A survey of exercise‐induced pulmonary haemorrhage in Quebec Standardbred racehorses

Lapointe, Julie; Vrins, André; McCARVILL, E.

doi:10.1111/j.2042-3306.1994.tb04054.x

Cited by 76 publications

(89 citation statements)

References 8 publications

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“…Thereafter, separate trials were undertaken to determine the work intensity eliciting maximal heart rate and stress failure of pulmonary capillaries (25) leading to EIPH. In agreement with previous work, it was observed that galloping at 14 m/s on a 3.5% uphill grade not only elicited maximal heart rate but also induced EIPH in all horses, as demonstrated by the presence of fresh blood in the trachea on postexercise airway endoscopic examination (7,10,23), and could not be sustained for Ͼ120 s despite vigorous humane encouragement. Thus this workload was selected for further experimentation as representing maximal exertion for our horses.…”

Section: Exercise Training and Work Intensity Eliciting Maximal Heartsupporting

confidence: 92%

Intrapulmonary arteriovenous shunts of >15 μm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

Manohar

Goetz²

2005

Journal of Applied Physiology

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Manohar, Murli, and Thomas E. Goetz. Intrapulmonary arteriovenous shunts of Ͼ15 m in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses. J Appl Physiol 99: 224 -229, 2005. First published March 17, 2005 doi:10.1152/japplphysiol.01230.2004.-The present study examined whether Thoroughbred horses performing strenuous exercise exhibit intrapulmonary arteriovenous shunting that may contribute to the observed arterial hypoxemia. Experiments were carried out on seven healthy, exercise-trained Thoroughbreds at rest, maximal exercise (galloping at 14 m/s on a 3.5% uphill grade for 120 s), and submaximal exertion (8 m/s on a 3.5% uphill grade for 150 s). Along with blood gas/hemodynamic parameters, intrapulmonary arteriovenous shunting was studied by injecting 15-m-diameter microspheres, labeled with different stable isotopes, into the right atrium while simultaneous blood samples were being withdrawn at a constant rate from the pulmonary artery and the aorta. Arterial hypoxemia was observed only during maximal exercise. Also, despite significant pulmonary arterial hypertension during submaximal and maximal exertion, 15-m microspheres did not traverse the pulmonary microcirculation to appear in the aortic blood. Thus our findings did not support a role for intrapulmonary arteriovenous shunts of Ͼ15 m in diameter in the exercise-induced arterial hypoxemia in racehorses. Interestingly, our observation that, in going from 30 to 120 s of maximal exertion, arterial O2 tension had remained unchanged despite significant reductions in mixed venous blood O 2 tension, hemoglobin-O2 saturation, and O2 content also discounts the importance of intrapulmonary arteriovenous shunts in causing arterial hypoxemia. This is because, assuming that a constant fraction of total pulmonary blood flow bypasses the gas-exchange areas of the equine lungs via intrapulmonary arteriovenous shunts during 30 -120 s of maximal exertion, the observed significant reductions in mixed venous blood oxygenation should cause a significant reduction in arterial O2 tension, which was not the case in our horses. Thus it is suggested that intrapulmonary arteriovenous shunting probably does not contribute to the exercise-induced arterial hypoxemia in racehorses.blood gas tensions during exertion; arterial desaturation during exercise; pulmonary microcirculation; microspheres IT IS WELL KNOWN THAT STRENUOUSLY EXERCISING racehorses experience significant arterial hypoxemia and desaturation of hemoglobin, and it is reported that these changes in arterial oxygenation limit athletic performance (1,3,8,(13)(14)(15)(16)24). A significant arterial hypercapnia is also observed in strenuously exercising Thoroughbred horses despite significantly increased alveolar ventilation. Although the inadequate alveolar hyperventilation during maximal exertion contributes to the observed reduction in arterial O 2 tension, this mechanism does not account for the entire decrease in arterial O 2 tension. Multiple inert-gas elimination studi...

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Section: Exercise Training and Work Intensity Eliciting Maximal Heartsupporting

confidence: 92%

Intrapulmonary arteriovenous shunts of >15 μm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

Manohar

Goetz²

2005

Journal of Applied Physiology

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“…Virtually all horses bred and trained for competitive racing show evidence of exercise-induced pulmonary hemorrhage (EIPH), which manifests as bleeding from the nose after exertion or the presence of red blood cells or hemosiderophages in the airways (3,6,21,39,47,53,58,67). The causative mechanism of EIPH was demonstrated experimentally when it was shown that high pulmonary capillary pressures can cause discrete breaks in the endothelium, epithelium, or the entire BGB in mammals (10,50,64,66).…”

mentioning

confidence: 99%

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

Watson¹,

Fu²,

West³

2007

American Journal of Physiology-Lung Cellular and Molecular Phys

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Watson RR, Fu Z, West JB. Morphometry of the extremely thin pulmonary blood-gas barrier in the chicken lung. Am J Physiol Lung Cell Mol Physiol 292: L769-L777, 2007. First published November 17, 2006; doi:10.1152/ajplung.00355.2006.-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 (ϳ86% 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. capillary stress failure; lung morphology; bird respiratory physiology; air capillary; extracellular matrix; interstitium IN THE VERTEBRATE LUNG, OPTIMAL thickness of the pulmonary blood-gas barrier (BGB) is affected by opposing selective pressures (65). The barrier thickness is minimized to allow efficient exchange of oxygen and carbon dioxide, yet the capillary walls must also be strong enough to withstand high pulmonary capillary pressures that are incurred during extreme physical exertion. The BGB is composed of three layers: capillary endothelium, an interstitial layer or extracellular matrix, and an epithelial layer (Fig. 1). Combined, these cellular layers are relatively thin, usually measuring Ͻ2 m in total thickness under normal conditions (5,33,36). This three-ply ultrastructure of the BGB appears to be evolutionally well conserved over a variety of vertebrate taxa, indicating that its basic structure is efficient and relatively immalleable (18,25,27,31,33). The strength of the pulmonary capillary walls is likely related to the morphometry of the BGB, where the thickness of the interstitium determines the fragility of the capillaries (5). Where the BGB is thinnest, the interstitial layer is composed of only the fused basement membranes of the endothelium and epithelium laye...

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“…For this reason, some authors suggest performing endoscopic observations 30 to 90 min post exercise, extending to the tracheal carina. Horses positive for EIPH are classified in grades from I to IV, depending on the amount and anatomic location of the blood found (Lapointe et al 1994). Over the years, flexible endoscopy has been complemented by other diagnostic techniques such as X-rays, which allow for the identification of lobe pulmonary haemorrhage (Pascoe 1996(Pascoe , 1997.…”

Section: Diagnosis Of Exercise Induced Pulmonary Haemorrhagementioning

confidence: 99%

“…However, West et al (1993) observed episodes of EIPH in horses just after walking and trotting. There is a trend related to age, where older horses have shown increased susceptibility to episodes of EIPH (Lapointe et al 1994). Derksen (2009) suggested that increased prevalence of EIPH in older horses is due to progressive lung damage from repeated episodes of bleeding and the development of diseases of the upper airways.…”

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confidence: 99%

Exercise-induced pulmonary haemorrhage in horses – review

Morán¹,

Folch²

2013

Acta Vet. Brno

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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. EIPH, pulmonary pressure, equine

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A survey of exercise‐induced pulmonary haemorrhage in Quebec Standardbred racehorses

Cited by 76 publications

References 8 publications

Intrapulmonary arteriovenous shunts of >15 μm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

Intrapulmonary arteriovenous shunts of >15 μm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

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

Exercise-induced pulmonary haemorrhage in horses – review

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