Endoscopic determination of exercise-induced pulmonary haemorrhage in Chilean Criollo horses

Occurrence of exercise-induced pulmonary haemorrhage in show jumping horses

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 1.20m, and High group (HG, n=24), with jump height between 1.30 and 1.50m. Physical examination was performed before and after competition, and airway endoscopy and tracheal wash (TW) were performed 1h 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 (r²=0.40, P<0.0001), post-exercise HR (r²=0.31, P<0.0001), and post-exercise RR (r²=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.

Exercise-induced pulmonary haemorrhage in horses – review

Exercise-induced pulmonary haemorrhage is a major cause of poor performance in the equine athlete. It is an important cause of exercise intolerance and results from strenuous exercise and pathophysiological changes in the equine lung and possibly in the airways. Endoscopic surveys of the respiratory tracts of horses after competitive events have shown that many horses experience exercise-induced pulmonary haemorrhage. The reported incidence of exercise-induced pulmonary haemorrhage in different breeds varies between 40–85%. The cause of bleeding in exercising horses has fostered considerable debate over the past three centuries, but currently, the most accepted hypothesis is that the source of haemorrhage is disruption of the pulmonary capillaries during exercise. Furosemide is the medication used most widely for the treatment and prevention of exercise-induced pulmonary haemorrhage. This review provides an update on the aetiology, clinical signs, physiopathology, diagnosis and treatment of exercise-induced pulmonary haemorrhage.

Morphometry of the extremely thin pulmonary blood-gas barrier in the chicken lung

The gas exchanging region in the avian lung, although proportionally smaller than that of the mammalian lung, efficiently manages respiration to meet the high energetic requirements of flapping flight. Gas exchange in the bird lung is enhanced, in part, by an extremely thin blood-gas barrier (BGB). We measured the arithmetic mean thickness of the different components (endothelium, interstitium, and epithelium) of the BGB in the domestic chicken lung and compared the results with three mammals. Morphometric analysis showed that the total BGB of the chicken lung was significantly thinner than that of the rabbit, dog, and horse (54, 66, and 70% thinner, respectively) and that all layers of the BGB were significantly thinner in the chicken compared with the mammals. The interstitial layer was strikingly thin in the chicken lung ( approximately 86% thinner than the dog and horse, and 75% thinner than rabbit) which is a paradox because the strength of the BGB is believed to come from the interstitium. In addition, the thickness of the interstitium was remarkably uniform, unlike the mammalian interstitium. The uniformity of the interstitial layer in the chicken is attributable to a lack of the supportive type I collagen cable that is found in mammalian alveolar lungs. We propose that the surrounding air capillaries provide additional structural support for the pulmonary capillaries in the bird lung, thus allowing the barrier to be both very thin and extremely uniform. The net result is to improve gas exchanging efficiency.