Tracheobronchoscopic assessment of exercise-induced pulmonary hemorrhage in horses

Atrial fibrillation as a risk factor for exercise-induced pulmonary haemorrhage following a standardised exercise test

BACKGROUND

Atrial fibrillation (AF) has been proposed as a risk factor for exercise-induced pulmonary haemorrhage (EIPH) due to increased pressure in the left atrium.

OBJECTIVE

To evaluate if AF was associated with EIPH following a standardised exercise test (SET) to fatigue.

STUDY DESIGN

Two-arm controlled experiment.

METHODS

Ten untrained Standardbred mares mean (standard deviation [SD]) age 6 (2) years performed a SET on the treadmill in sinus rhythm (SR) (SET1) and 25-44 days after induction of self-sustained AF (SET2). AF was induced by tachypacing using a pacing device. Endoscopy, including tracheal wash and bronchoalveolar lavage (BAL), was performed 48-72 h before and 24 h after the two SETs. In addition, endoscopic grading of tracheal blood was performed 2 h after each SET.

RESULTS

After SET1, none of the horses showed blood in the trachea, and two horses showed erythrophagocytosis. Following SET2, two horses had grade 1 blood in the trachea and free erythrocytes and erythrophagocytosis in the BAL, while another two horses had erythrophagocytosis in the BAL. In SET2, the overall performance on the treadmill was decreased with a lower maximum velocity (SET1 10.3 ± 0.8 m/s vs. SET2 8.9 ± 0.9 m/s, p = 0.004), a higher heart rate (284 ± 21 vs. 221 ± 18 bpm, p = 0.003) and more abnormal QRS complexes (p < 0.001) compared with SET1.

CONCLUSIONS

Two horses showed signs of EIPH, resulting in visible blood in the trachea, when exercising in AF compared with SR. However, a possible link between EIPH, pulmonary pressure and AF needs to be further elucidated.

Field-training in young two-year-old thoroughbreds: investigating cardiorespiratory adaptations and the presence of exercise induced pulmonary hemorrhage

BACKGROUND

Comparatively little is known regarding the initial cardiorespiratory response of young racehorses to training. The objectives were to compare physiological parameters before and after introductory training and determine whether young Thoroughbreds show endoscopic signs of exercise-induced pulmonary hemorrhage (EIPH). Ten Thoroughbreds (20-23 months) underwent 12-weeks of introductory training, including weekly speed sessions. Two 600 m high-speed exercise tests (HSET) were performed following weeks 4 and 12 while wearing a validated ergospirometry facemask. Peak oxygen consumption (V̇O2pk) and ventilatory parameters (tidal volume, VT; peak inspiratory and expiratory flow, PkV̇I, PkV̇E; respiratory frequency, Rf; minute ventilation, V̇E) were measured. The ventilatory equivalent of oxygen (V̇E/V̇O2) and the aerobic and anaerobic contributions to energy production were calculated. Maximal heart rate (HRmax) and HR at maximal speed (HRVmax) were determined. Post-exercise hematocrit, plasma ammonia and blood lactate were measured. Evidence of EIPH was investigated via tracheobronchoscopy post-exercise. Results were compared (paired t-test, P < 0.05).

RESULTS

Horses were faster following training (P < 0.001) and V̇O2pk increased 28 ml/(kg total mass.min) (28 ± 16%; P < 0.001). Ventilatory (V̇E, P = 0.0015; Rf, P < 0.001; PkV̇I, P < 0.001; PkV̇E, P < 0.001) and cardiovascular parameters (HRmax, P = 0.03; HRVmax, P = 0.04) increased. The increase in V̇E was due to greater Rf, but not VT. V̇E/V̇O2 was lower (26 ± 3.6 vs 23 ± 3.7; P = 0.02), indicating improved ventilatory efficiency. Anaerobic contribution to total energy production increased from 15.6 ± 6.1% to 18.5 ± 6.3% (P = 0.02). Post-exercise hematocrit (P < 0.001), plasma ammonia (P = 0.03) and blood lactate (P = 0.001) increased following training. Horses showed no signs of EIPH.

CONCLUSIONS

Young two-year-old Thoroughbreds responded well to introductory training without developing tracheobronchoscopic evidence of EIPH.

Cytological diagnosis of exercise-induced pulmonary haemorrhage: Comparison of tracheal wash and bronchoalveolar lavage in standardbred racehorses

BACKGROUND

Cytology of airway samples is sensitive for diagnosis of exercise-induced pulmonary haemorrhage (EIPH), but the association between tracheal wash (TW) and bronchoalveolar lavage fluid (BALF) is unknown. The objective of this study was to determine whether diagnosis of EIPH, using haemosiderophages/macrophages (H/M) ratio, differs when based on TW or BALF.

METHODS

A prospective cross-sectional study was conducted on 102 standardbred horses in training. TW and BALF were collected concomitantly from all horses at rest (at least 24 hours after their last training or race), and their H/M ratios were calculated. Spearman's correlation, Cohen's kappa and Gwet's coefficient tests were performed to evaluate the association between TW and BALF samples.

RESULTS

With BALF, 21 horses met the cytological inclusion criteria for an EIPH diagnosis from individual and/or pooled samples. With TW, 20 horses had occasional (H/M < 10%) haemosiderophages, and nine, one and three horses had small (10%-25%), moderate (25%-50%) and large (>50%) proportions, respectively. Poor correlations and inconsistent concordances between TW and BALF were found for H/M ratio.

LIMITATIONS

Limitations include the use of a single staining method and the absence of a total haemosiderin score.

CONCLUSION

No association between TW and BALF was found for the cytological diagnosis of EIPH. Based on H/M ratio, BALF remains the sample type of choice for cytological diagnosis of EIPH.

Associations between postrace atrial fibrillation and measures of performance, racing history and airway disease in horses

BACKGROUND

Atrial fibrillation (AF) is the most common performance limiting arrhythmia in racehorses. High dose exercise and airway disease promote AF in humans. Few studies have investigated epidemiological factors associated with AF in horses.

OBJECTIVES

Explore variables relating to performance, exercise volume and postrace endoscopic findings in horses with AF.

ANIMALS

A total of 164 horses with poor race performance and postrace AF were compared to 321 horses with poor performance without AF (PP) and 314 horses performing to expectation (TE).

METHODS

Horse-level and race-level variables for horses racing in Australia and Hong Kong from 2009 to 2021 were compared using univariable and multivariable logistic regression. Postrace endoscopic exercise-induced pulmonary hemorrhage (EIPH) and tracheal mucus accumulation (TMA) grades for AF and PP horses were compared using chi-squared analysis.

RESULTS

Variables that were significant in the multivariable model of AF compared to TE were distance (lengths) behind the winner, (odds ratio [OR]; 95% confidence interval [95% CI], 1.41 [1.32-1.51], P < .0001), cumulative prize money per start before the event (OR [95% CI] 1.02 [1.01-1.03], P = .01) and age (OR [95% CI] 0.72 [0.55-0.92], P = .01). More AF horses had EIPH grade ≥ 3 (23/109; 21.1%) than PP horses (7/213; 3.3%; OR [95%CI] 7.9 [3.3-20.2], P < .0001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Acute race performance was substantially impaired by AF but career earnings before the event were not inferior. Exercise volume did not promote AF. Higher grades of EIPH found in AF horses suggests a mechanistic relationship between these conditions.

Prevalence of Exercise-Induced Pulmonary Hemorrhage, Tracheal Mucus and Recurrent Laryngeal Neuropathy in Competitive Draft Pulling Horses

Respiratory disease is common in the horse population and is often associated with poor performance in equine athletes. Despite their outstanding strength and aerobic capacity, little regard is given to draft horses and the respiratory disorders they may encounter when performing athletic activity. For this reason, the objectives of this study were: (1) to determine the prevalence of exercise-induced pulmonary hemorrhage (EIPH), tracheal mucus (TM) and recurrent laryngeal hemiplegia (RLH) in a population of competitive draft pulling horses, and (2) to determine if there was an association between horse weight, height, age, amount pulled, or competition placing with EIPH, TM or RLH in draft pullers. Results of this study identified EIPH in 26% of the study population, RLH in 32% and TM in 82% of participating horses; however, no risk factors were identified for the development of these problems in draft pulling horses.

Associations between Medical Disorders and Racing Outcomes in Poorly Performing Standardbred Trotter Racehorses: A Retrospective Study

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.

Medical causes of poor performance and their associations with fitness in Standardbred racehorses

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.

Risk Factors for Epistaxis in Thoroughbred Flat Races in Japan (2001-2020)

We investigated the risk factors for epistaxis in Japanese flat races over a 20-year period. The veterinary records of horses identified as having epistaxis by endoscopy on the race day, and the official racing records of all flat races from April to September between 2001 and 2020, were reviewed. The racecourses (n = 10), surface type, surface condition, race class, race distance, race year, sex, age, two training centers, ambient temperature, and body weight on race days were assessed using multivariable logistic regression (p < 0.05). Of 475,709 race starts, 616 (1.30 cases per 1000 starts; 95% confidence interval [CI], 1.20-1.40) included an epistaxis event. Nine variables were significantly associated with epistaxis. Seven of the variables have been reported in previous studies: lower ambient temperature, soft surface conditions, shorter racing distances (≤1400 m), increasing age, females and geldings compared to males, training center, and race year. However, two novel variables were identified as significantly associated with epistaxis, increasing body weight per 20 kg (p < 0.001, odds ratio [OR], 1.33; 95% CI, 1.25-1.41) and the racecourses that the horses were running at (p < 0.001, especially Sapporo [OR; 4.74, 95% CI, 3.07-7.31], Hakodate [OR, 4.66; 95% CI, 3.05-7.11], and Kokura [OR, 4.14; 95% CI, 2.65-6.48] compared to the reference racecourse [Kyoto]). These results can facilitate developing interventions to reduce epistaxis in flat racing.

Upper and Lower Airways Evaluation and Its Relationship with Dynamic Upper Airway Obstruction in Racehorses

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.

Association between dynamic upper airway obstructions and fitness parameters in Standardbred racehorses during high-speed treadmill exercise

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.

Associations between Exercise-Induced Pulmonary Hemorrhage (EIPH) and Fitness Parameters Measured by Incremental Treadmill Test in Standardbred Racehorses

Simple Summary

Exercise-induced pulmonary hemorrhage (EIPH) frequently affects racehorses worldwide and has been widely associated with poor performance; however, scientific evidence supporting this observation is low. The present retrospective study aims to evaluate objectively whether the presence and grade of EIPH could affect some fitness parameters, measured during an incremental treadmill test, in poorly performing Standardbred racehorses. For this purpose, the association between EIPH and the results of a treadmill metabolic test (including blood lactate analysis and venous blood gas analysis) were evaluated in 81 Standardbred racehorses. No relationship between EIPH and aerobic/anaerobic capacity was observed, suggesting that EIPH may affect performance in a different manner. However, EIPH-affected horses were shown to reach higher hematocrit values during exercise compared to EIPH-negative horses; therefore, it may be hypothesized that hemoconcentration may take part in the pathogenesis of EIPH by increasing the pulmonary capillary pressure.

Abstract

Exercise-induced pulmonary hemorrhage (EIPH) is a condition affecting up to 95% of racehorses, diagnosed by detecting blood in the trachea after exercise and/or the presence of hemosiderophages in the bronchoalveolar lavage fluid (BALf). Although EIPH is commonly associated with poor performance, scientific evidence is scarce. The athletic capacity of racehorses can be quantified through some parameters obtained during an incremental treadmill test; in particular, the speed at a heart rate of 200 bpm (V200), and the speed (VLa4) and the heart rate (HRLa4) at which the blood lactate concentration reaches 4 mmol/L are considered good fitness indicators. The present retrospective study aims to evaluate whether EIPH could influence fitness parameters in poorly performing Standardbreds. For this purpose, data from 81 patients regarding their V200, VLa4, HRLa4, peak lactate, maximum speed, minimum pH, and maximum hematocrit were reviewed; EIPH scores were assigned based on tracheobronchoscopy and BALf cytology. The association between the fitness parameters and EIPH was evaluated through Spearman’s correlation analysis. No relationship between EIPH and V200, VLa4, and HRLa4 was observed. Interestingly, EIPH-positive horses showed higher hematocrit values (p = 0.0072, r = 0.47), suggesting the possible influence of the hemoconcentration on the increase of pulmonary capillary pressure as a part of the pathogenesis of EIPH.

The effect of lower airway inflammation on inflammatory cytokine gene expression in bronchoalveolar lavage fluid and whole blood in racing Thoroughbreds

BACKGROUND

Immunological mechanisms involved in the pathogenesis of mild to moderate equine asthma (MEA) are not completely understood. There are limited data on bronchoalveolar lavage fluid (BALF) and blood inflammatory cytokine profiles in racehorses with MEA, and the effect of racing on inflammatory cytokines is unknown.

HYPOTHESIS/OBJECTIVES

We hypothesized that inflammatory cytokine gene expression in BALF and resting blood would be higher in racehorses with lower airway inflammation compared to healthy controls, and that gene expression in blood collected immediately post-race would be increased compared to resting blood in racehorses with lower airway inflammation.

ANIMALS

38 racing Thoroughbreds (samples: 30 resting blood, 22 post-race BALF, 41 post-race blood).

METHODS

Prospective observational study. Inflammatory cytokine gene expression was determined in resting blood, post-race BALF and post-race blood from racehorses with lower airway inflammation and controls.

RESULTS

Lower airway inflammation was diagnosed in 79 % of racehorses (23 % neutrophilic, 67 % mastocytic, and 10 % mixed). There was no difference in gene expression in BALF or resting blood between racehorses with lower airway inflammation and controls. IL-8 gene expression was higher in post-race blood compared to resting peripheral blood, regardless of disease (p = 0052). BALF neutrophil proportions increased with increasing IL-1β gene expression in all sample types (p = 0.0025). BALF mast cell proportions increased with increasing TNF-α gene expression in post-race blood (p = 0.015).

CONCLUSIONS AND CLINICAL IMPORTANCE

Lower airway inflammation was common in a population of racehorses without respiratory signs or exercise intolerance. Exercise alone increased peripheral blood IL-8 gene expression. Inflammatory cytokine gene expression was not increased in BALF or resting blood in horses with subclinical lower airway inflammation, precluding its diagnostic utility in clinical practice.

Equine respiratory viruses, airway inflammation and performance in thoroughbred racehorses

Equine asthma is a common cause of poor performance in racehorses but it is unclear if respiratory viruses contribute to its etiology. The objective of the study was to determine if respiratory viruses were associated with clinical signs and bronchoalveolar lavage fluid (BALF) cytology in Thoroughbred racehorses. Equine herpesviruses (EHV-1, 2, 4, 5) and equine rhinitis A and B viruses (ERBV, ERAV) genomes were quantified by qPCR in nasopharyngeal, tracheal, and BALF samples collected after racing. The relationships between virus detection and load and clinical signs, performance, BALF cytology, and environmental exposures were examined with generalized linear mixed models. Ninety-two samples were collected from 31 horses. EHV-1 and ERAV were not found; EHV-4 was detected in only one sample. EHV-2, EHV-5 and ERBV were more likely to be detected in upper airway samples than in BALF (P < 0.0001). Neither respiratory virus detection nor load was associated with clinical signs or performance. Nasopharyngeal detection and load of ERBV and tracheal detection and load of EHV-5 were associated with increased proportions of neutrophils in BALF (P < 0.003). However, nasopharyngeal detection and load of EHV-5 was not (P = 0.11). Nasopharyngeal detection and load of EHV-2 were associated with decreased BALF mast cell proportions. Respirable dust exposures were significantly higher in horses with detection of ERBV when compared to horses with no detectable ERBV (P < 0.001). Our results suggest that ERBV, EHV-2 and EHV-5 are commonly present in upper airways of healthy racehorses; however, the role they play in the etiology of equine asthma remains unclear.

Validation of a Rapid Bronchoalveolar Lavage Fluid Colorimetric Evaluation for Assessing the Severity of Exercise-Induced Pulmonary Hemorrhage in Horses in Field Conditions

Diagnosis and assessment of severity of exercise-induced pulmonary hemorrhage (EIPH) relies on postexercise visualization of fresh blood in the airways via tracheobronchoscopic examination (TBE) and/or counting erythrocytes in bronchoalveolar lavage fluid (BALFRBC). Determining the BALFRBC is more sensitive than TBE but its usefulness is hampered by the need to have BALFRBC counted at a laboratory. We explored the feasibility of evaluating the severity of EIPH by using a color chart comprised of five shades of red and matching those colors with the color of BALF immediately following collection. To validate the technique, sets of ten BALF samples with known BALFRBC numbers were created and randomly shown to two groups of 18 observers who independently matched the color of the BALF with one of the shades of red displayed on the screen of a smartphone. Interobserver and intra-observer agreements regarding colors were > 0.9. The utility of the color chart was further validated under field conditions at two barrel racing events where 63 BALF samples were collected from 21 horses and BALF color was graded independently by three observers. The number of BALFRBC in the 63 samples ranged from 25-1,100,000/μL. EIPH was diagnosed in 39 samples based on the detection of color, and all 5 colors were matched multiple times with BALF samples. Overall, the color of the BALF was related to the number of BALFRBC. Colorimetric evaluation of BALF represents a practical and reliable option for rapid postexercise assessment of the presence and severity of EIPH.

Prevalence of exercise-induced pulmonary hemorrhage in competing endurance horses

OBJECTIVE

To assess the prevalence of exercise-induced pulmonary hemorrhage (EIPH) among elite endurance horses after competition in a long-distance race.

ANIMALS

20 endurance horses and 12 nonexercised or minimally exercised age-, breed-, and trainer-matched horses from the same environment (control horses).

PROCEDURES

Bronchoalveolar lavage fluid samples collected from endurance horses at 3 to 8 days (sample A) and 36 to 38 days (sample B) after the race (100 km in 1 day [n = 3], 70 km/d for 2 days [12], or 100 km/d for 2 days [5]) were cytologically examined for the presence of hemosiderophages. Samples from control horses were collected at the same time as sample B was obtained from respective matched endurance horses and similarly examined. Horses with bronchoalveolar lavage fluid samples in which > 1% of identified cells were hemosiderophages were considered to have evidence of EIPH.

RESULTS

Of 20 endurance horses, 9 (45%; 95% confidence interval, 25% to 66%) and 10 (50%; 95% confidence interval, 29% to 71%) had cytologic evidence of EIPH in samples A and B, respectively. Evidence of EIPH was present in 6 of 20 (30%) horses at both sample collection times, 3 (15%) at the first sample time only, and 4 (20%) at the second sample time only. In contrast, 1 of 12 control horses had cytologic evidence of EIPH.

CONCLUSIONS AND CLINICAL RELEVANCE

The prevalence of EIPH in these elite endurance horses (45% to 50%) was higher than previously reported estimates for poor-performing endurance horses; however, differences in criteria for identification of EIPH should be considered when comparing findings between studies.

Racetrack exercise vs treadmill exercise with respect to exercise-induced pulmonary haemorrhage (EIPH): implications for studies of putative treatments of EIPH

Multiple treadmill-based studies using low numbers of horses have evaluated potential prophylactic treatments for exercise-induced pulmonary haemorrhage (EIPH) and found no effect. However, the relevance of these findings to racing is unclear. Because severity of EIPH incurred on treadmills has not been compared to that following high-speed racetrack exercise in the same horses, we retrospectively performed this comparison using bronchoalveolar lavage fluid red cell numbers (BALFRBC) due to the relative insensitivity of tracheobronchoscopy. Six race-fit Thoroughbreds with recent tracheobronchoscopic EIPH scores ≥2 were exercised to fatigue on a treadmill at 115% V̇O2max (5% incline, 12.3-14.2 m/s), and maximally on a racetrack over 800 m and 1,100 m with average speeds ranging from 16.4-16.7 and 15.5-16.6 m/s, respectively. Run order varied but was not randomised. Bronchoalveolar lavage (BAL) was performed blindly using Bivona tubes 45-60 mins post-exercise. BALFRBC were determined using a haemocytometer. Data were expressed as median and interquartile range, and analysed using RM ANOVA with significance set at P<0.05. BALFRBC were greater after both racetrack runs than after treadmill exercise (P<0.05; treadmill: 10,305/μl (3,871-26,079); 800m: 25,000/μl (17,175-73,400); 1,100m: 19,500/μl (8,962-800,600). Treadmill exercise resulted in lower numbers and a narrower range in BALFRBC than racetrack exercise. Thus, when a small number of horses is used to study EIPH treatments on a treadmill, a lower BALFRBC would be anticipated following the baseline run than with a similar study using racetrack exercise, and might reduce the likelihood of demonstrating significant treatment effects. Results of this retrospective study raise concern regarding the advisability of extrapolating conclusions regarding efficacy of EIPH treatments from treadmill studies to racetrack scenarios.

Complete upper airway collapse and apnoea during tethered swimming in horses

BACKGROUND

There is limited knowledge of the breathing strategy and impact on the patency of the upper respiratory tract (URT) in swimming horses.

OBJECTIVES

To describe the respiratory responses and endoscopic appearance of the URT during tethered swimming in horses.

STUDY DESIGN

Prospective descriptive study.

METHODS

Ten race-fit horses, with no history of URT obstruction, were examined during tethered swimming. Endoscopic examination, heart rate, sound recordings and above and below water video recordings were obtained. Plasma lactate concentration was measured before and 5 min after swimming and tracheal endoscopy was performed 30 min after exercise to assess for presence of blood or mucus. Four horses also underwent endoscopy during exercise on the track.

RESULTS

Mean (±s.d.) breathing frequency was 28 ± 5 breaths/min during swimming, with a brief inspiration (mean ± s.d. T_I  = 0.51 ± 0.08 s), followed by a period of apnoea (1.59 ± 0.53 s) and then a short, forced expiration (T_E  = 0.42 ± 0.5 s). During apnoea all horses exhibited complete collapse of the URT including closure of the external nares, nasopharynx and rima glottidis (with bilateral adduction of the arytenoid cartilages and vocal folds) and, in two horses, epiglottic retroversion. No horses had URT collapse during overground exercise. Locomotor-respiratory coupling was not observed during swimming. Median (IQR) plasma lactate post swim was 4.71 mmol/L (2.08-8.09 mmol/L) vs 0.68 mmol/L (0.65-0.71 mmol/L) preswim. Post swim endoscopy revealed grade 1 exercise-induced pulmonary haemorrhage (EIPH) in 2 horses. Median mucus grade was 1 (range 0-3).

MAIN LIMITATIONS

Overground endoscopy was not performed in all horses.

CONCLUSIONS

Horses experienced complete URT collapse associated with post inspiratory apnoea when swimming. The reason for this is unknown but may be to aid buoyancy or associated with the mammalian dive response - a survival reflex to preserve oxygen stores and prevent water entering the lungs.

Effect of different protocols on the mitigation of exercise-induced pulmonary hemorrhage in horses when administered 24 hours before strenuous exercise

BACKGROUND

Public pressure exists in the United States to eliminate race-day furosemide administration despite its efficacy in decreasing the severity of equine exercise pulmonary hemorrhage (EIPH). No effective alternative prophylaxis strategies have been identified.

OBJECTIVE

To investigate alternative protocols to race-day furosemide that might mitigate EIPH.

ANIMALS

Seven fit Thoroughbreds with recent EIPH.

METHODS

Double-blinded placebo-controlled Latin square crossover using a treadmill followed by a blinded placebo-controlled crossover study at a racetrack. First, horses exercised supramaximally to fatigue 24 hours after initiating 5 EIPH prophylaxis protocols: 0.5 and 1.0 mg/kg furosemide IV 24 hours pre-exercise with and without controlled access to water, and 24 hour controlled access to water. Effects were compared to those measured after giving a placebo 24 hours pre-exercise, and 0.5 mg/kg furosemide IV 4 hours pre-exercise. Bronchoalveolar lavage (BAL) erythrocyte count was determined 45-60 minutes postexercise after endoscopy to assign an EIPH score. Data were analyzed using linear mixed effects models. The most promising protocol from the treadmill study was further evaluated in 6 horses using endoscopy and BAL after 1100 m simulated races.

RESULTS

Intravenous furosemide (0.5 mg/kg) administered 24 hours pre-exercise combined with controlled access to water decreased the severity of EIPH on the treadmill and at the racetrack.

CONCLUSION AND CLINICAL IMPORTANCE

Administering 0.5 mg/kg furosemide 24 hours pre-racing combined with controlling water intake may be a strategy to replace race-day furosemide administration for the management of EIPH. A larger study is indicated to further evaluate whether this protocol significantly mitigates EIPH severity.

Exercise-induced Pulmonary Hemorrhage: Is It Important and Can It Be Prevented?

Exercise-induced pulmonary hemorrhage (EIPH) occurs commonly in horses undergoing strenuous exercise. Reported risk factors include racing in cold temperatures and wearing of bar shoes. In horses with documented moderate to severe EIPH, increasing the interval between races and adopting a negative race pace strategy may reduce the severity of EIPH in subsequent races. EIPH seems to have an impact on performance only when moderate to severe. This occurs in a small number of starters, approximately 6%. EIPH often is erratic in severity from race to race, although across a population it is weakly progressive over increasing race starts.

Bronchoalveolar lavage fluid from both lungs in horses: Diagnostic reliability of cytology from pooled samples

Cytology of bronchoalveolar lavage fluid (BALF) from one lung may not predict findings in the contralateral lung of the same horse. The aim of this study was to determine whether a pooled BALF from both lungs was representative of corresponding individual samples. Fifty-one horses referred for poor performance and/or respiratory signs and for which a BALF was collected from both lungs, were included in the study. Cytology of pooled and individual BALF samples were performed using a masked protocol. Based on clinical signs and individual BALF cytologies, horses were classified as control (CTL), mild equine asthma (mEA), severe equine asthma (sEA) and/or exercise-induced pulmonary haemorrhage (EIPH). No significant difference was observed between pooled and individual BALF samples for all cell types (P>0.05). Correlations between pooled and individual BALF samples were good (r≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio, and moderate (r≥0.4) for metachromatic cell and eosinophil proportions. Similarly, intraclass correlation coefficient (ICC) were good (ICC≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio and substantial (ICC≥0.6) for metachromatic cell proportions. Based on threshold values for pooled samples as determined by receiver operating characteristic (ROC) analysis, categorical agreements were good (κ≥0.97) for diagnosis of mEA/sEA, and substantial (κ=0.74) for EIPH. Using a pooled BALF sample, only one horse was incorrectly classified as CTL instead of mEA and three horses were classified as EIPH instead of CTL. In conclusion, BALF cytology from pooled sample is representative of both individual lungs, and constitutes a valid method to diagnose EA.

An observational study of environmental exposures, airway cytology, and performance in racing thoroughbreds

Background

Mild equine asthma is presumed to arise in response to environmental exposures but the relative impact of differing inflammatory phenotypes upon performance are largely unexplored.

Hypotheses: Airway inflammation negatively affects performance and cytological phenotype varies with environmental exposure.

Animals

Thoroughbred racehorses in active training and racing.

Methods

Thoroughbreds were recruited 24‐48 hours before racing. Each horse was eligible for re‐enrollment with each race entry. Within one hour of race completion, physical examination, respiratory endoscopy, and BAL were performed. Respirable and inhalable dust, respirable endotoxin, and respirable β‐glucan exposures were measured at the breathing zone within one week after racing. Controlling for age, trainer, and pulmonary hemorrhage, the relationship between performance, bronchoalveolar lavage fluid (BALF) cytology, and measures of exposure were modeled.

Results

Performance and BALF data were collected on 64 individual horses from 8 stables for a total of 98 race performances and 79 dust exposure assessments. Evidence of mild equine asthma was found in 80% (78/98) of BALF samples from 52/64 horses. For each percent increase in BALF mast cell and neutrophil proportions, speed figures were reduced by 2.9 (P = .012) and 1.4 (P = .046) points, respectively. Respirable dust concentration was associated with BALF neutrophil proportions (P = .015). Bronchoalveolar lavage fluid mast cell proportions were only associated with respirable β‐glucan exposures (P = .030).

Conclusions and Clinical Importance: Mild equine asthma is common in racing horses and negatively impacts performance. The data support that respirable, rather than inhalable, dust exposure measures are pertinent to equine airway health.

Exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 are associated with lower airway inflammation and airway cytology in the horse

BACKGROUND

Exhaled breath condensate (EBC) analysis is a noninvasive method to assess the lower respiratory tract. In human subjects, EBC hydrogen peroxide (H₂ O₂ ), pH and leukotriene B₄ (LTB₄ ) are useful for detection and monitoring of inflammatory lung diseases, including asthma.

OBJECTIVES

To determine associations between EBC biomarkers and cytological and endoscopic definitions of lower airway inflammation (LAI) while controlling for sampling and environmental variables.

STUDY DESIGN

Prospective, cross-sectional study.

METHODS

Clinical, endoscopic and airway cytological findings from 47 horses were compared with EBC pH and concentrations of H₂ O₂ and LTB₄ by univariate and multivariable analyses. Dichotomous (presence/absence of airway inflammation) and continuous outcome variables (differential cell counts in tracheal aspirate and bronchoalveolar lavage fluid, BALF) were evaluated and potential effects of collection and methodological factors were included.

RESULTS

EBC pH and H₂ O₂ concentrations were higher in horses with LAI and both were positively associated with the percentage of neutrophils in BALF (P<0.05). Mast cell percentage in BALF was negatively associated with EBC pH, and BALF eosinophil percentage was positively associated with EBC LTB₄ (P<0.05). Ambient temperature, relative humidity and assay methodology significantly impacted some analytes.

MAIN LIMITATIONS

LAI is challenging to categorise due to a variety of clinical and cytological phenotypes. Although the study was designed to overcome this limitation, numbers of horses were small in some categories.

CONCLUSIONS

EBC pH and H₂ O₂ concentrations are altered by airway inflammation, suggesting a role for these biomarkers in the diagnosis and monitoring of airway disease. Environmental and methodological factors can influence these biomarkers and should be considered in the interpretation of results.

ACE activity post-race is influenced by furosemide administration

Exercise induced pulmonary haemorrhage (EIPH) affecting racehorses continues to raise questions regarding animal welfare and to-date no effective treatment has been identified. The mode of action of furosemide on EIPH, the only medication for the condition accepted in some racing jurisdictions, has not been completely elucidated. This research investigated the interaction between furosemide on angiotensin converting enzyme (ACE) as a potential pathway for future investigation of EIPH treatment options in a prospective case-control analytical study. ACE is a potent vasoconstrictor and substances reducing its activity could potentially contribute to decreasing blood pressure and EIPH. Horses racing on 8 official race days at Gávea Racetrack, Brazil had respiratory endoscopy data and blood samples collected after the race and were grouped into furosemide medicated and non-furosemide medicated horses. ACE measurement was conducted using fluorescence in a previously validated method. Environmental, race and haematological data were also recorded. A multiple regression model was used to analyse the data collected, with further analysis including Fisher’s exact test and Pearson’s chi-squared test with Yates’ continuity correction; a Welch two sample t-test and a simple linear regression model. 73 horses were included in the study. ACE activity between horses not medicated and medicated with furosemide was significantly different. Pre-race furosemide significantly influenced ACE activity post-race, while distance raced, temperature, humidity, and haematocrit did not. Horses medicated with pre-race furosemide still demonstrated some degree of bleeding after the race and were at higher risk of presenting EIPH than non-medicated horses. Horses medicated with furosemide have lower circulating ACE activity which might indicate a protective effect of furosemide. Furosemide might reduce EIPH severity after a single bout of exercise, but it does not abolish or reduce its occurrence.

Exercise-induced pulmonary hemorrhage in barrel racing horses in the Pacific Northwest region of the United States

Background

Exercise‐induced pulmonary hemorrhage (EIPH) refers to bleeding from the lungs in association with strenuous exercise. It has been documented in race horses but little information exists on EIPH in barrel racing horses.

Hypothesis/Objectives

Our goals were to evaluate the presence of EIPH in barrel racing horses and estimate its prevalence in the Pacific Northwest.

Animals

149 barrel racing horses enrolled at events in WA (11), ID (3), and MT (33).

Methods

Observational cross‐sectional study. Data collected included signalment, history of illness, respiratory disease, race division, and pre‐race medications. Endoscopy was performed and tracheobronchoscopic (TBE) EIPH score was assigned based on quantity of blood in the trachea (0 = no blood to 4 = abundance of blood within the trachea). After TBE, bronchoalveolar lavage (BAL) was performed. Erythrocyte (red blood cell, RBC) counts were obtained from bronchoalveolar lavage fluid (BALF). Statistical analysis included linear and logistic regression, Fisher's exact t test, and calculation of correlation coefficient. Significance was set at P < .05.

Results

The prevalence of EIPH based on TBE EIPH score was 54%. When based on BALF RBC count >1,000 cells, EIPH prevalence was 66%. Race time did not significantly affect the presence of EIPH. A significant (P < .0001) positive linear relationship between the TBE and BAL erythrocyte count was identified, but its strength was poor (r² = .15).

Conclusions and Clinical Importance

EIPH occurs in over 50% of barrel racing horses in the Pacific Northwest. Precise determination of the impact of EIPH on health of barrel racers requires further study.

Tracheobronchoscopic Assessment of Exercise-Induced Pulmonary Hemorrhage and Airway Inflammation in Barrel Racing Horses

Background

Poor performance is often suspected to be associated with EIPH in barrel racing horses; however, there are no published reports of EIPH for this discipline. The prevalence of EIPH in barrel racing horses is also unknown.

Objectives

This study was performed to determine the prevalence of EIPH and signs of airway inflammation in barrel racing horses under normal racing conditions in Alberta.

Animals

About 170 barrel racing horses.

Methods

Observational cross‐sectional study. Tracheobronchoscopic examinations were performed at least 30 minutes postrace. Video recordings were scored off‐site independently by two observers for EIPH and tracheal mucus accumulation (TMA). Horses with an EIPH score ≥2 were not assessed for TMA. Interobserver agreement was calculated by weighted κ statistics. Run times, environmental variables, and clinical information were also recorded for analysis.

Results

77/170 (45.3%) of horses examined showed evidence of EIPH (grade ≥ 1). Interobserver agreement was 0.94. 140/141 (99.3%) of horses assessed for TMA showed evidence of tracheal mucus accumulation (grade ≥ 1) with 104/141 (73.8%) having a TMA score ≥ 2. Interobserver agreement was 0.73. A weak positive association was found between EIPH scores and average run speed, the presence of cough at rest reported by the riders, increased recovery time, exercise intolerance, and outdoor pattern.

Conclusions and clinical importance

The high prevalence of EIPH observed in the sampled population indicates that barrel racing induces substantial stress on the lungs. The presence of EIPH did not impact negatively on performance. Factors such as environmental dust and frequent traveling might have contributed to the high prevalence of TMA observed.

Exercise induced pulmonary hemorrhage in horses: American College of Veterinary Internal Medicine consensus statement

Background

Published studies of exercise‐induced pulmonary hemorrhage (EIPH), when assessed individually, often provide equivocal or conflicting results. Systematic reviews aggregate evidence from individual studies to provide a global assessment of the quality of evidence and to inform recommendations.

Objectives

Evaluate evidence to determine: if EIPH adversely affects the health, welfare or both of horses; if EIPH affects the athletic capacity of horses; the efficacy of prophylactic interventions for EIPH; and if furosemide affects the athletic capacity of horses.

Animals

None.

Materials and Methods

Systematic review. A panel of 7 experts was formed to assess evidence in the peer reviewed literature addressing each of the 4 objectives. Methodology followed that of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). Publications were assessed for quality of evidence by working groups of the panel, and a summary of findings was presented in tables. Recommendations were based on quality of evidence and were determined by a vote of the panel.

Results

Much of the evidence was of low to very low quality. Experimental studies frequently lacked adequate statistical power. There was moderate to high quality evidence that EIPH is progressive, is associated with lung lesions, that it adversely affects racing performance, that severe EIPH (Grade 4) is associated with a shorter career duration, that furosemide is efficacious in decreasing the incidence and severity of EIPH, and that administration of furosemide is associated with superior race performance.

Conclusions and clinical significance

Strong recommendation that EIPH be considered a disease and a weak recommendation for use of furosemide in management of racehorses with EIPH.

Inflammatory Airway Disease of Horses--Revised Consensus Statement

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.

Exercise-induced pulmonary haemorrhage impairs racing performance in Thoroughbred racehorses

REASONS FOR PERFORMING STUDY

Exercise-induced pulmonary haemorrhage (EIPH) occurs commonly in Thoroughbred racehorses worldwide. While EIPH is believed to be an important cause of impaired performance in these horses, there is limited evidence from sufficiently powered studies to evaluate this association.

OBJECTIVES

To evaluate whether EIPH is associated with finishing position, distance finished behind race winners and differences in race earning among Thoroughbred horses racing in South Africa.

STUDY DESIGN

Prospective cross-sectional study.

METHODS

One thousand Thoroughbred horses racing in South Africa were enrolled prior to a single race and underwent tracheobronchoscopic examination within 2 h of racing. Three observers, blinded to the horses' identity and race performance, independently evaluated EIPH occurrence and severity using video recordings of the examination. Data were analysed using multivariable logistic and linear regression while controlling for important horse and race factors as potential confounding variables.

RESULTS

Overall, 68% of horses had evidence of EIPH (grade ≥1). Horses without evidence of EIPH (severity grade 0), when compared with horses with any evidence of EIPH (grade ≥1), were >2 times more likely to win races (odds ratio = 2.3; 95% confidence interval 1.4-3.7; P = 0.001), finished an average of one length ahead of horses with EIPH (P = 0.03), and were 2.5 times more likely to be in the highest decile in race earnings (odds ratio = 2.5, 95% CI 1.5-4.1, P<0.001). However, no association was identified regarding finishing in the top 3 positions or earning money when analysed as a continuous variable or analysed as any winnings vs. none.

CONCLUSIONS

Exercise-induced pulmonary haemorrhage was associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips. These findings provide strong corroboration of previous research indicating that the occurrence of EIPH has a major impact on the ability of Thoroughbred racehorses to compete successfully as elite athletes.

Lung region and racing affect mechanical properties of equine pulmonary microvasculature

Exercise-induced pulmonary hemorrhage is a performance-limiting condition of racehorses associated with severe pathology, including small pulmonary vein remodeling. Pathology is limited to caudodorsal (CD) lung. Mechanical properties of equine pulmonary microvasculature have not been studied. We hypothesized that regional differences in pulmonary artery and vein mechanical characteristics do not exist in control animals, and that racing and venous remodeling impact pulmonary vein mechanical properties in CD lung. Pulmonary arteries and veins [range of internal diameters 207-386 ± 67 μm (mean ± SD)] were harvested from eight control and seven raced horses. With the use of wire myography, CD and cranioventral (CV) vessels were stretched in 10-μm increments. Peak wall tension was plotted against changes in diameter (length). Length-tension data were compared between vessel type, lung region, and horse status (control and raced). Pulmonary veins are stiffer walled than arteries. CD pulmonary arteries are stiffer than CV arteries, whereas CV veins are stiffer than CD veins. Racing is associated with increased stiffness of CD pulmonary veins and, to a lesser extent, CV arteries. For example, at 305 μm, tension in raced and control CD veins is 27.74 ± 2.91 and 19.67 ± 2.63 mN/mm (means ± SE; P < 0.05, Bonferroni's multiple-comparisons test after two-way ANOVA), and 16.12 ± 2.04 and 15.07 ± 2.47 mN/mm in raced and control CV arteries, respectively. This is the first report of an effect of region and/or exercise on mechanical characteristics of small pulmonary vessels. These findings may implicate pulmonary vein remodeling in exercise-induced pulmonary hemorrhage pathogenesis.

Prospective study of the association between exercise-induced pulmonary haemorrhage and long-term performance in Thoroughbred racehorses

REASONS FOR PERFORMING STUDY

Exercise-induced pulmonary haemorrhage (EIPH) is associated with impaired short-term race performance but consequences to long-term race performance of Thoroughbred racehorses are unknown. Knowledge of effects of EIPH on performance over a prolonged time would inform the need for management and treatment of this disorder.

OBJECTIVES

To determine the relationship between EIPH detected on a single occasion and long-term athletic performance in Thoroughbred racehorses.

STUDY DESIGN

Prospective, longitudinal, observational epidemiological study conducted from 2003 to 2012.

METHODS

Seven hundred and forty-four Thoroughbred racehorses underwent a single tracheobronchoscopic examination to determine presence and severity of EIPH in 2003. Following retirement of all the horses from racing, career after examination and lifetime performance data (including career duration, earnings, starts, wins and placings) were abstracted from a commercial database. The association between presence and severity of EIPH and individual performance variables were analysed using survival analysis, linear regression and negative binomial regression.

RESULTS

No association was detected between the presence of any EIPH (grade ≥1) and all measures of long-term performance examined except that horses with EIPH (grade ≥2) had fewer earnings after endoscopic examination than did horses with mild EIPH or no EIPH (grades ≤1). Multiple associations were detected between the most severe form of EIPH (grade 4) and measures of long-term performance suggesting that the severity of EIPH commonly associated with epistaxis adversely affects either the horse's opportunity to race or physiologic capacity to race.

CONCLUSIONS

We conclude that there is no association between EIPH grades 0, 1, 2 and 3 and long-term racing performance of Thoroughbred racehorses. These results are based on a single endoscopic evaluation of EIPH grade made during a horse's career. Further studies are required to determine the reasons for an association of severe (grade 4) EIPH with impaired long-term race performance.

Lung physiology at play: Hemoptysis due to underwater hockey

Hemoptysis can be a very concerning symptom, and the workup of a patient with hemoptysis may be expensive and invasive. Over the past decade, there has been increasing recognition of hemoptysis that occurs in highly trained athletes under conditions of extreme physical exertion and is explained by “pulmonary capillary stress failure”. This report highlights the physiological mechanisms of pulmonary capillary stress failure in the highly trained athlete, with emphasis on the predisposition to develop this condition in underwater sports. We describe the case of an otherwise healthy 34 year-old competitive underwater hockey player who reported hemoptysis following particularly strenuous games. We postulate that the hemoptysis was a result of the pulmonary capillary stress failure caused by the cumulative hemodynamic effects of a markedly elevated cardiac output, the increased central blood volume caused by the hydrostatic effects of submersion in water, and the negative intrathoracic pressure produced by voluntary diaphragmatic contractions.

Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung

Exercise-induced pulmonary hemorrhage (EIPH), which has been reported in humans and a variety of domestic animals following strenuous exercise, is most often documented in racehorses. Remodeling of pulmonary veins (VR) in equine EIPH was recently described, suggesting that it contributes to the pathogenesis of the disease. The cause of VR is unknown. We tested the hypothesis that the development of VR follows pulmonary blood flow distribution, preferentially occurring in the caudodorsal lung region. Furthermore, we hypothesized that VR underpins development of the other lesions of EIPH pathology. The lungs of 10 EIPH-affected horses and 8 controls were randomly sampled for histopathology (2,520 samples) and blindly scored for presence and severity of VR, hemosiderin (H), and interstitial fibrosis (IF). Mean sample score (MSS), mean lesion score, and percent samples with lesions were determined in four dorsal and three ventral lung regions, and the frequency, spatial distribution, and severity of lesions were determined. MSS for VR and H were significantly greater dorsally than ventrally (P < 0.001) and also decreased significantly in the caudocranial direction (P < 0.001). IF decreased only in the caudocranial direction. The percent samples with lesions followed the same distribution as MSS. VR often was accompanied by H; IF never occurred without VR and H. Similarity of the distribution of EIPH lesions and the reported fractal distribution of pulmonary blood flow suggests that VR develops in regions of high blood flow. Further experiments are necessary to determine whether VR is central to the pathogenesis of EIPH.

Subclinical diseases underlying poor performance in endurance horses: diagnostic methods and predictive tests

Thirty-eight endurance horses underwent clinical and ancillary examinations, including haematological and biochemical evaluation, standardised exercise tests both on a treadmill and in the field, Doppler echocardiography, impulse oscillometry, video endoscopy and collection of respiratory fluids. All of the examined poorly performing horses were affected by subclinical diseases, and most of them had multiple concomitant disorders. On the contrary, the well-performing horses were free of any subclinical disease. The most frequently diagnosed diseases were respiratory disorders, followed by musculoskeletal and cardiac problems. Poor performers exhibited lower speeds at blood lactate concentration of 4 mmol/l (VLA4) and at heart rates of 160 (V160) and 200 bpm (V200) on the treadmill and in the field, as well as slower recovery of heart rate.

Thromboelastometric profiles of horses affected by exercise-induced pulmonary hemorrhages

Exercise-induced pulmonary hemorrhage (EIPH) commonly occurs in race horses. Thromboelastometry (TEM) investigates the whole hemostatic process by evaluating the viscoelastic properties of the blood clot from its formation to fibrinolysis. The aim of this study was to assess whether horses with EIPH have abnormal thromboelastometric profiles. Intrinsic and extrinsic pathways, fibrinogen activity and fibrinolysis were investigated by TEM before and after the race in negative controls and in horses on which EIPH was confirmed by bronchoscopy. Compared with controls, horses with EIPH had an increased coagulability in both pre- and postrace samplings, especially for the intrinsic pathway and for the fibinrolytic activity. These results suggest that coagulation is preactivated in horses prone to develop EIPH, possibly due to recent or recurrent hemorrhage.

Evaluation of race distance, track surface and season of the year on exercise-induced pulmonary haemorrhage in flat racing Thoroughbreds in Brazil

REASONS FOR PERFORMING STUDY

To our knowledge no studies evaluating risk factors to EIPH have been undertaken with such a population of horses in Brazil, which is one of the few countries in the racing community to accept the use of frusemide (FUR) as a prerace medication for bleeders. We also compared national results with those already in the literature.

OBJECTIVES

To verify the influence of variables such as distance of the race, racetrack surface, going and season of the year in the recurrence and severity of EIPH and its effect on the finishing position of flat racing Thoroughbreds in Brazil.

METHODS

2118 post race respiratory endoscopies were recorded, in a total of 1003 individual horses. All horses in the study were certified bleeders (deemed positive by registered veterinarians following one or more endoscopies) and were administered FUR prior to each race. Data was analysed using both ordinary logistic regression and multiple logistic regression.

RESULTS

The results suggest that race distance, season of the year and racetrack surface affect the recurrence of EIPH. Also, despite the use of FUR, the majority (62%) of horses continued to display some degree of haemorrhage.

CONCLUSIONS

There was a tendency for horses that remained positive despite the use of FUR to finish unplaced in a race. Horses which had a significant reduction in bleeding and became HPIE negative after the use of FUR, tended to finish in top positions. It was not possible to determine a pattern of severity of EIPH in horses with more than one endoscopy. Further studies are required to improve our understanding of this syndrome and its correlations to performance in the racing Thoroughbred, together with the role of FUR and its possible enhancing performance effects and efficacy in consistently diminishing EIPH.

POTENTIAL RELEVANCE

This study enabled a better understanding of the use of FUR in Brazilian Thoroughbred racehorses and showed there was a tendency towards improvement in performance after administrion of FUR in bleeders. The fact that a large number of horses remained positive for EIPH despite the use of FUR should encourage the scientific community to search for better ways of reducing, or preventing, this syndrome.