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

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.

Impact of Lower Airway Inflammation on Fitness Parameters in Standardbred Racehorses

“…Finally, the effect of age and sex on fitness parameters was also noticed. In particular, age was positively correlated with VLa4 and the maximal speed reached during the treadmill test; an explanation for these results may be that adult horses are probably fitter and more physically mature, in agreement with previous studies [ 21 , 48 ]. Similarly, males showed better fitness parameters compared with females, in agreement with previous reports [ 21 , 49 , 50 ].…”

“…In particular, age was positively correlated with VLa4 and the maximal speed reached during the treadmill test; an explanation for these results may be that adult horses are probably fitter and more physically mature, in agreement with previous studies [ 21 , 48 ]. Similarly, males showed better fitness parameters compared with females, in agreement with previous reports [ 21 , 49 , 50 ]. However, as all groups were age and sex-matched, it is likely that the contribution of age and sex to influencing fitness parameters was equal among different groups and that detected differences between MEA subtypes are exclusively attributable to lower airway inflammation.…”

“…All included horses ( n = 116) were in full training upon admission and were subjected to a complete diagnostic protocol, which included collection of history, clinical examination and lameness evaluation, laboratory analyses, electrocardiogram at rest, upper airway endoscopy at rest, incremental treadmill exercise test, high-speed treadmill endoscopy, tracheobronchoscopy 30 min post-exercise for the evaluation of exercise-induced pulmonary hemorrhage, TW and BAL collection with a cytological examination of the BAL, and a microbiological examination of the TW [ 21 ].…”

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

“…A few drops of pooled BALf were cytocentrifugated (Rotofix 32, Hettich Cyto System, Tuttlingen, Germany) at 500 rpm for 5 min. The slides were air dried, stained with May–Grünwald Giemsa and Perl’s Prussian blue and observed under a light microscope at 400× and 1000× for 400-cell leukocyte differential count and the calculation of a simplified total hemosiderin score (THS) [ 47 ].…”

Effect of the Administration of a Nutraceutical Supplement in Racehorses with Lower Airway Inflammation

“…To perform the cytological examination, a few drops of pooled BALf were cytocentrifugated (Rotofix 32, Hettich Cyto System, Tuttlingen, Germany) at 26 g for 5 min. The slides were air dried, stained with May-Grünwald Giemsa and Perl’s Prussian blue, and observed under a light microscope at 400× and 1000× for 400-cell leukocyte differential counting [ 23 ]. In order to be included in the study, the cytological examination of BALf had to be consistent with MEA, presenting a percentage of neutrophils > 5%, and/or mast cells > 2% and/or eosinophils > 1% [ 24 ].…”