The displaced equine soft palate as a source of abnormal respiratory noise during expiration

Upper airway endoscopy in exercising horses: Findings in 164 barrel racing horses with respiratory clinical signs and/or poor performance

Barrel racing involves sprinting through a cloverleaf pattern in under 20 s. The prevalence of upper airway obstructions (UAO) in barrel racers is unknown, thus a retrospective analysis of 164 client-owned horses referred for overground endoscopy (OGE) between 2014 and 2022 was performed. Referring complaints included respiratory noise, cough, epistaxis, behaviour (owner reported stress/anxiety, refusal to enter arena, excessive head shaking), and/or poor performance. Horses performed a standardized exercise test with low and high-speed components. Videoendoscopic recordings were systematically scored by one experienced clinician. Exercising abnormalities included palatal instability (PI), intermittent dorsal displacement of the soft palate (iDDSP), nasopharyngeal collapse (NPC), recurrent laryngeal neuropathy (RLN), ventro-medial luxation of the apex of the corniculate process of the arytenoid (VLAC), medial deviation of the aryepiglottic fold (MDAF), vocal fold collapse (VFC), and cricotracheal ligament collapse. Associations between co-existing UAOs, age and sex were examined (McNemar's test; logistic regression; P < 0.05). During exercise, 24/164 (15%) horses had no UAO. In the remaining 140 horses, 56% had two or more. NPC was observed in 68/140 (49%), PI in 59/140 (42%), iDDSP in 55/140 (39%), VFC in 38/140 (27%), RLN in 27/140 (19%), VLAC in 14/140 (10%), MDAF in 8/140 (6%) and cricotracheal ligament collapse in 8/140 (6%). Nasopharyngeal collapse and RLN were primarily Grade 3 and Grade B, respectively. Associations exist between several co-existing UAOs, but not age or sex. Abnormalities were more frequent at low-speed (55%) than high-speed (22%), highlighting the importance of OGEs at different exercise intensities. Multiple UAOs appear common in barrel racers with clinical presentations.

Laryngeal tie-forward in standing sedated horses

OBJECTIVES

To investigate the feasibility and describe the clinical experience of performing laryngeal tie-forward (LTF) in standing horses unaffected (experimental) and affected (clinical) by intermittent dorsal displacement of the soft palate (iDDSP).

STUDY DESIGN

Experimental study and case series.

ANIMALS

Five normal experimental controls and five client owned horses affected by iDDSP.

METHODS

Standing LTF was performed and evaluated in five experimental horses and five clinical cases diagnosed with iDDSP. Standing LTF was performed under endoscopic guidance with horses sedated and the surgical site desensitized with local anesthetic solution. Short term outcome was assessed using radiography, resting and (in clinical cases) dynamic upper respiratory tract (URT) endoscopy.

RESULTS

Standing LTF was well tolerated and completed in all horses. Radiographic assessment demonstrated that compared to preoperatively, the basihyoid bone and thyrohyoid-thyroid articulation were positioned dorsally (9.6 mm, p = .006 and 20.4 mm, p = .007, respectively) at 2 days postoperatively. During repeat dynamic URT endoscopy at 48 hours postoperatively, 3/5 horses showed resolution of iDDSP and 2/5 marked improvement. One horse experienced brief iDDSP associated with neck flexion which corrected after swallowing. The second achieved a greater speed and total distance prior to iDDSP.

CONCLUSIONS

Standing LTF did not incur any major peri- or postoperative complications. The laryngohyoid apparatus was repositioned dorsally and in a small case series had a similar surgical effect on laryngeal position.

CLINICAL SIGNIFICANCE

Standing LTF is feasible, mitigates the risk of general anesthesia related complications and reduces cost.

Physiological measurements and prevalence of lower airway diseases in Trotters with dorsal displacement of the soft palate

REASONS FOR PERFORMING STUDY

Dorsal displacement of the soft palate (DDSP) is one of the most common obstructive conditions of the upper respiratory tract in the racehorse. This condition has a complex aetiology which may be caused or exacerbated by pharyngeal inflammation. Additionally, lower respiratory airway diseases may be associated with DDSP thereby contributing to exercise intolerance in these horses.

OBJECTIVE

The aim of this study was to measure physiological variables during a standardised exercise test and to assess the prevalence and consequences of lower respiratory airway disease in horses with DDSP.

METHODS

A total of 46 horses were included in this study: 22 in the control and 24 in the DDSP groups. All horses performed a SET with measurement of heart rate (HR) and blood lactate concentration. One hour post exercise, respiratory samples were collected for cytological and bacteriological analysis.

RESULTS

During exercise, the DDSP group had higher blood lactate concentration than the control group. According to BAL results, 50 and 63% of control and DDSP group horses, respectively, had evidence of inflammatory airway disease (IAD). In the DDSP group, 42% of horses had a syndrome of tracheal inflammation (STI) with 71% of this group having bacteria isolated at >10(5) CFU/ml.

CONCLUSIONS

Horses with DDSP showed evidence of a high prevalence of IAD and STI with an associated positive bacteriology in 55% of the cases. Even if DDSP is treated by surgery, the authors' recommendation would be to investigate the possibility of lower respiratory airway problems which may also be impacting the horse's performance and/or surgery efficiency.

Histological and biomechanical effects of palatal sclerotherapy in the horse using sodium tetradecyl sulfate

Palatal sclerotherapy using sodium tetradecyl sulfate has been suggested as a treatment for dorsal displacement of the soft palate in young Standardbred horses. The present study evaluated histological and biomechanical changes in the equine soft palate following trans-endoscopic treatment with a low dose of this compound. Two horses were euthanased and examined at 2 weeks and at 1, 2, 4 and 6 months post-sclerotherapy, while two further horses served as untreated controls. The technique was easily performed in all cases without major complications. On histological examination there was no evidence of palatal necrosis, inflammation or fibrosis in any of the treated or control animals. There was no variation in the density of palatal connective tissue between individuals, and on biomechanical assessment no significant difference in the stiffness of the palatal tissue was found between treated and control horses at any time. The lower dose of sodium tetradecyl sulfate used in this study relative to previous reports, might explain the absence of tissue alterations. This method of sclerotherapy did not alter the morphology or biomechanical properties of normal equine soft palates.