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.

Exercise-induced pulmonary hemorrhage (EIPH) and asthma in barrel racing horses is a common disease across the United States. Limited information is available on non-infectious respiratory diseases in this population, the interaction between these two diseases, and the occurrence of both EIPH and asthma in the horse. The purpose of this study was to evaluate the bronchoalveolar lavage (BAL) fluid cytological results of barrel racing horses with EIPH, asthma, or both. A retrospective study was conducted using the medical records of horses that presented with cough and decreased athletic performance and BAL results that met the criteria for inclusion. Data from 95 horses were included from a private practice referral hospital in Texas. No statistical difference was found in the frequency of neutrophilia, eosinophilia, or mastocytosis between diagnoses of EIPH, asthma, or concurrent diagnoses of EIPH and asthma. Bronchoalveolar lavage of horses suspected of EIPH is warranted to fully characterize the noninfectious respiratory disease of barrel racing horses.

BACKGROUND: Exercise-induced pulmonary hemorrhage (EIPH) is diagnosed and its severity assessed by post-exercise tracheobronchoscopy, and enumeration of bronchoalveolar lavage fluid red blood cells (BALFRBC). Minimal information is available regarding the relationship of tracheobronchoscopy score to BALFRBC number.
OBJECTIVE: Evaluate the relationship between BALFRBC number and tracheobronchoscopy scores and determine their diagnostic sensitivities.
METHODS: Nine sedentary horses, 21 fit Thoroughbreds, 129 Barrel Racers.
METHODS: Normal BALFRBC number and the effect of bronchoalveolar lavage (BAL) on it were evaluated by performing 2 BALs 24 hours apart in sedentary horses. Tracheobronchoscopy followed by BAL was performed 247 times on 150 horses after treadmill, racetrack, or barrel racing exercise. Lastly, a BALFRBC diagnostic threshold number that optimized the geometric mean of the sensitivity and precision (F1-score) was determined using Bayesian analysis.
RESULTS: No increase in BALFRBC occurred after the second BAL (mean ± SD, 304 ± 173/μL). Tracheobronchoscopy scores ranged from 0 (n = 112) to 4 (n = 4) and BALFRBC ranged from 102 to 4605268/μL. Spearman correlation between tracheobronchoscopy score and BALFRBC was weak (P < .001; rs = 0.42) with large ranges of BALFRBC associated with each tracheobronchoscopy score. The highest F1-score occurred for a BALFRBC threshold number = 992/μL. Seventy-five tracheobronchoscopy scores equaled 0 although BALFRBC number was ≥992/μL. Sensitivity of tracheobronchoscopy for diagnosing EIPH was poor (0.59; 95% confidence intervals [CI], 0.49-0.68), compared to BALFRBC number ≥992/μL (0.93; 95% CI, 0.88-0.96).
CONCLUSIONS: False negatives are common with tracheobronchoscopy. Follow-up determination of BALFRBC may be indicated for tracheobronchoscopy scores = 0 before EIPH can be ruled out.