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Dynamic respiratory videoendoscopy in ridden sport horses: Effect of head flexion, riding and airway inflammation in 129 cases
Equine Veterinary Journal
Abstract
Dynamic upper airway obstruction (UAO) is a cause of respiratory noise and sometimes poor performance in sport horses. Riding, head flexion and airway inflammation may impact upper respiratory tract stability during exercise.
To evaluate upper airway mechanical behaviour in ridden sport horses using overground endoscopy and the effect of head flexion, rider intervention and underlying airway inflammation on the pharynx and larynx.
Resting and exercising videoendoscopic recordings during ridden exercise were obtained in 129 sport horses referred mainly for respiratory noise, poor performance or routine evaluation. The rider modified poll flexion and way of riding during the test and associated changes in UAO were recorded. Presence of upper and lower airway inflammation was also assessed.
Dynamic UAO was diagnosed in 91% (64/70) of the horses referred for respiratory noise and in 71% (29/41) of horses referred for poor performance. Pharyngeal instability was the most frequently diagnosed problem. However, differences were observed between dressage horses and showjumpers. Rider interaction and head flexion exacerbated upper airway instability and promoted the occurrence of complex UAO. Both lower airway inflammation and pharyngeal lymphoid hyperplasia were associated with pharyngeal instability, but not with any other UAO.
Rider intervention during ridden exercise (i.e. the various movements a horse might be asked to perform) influences upper airway morphology and function and, in cases of upper airway dynamic obstruction, can contribute to increasing laryngeal and/or pharyngeal instability in sport horses.
As these are changes that would not usually be seen with treadmill videoendoscopy, ridden videoendoscopy should be the preferred method for evaluation of the upper airway in sport horses.
... In pleasure horses with PI and concurrent SEA, PI may resolve after the inflammation of lower airways has been treated [7]. Also, in sport horses with concurrent PI and MEA, as well as those with nasopharyngeal collapse and MEA, a similar outcome after anti-inflammatory treatment has been reported [11]. The exact basis of this connection is still not fully understood; however, the impact of increased negative pressure due to lower respiratory tract obstruction and the spreading of the inflammatory process is suspected [6]. ...
... Upper airway diseases, such as rhinitis, chronic rhinosinusitis, and nasal polyps, have been linked to concurrent lower airway disorders like asthma, chronic obstructive disease, cystic fibrosis, and obstructive sleep apnea [3][4][5]. A similar link has been postulated in equine medicine [6][7][8][9][10][11][12][13], predominantly between equine asthma (EA) and various lower and upper airway diseases. EA is the most common equine lower airway disease associated with an increase in the negative pressure in the airways due to chronic airway inflammation, bronchospasm, excessive mucus secretion, and airway remodeling [14]. ...
... Only a positive but weak correlation was observed in SEA, which may suggest that SEA horses produce such an excess of mucus in the trachea that, during expectoration [17], it also accumulates in the nasopharyngeal area, affecting the local mucus amount. This smaller number and the strength of correlations between the amount of mucus in the studied locations, compared to what was assumed in the third hypothesis, may reflect a certain independence between upper and lower airway inflammation [11,28], especially since Koblinger et al. noted a similar lack of correlation [20]. However, even if the PLH grade does not correlate with tracheal mucus grade, some associations may still be investigated. ...
With the increasing awareness of the “united airway disease” theory, more horses, not only sport horses but also pleasure horses, undergo detailed examinations of the respiratory tract. Using endoscopy, equine asthma (EA) is most commonly diagnosed in the lower airway, while pharyngeal lymphoid hyperplasia (PLH) is common in the upper airway. Grading EA as mild–moderate (MEA) and severe (SEA), this study aims to compare the co-occurrence and investigate the possible relationship between the clinical symptoms and endoscopic signs of MEA/SEA and PLH in pleasure horses. In this retrospective study, 80 out of 93 pleasure horses suspected of EA were enrolled and underwent a standardized protocol for a complete airway examination, including resting endoscopy with mucus accumulation assessment and cytology. The obtained results were scored and analyzed. In the studied pleasure horses, PLH co-occurred more frequently in horses with EA than without (p < 0.0001) and more in horses with SEA than with MEA (p = 0.025). However, when EA and PLH co-occurred, the severity of the clinical symptoms of EA did not increase (p > 0.05). In both EA and PLH, the amount of tracheal and nasopharyngeal mucus increased with the severity of the disease; however, it was positively correlated (ρ = 0.33; p = 0.02) only in SEA horses. In conclusion, it is likely that EA is often accompanied by PLH; however, PLH did not play a role in increasing the severity of EA’s clinical symptoms. The role of the severity of accumulated mucus in the lower and upper airways when EA/PLH co-occur requires further research to confirm the morphological and functional unity of the respiratory tract, aligning with the concept of “united airways disease”.
... Additionally, NPC can be exacerbated with poll flexion, as demonstrated in Standardbreds, Warmbloods, trotters and sport horses. 2,[10][11][12][13][14][15] This is not an uncommon finding for many dynamic upper airway conditions due to a further drop in the negative peak inspiratory tracheal pressures and an increased upper airway impedance associated with poll flexion. [11][12][13][16][17][18] Increased soft tissue compliance during head flexion may also contribute to the dynamic collapse of the nasopharyngeal components during negative inspiratory pressures. ...
... 2,[10][11][12][13][14][15] This is not an uncommon finding for many dynamic upper airway conditions due to a further drop in the negative peak inspiratory tracheal pressures and an increased upper airway impedance associated with poll flexion. [11][12][13][16][17][18] Increased soft tissue compliance during head flexion may also contribute to the dynamic collapse of the nasopharyngeal components during negative inspiratory pressures. 11,14 The dorsoventral pharyngeal diameter is the smallest when the horse's head is at an elevated and flexed position based on resting endoscopy and radiographic evaluation. ...
... As discussed earlier, head and neck flexion increases upper airway impedance and may accelerate neuromuscular fatigue. [11][12][13][16][17][18] Additionally, in humans, there is a strong correlation between obesity and upper airway collapsibility due to increased peripharyngeal fat deposition leading to pharyngeal wall narrowing or reduction in wall tension. 32 Central adiposity also plays a role via reductions in lung volume with a resultant increase in mechanical loads on the respiratory system, as well as through modulations in upper airway neural responses. ...
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.
... Different authors reported that inflammation of the nasopharyngeal region, visible at endoscopy as pharyngeal lymphoid hyperplasia (PLH), may impair the function of pharyngeal mechanoceptors [25] and contribute to the neuromuscular dysfunction and instability of the upper airway, predisposing horses to the onset of DUAOs, such as DDSP, NPC and ER [8,9,[26][27][28][29][30]. Recently, the "one airway, one disease" concept, long known in human medicine and describing a relationship between the health of the upper and lower airways, has also been proposed and investigated in equine medicine [31]. ...
... Different authors reported that inflammation of the nasopharyngeal region, visible at endoscopy as pharyngeal lymphoid hyperplasia (PLH), may impair the function of pharyngeal mechanoceptors [25] and contribute to the neuromuscular dysfunction and instability of the upper airway, predisposing horses to the onset of DUAOs, such as DDSP, NPC and ER [8,9,[26][27][28][29][30]. Recently, the "one airway, one disease" concept, long known in human medicine and describing a relationship between the health of the upper and lower airways, has also been proposed and investigated in equine medicine [31]. Lower airway inflammation (LAI) has been associated with DUAO [9,28,[30][31][32][33], probably because of the increased negative pressure driven by lower respiratory tract obstruction and increased respiratory impedance and work of breathing, which may impair upper airway patency and accelerate the onset of neuromuscular fatigue [30,31,[33][34][35]. Another proposed theory is that DUAO may predispose horses to lower airway disease via unknown mechanisms [9,33]. ...
... Different authors reported that inflammation of the nasopharyngeal region, visible at endoscopy as pharyngeal lymphoid hyperplasia (PLH), may impair the function of pharyngeal mechanoceptors [25] and contribute to the neuromuscular dysfunction and instability of the upper airway, predisposing horses to the onset of DUAOs, such as DDSP, NPC and ER [8,9,[26][27][28][29][30]. Recently, the "one airway, one disease" concept, long known in human medicine and describing a relationship between the health of the upper and lower airways, has also been proposed and investigated in equine medicine [31]. Lower airway inflammation (LAI) has been associated with DUAO [9,28,[30][31][32][33], probably because of the increased negative pressure driven by lower respiratory tract obstruction and increased respiratory impedance and work of breathing, which may impair upper airway patency and accelerate the onset of neuromuscular fatigue [30,31,[33][34][35]. Another proposed theory is that DUAO may predispose horses to lower airway disease via unknown mechanisms [9,33]. ...
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.
... Leistungsschwäche kombiniert mit anderem Vorbericht | Complaint of Poor Performance associated to respiratory or musculoskeletal problems Pferde, welche weder ein Atemgeräusch unter Belastung noch Ruhebefunde aufweisen, trotzdem eine Erkrankung der oberen Atemwege und das Vorhandensein eines Geräusches oder eines Ruhebefundes erlaubt keine exakte Diagnose (Witte et al. 2011, Davison et al. 2017). Eine wirkliche Beurteilung der klinischen Relevanz ist nicht hundertprozentig möglich (Kannegieter und Dore 1995, Martin et al. 2000, Franklin et al. 2006, Davidson et al. 2010, Davidson und Parente 2011, Van Erck-Westergren et al. 2013), da die Korrelation zwischen Ruhe-und Belastungsbefunden an Larynx und Pharynx recht schwach ist(Sullivan und Parente 2003, Van Erck 2011, Barakzai und Cheetham 2012, Davison et al. 2017. Ein einzelner Befund in Ruhe schließt zudem ein Vorhandensein von anderen dynamischen Stenosen der oberen Atemwege unter Belastung nicht aus, da, wie gesagt, nicht selten mehrere Pathologien gleichzeitig bestehen(Allen et al. 2006, Davidson und Parente 2011, Van Erck 2011, Mirazo et al. 2014.Daher sollte für die Bewertung der klinischen Relevanz eine endoskopische Untersuchung unter Belastung durchgeführt werden(Parente 1996, Davidson et al. 2010, Davidson und Parente 2011, Van Erck 2011, Barakzai und Cheetham 2012, Van Erck-Westergren et al. 2013, Melkova et al. 2016, Parente 2018, Wysocka und Kluciński 2018. ...
... Eine wirkliche Beurteilung der klinischen Relevanz ist nicht hundertprozentig möglich (Kannegieter und Dore 1995, Martin et al. 2000, Franklin et al. 2006, Davidson et al. 2010, Davidson und Parente 2011, Van Erck-Westergren et al. 2013), da die Korrelation zwischen Ruhe-und Belastungsbefunden an Larynx und Pharynx recht schwach ist(Sullivan und Parente 2003, Van Erck 2011, Barakzai und Cheetham 2012, Davison et al. 2017. Ein einzelner Befund in Ruhe schließt zudem ein Vorhandensein von anderen dynamischen Stenosen der oberen Atemwege unter Belastung nicht aus, da, wie gesagt, nicht selten mehrere Pathologien gleichzeitig bestehen(Allen et al. 2006, Davidson und Parente 2011, Van Erck 2011, Mirazo et al. 2014.Daher sollte für die Bewertung der klinischen Relevanz eine endoskopische Untersuchung unter Belastung durchgeführt werden(Parente 1996, Davidson et al. 2010, Davidson und Parente 2011, Van Erck 2011, Barakzai und Cheetham 2012, Van Erck-Westergren et al. 2013, Melkova et al. 2016, Parente 2018, Wysocka und Kluciński 2018. ...
... Eine wirkliche Beurteilung der klinischen Relevanz ist nicht hundertprozentig möglich (Kannegieter und Dore 1995, Martin et al. 2000, Franklin et al. 2006, Davidson et al. 2010, Davidson und Parente 2011, Van Erck-Westergren et al. 2013), da die Korrelation zwischen Ruhe-und Belastungsbefunden an Larynx und Pharynx recht schwach ist(Sullivan und Parente 2003, Van Erck 2011, Barakzai und Cheetham 2012, Davison et al. 2017. Ein einzelner Befund in Ruhe schließt zudem ein Vorhandensein von anderen dynamischen Stenosen der oberen Atemwege unter Belastung nicht aus, da, wie gesagt, nicht selten mehrere Pathologien gleichzeitig bestehen(Allen et al. 2006, Davidson und Parente 2011, Van Erck 2011, Mirazo et al. 2014.Daher sollte für die Bewertung der klinischen Relevanz eine endoskopische Untersuchung unter Belastung durchgeführt werden(Parente 1996, Davidson et al. 2010, Davidson und Parente 2011, Van Erck 2011, Barakzai und Cheetham 2012, Van Erck-Westergren et al. 2013, Melkova et al. 2016, Parente 2018, Wysocka und Kluciński 2018. ...
Poor performance is a common complaint in equine veterinary practice and can pose a diagnostic challenge to the equine practitioner as the triggering pathology can be located in almost every organ system and very often more than one problem causes the performance deficit. Most studies regarding this topic have been conducted on racehorses with poor racing performance. Due to the very different demands the Olympic disciplines present to the equine athlete compared to racing, performance limiting medical conditions manifest in different ways. For example, sport horses rather present with problems under the rider as difficulties to collect or to keep contact with the bit or difficulties performing specific maneuvres in dressage or making distances or sharp turns in the show-jumping ring. The most common medical conditions affecting horses with a complaint of performance problems are respiratory diseases and orthopedic problems like subtle lameness or back pain. However, also cardiac, neurologic and muscular problems, as well as metabolic and hormonal imbalances can limit the performance potential of the equine athlete. For diagnosing the cause of poor performance, a detailed anamnesis and thorough clinical examination are of utmost importance. Further diagnosis is then based on the results of the anamnesis and the clinical exam. Besides an examination at rest an examination during and after exercise is important to detect any abnormalities that may not be present at rest and to evaluate the clinical significance of any findings. This review shall give an overview about the causes and manifestations of poor performance in the horse with special focus on warmblood sport horses competing in dressage, show jumping and eventing. Moreover, diagnostic possibilities in the field are discussed.
... Furthermore, the present study found that in general, flexion of the head and neck does contribute to an increased risk of dynamic structural disorders and UAO, in agreement with previous studies on this matter [16,17,22]. The dynamic structural disorders found in this study may be linked to a reduction in both pharyngeal and laryngeal diameter [12,15], as this has also been found in previous studies [33]. A significant increase in the number of dynamic structural disorders was found during trot and canter compared with halt and walk. ...
... Because of the high percentage of affected horses, it was not possible to make any statistical evaluation on the influence of the presence of PLH on rein tension or dynamic structural disorders. Previous studies have suggested a connection between PLH and UAO caused by a theoretical neuromuscular dysfunction of the pharynx [33,34], and it could also be theorized that horses with PLH would have higher rein tension because of discomfort when flexing the neck. PI 12 19 17 14 62 cNPC 3 8 6 4 21 MDFA 3 3 4 5 15 dNPC 0 4 5 3 12 Abbreviations: cNPC, circumferential nasopharyngeal collapse; dNPC, dorsal nasopharyngeal collapse; MDFA, medial deviation of the aryepiglottic folds; PI, palatal instability. ...
... The dynamic upper airway disorders diagnosed in this study were (listed in order of frequency): PI, cNPC, MDAF, and dNPC. These findings do not correspond with results in previous studies describing the frequency of the different UAOs observed in sport horses [18,33,35,36]. However, earlier studies included horses with a history of respiratory noise or poor performance, making comparison with the findings of the present study of healthy, highperformance horses difficult. ...
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.
... These were generally associated with the improvement in respiratory health, associated with a reduction in lower airways contamination and inflammation [2]. This airway inflammation or inflammatory airways disease (IAD) had been statistically linked with cases of PI [8]. ...
... After this, they were often willing to move on again. In addition galloping on an increasing incline was accepted as a means of increasing the negative pressures being applied to the upper airways in exercising horses and thus could promote PI [12] and UAO [8]. ...
... In a recent study of 129 sports horses that presented for respiratory noise, poor performance or routine evaluation PI was diagnosed in 91% (64/70) of the horses referred for respiratory noise and in 71% (29/41) of horses referred for poor performance [8]. In the past this condition was thought to be only associated with racehorses. ...
... To allow comparison between studies and maximise sample size, data from horses with a grade of 3 on a 5-point scale [12] were merged with grade 2 on the 4-point consensus scale [4]. All studies, with the exception of [13] and [14], made use of a high-speed treadmill for dynamic evaluation of the airway. Horses were allowed to train on the treadmill prior to testing. ...
... Horses were allowed to train on the treadmill prior to testing. Two studies [13] and [24] made use of a portable videoendoscope (DNS, DR-V2) a to obtain images of horses under saddle in the horses' usual working environments. As all studies were reports of exercising populations, we judged that selective reporting within studies was unlikely. ...
... A total of 6,264 studies matching the search terms were initially identified. Refining the search to include only reports meeting the selection criteria produced 12 studies [5,10,11,13,14,[18][19][20][22][23][24][25] that included 2272 horses (Fig 1). Mean (s.d.) age of the population was 6.3 (1.9) years with a range from 1 to 20 years. ...
Background
Resting endoscopy has commonly been used as a method to predict laryngeal function at exercise.
Objectives
To perform a meta‐analysis to determine the sensitivity and specificity of resting laryngeal endoscopy to predict clinical recurrent laryngeal neuropathy at exercise.
Study design
Meta‐analysis.
Methods
Manuscripts were included if data were available for both resting and exercising airway function on all or a subset of horses. Normal resting endoscopy was defined as laryngeal grades 1 or 2 on a 4‐/7‐point scale or 1, 2 or 3 on a 5‐point scale and normal dynamic endoscopy as a dynamic laryngeal grade A.
Results
Twelve studies including 1827 horses were evaluated. A small proportion of horses with grade 1 or grade 2 laryngeal function at rest, 3.5 and 11.9%, respectively, were identified as having abnormal laryngeal function at exercise. Within the horses with grade 3 laryngeal function at rest, 16% were classified as grade A, 26.4% as grade B and 57.6% as grade C at exercise. Worsening subgrades within resting grade 3 demonstrated an increasing proportion of complete or partial paralysis at exercise. The sensitivity and specificity of resting endoscopy was 74.4 and 95.1%, respectively, and the positive and negative predictive values were 85.6 and 90.5% respectively.
Main limitations
Use of two separate grading systems for evaluating resting laryngeal function. Other forms of dynamic airway collapse were not evaluated.
Conclusions
Resting endoscopy is sensitive and highly specific for predicting laryngeal function at exercise. Dynamic endoscopy is important to assess multiple causes of airway collapse.
... A lehetséges dinamikus típusú felsõ légúti mûködés zavara még a hang szalagkollapszust (vocal cord collapse -VCC) is. Ez az elváltozás gyakran kiegészítõ jelenség az egyéb megbetegedések mellett (48). ...
... Hátránya azonban, hogy kellõ hozzászoktatás után a futópadon a lovat nem érik olyan stresszhatások, mint például egy galoppversenyen, és nem ül rajta zsoké/lovas, aki befolyásolná a szabad mozgást. A terhelés jellege tehát összességében nem egyezik meg a tüneteket kiváltó napi terheléssel, és sokszor emiatt nem jelennek meg azok az elváltozások, amelyek lovaglás során a teljesítmény csökkenését okozzák (48). A futópados terhelés és a hagyományos terepen végzet munka között különböznek az adott sebességhez tartozó pulzus-, vérlaktátszint-, lépéshossz és lépésfrekvencia-értékek is. ...
... A lovak vizsgálat elõtti és alatti munkabírása között nincs jelentõs különbség (38). A lovas alatti munka során készített felvétel esetén adat nyerhetõ arról is, hogy mennyire játszik szerepet a betegség kialakulásában a lovas, a túlzott szárra állítás (a nyak beszegése) (48). A lágyszájpadinstabilitás és a garatkollapszus, de a hangszalagok és a kannaporcok kollapszusa is gyakran csak szárra állítás során fi gyelhetõ meg. ...
A szerzők irodalmi adatok alapján bemutatják a felső légutak élettanát és működését lovakban. Tárgyalják a felső légutakat érintő kóros – többnyire térszűkítő – elváltozásokat, amelyek gyakran megváltozott hangképzéshez és a teljesítmény romlásához vezetnek. Az elváltozások közül részletesen bemutatják az idiopatikus baloldali gégebénulást, a lágyszájpad dorsalis helyzetváltozását, valamint a rostralis és dorsalis pharyngealis kollapszust, továbbá a ritkábban előforduló elváltozások közül az aryepiglottikus redők tengelyirányú kitérését, a gégefedő beékelődését, a gégefedő visszahajlását és a hangszalag kollapszusát. A vizsgálati módszerek közül ismertetik az álló helyzetű endoszkópos vizsgálatot, a futópados módszert és a fejre szerelhető terepi viszonyok között is jól alkalmazható overground endoszkópot.
... Reports of dynamic airway obstructions are primarily concerned with racehorse populations, whereas reports on such obstructions in sport horses are scarce [9]. Van Erck-Westergren [10] evaluated the effect of head flexion, riding, and airway inflammation in sport horses. For further investigation of this topic, the present report documents 19 cases of dynamic URT obstructions using OE. ...
... Based on our results, in complex cases where grade C ACC, VCC, and DDSP occur simultaneously, alternatively a ventriculocordectomy could sufficiently decrease the negative pressure and therefore might prevent the soft palate from having a tendency to become displaced dorsally. A characteristic abnormal respiratory noise of racehorses during DDSP is the gurgling sound [20], but the functional disease can also stay silent or occasionally generate coughing [10]. In our case series, each horse was coughing during DDSP, which could be explained by hypersensitivity of the airways due to URT and/or LRT inflammation. ...
... In our case series, each horse was coughing during DDSP, which could be explained by hypersensitivity of the airways due to URT and/or LRT inflammation. The absence of the gurgling sound in sport and pleasure horses might be explained by the fact that their expiratory airflow does not reach a speed at which the free border of the soft palate resonate in the same way like in racehorses, as reported in the study by Van Erck–West- ergren [10]. LHP is a distal axonopathy of the recurrent laryngeal nerve with clinical manifestation predominantly (95%) on the left side. ...
Any factors that increase negative pressure in the upper respiratory tract (URT) can influence its mechanics. The aim of this report was to describe the results of URT diagnostic evaluation with overground endoscopy in sport and pleasure horses. The URT and plasma lactate levels were evaluated during rest and during overground endoscopic examination in 19 cases. Horses performed their normal training session. When history and clinical examination suggested a lower airway obstruction, we performed bronchoalveolar lavage. Dorsal displacement of the soft palate (DDSP) was diagnosed in 8 of 19 horses, which might have developed secondary to URT or lower respiratory tract inflammation or obstruction. DDSP was also detected at rest in four cases. Laryngeal hemiplegia (LHP) was diagnosed in 15 of 19 horses, 11 of which were complex cases with other types of URT obstructions. Severe pharyngeal collapse (PHC), suspected already at rest, was visible in two cases during exercise. In contrast, PHC diagnosed with nasal occlusion at rest in two cases was fully compensated under the rider. Plasma lactate levels significantly decreased during exercise. All DDSP cases were suspected to be of inflammatory or obstructive origin, which is different from findings in racehorses, where extrinsic causes are more common. Resting endoscopic examinations were sensitive in cases of obstructive origin. LHP and PHC could not be predicted on the basis of findings at rest, and increased neuromuscular activity during exercise could compensate for the problem in less severe cases. Decreased levels of lactate could be explained by the increased clearance during exercise.
... This is of course unless there is a disruption of the seal during exercise which does occur during periods of PI and IDDSP. It had also been reported that emerging data supported a role for chronic microaspiration in some forms of pulmonary pathology [32]. A possible relationship between the chronic microaspiration of oral material during periods of PI and DDSP on the linings of the nasopharynx, larynx and major airways had been suggested but not yet investigated [3]. ...
... A possible relationship between the chronic microaspiration of oral material during periods of PI and DDSP on the linings of the nasopharynx, larynx and major airways had been suggested but not yet investigated [3]. However a statistical association between PI and inflammatory airways disease IAD in sports horses had been demonstrated [32]. Another study in trotters found that in 42% of the DDSP afflicted group, a syndrome of tracheal inflammation STI was evident and that 71% of this group had bacteria isolated at greater than10(5) CFU/ml [33]. ...
It had been suggested that obligate nasal breathing had evolved to enhance a horses ability to detect predator scents whilst grazing. The singular opening of the vomeronasal organ into the nasal cavity had certainly developed in a manner that supported this form of breathing and thence theory. A horses ability to carry feed in its mouth, without this being drawn into the airway during flight, was another theory put forward to explain this obligation.
The horse as a species is heavily reliant on flight as a means of defence and thence survival. Any reduction in nasopharyngeal patency would logically compromise a horses ability to maintain acceleration and thence its ability to evade a predator. The likelihood that a horse would elect to supplement a compromised nasal air supply with orally inspired air whilst fleeing a predator, seemed logical. Nasopharyngeal and upper tracheal intraluminal pressure measurements recorded during periods of intermittent dorsal displacement of the soft and experimentally induced palatal instability indicated that air was being acquired orally in these situations.
... A further example for the interplay between the upper and lower airway disorders had been demonstrated in sport horses, where it was concluded that the palatal instability or nasopharyngeal collapse was significantly affected not just by the presence of the upper (pharyngeal), but the lower airway inflammation as well [11]. Finally, it was suggesteddin our preliminary studydthat equine asthma may cause dorsal displacement of the soft palate (DDSP) [12]. ...
... In the case series of the present study, each horse was coughing during DDSP. The absence of the typical gurgling sound in racehorses might be explained by the fact that their expiratory airflow in the cases of sport and pleasure horses does not reach a speed at which it could make the free border of the soft palate resonate, as this has been described already in literature [11]. ...
It is important to treat the upper and lower respiratory tracts as a single unit, as lower respiratory tract diseases can often cause upper respiratory functional disorders, whereas upper respiratory obstructions could be a factor in lower respiratory problems. The present study aimed to investigate the hypothesis that asthmatic diseases may be an underlying cause of dorsal displacement of the soft palate in horses. Pleasure or sport horses (n = 57) with a history of asthmatic disease were incorporated in the study. All horses were examined in the exacerbation phase of the asthmatic disease. Bronchoalveolar cytology and tracheal lavage bacteriology were performed in all cases. The upper respiratory tract was evaluated at rest in all horses and during exercising endoscopy in 11/57 with severe equine asthma. Binomial tests with P ≤ .05 significance were used to establish estimated intervals of the measured frequencies of dorsal displacement of the soft palate (DDSP) occurring in the studied groups. It was observed that more than 60% of horses with mild or moderate equine asthma and more than 79% of horses with severe equine asthma are presented with DDSP during resting endoscopy examination. During the exercising endoscopy, DDSP was detected in all cases of severe equine asthma. These findings support the proposed hypothesis that DDSP was common in horses with equine asthma. Both increasing negative pressure in the airways due to bronchoconstriction and inflammatory processes could be factors in the development of DDSP. The consequent step would be to investigate the same population of horses in the remission phase of the equine asthma.
... There were however other factors that were conjectured to encourage a horse to open its mouth whilst being ridden such as upper airways dysfunctions. 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]. ...
... 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.
... In the authors opinion this was typical of the changes seen in cases of chronic PI [9,11]. In the absence of any other etiological avenues, the possibility that PI [9] or pharyngeal instability [12] with resultant UAO may have been impacting negatively on the horse's ability to experience sufficient paradoxical sleep was discussed with the owner. It was then agreed that the horse would undergo an oral palatopharyngoplasty (OPP) [13] procedure in an attempt to reduce the incidence of this instability. ...
... In equids there had been considerable research into upper airways collapse during exercise [10] but non to date on the possibility that similar obstructions could occur during recumbent or deep sleep. Pharyngeal instability or PI during exercise had been frequently diagnosed in both racing [10] and sport horses [12] and was often associated with periods of decreased pharyngeal muscular tone or tension. During deep or paradoxical sleep muscular tone including pharyngeal was at its lowest [4]. ...
A six year old thoroughbred gelding presented with a two year history of somnolence and altered behavior of two years duration. In the three months immediately preceding presentation episodes of sleep attacks and accompanying sleep terrors were observed. There had been no evidence of recumbent or paradoxical sleep during this period. An examination of the upper airways revealed evidence of palatal instability (PI). An oral palatopharyngoplasty (OPP) was performed to reduce this instability (PI). Clinical observations in the eight months following surgery suggested a possible link between PI, upper airways obstruction (UAO) and a horse’s ability to achieve adequate paradoxical sleep.
... The distribution of disorders observed in draught horses in the current study differs from that reported in both ridden and driven racehorses with abnormal respiratory noise and/or poor performance, in which palatal dysfunction accounts for a higher percentage of respiratory abnormalities detected [1,12]. The distribution of disorders in draught horses also differs from previous reports in non-racing performance horses [2,23]. Of note in this regard, was the lack of observation of circumferential, lateral wall or dorsal pharyngeal collapse abnormalities. ...
... A comparatively low incidence of pharyngeal disorders in draught horses might also be related to variation in exercise intensity between equestrian disciplines. Despite a different distribution of URT disorders, a similar percentage of draught horses presenting with abnormal respiratory noise and/or poor performance displayed an URT disorder when compared to horses in other disciplines [1,2,12,23,24]. As with other disciplines, combining resting and exercising examination in draught horses improved assessment and identification of airway disorders [1,22]. ...
Background
Upper respiratory tract (URT) endoscopy at rest is commonly used to evaluate competition draught horses with URT conditions. Overground endoscopy might be preferred for draught horse URT evaluation as it allows the horses to be driven with harness, overcheck and cart‐load under similar conditions to those experienced in the show ring where airway conditions are most prominent.
Objective
To describe the exercising URT findings of competition draught horses with abnormal respiratory noise and/or poor performance.
Study design
Case series.
Methods
Medical records of competition draught horses undergoing overground endoscopic evaluation between January 2013 and January 2018 with a presenting complaint of abnormal respiratory noise and/or poor performance were reviewed. Video recordings of resting and overground endoscopy were evaluated in all horses. Spearman's rank correlation coefficient was calculated between laryngeal function at rest and at exercise.
Results
Fifty competition draught horses were examined. Thirteen had previously undergone URT surgery. There was significant correlation between resting and exercising laryngeal function (ρ = 0.77, P<0.01). Abnormalities were detected in 46 horses and included arytenoid cartilage collapse (n = 31), vocal fold collapse (n = 27), palatal dysfunction (n = 14), epiglottic disorders (n = 11), dynamic laryngeal collapse (n = 1), rostral deviation of the palatopharyngeal arch (n = 3) and medial deviation of the aryepiglottic folds (n = 16). The majority of horses had a complex of abnormalities (n = 31) or required exercising examination for identification (n = 41). Incidental upper oesophageal incompetence was observed in nine horses.
Main limitations
Retrospective collection of data.
Conclusions
Overground endoscopic evaluation was a useful technique for identifying URT disorders in competition draught horses. The spectrum of upper airway conditions identified in exercising draught horses supports the use of overground endoscopy as a diagnostic technique and could influence treatment considerations.
The Summary is available in Portuguese – see Supporting Information
... Increased heart rate, cortisol concentrations, or decreased heart rate variability, were physiological indicators showing that this HNP was associated with distress and compromised welfare (König von Borstel et al., 2009;Ludewig et al., 2013;Zebisch et al., 2013a;Hall et al., 2014;Kienapfel et al., 2014;Smiet et al., 2014). In addition, some studies detected impaired breathing (vanErck, 2011;Sleutjens et al., 2012;Zebisch et al., 2013b) and potentially detrimental occurrences in the neck (Clayton et al., 2010;Elgersma et al., 2010;Fjordbakk et al., 2013;Kienapfel, 2014;Nestadt et al., 2015) when horses were ridden with the noseline behind the vertical. ...
... For example, some studies are performed on Standardbred trotters [4,9,13], others on Thoroughbreds [2,8], and others on mixed populations [3,5,10,11]. Lower airway inflammation could be evaluated by BAL [22,24,50] or tracheal wash cytology [4,21,51], DUAOs may be diagnosed by overground [52,53] or high-speed treadmill endoscopy [13,54], and the diagnosis of EIPH may be based on single or multiple tracheobronchoscopies or on BAL cytology [55]. Finally, some studies quantify performance by the measurement of physiological parameters during exercise tests [4,17,25,30], while others quantify performance by collecting racing results [21,22,51]. ...
Poor performance in racehorses is commonly associated with subclinical diseases. This study aims to evaluate the associations between medical disorders and racing results in Standardbred trotters. The clinical records of 248 poorly performing Standardbreds were retrospectively reviewed, and their racing results were extracted from an online database, concerning the periods 3 months before and 6 months after hospitalization and the entire lifetime. Generalized linear models were used to evaluate the effects of different disorders on racing outcomes. Airway neutrophilia was associated with limiting lifetime starts and wins pre- and post-hospitalization, while mastocytosis was associated with less wins in the post-hospitalization period. Therefore, lower airway inflammation showed both short- and long-term impacts on racing performance. Severe upper airway obstructions and gastric ulcers showed associations with less placings in the post-discharge period but no long-term influence on performance. The significance of exertional rhabdomyolysis was indeterminable, yet interference with the number of starts in the post-discharge period was reported and associated with lower total career earnings. Exercise-induced pulmonary hemorrhage and cardiac arrhythmias were not associated with worse racing outcomes: therefore, their role in poor performance remains unclear.
... Les obstructions des voies respiratoires supérieures à l'exercice sont une cause courante de contreperformance [19][20][21]. Au début des années 2000, les endoscopies à l'exercice, initialement sur tapis roulant puis, depuis une quinzaine d'années, celles embarquées sur le terrain, se sont imposées comme le gold standard de leur diagnostic. Des affections fréquentes sont alors bien décrites comme l'hémiplégie laryngée, le collapsus des cordes vocales (CCV), la déviation axiale des replis ary-épiglottiques (DARAE), l'instabilité pharyngée, le collapsus pharyngé, le DDIVP, la subluxation du processus corniculé, la rétroversion de l'épiglotte ( ...
Once the clinical examination has been performed, various imaging techniques can be used to investigate the upper respiratory system of the horse. Resting endoscopy makes it possible to observe the luminal aspect of the nasal cavities, pharynx, larynx, guttural pouches and trachea. It allows to appreciate the anatomy of these structures, to have an idea of the laryngeal function and to detect pathological abnormalities. Small diameter endoscopes now allow direct sinus exploration. Dynamic endoscopy is the technique of choice for investigating laryngeal function during exercise in the event of respiratory noise or poor performance, whatever the discipline of the horse. Radiography retains an important place in the diagnosis of upper respiratory conditions, particularly for sinuses and associated structures. However, the superimpositions in the region of the head can make its interpretation difficult. Laryngeal ultrasound can assess the extraluminal structures and assess its function. It is particularly interesting in the diagnosis of displacement of the soft palate, laryngeal hemiplegia or laryngeal dysplasia. CT scan is now considered the technique of choice in the evaluation of the nasal cavities and sinuses of the horse. It eliminates the superimpositions encountered with conventional radiography and can easily be performed on the standing sedated horse in certain hospitals. MRI and scintigraphy, although less available, may also be of interest in the evaluation of the horse’s upper respiratory tract.
... Other studies, however, found no association between DUAO and EIPH.24,72 Similarly, many studies reported associations between DUAO and MEA, hypothesizing that DUAO may predispose to lower airway inflammation or vice versa.20,23,69,[73][74][75] Conversely, other authors did not find any relationship between MEA and DUAO.7,72,76 ...
Background
Poor performance is a multifactorial syndrome of racehorses, commonly associated with subclinical disorders, which can be diagnosed by exercise testing.
Objectives
Describe the prevalence of medical causes of poor performance in Standardbreds unassociated with lameness, and evaluate their relationships with fitness variables measured by exercise treadmill test.
Animals
Hospital population of 259 nonlame Standardbred trotters referred for poor performance.
Methods
The horses' medical records were retrospectively reviewed. Horses underwent a diagnostic protocol including resting examination, plasma lactate concentration, treadmill test with continuous ECG and assessment of fitness variables, creatine kinase activity, treadmill endoscopy, postexercise tracheobronchoscopy, bronchoalveolar lavage (BAL), and gastroscopy. The prevalence of different disorders was evaluated, including cardiac arrhythmias, exertional myopathies, dynamic upper airway obstructions (DUAOs), exercise‐induced pulmonary hemorrhage (EIPH), moderate equine asthma (MEA), and gastric ulcers (EGUS). The associations of these disorders with fitness variables were investigated individually and using multivariable models.
Results
Moderate equine asthma and EGUS were the most common disorders, followed by EIPH, DUAOs, cardiac arrhythmias, and exertional myopathies. Hemosiderin score was positively correlated with BAL neutrophils, eosinophils, and mast cells; increased creatine kinase activity was associated with BAL neutrophilia, DUAOs, premature complexes, and squamous gastric disease. Treadmill velocity at a plasma lactate concentration of 4 mmol/L and at heart rate of 200 beats per minute was negatively affected by BAL neutrophilia, multiple DUAOs, exertional myopathies, and squamous gastric disease.
Conclusions
The multifactorial nature of poor performance was confirmed, with MEA, DUAOs, myopathies and EGUS representing the main diseases involved in fitness impairment.
... 35 In contrast, overground endoscopy (OE) has the advantage to be performed in the usual environment of the horse and allows interventions from the rider or driver; a ridden examination is of particular importance in nonracing sport horses, as specific equitation maneuvers and movements, such as head flexion, have been proven to contribute to the development of upper airway instability during exercise. 36,37 However, in racehorses, OE is less likely to result in a diagnosis of DUAO, as HSTE examinations are performed under more strenuous conditions than during examinations on track 35 ; moreover, in some institutions, horses are tested while wearing bit and bridles and periods of head flexion are included during the HSTE, especially when the trainers refer that abnormal respiratory noises occur or worsen when the horse is on the bit. 33 In our study, DUAOs were diagnosed in 43.46% of the horses; the prevalence of DUAOs reported in the literature varies among different studies on the basis See Table 3 for key. of the athletic activity of enrolled horses (ie, racehorses or other sport horses), inclusion criteria (random horses from a population and horses referred for poor performance or abnormal respiratory noise), and type of dynamic endoscopy (HSTE or OE). ...
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.
... Respiratory tract disorders in horses are common and are important causes of poor performance (Morris and Seeherman, 1991;Martin et al., 2000;Van Erck, 2011). Endoscopic evaluation of the equine upper respiratory tract (URT) is the most commonly used diagnostic technique as the nasal passage, pharynx, larynx, guttural pouches, sinus ostia, ethmoidal labyrinth, pharyngeal recess and trachea can be visualised (Davidson and Martin, 2003;Sheta and Ashour, 2017). ...
Background
Endoscopy is essential for the diagnosis of upper respiratory tract (URT) disorders in horses but equipment is expensive. An industrial borescope might be used to visualise the URT when an endoscope is not available.
Objectives
To investigate the applicability of a cheap, smartphone‐connected, flexible and steerable borescope to perform URT endoscopy in horses.
Study design
Prospective descriptive study.
Methods
In horses with a clinical indication, endoscopy was first performed with a borescope and subsequently with a veterinary endoscope, which was used as gold standard. Typical URT structures of interest (depending on clinical signs) were digitally recorded. Recordings of both examinations were reviewed by a blinded observer.
Results
One hundred horses underwent both endoscopic examinations via the right (n = 100) and left (n = 24) nasal passage. In 81/83 attempts, the ethmoidal labyrinth and sinus ostia were visualised on the right side and in 22/24 attempts on the left side. Pharyngeal and laryngeal structures could always be visualised except in 6 horses where the tip of the epiglottis could not be seen due to technical failure of the steering mechanism. In 66/72 attempts, the trachea could be visualised proximally, of which the carina was visualised in 59. Borescope and endoscope grading scores for pharyngeal lymphoid hyperplasia, recurrent laryngeal neuropathy and tracheal mucus were identical in 88/100, 93/100 and 48/59 horses, respectively. The remainder differed only one or two subgrades. The borescope was replaced halfway through the study as the steering mechanism started to fail after 45 to 50 examinations.
Main limitations
Lack of reliability and the absence of a working channel of this particular borescope model.
Conclusions
A flexible, steerable borescope, connected to a smartphone, allows visualising specific parts of the URT in horses.
... The occurrence of EIPH is common, and its severity may vary among horses as well as in EIPH episodes in the same animal (Preston et al., 2015). It has been shown that the rider interference causes upper airway instability increasing the risk of EIPH in show jumping horses (Van Erck, 2011;Bonomo et al., 2019). Many veterinarians consider that upper airway diseases and tracheal findings may influence the occurrence of EIPH, but no studies have demonstrated this relationship statistically. ...
... Upper airways conditions and instability that increase negative pressure in the airways are considered as additional mechanisms of increased alveolar pressure and risk factors of EIPH in jumping horses (van Erck, 2011). During the post-competition endoscopic examination in the present study, the horses showed no evidence of upper airway instability; however, Van Erck (2011) performed dynamic endoscopic examination and reported instability during exercise due to rider interference, which was not assessed in the present study. ...
Pulmonary haemorrhage occurs in sport horses performing high-intensity exercise, but the factors involved in the occurrence of pulmonary haemorrhage in jumping horses have not been elucidated. This study aimed to determine the occurrence of pulmonary haemorrhage and factors involved in competitive jumping horses. Fifty adult jumping horses competing in the city of São Paulo, Brazil, were included. The horses were divided into two groups based on jump height at competition: Low group (LG, n = 26), with jump height between 1.00 and 1.20 m, and High group (HG, n = 24), with jump height between 1.30 and 1.50 m. Physical examination was performed before and after competition, and airway endoscopy and tracheal wash (TW) were performed 1 h after competition. Heart rate (HR; P < 0.010), respiratory rate (RR; P < 0.010), rectal temperature (RT; P < 0.010), and frequency of endoscopic observations of blood in the tracheal lumen (P < 0.013) were significantly higher in HG than in LG. TW cytology was not different between the two groups. Incidence of pulmonary haemorrhage was positively correlated with jump height (r ² = 0.40, P < 0.0001), post-exercise HR (r ² = 0.31, P < 0.0001), and post-exercise RR (r ² = 0.19, P < 0.002). In conclusion, pulmonary haemorrhage in jumping horses was associated with the level of performance. Further studies on the pathophysiology of exercise-induced pulmonary haemorrhage in this type of horses are required.
... Overground endoscopy (OGE) is now commonly used for diagnosis of upper respiratory tract (URT) disorders in horses during exercise [1][2][3][4][5][6]. However, variability in exercising endoscopy findings have been recognised to occur in association with different exercise intensities, head positions, tack and inter-observer variation in URT disorder grading [7][8][9][10][11][12]. ...
Background
Endoscopic tip placement in the pharynx and water flushing interval (FI) may affect exercising upper respiratory tract (URT) endoscopic results.
Objectives
To determine associations between the endoscopic tip position in the pharynx and automated FI with overground endoscopic (OGE) results.
Study design
Randomised balanced 2X5 factorial design.
Methods
A total of n = 200 horses undergoing OGE were randomly assigned into 10 groups (n = 20/group) of different automated endoscopic FIs (no flushing, 60, 120, 180, 240 s) with the endoscope tip positioned either rostrally (position A) or caudally (position B) in the pharynx. Endoscopic videos were analysed and all URT abnormalities graded using published scales. Disorders with ≤10% prevalence were excluded from the final analysis with only arytenoid asymmetry at exercise (AAex), vocal fold collapse (VFC), palatal dysfunction (PD) and medial deviation of the aryepiglottic folds (MDAF) included. The association of endoscope position and FI with URT disorders was assessed using ordinal regression models with P≤0.05 significant.
Results
Endoscope tip positioning was significantly associated with PD grading (P = 0.002), with 63/100 horses diagnosed with PD in position A and 45/100 in position B. No other significant direct associations between URT disease and endoscope tip position were identified, although interactions between exercise velocity and endoscope position affected MDAF grade. FI was not directly associated with alterations in disorder grading, although interactions between exercise velocity and FI appeared to affect MDAF grade.
Main limitations
The same horse was not evaluated under each test condition potentially resulting in sample bias. Interactions between disorders were not evaluated. The sample size was insufficient to conclusively explore relationships between all factors and disorder grading.
Conclusions
Position of the endoscope tip within the pharynx appears to affect grading of PD during OGE examination. Exercise velocity may affect MDAF grade through interactions with endoscope position and FI.
... Despite continuous improvement and implementation of new diagnostic methods, including portable dynamic endoscopes, the high-speed treadmill exercise test remains a highly efficient tool for diagnosing dynamic disorders in the pharynx and larynx (Franklin et al. 2010, Van Erck 2011. ...
The goal of the present study was to establish the occurrence of structural disorders in the larynx and pharynx during treadmill exercise tests in horses diagnosed with Equine Asthma (EA). Investigation was performed in 29 horses, patients of the Equine Clinic of the Warsaw University of Life Sciences in Poland, admitted with poor exercise performance. Upper and lower airway examinations were performed in all patients revealing both mild to moderate Equine Asthma (13 horses), and no lower airway abnormalities (16 animals). In the group of horses with EA, 11 did not have structural disorders of the pharynx and larynx at rest. During exercise two horses were free of abnormalities, while 11 had structural disorders, eight of them solely in the pharynx, two in the larynx, and one in both the pharynx and larynx. In the non- asthmatic group, 11 horses had no structural disorders during resting endoscopy. Endoscopy performed during exercise revealed disorders of the larynx in 10 horses, of the pharynx in three horses, and in both the larynx and pharynx in the remaining three horses.
In conclusion:
horses with diagnosed EA frequently have disorders of the pharynx during treadmill exercise tests, while without EA, often have disorders of the larynx. Endoscopy of upper airways during exercise testing is a valuable tool in the diagnosis of poor performance in horses with lower airway inflammatory disease.
... Varios estudios concordaron que las patologías más frecuentes de caballos sometidos a endoscopía dinámica con antecedentes de ruidos respiratorios y/o intolerancia al ejercicio fueron las siguientes: desviación axial de los pliegues ariepigloticos (11% a 40%), el colapso de las cuerdas vocales (7% a 41%), neuropatía laríngea recurrente (8% a 38%) y el desplazamiento dorsal del paladar blando (16% a 40%). Las cuales se presentaron como patologías múltiple (24% a 57% de los equinos) o únicas (Barakzai y Dixon 2011;Van Erck et al., 2011;Witte et al., 2011;Barakzai y Cheetham 2012;Strand et al., 2012;Mirazo et al., 2014). ...
... There is also some circumstantial evidence that IAD may be more prevalent in horses with pharyngeal dysfunction and laryngeal surgery. 110,111 Conversely, severity of upper and lower airway inflammation and endoscopic scores were found to be independent. 11 ...
The purpose of this manuscript is to revise and update the previous consensus statement on inflammatory airway disease (IAD) in horses. Since 2007, a large number of scientific articles have been published on the topic and these new findings have led to a significant evolution of our understanding of IAD.
... For example, an overground-endoscopy study of 109 sport horses found that the most commonly diagnosed problem was pharyngeal instability. IAD was associated with the latter but not with other other upper airway abnormalities [49]. Another upper airway endoscopy study of 138 trotters found no significant difference in the pharyngitis grade or laryngeal hemiplegia score between IAD-affected horses (n=102) and controls (n=26) [Couroucé-Malblanc, unpublished data]. ...
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.
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.
The dynamic upper airway functional (URT) problems of Colombian paso horses (CPH) have not been investigated in literature up to date. These horses perform special walking gaits with high poll flexion of the neck. Our goal is to evaluate the upper airway mechanics in CPH, showing abnormal respiratory sounds and poor performance during exercise. Resting and overground endoscopy was performed in 40 CPHs. Statistical analyses were performed using the scipy package. One-tailed Fisher exact tests were used to check for positive contingency between each pair of URT disorder (P<0.05). Arytenoid cartilage collapse was observed in 35 out of 40 cases during exercise. Among these, dynamic laryngeal collapse (DLC) was the most significant finding, but ventro-medial luxation of the apex of the corniculate process of the arytenoid (VLAC) and recurrent laryngeal neuropathy was also observed. Dorsal displacement of the soft palate (DDSP) was only detected in 4 out of 40 cases. DLC was significantly associated with vocal cord collapse, nasopharyngeal collapse (NPC), medial collapse of the margins of the epiglottis (MCME) and MCME was associated with NPC. DLC is only a typical feature in some special breeds worldwide. We suggest that the extensive poll flexion and the relatively small laryngeal lumen and high intensitivity workload are the most important predisposing factors of DLC. VLAC was over-represented in our caseload, compared to other studies. Whereas, despite the intensive workload, DDSP was relatively uncommon. We presume that this could also be tailored to the high poll flexion performed during the special gaits.
Advances in Animal Health, Medicine and Production
pp 485-509
No Room to Breathe: Airway Conditions Affecting the Equine Athlete
Authors and affiliations
P. Tilley, J. Simões, V. Pessoa, R. Fonseca, J. P. Sales-Luis
First Online: 22 November 2020
Abstract
During exercising endoscopy, head flexion has been shown to be an important predisposing factor for upper respiratory tract collapse and is associated with conflict behaviour. Based on the substantial number of studies on the impact of hyperflexed postures on horse welfare, it was recently suggested for further research to be done on the physiological/psychological effects of a lesser degree of flexion. Our group evaluated horses ridden in two very close head positions and were able to identify significant differences for various parameters.
Inflammatory airway disease (IAD) could be the effect of repeated episodes of nasopharyngeal asphyxia, its sequel being exercise induced pulmonary haemorrhage (EIPH). EIPH and IAD account for a wide number of horses failing to perform to their potential. The American College of Veterinary Internal Medicine consensus statement proposed equine asthma syndrome (EAS) to describe horses with mild or moderate (IAD) to severe (RAO) airway disease.
Insect bite hypersensitivity has been associated with airway hyperreactivity, suggesting a probable link with EAS, and multiple hypersensitivities are significantly associated with the absence of nematode eggs in faeces.
Because severe EAS is a chronic disease with significant impact on the equine population, the development of staging methods for this disease by our group became essential to optimise equine medical care.
Keywords
Endoscopy URT collapse Head hyperflexion Equine Asthma Syndrome (EAS) Staging Hypersensitivity
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Acknowledgements
The authors thank CIISA and in particular Project FCT UIDP/CVT/00276/2020.
Ewe Neck is a relatively common morphological defect in Pura Raza Español (PRE) horses and other Baroque type horse breeds, which adversely affects the breeding industry; (1) objectives: to establish the within-breed prevalence, possible associated factors, and heritability of Ewe Neck in PRE horses; (2) methods: the database included evaluations of 35,267 PRE horses. The Ewe Neck defect, 16 morphological traits, and 4 body indices were recorded. A Bayesian genetic animal model included the following systematic effects: sex, age, coat color, geographical area of the stud, and birth stud size were used; (3) results: in this PRE population, a total of 27.12% was affected. All the risk factors studied were significantly associated with the Ewe Neck score. The heritability coefficient for Ewe Neck score ranged from 0.23 to 0.34. Morphological traits (height at chest, length of back, head-neck junction, and bottom neck-body junction) and the indices (head and thoracic index) were those most closely related with the appearance of Ewe Neck; (4) conclusions: Ewe Neck is a relatively frequent defect in PRE horses, associated with risk factors and other morphological traits, with a moderate level of heritability. Breeding to select against this condition may therefore be beneficial in this breed.
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.
Many abnormalities of the upper airway that can inhibit performance are determined on a critical resting endoscopic evaluation. Some dynamic abnormalities can only be seen during an exercising endoscopic evaluation, which should be performed whenever the history of abnormal noise or performance limitations is not completely consistent with the resting endoscopic findings. Head and neck position may play a critical role in the evaluation process and the exact position during performance should be reproduced during the clinical examination to definitively define the abnormality. Treatments and prognoses are presented.
The correct diagnosis of upper airway conditions in the horses is imperative to ensure that the horse receives the correct and most appropriate treatment and management. With the introduction of overground exercising endoscopy, examination of the patient is now readily available. Ultrasonography of the upper airway has also entered into the diagnostic repertoire of the clinician. However, interpretation of these examinations is not always straightforward with some conditions, most notably dorsal displacement of the soft palate, still sometimes questionably elusive. Additionally, many horses are found to have multiple forms of upper airway obstruction, so a complete diagnosis is essential to ensure that some conditions are not overlooked.
This paper introduces the key challenges encountered when investigating the human–horse interface. With a focus in recent research on the application of learning theory in horses, it reviews the progress made in the emergent discipline of equitation science over the past decade. An appreciation of the role of learning theory in horse training is still in its infancy and is still refuted by traditionalists who believe that the horse can be trained as a willing participant that knows what is being asked of it. Despite this predictable resistance, the growing body of peer-reviewed evidence shows how equitation science reveals equestrian techniques that are difficult to justify within an ethical framework. Regardless of what some traditional critics claim, equitation science does nothing to undermine the emotional bonds that humans share with horses. On the contrary, it forces those who use horses to adopt a horse-centric approach to their training; an approach that ensures the cognitive powers of their trainees is not overestimated. The strength of this approach lies in acknowledging that training deficits are the main cause of poor performance, and that rider safety and horse welfare can be compromised by sloppy application of learning theory. The present paper describes the tools being used to study rider–horse interactions and concludes with a summary of the abiding challenges in applying learning theory to equitation.
Based upon the available literature, the authors describe the physiology and the mechanisms of the upper respiratory tract. They present disorders of the upper respiratory tract resulting in poor performance and abnormal respiratory noise. From the disorders, idiopathic left laryngeal hemiplegia, dorsal displacement of the soft palate and rostral and dorsal pharyngeal collapse are outlined in details. More rarely occurring disorders, such as axial deviation of the aryepiglottic fold, epiglottic entrapment, epiglottic retroversion and vocal cord collapse are also defined. As regards the diagnostic methods, resting endoscopy, high speed treadmill endoscopy and overground endoscopy, the latter allowing the examination of horses in their natural environment and under their usual workload, are presented.
Horses with endoscopic evidence of complete paralysis of the laryngeal cartilage at rest are easy to diagnose and their impact on performance is clear. Affected horses have upper airway obstruction and abnormal respiratory noise during strenuous exercise because of dynamic collapse of the affected arytenoid cartilage. Treadmill endoscopy is performed with the horse exercising on a high-speed treadmill. Whether the upper airway examination is performed on the treadmill or in the field, the goal of the examination in horses with recurrent laryngeal neuropathy (RLN) is to assess dynamic laryngeal function. Bilateral laryngeal dynamic collapse is an abnormality that has been primarily reported in Norwegian Coldblooded Trotters. Dynamic collapse of the apex of the corniculate process of the arytenoid cartilage is an uncommon laryngeal obstructive disorder. In some horses with RLN, dynamic arytenoid cartilage collapse is only evident or markedly exacerbated when horses are exercised with enforced poll flexion.
Dorsal displacement of the soft palate (DDSP) is one of the most common upper respiratory dysfunctions in performance. In many instances a diagnosis of DDSP is based on historical or clinical signs such as a sudden deterioration in performance (i.e., abrupt decrease in speed), gurgling upper respiratory noise, and standing endoscopic findings. Resting endoscopic examination is performed to assess nasopharyngeal function and to rule in or out other causes of abnormal airway noise and exercise intolerance. The current gold standard for diagnosis of intermittent DDSP is exercising examination via treadmill or overground endoscopy. Dynamic tests that include exercising the horse to the point of fatigue or altering the speed, for example, exercising at maximal speed then rapid decrease in speed then return to maximal speed, should be performed when appropriate. Ulceration involving the dorsal aspect of the caudal soft palate is often associated with intermittent DDSP.
At an individual horse level, the best assessment of postoperative outcome is direct evaluation of the upper airway through dynamic video endoscopy either on a treadmill or using an overground endoscope. Overground endoscopy has a number of practical advantages over high-speed treadmill endoscopy, in particular that the horse does not need to travel to a referral center and can be exercised under normal training conditions. When assessing performance following a surgical intervention at a population level, it is important to consider the level of evidence that a particular study provides. Randomized controlled trials (RCTs) and systematic reviews represent the highest level of evidence. In summary, while the indirect assessment of postoperative function through proxy measures such as race performance will necessarily continue for some time, there is likely to be an increasing emphasis of direct assessment using dynamic endoscopy.
In contrast to other athletic species such as people and greyhounds, which switch from nasal breathing at rest to oral breathing during exercise, the horse is an obligate nasal breather even during strenuous exercise. Dorsal displacement of the soft palate (DDSP) is a condition that occurs during exercise when the caudal border of the soft palate becomes displaced to a position above the epiglottis, resulting in obstruction of the rima glottidis during expiration. DDSP is considered to be the most common equine dynamic upper respiratory tract obstruction and is most prevalent in racehorses, but can also occur in sport and pleasure horses. This article gives an overview of DDSP and describes the more common treatments currently applied in the UK.
The purpose of this consensus statement is to provide a review of current knowledge and opinions concerning inflammatory airway disease (IAD) and to help practitioners differentiate IAD from heaves (or recurrent airway obstruction; RAO) and other inflammatory respiratory diseases of horses.
High speed treadmill endoscopy provides a true assessment and diagnosis of the dynamic obstructions of the upper equine respiratory tract (DO-URT). However, treadmills do not always allow reproduction of the exact conditions of dynamic collapse of the URT. The availability of on-board endoscopes, which could be used without a treadmill, would make exercising endoscopy readily available to more equine practices.
To develop and validate an innovative endoscope which could be used for the examination of the URT at exercise in ridden and harnessed sport horses performing in natural conditions.
Authors worked closely with engineers of a company manufacturing veterinary endoscopes. Over a 2-year period several prototypes were tested on more than 20 cooperative horses performing either in trot, gallop, jumping or endurance. The final Dynamic Respiratory Scope (DRS) allows real-time visualisation of the URT and video recordings for post test reviewing and archiving. The DRS was then tested in 2 equine livery yards. Performance horses presented for investigation of abnormal respiratory noises at exercise and/or poor performance were subjected to exercising endoscopy. Endoscopic images of the URT were recorded and video recordings of the URT were reviewed post test.
A total of 68 horses were examined: 39 harnessed Standardbred and 29 mounted horses (16 Thoroughbred and 13 saddle horses). Of these, 44 were diagnosed with a URT abnormality. Good quality videos were obtained even at maximum speed in all cases. The innovative insertion tube provided very stable images compared to those obtained with flexible video endoscopes on treadmills.
This study validates the safety and the reliability of the DRS for imaging the equine URT during natural exercising conditions.
Most common causes of DO-URT can be diagnosed easily during any type of performance without a treadmill and the DRS offers a great potential for further URT clinical research.
Exercising upper airway endoscopic evaluation was performed in 7 horses with a history of poor performance after partial arytenoidectomy. Treadmill endoscopy revealed axial deviation of the ipsilateral aryepiglottic fold in all horses. Dynamic collapse of one or more additional upper airway structures was also observed. In 4 horses, laser resection of soft tissue structures that obstructed the upper airway was performed. After laser surgery, 3 horses raced and one performed adequately as a riding horse. Of the remaining 3 horses, 2 raced at a lower class and one performed adequately as a riding horse. In this population of horses, dynamic endoscopy of the upper airway was critical for case management. Based on our observations, horses post arytenoidectomy can have dynamic collapse of the ipsilateral aryepiglottic fold and laser resection of the fold may help resolve the performance problem.
The objective of the present study was to determine the effect of head and neck position on upper airway flow mechanics in exercising horses. Five Standardbred horses (452 ± 16.5 kg bwt; 4.7 ± 0.9 years [mean ± s.e.]) were exercised at 75% (Period A) and at 100% of maximal heart rate (Period B) with head and neck unrestrained, extended, or flexed. Airflow was measured using a facemask mounted pneumotachograph, while tracheal pressure during inhalation and exhalation (PUI and PUE) was measured using a nasotracheal catheter. With head and neck unrestrained, PUI, PUE, inspiratory and expiratory impedance (ZI, ZE), respiratory frequency (f) and indices describing the tidal breathing flow-volume loops (TBFVLs) were similar to those previously reported. There were no significant changes in the extended position, except that expiratory time (Te) and ratio of peak expiratory flow and peak inspiratory flow (PEF/PIF) were significantly increased in Periods A and B, respectively. In contrast, in the flexed position, ZI was significantly increased in Period B. Also, inspiratory flow at 50% of tidal volume (IF50) was significantly decreased, and PEF/PIF and EF50/IF50 were significantly increased. At period A, PUI was increased and Te was prolonged. We conclude that during strenuous exercise head and neck extension has little effect on upper airway flow mechanics, but that head and neck flexion causes upper airway obstruction.
The importance of undertaking appropriate exercise tests for the diagnosis of dynamic upper respiratory tract (URT) obstructions has been previously documented. Dynamic URT collapse is usually most severe during peak exercise; however, there are occasions when an URT collapse appears more severe during the immediate recovery period. In addition, equitation factors such as head and neck flexion and factors relating to the bit and bridle may induce or exacerbate dynamic URT collapse. The purpose of this paper was to review the literature and 5 cases within the authors' experience have also been included.
The necessary degree of arytenoid cartilage abduction (ACA) to restore airway patency at maximal exercise has not been determined.
Use computational fluid dynamics modelling to measure the effects of different degrees of ACA on upper airway characteristics of horses during exercise.
Maximal ACA by laryngoplasty is necessary to restore normal peak airflow and pressure in Thoroughbred racehorses with laryngeal hemiplegia.
The upper airway was modeled with the left arytenoid in 3 different positions: maximal abduction; 88% cross-sectional area of the rima glottis; and 75% cross-sectional area of the rima glottis. The right arytenoid cartilage was maximally abducted. Two models were assumed: Model 1: no compensation of airway pressures; and Model 2: airway pressure compensation occurs to maintain peak airflow. The cross-sectional pressure and velocity distributions for turbulent flow were studied at peak flow and at different positions along the airway.
Model 1: In the absence of a change in driving pressure, 12 and 25% reductions in cross-sectional area of the larynx resulted in 4.11 and 5.65% reductions in peak airflow and 3.68 and 5.64% in tidal volume, respectively, with mild changes in wall pressure. Model 2: To maintain peak flow, a 6.27% increase in driving tracheal pressure was required to compensate for a cross-sectional reduction of 12% and a 13.63% increase in driving tracheal pressure was needed for a cross-sectional area reduction of 25%. This increase in negative driving pressure resulted in regions with low intraluminal and wall pressures, depending on the degree of airway diameter reduction.
Assuming no increase in driving pressure, the decrease in left ACA reduced airflow and tidal volume. With increasing driving pressure, a decrease in left ACA changed the wall pressure profile, subjecting the submaximally abducted arytenoid cartilage and adjacent areas to airway collapse.
The surgical target of ACA resulting in 88 % of maximal cross-sectional area seems to be appropriate.
Dorsal displacement of the soft palate (DDSP) is an intermittent obstructive upper airway condition that occurs in athletic horses during high-intensity exercise. The pathogenesis of this condition is unknown, but may involve epiglottic hypoplasia, malformation, or neuromuscular dysfunction. In this paper, we report on investigations into the pathophysiology of DDSP. In 3 separate experiments, Standardbred horses were exercised on a high-speed treadmill at speeds corresponding to 50, 75 and 100% of maximum heart rate. The upper airway was evaluated by videoendoscopy and measurement of tracheal pressures.
In experiment 1, we examined the effect of bilateral hypoglossal and glossopharyngeal nerve block on epiglottic function in exercising horses. This nerve block caused epiglottic retroversion and inspiratory upper airway obstruction. However, DDSP did not occur. In experiment 2, we evaluated the hypothesis that tensor veli palatini muscle dysfunction is involved in the pathogenesis of DDSP. Bilateral tensor veli palatini muscle tenectomy did not cause DDSP, but caused instability of the rostral half of the soft palate and a modest inspiratory upper airway obstruction. In experiment 3, we hypothesised that palatinus and palatopharyngeal dysfunction causes DDSP. The pharyngeal branch of the vagus nerve was blocked bilaterally in the guttural pouch. This block caused DDSP in all horses within 2–15 min after nerve block. Furthermore, DDSP created an expiratory nasopharyngeal obstruction. Because the pharyngeal branch of the vagus nerve is in close proximity to the retropharyngeal lymph node chain, we suggest that retropharyngeal lymphadenopathy may cause neural dysfunction and thereby be involved in the pathogenesis of clinical DDSP.
The purpose of this consensus statement is to provide a review of current knowledge and opinions concerning inflammatory airway disease (IAD) and to help practitioners differentiate IAD from heaves (or recurrent airway obstruction; RAO) and other inflammatory respiratory diseases of horses.
Videoendoscopy of the upper respiratory tract (URT) during high-speed treadmill exercise has proved to be invaluable in the assessment of URT dysfunction in racehorses. However, very little information exists regarding dynamic airway collapse in other sport horses used in nonracing equestrian disciplines.
To evaluate the videoendoscopic findings at rest and during exercise in a mixed population of sport horses referred for investigation of poor athletic performance and/or abnormal respiratory noise.
Videoendoscopy of the upper airway was performed at rest and during high-speed treadmill exercise in 93 horses.
Dynamic airway obstructions were diagnosed in 77% of horses and were frequently complex in nature. The most common forms of dynamic collapse included soft palate dysfunction (54%), dynamic laryngeal collapse (38%), axial deviation of the aryepiglottic folds (24%) and pharyngeal wall collapse (18%). In the majority of horses, no obvious abnormalities were identified at rest. Enforced poll flexion was found to be a contributing factor in 24% of cases.
Dynamic obstructions of the URT were a common cause of poor performance and/or abnormal respiratory noise in sport horses referred for investigation of performance problems.
This study highlights the importance of videoendoscopic evaluation of the URT during exercise in horses utilised for equestrian sports where exercise during competition is submaximal in nature.
Although well documented in racehorses, there is paucity in the literature regarding the prevalence of dynamic upper airway abnormalities in nonracing performance horses.
To describe upper airway function of nonracing performance horses with abnormal respiratory noise and/or poor performance via exercising upper airway videoendoscopy.
Medical records of nonracing performance horses admitted for exercising evaluation with a chief complaint of abnormal respiratory noise and/or poor performance were reviewed. All horses had video recordings of resting and exercising upper airway endoscopy. Relationships between horse demographics, resting endoscopic findings, treadmill intensity and implementation of head and neck flexion during exercise with exercising endoscopic findings were examined.
Dynamic upper airway obstructions were observed in 72% of examinations. Head and neck flexion was necessary to obtain a diagnosis in 21 horses. Pharyngeal wall collapse was the most prevalent upper airway abnormality, observed in 31% of the examinations. Complex abnormalities were noted in 27% of the examinations. Resting laryngeal dysfunction was significantly associated with dynamic arytenoid collapse and the odds of detecting intermittent dorsal displacement of the soft palate (DDSP) during exercise in horses with resting DDSP was only 7.7%. Exercising endoscopic observations were different from the resting observations in 54% of examinations.
Dynamic upper airway obstructions were common in nonracing performance horses with respiratory noise and/or poor performance. Resting endoscopy was only helpful in determining exercising abnormalities with recurrent laryngeal neuropathy.
This study emphasises the importance of exercising endoscopic evaluation in nonracing performance horses with abnormal respiratory noise and/or poor performance for accurate assessment of dynamic upper airway function.
Inflammatory airway disease (IAD) is a nonseptic condition of the lower respiratory tract. Its negative impact on respiratory function has previously been described using either forced expiration or forced oscillations techniques. However, sedation or drug-induced bronchoconstriction were usually required. The impulse oscillometry system (IOS) is a noninvasive and sensitive respiratory function test validated in horses, which could be useful to evaluate IAD-affected horses without further procedures.
To determine the sensitivity of IOS in detecting alterations of the respiratory function in subclinically IAD-affected horses without inducing bronchoprovocation and to characterise their respiratory impedance according to frequency for each respiratory phase.
Pulmonary function was evaluated at rest by IOS in 34 Standardbred trotters. According to the cytology of bronchoalveolar lavage fluid (BALF), 19 horses were defined as IAD-affected and 15 horses were used as control (CTL). Total respiratory resistance (Rrs) and reactance (Xrs) from 1-20 Hz as well as their inspiratory and expiratory components were compared between groups.
A significant increase of Rrs at the lower frequencies (R1-10 Hz) as well as a significant decrease of Xrs beyond 5 Hz (X5-20 Hz) was observed in IAD compared to CTL horses. IOS-data was also significantly different between inspiration and expiration in IAD-affected horses. In the whole population, both BALF eosinophil and mast cell counts were significantly correlated with IOS measurements.
Functional respiratory impairment may be measured, even in the absence of clinical signs of disease. In IAD-affected horses, the different parameters of respiratory function (Rrs or Xrs) may vary depending on the inflammatory cell profiles represented in BALF.
Impulse oscillometry could be used in a routine clinical setting as a noninvasive method for early detection of subclinical respiratory disease and of the results of treatment in horses.
There are potential advantages to imaging the upper portion of the respiratory tract (URT) of horses during ridden exercise. With the advent of a wireless endoscope, this is now possible. However, there has been no detailed validation of the technique and findings have not been compared to ridden speed.
To assess the combined use of a Dynamic Respiratory Scope (DRS) and global positioning system (GPS) receiver for examining the URT of a group of Thoroughbred racehorses randomly selected from a single flat racehorse training establishment.
Horses were selected randomly from a population of Thoroughbred horses in training at the same training yard. Endoscopic images of the URT were recorded during a ridden exercise test on an 'all-weather-gallop' and were reviewed post testing. Speed was measured using a wrist mounted GPS receiver.
A total of 67 (34%) of the 195 horses in training were examined. Endoscopic findings included: normal URT function (44 cases); dorsal displacement of the soft palate (DDSP) (13 cases); laryngeal asymmetry (4 cases); and axial deviation of the aryepiglottic folds (3 cases). Maximum speed obtained by individual horses ranged from 41.8-56.3 km/h. Ridden speed was variably affected by DDSP.
The DRS provides a safe effective system for imaging the equine URT during ridden exercise at speed. The abnormalities of the URT identified were similar to those observed during treadmill endoscopy studies reported in the literature. The effect of URT abnormalities on ridden speed requires further investigation.
This technique can be used to diagnose common causes of URT associated with poor performance in horses during normal training. This has substantial implications for future clinical diagnosis and treatment of URT pathology.
Dynamic laryngeal collapse (DLC) associated with poll flexion is a newly diagnosed upper respiratory tract obstructive disorder that causes poor racing performance.
To determine if Norwegian Coldblooded Trotters (NCTs) affected with DLC associated with poll flexion differ from normal, elite NCTs based on simple airway mechanics measurements.
Five normal elite NCTs and 6 NCTs diagnosed previously with DLC underwent treadmill videoendoscopy while tracheal pressures were measured continuously. Alternating head positions were used such that horses were exercised with free head carriage and induced poll flexion at heart rates >200 beats/min.
Peak inspiratory tracheal pressures were significantly more negative for horses with DLC compared to the elite horses. This difference was only significant during the exercise phases when the poll region was flexed, P = 0.0015. Head position significantly affected peak inspiratory pressure for both elite and affected horses, P < 0.0001.
Induced poll flexion significantly affected peak inspiratory pressure (PIP) in all horses; however, PIPs were significantly more negative in those affected with DLC. Based upon the tracheal pressure measurements recorded in this study, DLC in NCTs is a severe obstructive upper respiratory tract disorder that is induced by poll flexion.
Dynamic collapse of the upper respiratory tract (URT) is a common cause of poor performance in horses. These conditions occur predominantly during strenuous exercise when the URT is unable to maintain dilation in the face of high inspiratory pressures. In most cases, these disorders cannot be accurately diagnosed during a resting endoscopic examination. To date, a definitive diagnosis of dynamic URT obstructions has been possible only by performing an endoscopic examination during high-speed treadmill exercise. However, recent technological advances now enable URT endoscopy to be performed while the horse is exercising in its normal environment.
The objective of this study was to examine the association of pharyngeal lymphoid hyperplasia (PLH), recurrent laryngeal neuropathy (RLN), mucus accumulation (MA) score and tracheobronchial secretion neutrophil percentage (TBS-N) with rider-assessed performance in sport horses. Airway endoscopy scores, tracheobronchial secretion cytology, rider-assessed general impression and willingness to perform were investigated in 171 top-level sport horses. Increased MA appears to be associated with poor willingness to perform in sport horses. Older horses had decreased PLH scores and increased TBS-N. Mucus accumulation scores > or =3 were associated with increased odds (mean 9.92; upper and lower 95% confidence intervals: 1.5-64.6) of poor rather than excellent willingness to perform. A TBS-N of 20-50% compared with <20% was associated with decreased odds (median 0.11; upper and lower 95% CI: 0.02-0.66) of poor rather than excellent willingness to perform. In addition, horses with an RLN grade > or =2 had significantly higher odds for giving a poorer general impression and willingness to perform. This finding, however, must be interpreted with caution, since only two horses had significant RLN (grade > or =3).
Normal Standardbred horses were given an incremental exercise test on a horizontal treadmill to evaluate the influence of exercise on gas exchange, resistance, dynamic compliance and inertance of the respiratory system. The exercise test consisted of 2 min exercise steps at each of the following speeds: 2.4 m/sec (walk), 4.5 m/sec (slow trot), 7.0 m/sec (fast trot) and 10 m/sec (gallop). At rest and after 1 min of exercise at each step, airflow, tidal volume, respiratory frequency, pharyngeal, mid-oesophageal and transdiaphragmatic pressures and arterial blood gas tensions were measured. The same horses were subsequently treated intravenously with clenbuterol (0.8 microgram/kg) and an identical exercise test and measurement performed 10 min after clenbuterol injection. In response to exercise, there were large increases in tidal volume, respiratory frequency, airflow and pressures. Exercise was associated with a decrease in upper airway resistance but total pulmonary resistance was unchanged. Exercise did not alter inertance or dynamic compliance, horses became hypoxaemic, and at 10 m/sec (galloping) also developed hypercarbia. Treatment with clenbuterol did not alter any of these measurements in response to exercise. These data suggest that dilation of upper airways occurs during exercise, and that inertial forces are important in strenuously exercising horses and may influence the accuracy of dynamic compliance determinations at high exercise intensities.
Videorecordings of the laryngeal activity of 108 unsedated horses were obtained at rest by passing a flexible videoendoscope into the nasopharynx through the right ventral meatus. All videotaped images were reviewed once, and 72 were reviewed twice, by three veterinarians. Laryngeal cartilage movement was assessed subjectively with a five-tier grading system. The mean intraobserver agreement was 83.3% (range, 75.0%-90.2%) with a kappa statistic of .65 to .98. The mean interobserver agreement was 79.0% (range, 70.4%-80.6%) with a kappa statistic of .51 to .90. A computer program was developed to measure the left:right ratio of the rima glottidis. The mean left:right ratio for horses assigned a median laryngeal grade of I was 0.84 (range, 0.55-1.03); for grade II, 0.82 (0.50-1.12); for grade III, 0.59 (0.39-0.91); and for grade IV, 0.24 (0.07-0.35).
Upper airway pressure was measured during maximal exercise in 10 Thoroughbred racehorses with naturally occurring upper airway obstruction. Left laryngeal hemiplegia and arytenoid chondropathy resulted in substantial increases (30-40 cm H2O) in inspiratory upper airway pressure (Pl), whereas complicated aryepiglottic entrapment and subepiglottic cysts produced only modest increases (15 cm H2O) in Pl. Uncomplicated aryepiglottic entrapment and grade IV pharyngeal lymphoid hyperplasia produced only slight increases (3-5 cm H2O). In general, surgical procedures restored airway pressures to within normal limits. Subtotal arytenoidectomy improved but did not normalize airway pressures in horses with arytenoid chondropathy. Pharyngeal lymphoid hyperplasia appeared to have little effect on upper airway function.
Arterial blood gas and acid-base values during maximal exercise over a 1.2 km distance were recorded in four Thoroughbred horses before and after the chemical induction of pharyngeal lymphoid hyperplasia (PLH). Samples were collected after galloping 0.8 km and 1.2 km, immediately upon stopping and 5 mins after exercising. In only one horse was any difference noted in the pre and post PLH induction results. The horse was more hypercapnoeic at the 1.2 km mark and also took much longer to complete the gallop when it had PLH. However, it also had signs of lower respiratory disease. In the other horses, the only changes which could be attributed to PLH were seen immediately upon stopping. It seems that PLH does not inhibit gas exchange during exercise unless the lesions are extremely severe.
The histologic and histochemical features of palatine muscles from 53 horses were studied; 25 of the horses were racehorses that had upper airway obstruction associated with dorsal displacement of the soft palate and 28 of the horses did not have any respiratory disorders and served as controls. Pathologic features observed included myonecrosis, phagocytosis, mononuclear cell infiltration of perimysial connective tissue, alkaline phosphatase-positive myofibers, and myofibers with cytoarchitectural changes that included irregular staining of the intermyofibrillar sarcoplasm and sarcoplasmic masses. These histopathologic features were judged to be indicative of myositis. Those features were found in both control horses and horses with dorsal displacement of the soft palate; however, their prevalence was higher in horses with dorsal displacement of the soft palate. For the control horses as well as the horses with dorsal displacement of the soft palate, the inflammatory changes were more prevalent in older horses. The finding of myositis suggests that palatal muscle weakness may contribute to the development of dorsal displacement of the soft palate; however, the myositis might have been secondary to trauma associated with displacement of the soft palate. We could not distinguish between these 2 possibilities. A large number of horses with dorsal displacement of the soft palate also had concurrent pharyngeal lymphoid hyperplasia. Extension of the mucosal inflammatory changes associated with pharyngeal lymphoid hyperplasia into the underlying palatine muscle might have accounted for the myositis.
Repeatability of measurements of peak and mean tracheal and pharyngeal pressures in exercising horses was determined. Five athletically fit horses were subjected to repeated (n = 5) standardized exercise trials. Static pressures in the trachea, nasopharynx, and mask were determined. At least 96% of all mean pressure measurements were within 5 cm of H2O of the mean value for any horse. Peak pressure measurements were less repeatable, but at least 96% of all measurements were within 10 cm of H2O of the mean peak measurements for any horse. In 10 horses galloping at 14 m/s, the 95% confidence interval for peak tracheal and pharyngeal inspiratory pressures ranged from -40 to -50 cm of H2O and -20 to -26 cm of H2O, respectively. During expiration, the 95% confidence interval for peak tracheal and pharyngeal pressure at the same speed ranged from 15 to 28 cm of H2O and 10 to 24 cm of H2O respectively. During inspiration, horses with induced laryngeal hemiplegia had static pressure measurements generally outside that range. We conclude that determination of tracheal and pharyngeal pressures is a potentially useful adjunct for assessment of the proximal portion of the respiratory tract.
The influences of facial airflow, exercise and wearing a facemask on gas exchange and upper airway (Pu), transpulmonary (PTP) and transdiaphragmatic (PTD) pressures were investigated in 6 horses performing an incremental exercise test on an inclined (10%) treadmill. The test consisted of a 2 min walk followed by two 2 min exercise bouts at intensities which produced 40% and 80% of maximal oxygen consumption. Horses performed the test 4 times, once for each of 4 protocols, which involved not wearing a facemask (A), wearing a mask with either no biased flow through it (B), with an expiratory bias of 6300 L/min through it (C), or with an inspiratory bias of the same magnitude (D). Although no statistically significant differences in arterial blood gases, Pu, PTP, or PTD could be attributed to the various protocols, trends that may have been physiologically important were detected. Hypoxemia and hypercapnia associated with exercise were most marked with protocol B and least severe with protocols A or D. PTP was lowest for all tests with protocol D. Of the 3 conditions that required the wearing of a mask, protocol D was associated with the lowest Pu. While impelling air into the respiratory tract, as presumedly occurs with horses exercising over ground, may enhance respiratory function during exercise, this preliminary study does not clearly demonstrate this. Because this is an important consideration when conducting studies involving horses on treadmills, further investigations at higher exercise intensities and with additional methodologies are needed to clarify the issue.
Effects of respiratory tract obstructions on ventilatory mechanics in horses exercising at high speeds were tested with a fibreglass replica of the airways (nares to mainstem bronchi) of an adult horse. Segmental pressures were recorded at six sites along the model at four different unidirectional flows (1300-4100 litre min-1), and the respective resistances (R) to airflow were calculated. The external nares and the larynx made the greatest contributions to the total resistance (RTOT) when no obstruction was present. Modifying the model to simulate severe pharyngeal lymphoid hyperplasia (PLH) had no effect on R at the larynx or at any point in the trachea under these flow conditions. Two 16 litre anaesthetic rebreathing bags were attached to the bronchial end of the model, and tidal ventilation generated by a piston pump. Upper (nares to pharynx) and lower tract R (RU and RL) and RTOT, and dynamic compliance were determined for pump volumes (Vp) of six and 12 litres, at pumping frequencies (fp) of 20-100 min-1 while the airway was clear, and after modifying it to simulate either PLH or partial bronchial obstruction. Model condition had no effect on RU. However, RL and RTOT were higher in the PLH simulated condition when fp > or = 90 and Vp = 12 litres (P < 0.05). This suggested that severe PLH may significantly interfere with airflow distal to the site of the lesions during high frequency high volume ventilation of the type seen in galloping horses. With partial bronchial obstruction RL and RTOT were increased when fp > 34 with each Vp. The applicability of the model was verified by comparing results from the unobstructed state with those from normal horses exercising on a 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 evaluate the association among clinical signs, results of cytologic evaluation of bronchoalveolar lavage (BAL) fluid, and measures of pulmonary function in horses with inflammatory respiratory disease.
9 healthy horses, 5 horses with inflammatory airway disease (IAD), and 9 horses with chronic obstructive pulmonary disease (COPD).
Clinical examination, lung function tests, and BAL were performed on each horse.
Standard lung mechanics of horses with exacerbated COPD differed significantly from those of healthy horses; however, there were few differences among horses with IAD, horses with COPD during remission, and healthy horses. Most variables for forced expiration (FE) in horses with COPD or IAD differed significantly from those for healthy horses. Results of clinical examination had low to moderate sensitivity and predictive values for a diagnosis of COPD (range, 67 to 80%). Results of FE tests had high sensitivity, specificity, and predictive values for a diagnosis of COPD (79 to 100%), and results of standard lung mechanics tests had low sensitivity and predictive values (22 to 69%). Percentage of neutrophils in BAL fluid was highly sensitive (100%) but moderately specific (64%) for a diagnosis of COPD.
Clinical examination is moderately accurate for establishing a diagnosis of COPD. Forced expiration tests can specifically detect early signs of airway obstruction in horses with COPD and IAD that may otherwise be inapparent. Cytologic evaluation of BAL fluid allows early detection of inflammatory respiratory disease, but it is not specific for COPD.
To determine the effect of desensitization of the laryngeal mucosal mechanoreceptors on upper airway mechanics in exercising horses.
6 Standardbreds.
In study 1, videoendoscopic examinations were performed while horses ran on a treadmill with and without topical anesthesia of the laryngeal mucosa. In study 2, peak tracheal and nasopharyngeal pressures and airflows were obtained from horses during incremental treadmill exercise tests, with and without topical anesthesia of the laryngeal mucosa. A nasal occlusion test was performed on each horse while standing during an endoscopic examination for both trials.
In study 1, horses had nasopharyngeal collapse while running on the treadmill when the laryngeal mucosa was anesthetized. In study 2, inspiratory upper airway and nasopharyngeal impedance were significantly higher, and peak tracheal inspiratory pressure, respiratory frequency, and minute ventilation were significantly lower in horses when the laryngeal mucosa was anesthetized, compared with values obtained when horses exercised without topical anesthesia. Peak inspiratory and expiratory airflows were lower in horses when the laryngeal mucosa was anesthetized, although differences did not quite reach significance (P = 0.06 and 0.09, respectively). During a nasal occlusion test, horses had episodes of nasopharyngeal collapse and dorsal displacement of the soft palate when the laryngeal mucosa was anesthetized. Upper airway function was normal in these horses without laryngeal mucosal anesthesia.
Receptors within the laryngeal mucosa may be important in maintaining upper airway patency in exercising horses.
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.
Pharyngeal disorders are complex and difficult to treat. Disorders that lead to anatomic derangement, such as trauma and neoplasia, can significantly affect the function of this organ. Pharyngeal dysfunction can manifest as dysphagia, persistent palatal displacement, or exercise intolerance. Secondary complications are serious and life threatening and include aspiration pneumonia, weight loss, and death. Pharyngeal disorders that are only recognizable during strenuous exercise are difficult to diagnose and are treated with limited success, even though they are responsible for significant economic losses with performance animals.
Horses housed in conventional stable environments are exposed to high dust loads. Long-term exposure to inhaled dust may lead to subclinical airway disease.
Airway inflammation and mucus accumulation are 1) common in asymptomatic well-performing sport horses, 2) increased in older compared to younger individuals and 3) correlated.
Mucus quantity and quality (endoscopic scoring) and BALF differential cytology were assessed in 13 younger horses (mean age 5 years) and 13 older horses (mean age 15 years), which had no historical or clinical evidence of lower airway disease, were performing well and were housed permanently in a conventional stable environment.
1) Airway inflammation and/or mucus accumulation were very common. All sport horses showed evidence of subclinical inflammatory airway disease (IAD). 2) Older horses, having been exposed for 10 more years to a conventional stable environment, did not show increased subclinical airway inflammation or mucus accumulation. The only differences between the age groups were increased BALF total and lymphocyte cell counts in the younger horses. 3) Mucus quantity and quality scores were not significantly correlated with each other or with BALF neutrophil percentages and absolute numbers.
Although clinically healthy and performing well, all of the examined horses housed in a conventional stable environment showed evidence of IAD. The degree of IAD was not increased in older horses that had not developed clinical signs.
The effect of subclinical degrees of IAD on performance in dressage and show jumping should be investigated further to better understand the clinical significance of IAD in sport horses.
Show and performance horse with laryngeal hemiplegia (LH) often present for excessive respiratory noise rather than significant exercise intolerance. Therefore, the goal of surgery in these horses is to reduce respiratory noise but there are no quantitative studies evaluating the effect of any upper-airway surgery in LH-affected horses.
To determine whether bilateral ventriculocordectomy (VC) reduces respiratory noise in exercising horses with laryngeal hemiplegia.
Six Standardbred horses with normal upper airways were used in this study. Respiratory sounds and inspiratory trans-upper airway pressure (Pui) were measured in all horses before and after induction of LH, and 30, 90 and 120 days after VC. In horses with LH, spectrogram analysis revealed 3 inspiratory sound formants centred at approximately 400, 1700 and 3700 Hz. Inspiratory sound levels (SL) and the sound intensity of the 3 inspiratory formants (F1, F2, F3 respectively) were measured using a computer-based sound analysis programme.
In LH-affected horses, Pui, inspiratory SL and the sound intensity of F2 and F3 were significantly increased compared to baseline values. At 90 and 120 days after VC the sound intensities of F2 and F3 returned to baseline values. The Pui and SL, were significantly decreased compared to LH values, but remained different from baseline.
VC effectively reduces inspiratory noise in LH-affected horses by 90 days following surgery. Inspiratory trans-upper airway pressures are improved 30 days following VC, but do not return to baseline values.
VC can be recommended as a surgical treatment of LH-affected horses if reduction of respiratory noise is the primary objective of surgery. Further studies are required to determine if variations of the surgical technique used in this study will have similar results.
The primary goal was to investigate the relationship between dynamic upper airway abnormalities and arterial blood gas tensions during exercise. Horses that completed a high‐speed treadmill examination consisting of upper‐airway videoendoscopy, blood gas evaluation and electrocardiogams and, postexercise, echocardiograms and tracheal washes, were included. An age‐matched group of fit, healthy Thoroughbreds, trained to run on a high‐speed treadmill, served as controls for blood gas values at specific exercise speeds.
One hundred and nineteen horses completed the treadmill examination. Sixty (50%) were Thoroughbreds (TB), 51 (43%) Standardbreds (STD) and 8 (7%) other breeds. Mean ± s.d. age TB 3.8 ± 2.2 years and STD 4.0 ± 1.7 years, with no gender predilection. Fifty‐four horses (45%) had abnormal upper respiratory tract (URT) abnormalities alone or in combination with abnormalities in another body system. Thirty‐eight (70%) were TB, 14 (26%) were STD and 2 (4%) were other breeds. Of these, 24 (45%) had exercising Pao 2 values significantly lower than those observed in healthy TB. Nineteen (35%) horses also had significantly elevated exercising PaCo 2 . Only 14 (12%) horses had abnormal clinical findings in the URT alone, and of these, only 3 (21%) had an abnormally low Pao 2 and/or elevated Paco 2 . Multiple URT abnormalities were more commonly associated with abnormal exercising blood gases than were single disorders, but pharyngeal collapse (PC) was much more commonly associated with abnormal values if only one disorder was detected. Fifty‐five percent (n = 65) of all cases admitted had no evidence of URT disease. Twenty‐two (35%) were TB and 37 (57%) were STD. Twenty (31%) of these had abnormally low Pao 2 and 14 (22%) had elevated PaCo 2 values. Seventy percent (14) of the horses with abnormal Pao 2 were STD, while almost 80% (11) of the horses with elevated Paco 2 were STD.
These data suggest that dynamic URT dysfunction can adversely affect gas exchange during exercise. While multiple abnormalities were more commonly associated with gas exchange problems than were single disorders, pharyngeal collapse, either alone or in combination with other URT problems, was the disorder most frequently associated with blood gas abnormalities. Additionally, URT disease was more commonly seen in TB, and the proportion of URT diagnoses in horses with abnormal blood gases reflected this percentage, while STD without URT disease had a much higher incidence of abnormal blood gases than did TB without URT abnormalities.
There are a variety of reasons for poor performance in racehorses. Exercise intolerance has often been associated with subclinical respiratory abnormalities, and diagnostic aids are therefore used to enhance clinical detection. Physiological variables can also be measured in order to evaluate the metabolic reponse to exercise. This study evaluated the relationship between physiological measurements and upper airway videoendoscopy during a standardised treadmill exercise test and bronchoalveolar lavage (BAL) cytology in control horses (good racing performance, n = 14) and poor performers (n = 27). The poor performers were divided into 2 groups: Group 1 = both upper and lower respiratory airway abnormal findings (n = 10); Group 2 = lower respiratory airway abnormal findings (n = 17). Horses in Group 2 were divided into 3 categories: Group 2A = exercise-induced pulmonary haemorrhage (EIPH ; n = 5); Group 2B = small airway inflammation (SAI +/- EIPH; n = 7) and Group 2C = other (n = 5). During exercise, the poor performers had significantly lower arterial PaO2 and higher HR and blood lactate concentrations compared to controls. Total nucleated cell count of BAL fluid collected from poor racing performers was significantly higher than in controls; also, epithelial cells and haemosiderophage percentage collected from poor racing performers were significantly higher than in controls. Eight horses with dorsal displacement of the soft palate also had cytological evidence of lower respiratory airway disease. The results of this study suggest that there is a significantly different metabolic response (HR, blood lactate, PaO2) to exercise in poor compared to good performers. As both upper and/or lower respiratory problems can be associated with poor racing performance, a detailed examination of the upper and lower respiratory tracts at rest, during and after exercise is advised.
Laryngoplasty is the technique of choice for treatment of laryngeal hemiplegia, with the aim of improving airway function and/or eliminating respiratory noise. However, there are no quantitative data in the literature describing the effect of laryngoplasty on upper airway noise or its relationship to upper airway mechanics in horses with laryngeal hemiplegia.
To determine whether laryngoplasty reduces respiratory noise in exercising horses with laryngeal hemiplegia; and to establish whether the degree of upper airway obstruction can be predicted by upper airway noise, or the degree of arytenoid abduction correlated with airway obstruction and noise production.
Six Standardbred horses with normal upper airways during maximal exercise were used. Respiratory sounds and inspiratory transupper airway pressure (Pui) were measured in all horses before and after induction of laryngeal hemiplegia and 30, 60 and 90 days after laryngoplasty. Inspiratory sound level (SL) and the sound intensity of the 3 inspiratory formants (F1, F2 and F3, respectively) were measured using a computer-based sound analysis programme. The degree of abduction was graded by endoscopic visualisation 1, 30, 60 and 90 days post operatively. Linear regression analysis was used to determine correlations between Pui, sound indices and grades of arytenoid abduction.
In laryngeal hemiplegia-affected horses, Pui, inspiratory SL and the sound intensity of F1, F2 and F3 were significantly increased. At 30 days following laryngoplasty, the sound intensity of F1 and Pui returned to baseline values. The sound intensities of F2, F3 and SL were significantly improved from laryngeal hemiplegia values at 30 days post operatively, but did not return to baseline at any measurement period. Sound level, F2 and F3 were significantly correlated with Pui (P<0.05), but the correlations were weak (r2 = 0.26, 035 and 0.40, respectively). Grade of abduction and F2 were positively and significantly correlated (P<0.006, r2 = 0.76). Grade of arytenoid abduction and Pui were not correlated (P = 0.12).
Laryngoplasty reduced inspiratory noise in laryngeal hemiplegia-affected horses by 30 days following surgery, but did not return it to baseline values. While upper airway noise and Pui were correlated, this relationship was insufficiently strong to predict Pui from noise in individual animals. The degree of arytenoid abduction was not correlated with Pui, but was positively correlated with noise production.
Laryngoplasty reduces upper airway noise in horses with laryngeal hemiplegia, but is not as effective as bilateral ventriculocordectomy in this regard, although respiratory noise reduction occurs more rapidly than with bilateral ventriculocordectomy. Residual noise during exercise cannot be used as a predictor of improvement in upper airway function in individual horses following laryngoplasty. The degree of arytenoid abduction obtained following surgery does not affect upper airway flow mechanics. Interestingly, we found that the greater the arytenoid abduction, the louder the respiratory noise.
Endoscopic scoring of airway mucus quantity and quality has not been critically assessed.
To evaluate mucus scores for 1) observer- and horse-related variance and 2) association with inflammation, mucus viscoelasticity and measured volume.
Variance of scoring within and between observers and over time within horses were determined for airway mucus accumulation, apparent viscosity, localisation and colour, and correlations of mucus accumulation scores with neutrophil ratios in secretions. The relationship of accumulation score to measured volumes of 'artificial mucus' was investigated. Correlations of mucus accumulation, apparent viscosity and colour scores with measured viscoelasticity were tested. Viscoelasticity was compared between tracheal secretion samples collected ventrally and dorsally.
Mucus accumulation scoring showed excellent interobserver agreement and moderate horse-related variance, was related to measured volumes of 'artificial mucus', and correlated well with neutrophilic airway inflammation. Scores of mucus viscosity, colour and localisation showed high observer-related variance. Mucus accumulation, apparent viscosity and colour scores did not correlate with measured tracheal mucus viscoelasticity, but dorsally-localised mucus showed 2-fold higher measured viscoelasticity than ventrally-localised samples.
Mucus accumulation scores are a reproducible measure of mucus volumes in the trachea.
Endoscopic scoring of mucus accumulation is a reliable clinical and research tool. In contrast, apparent viscosity, localisation and colour scores should be interpreted with caution.
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.
Accumulations of mucus within the trachea are often found during endoscopic examinations of the airways of poorly performing racehorses, but the clinical importance of this finding is unknown.
To determine the effect of tracheal mucus, pharyngeal lymphoid hyperplasia (PLH) and cytological indices of tracheal aspirate on racing performance in Thoroughbred horses assessed by race place and whether the horse was raced.
Endoscopic examination of the nasopharynx, larynx and trachea was performed, and a tracheal aspirate obtained monthly at Thistledown racetrack from April to December, 2002 and 2003. Horses received a score of 0-4 for the degree of PLH and 0-4 for the amount of mucus visible in the trachea. The tracheal aspirate was assessed for turbidity, and total and differential cell counts. Generalised estimating equations models were used as repeated measures models for each risk factor and the level of association assessed through the risk factor's P value in the model.
Moderate to severe tracheal mucus (2-4) was a risk factor for poor racing performance. There was no association between degree of PLH, cell counts or turbidity of tracheal wash fluid and racing performance. However, horses that raced had higher total neutrophil counts in tracheal wash aspirates than horses that did not race.
Grades 2-4 tracheal mucus should be considered a potential cause of poor racing performance in Thoroughbred horses.
Because moderate to severe tracheal mucus accumulation, and not increased tracheal neutrophils, was a risk factor for poor racing performance, functionally significant airway inflammation may best be confirmed by the presence of mucus rather than increased number of neutrophils in the trachea.