADAF is recommended, clinical experience indicated that it is not required to resolve ADAF in all horses. However, owners and trainers of horses that had surgery were more satisfied with outcome than those with horses managed conservatively.
Diagnosis of ADAF can only be made by videoendoscopic evaluation during high-speed exercise. Transendoscopic laser excision of the collapsing portion of the aryepiglottic folds can be performed safely in standing horses and results in resolution of airway obstruction and rapid return to training.
More attention has been given to vocal cord dysfunction (VCD) in the past years. Even though the disease is known since 1983 and was brought to mind at least casuistically through the years, often VCD was not diagnosed as such, being mistaken for bronchial asthma - at times with grave consequences for the patient. VCD causes the acute onset of stridulous respiration with acute dyspnea making the differential diagnosis of asthma quite suggestive. The inspirational stridor and a peracute progression of the disease should cause doubts as to the diagnosis of asthma. We collected case reports and describe the symptoms and diagnostic approaches to VCD as well as showing discriminating findings towards bronchial asthma. We report on five children suffering from VCD (4 girls, 1 boy) aged from 2 to 13 years. It could be shown that VCD is caused by a multifactoral pathomechanism, which has both somatic and psychological aspects. A surprising find was that all of the children were diagnosed with a pathological gastroesophageal reflux, partly in serious dimensions, without showing the typical symptoms such as retrosternal pain, stomach-ache or recurrent vomiting (so called silent reflux). Since there is a multitude of pathomechanisms involved and the disease often coincides with allergic asthma, an individual therapy plan is needed for each patient.
Examination of the long-term histories and clinical findings was performed in 351 horses suffering from recurrent laryngeal neuropathy (RLN) to examine for possible evidence of progression of this disorder. Fifty-two out of 351 cases (15%) had evidence of progression of the degree of laryngeal dysfunction over a median period of 12 months (range 1.5-48 months) with the onset of progression occurring at median age 7 years. In 30 cases, there was both endoscopic (median deterioration of 3 endoscopic grades; range 1-5 grades) and clinical evidence, with 29 (97%) of these horses concurrently developing sudden-onset, abnormal exercise-related respiratory 'noises' and 13 (43%) concurrently reporting reduced exercise performance. In the remaining 22 horses there was solely clinical evidence of RLN progression, including the sudden onset of abnormal exercise-related respiratory sounds in 16 (73%) and the worsening of such sounds in 6 (23%), associated with reduced exercise performance in 13 (59%) of these 22 cases. Endoscopically, 13 (59%) of the latter 22 cases had marked (total or almost total) RLN that did not appear compatible with their previous exercise-performance histories. This evidence of progression of RLN may be of particular significance in disputes concerning horses that are apparently normal at pre-purchase examination but are later shown to have RLN and also in the surgical treatment of less severe cases of RLN.
To evaluate the occurrence of dorsal displacement of the soft palate (DDSP) during high-speed treadmill (HSTM) exercise in racehorses, and determine treatment efficacy relative to the endoscopic findings observed during resting and HSTM endoscopic examination.
Retrospective study. Animals-Ninety-two racehorses (74 Thoroughbreds, 18 Standardbreds).
The signalment, history (clinical and race), treatments, and video recordings made during resting and HSTM endoscopy were reviewed in 92 racehorses that developed DDSP during HSTM exercise. Only horses that completed 3 starts before and after HSTM examination were included in performance-outcome analysis. Statistical associations were made between the independent variables (the historical findings and the resting and HSTM endoscopic findings) and performance outcome.
Forty-five horses (49%) displaced their palate in an uncomplicated manner, whereas the other horses either had another upper-respiratory abnormality in association with DDSP (35) or displaced after swallowing (12). Although respiratory noise was not recorded during HSTM exercise, only 57 horses (62%) that developed DDSP during HSTM examination had a history of abnormal upper-respiratory noise. For the 45 horses that met the criteria for performance outcome analysis, there were no independent variables recorded during resting or HSTM endoscopy that had a significant association with performance outcome. Treatment for DDSP varied by clinician. Overall, 29 horses (64%) had improved average earnings per start after diagnosis and treatment.
Thirty-five horses (38%) that had DDSP during HSTM endoscopy had no previous history of abnormal upper-respiratory noise, and 74 (80%) had no structural abnormalities noted on resting endoscopic examination.
HSTM examination is an excellent tool for diagnosis of DDSP and the manner in which it occurs. DDSP did not occur similarly in all horses, and was often associated with another upper-respiratory abnormality. Thus, it is unlikely that a single treatment can be applied effectively for all horses that experience DDSP. Both surgical and medical treatments can be beneficial in improving a horse's performance after a diagnosis of DDSP is made. Neither resting nor HSTM endoscopic findings were clearly prognostic.
To determine whether the hyoepiglotticus muscle has respiratory-related electromyographic activity and whether electrical stimulation of this muscle changes the position and conformation of the epiglottis, thereby altering dimensions of the aditus laryngis.
6 Standardbred horses.
Horses were anesthetized, and a bipolar fine-wire electrode was placed in the hyoepiglotticus muscle of each horse. Endoscopic images of the nasopharynx and larynx were recorded during electrical stimulation of the hyoepiglotticus muscle in standing, unsedated horses. Dorsoventral length and area of the aditus laryngis were measured on images obtained before and during electrical stimulation. Electromyographic activity of the hyoepiglotticus muscle and nasopharyngeal pressures were measured while horses exercised on a treadmill at 50, 75, 90, and 100% of the speed that produced maximum heart rate.
Electrical stimulation of the hyoepiglotticus muscle changed the shape of the epiglottis, displaced it ventrally, and significantly increased the dorsoventral length and area of the aditus laryngis. The hyoepiglotticus muscle had inspiratory activity that increased significantly with treadmill speed as a result of an increase in phasic and tonic activity. Expiratory activity of the hyoepiglotticus muscle did not change with treadmill speed in 4 of 6 horses.
Findings reported here suggest that contraction of the hyoepiglotticus muscle increases dimensions of the airway in horses by depressing the epiglottis ventrally during intense breathing efforts. The hyoepiglotticus muscle may be an important muscle for dilating the airway in horses, and contraction of the hyoepiglotticus muscle may induce conformational changes in the epiglottis.
Diagnosis and medical intervention for exercise-induced bronchospasm (EIB) are often based on self-reported symptoms, without spirometric confirmation. Inspiratory stridor (IS), a symptom of vocal cord dysfunction (VCD), is frequently mistaken for EIB wheeze. Athletes with exercise IS that spontaneously resolves on activity cessation are suspect for VCD and may not have EIB. This study estimated IS prevalence in elite athletes and determined its relationship to EIB. Subjects/methods: Three hundred seventy athletes (174 female and 196 male subjects) provided a medical history, and underwent spirometry before and after exercise challenge. Exercise challenges were conducted in cold, dry ambient conditions. EIB positive (EIB +) was defined as a > or = 10% postexercise fall in FEV(1). Athletes were monitored for IS during exercise; 78.4% of the athletes in this study (n = 290) were tested on multiple occasions.
EIB was identified in 30% of 370 athletes tested (58 female and 53 male subjects). IS was observed in 5.1% (18 female and 1 male subjects) during exercise and spontaneously resolved in these subjects within 5 min after exercise cessation. Ten IS-positive (IS +) athletes (52.6%) were EIB +, and 8 of these athletes had a previous EIB diagnosis; however, beta(2)-agonist treatment resolved IS in only 2 subjects. Eight of nine IS +/EIB-negative (EIB -) athletes had a previous EIB diagnosis; seven subjects received beta(2)-agonist treatment with no IS resolution. Resting spirometric measurements did not distinguish IS, but postexercise mid-flow (FEF(50)/FIF(50)) ratio > 1.5 was more frequent (33%, p < 0.05) among IS + athletes. The FEF(50)/FIF(50) ratio was higher for IS +/EIB + athletes than for IS -/EIB + athletes (1.97 +/- 1.69 vs 0.81 +/- 0.39, p < 0.05). The postexercise fall in FVC was greater (p < 0.05) for IS +/EIB - athletes (9.2 +/- 5.0%) than for IS-negative (IS -) /EIB - athletes (5.3 +/- 4.3%). No difference in postexercise FEV(1) was identified between IS + and IS - athletes (within EIB + or EIB - groups).
Five percent of athletes were IS +, with EIB comorbidity observed in 53% of these subjects. Misdiagnosis of IS as EIB is common. The lack of a beta(2)-agonist response in combination with postexercise serial spirometry can be useful in excluding solitary IS and confirming EIB diagnosis.
It has long been recognised that the production of abnormal respiratory sounds by horses during exercise is frequently associated with upper airway obstructions. Respiratory acoustic measurements have shown promise in investigation of upper airway disorders in man and, more recently, in horses with experimentally-induced obstructions.
To evaluate sounds from exercising horses with naturally occurring dynamic obstructions of the upper respiratory tract and to compare these with those from normal horses in order to determine whether different obstructions produce characteristic spectral patterns.
The audio signal, airflow and videoendoscopic images were recorded simultaneously during an incremental exercise test on a high-speed treadmill.
Spectral analysis of the audio signal showed marked differences between control and clinically afflicted horses. Dorsal displacement of the soft palate was characterised by a narrow low frequency (20-80 Hz) peak during expiration. Horses with dynamic laryngeal collapse produced inspiratory sounds characterised by a broad band high frequency spectral component in the range 1.1-2.7 kHz.
Spectral analysis of respiratory sounds in horses has potential as a diagnostic technique for field use especially when facilities for high-speed treadmill assessment are not practicable.
Contributes to the understanding of the pathogenesis of dorsal displacement of the soft palate during exercise so that management of this condition could be enhanced.
That the thyrohyoid muscles play an important role in the stability of the laryngo-palatal relationship and that dysfunction of these muscles leads to dorsal displacement of the soft palate (DDSP) during exercise.
Ten horses were exercised on a high-speed treadmill under 4 different treatment conditions: control conditions (n = 10), after resection of thyrohyoid muscles (TH, n = 10), after sham-treatment (n = 5), or after restoration of function of the thyrohyoid muscles with surgical sutures (prosthesis-treatment, n = 6). During trials, the following determinations were made: videoendoscopy of the upper airway, gait frequency and pharyngeal and tracheal static pressures.
None of the 10 horses developed DDSP during 2 separate treadmill-exercise trials under the control conditions. Seven of the 10 horses developed DDSP after resection of the TH muscles, 4 of 5 of these horses still experienced DDSP after sham-treatment, but 5 of 6 horses no longer experienced DDSP at exercise after the prosthesis-treatment. There were significant anomalies in airway pressures, respiratory frequency, and occurrence of DDSP in both the TH resection and sham-treatment conditions compared to control conditions. In contrast, no statistical differences were noted in any of the parameters measured between the prosthesis-treatment and control conditions.
That the function of the TH muscles is important to the stability of the laryngo-palatal relationship and plays a role in the pathophysiology of exercise-induced DDSP.
Management of horses with DDSP could be enhanced by restoring the function of the TH muscles.
OBJECTIVE: To describe a treatment strategy for paradoxical vocal-cord dysfunction (PVCD) as it applies to an athletic population. BACKGROUND: Paradoxical vocal-cord dysfunction has been identified as a cause of dyspnea and stridor in athletes. The basic element of PVCD is an inappropriate closure of the vocal cords during respiration, resulting in airway obstruction. This condition is familiar to speech-language pathologists and otolaryngologists yet remains poorly understood in the sports medicine community. Treatment strategies are even less understood. A therapeutic exercise program designed to promote diaphragmatic breathing may allow an athlete to gain control during episodes of dyspnea. Elimination of contributing or concomitant conditions is critical to resolution of the condition. DESCRIPTION: The treatment of PVCD requires an understanding of the pathoanatomy of the condition. The focus of the exercise program is on relaxation of the larynx and conscious activation of the diaphragm and abdominal muscles during respiration. The athlete must have a sense of laryngeal control while performing the exercises. In addition, the patient and practitioner must realize the amount of neuromuscular reeducation required to change breathing patterns. CLINICAL ADVANTAGES: This therapy may allow the athlete to gain control over episodic dyspnea, participate in athletic activities with fewer complications, and, perhaps, reduce or eliminate medications prescribed to treat suspected bronchospasm.
There has been no objectively assessed case-control study of the efficacy of surgery to correct dorsal displacement of the soft palate (DDSP) previously reported.
Composite surgery has a beneficial result on racing performance in horses affected with DDSP as compared to a matched control population.
Race records were obtained for 53 racing Thoroughbreds which underwent composite staphylectomy, sternothyrohyoideus myectomy and ventriculectomy for correction of idiopathic DDSP at the University of Bristol between 1990 and 1996. Each surgical case was matched for age, sex and training yard with 2 control horses. The racing performance, based on prize money won, of surgical cases and control horses were compared for 3 races run before and after the date of surgery.
Ninety-two percent of the surgical cases returned to racing after surgery. There was a significant increase in earnings of the surgical group before and after surgery (P = 0.011), but there was no significant difference in earnings of the control group before and after the date of surgery (P = 0335). Sixty percent of the surgical group had higher earnings after surgery than before, compared to 40% of controls. When horses which underwent surgery were ranked relative to their 2 matched controls, surgical cases did not significantly change in rank (P = 033), whereas control horses significantly decreased in rank (P = 0.012). Additionally, horses within the surgical group were more likely (P < 0.01) to start in 3 post operative races than those in the control group.
Composite surgery had a beneficial effect on racing performance of horses afflicted with idiopathic DDSP, and further studies to evaluate objectively the usefulness of other surgical techniques are warranted.
The purpose of the study was to describe the prevalence of upper airway abnormalities and establish if any significant associations existed between study variables and the two most frequently identified disorders; axial deviation of the aryepiglottic folds and dorsal displacement of the soft palate. The clinical records and video-recordings of all horses referred for upper respiratory tract evaluation during high-speed treadmill videoendoscopy between November 1997 and September 2003 were reviewed. Of 291 horses included in the study, 265 underwent resting endoscopy and 42% (112/265) had a recognised abnormality. More than one abnormality was identified in 49% of horses. In general, horses referred specifically for evaluation of a respiratory tract noise were more likely to have an abnormality detected during exercise than those referred for high-speed treadmill videoendoscopy for poor performance (82% versus 49%). Axial deviation of the aryepiglottic folds (105/192, 55%) was the most common abnormality identified, followed by dorsal displacement of the soft palate (74/192, 39%) and idiopathic left laryngeal hemiplegia (65/192, 34%). Other abnormalities identified included arytenoid collapse, vocal fold collapse, dynamic pharyngeal collapse, epiglottic fold entrapment, epiglottic retroversion, rostral displacement of the palatopharyngeal arch and right laryngeal hemiplegia. In horses with axial deviation of the aryepiglottic folds there was a significant association between the increasing severity of the deviation and the increasing number of abnormalities detected. There were no other associations found. High-speed treadmill videoendoscopy is an important component of the evaluation of poor performance, particularly in horses with a history of respiratory noise. The occurrence of multiple abnormalities in a large proportion of horses suggests that high-speed treadmill videoendoscopy should be recommended, where possible, to make an accurate diagnosis, advise on appropriate treatment options and provide a prognosis for affected horses.
The reliability of diagnoses of obstructive conditions of the upper respiratory tract (URT) based on examinations performed at rest vs. at exercise is controversial.
To compare diagnosis of URT by endoscopy at rest with that achieved during high-speed treadmill exercise (HSTE).
Endoscopy of URT at rest, when performed in isolation from other simpler techniques is unreliable in the prediction of dynamic respiratory obstructions.
Endoscopic findings of 600 Thoroughbred racehorses during quiet breathing were compared with findings during high-speed treadmill exercise. Other parameters were also assessed for their specificity in diagnosis.
Endoscopy of the resting horse showed low sensitivity (0.15) in the diagnosis of dorsal displacement of the soft palate (DDSP) and palatal instability (PI). When endoscopy and reported noises were taken together there was still a 35% misdiagnosis rate. Although there was significant association between resting laryngeal function score (LFS) and dynamic vocal cord and/or arytenoid cartilage collapse at exercise, 19% of horses with a grade 4/5 LFS were able to attain and maintain full abduction during exercise and 7% of those with 'normal' grades 1 or 2 LFS at rest showed dynamic laryngeal collapse when exerted. Sensitivity of the diagnostic model was greatly increased (80%) when a history of inspiratory noise and palpable intrinsic muscle atrophy were included.
Endoscopy of the upper respiratory tract of static horses is unreliable in the diagnosis of dynamic obstructions of the URT and should not be used in isolation in surgical decision-making or in the assessment of horses at the time of sale.
The soft palate (palatum molle) as a cause of dyspnoea in two racehorses
- Quinlan
Vocal cord dysfunction in children and adolescents
- Ahrens
Studies of Dorsal Displacement of the Soft Palate in Thoroughbred Racehorses
- S H Franklin
The role of treadmill endoscopy in the diagnosis of dynamic obstruction of the upper airway
- Hackett
Correlation between standing endoscopic examinations and those made during high speed exercise in horses - 150 cases
- Parente
The treatment of dorsal displacement of the soft palate by thermal cautery: a review of 252 cases Proceedings of the
- R M Ordidge