Exercise-induced pulmonary hemorrhage: where are we now?

Figure 1. Epistaxis, bleeding from the nostrils, is the most visible form of exercise-induced pulmonary hemorrhage. Note: Photograph courtesy of Professor M Roger Fedde.

Figure 2. The acclaimed racehorse Eclipse, whose great Grandsire was Bleeding (Bartlett’s) Childers (1764–1789). Note: Reproduced from Youatt W. The Horse. London: Longmans, Green, and Co.; 1874.21

Figure 3. Left: Marcello Malpighi, professor of medicine and extraordinary anatomist and physiologist (1628–1694). Right: Malpighi’s depiction of the pulmonary capillaries and alveoli. I: 2 lungs with the alveoli on the left and the capillaries on the right. II: pulmonary capillaries in the alveolus dissected open reveal the incredible density of capillaries that form the blood–gas barrier. Note: Adapted from Malpighi M. De Pulmonibus [Lungs]. London: Philosophical Transactions of the Royal Society; 1661. Latin.29

Figure 4. Blood in the trachea of a racehorse after maximal exercise as revealed by endoscopy.

Figure 5. Lungs excised from a horse with a rare fatal instance of exercise-induced pulmonary hemorrhage. Note: Photograph courtesy of Dr Kurt J Williams.

Figure 6. Schematic depicting cross-section of a pulmonary capillary. Notes: Alveolar negative and capillary luminal positive pressures summate across the perilously thin (0.5 μm total thickness, 50 nm basement membrane thickness) blood–gas barrier. Pressures shown are for maximal exercise in the horse.

Figure 7. Left: Schematic showing exercise-induced pulmonary hemorrhage in the horse. Right: Scanning electron micrograph of the cranial lobe of an exercised pony reveals red blood cells (R) and proteinaceous material (P) in the alveoli. Bar =5 μm. Notes: Left diagram courtesy of Flair, LLC by Brad Gilleland. Right figure adapted with permission from Erickson HH, McAvoy JL, Westfall JA. Exercise-induced changes in the lung of Shetland ponies: ultrastructure and morphometry. J Submicrosc Cytol Pathol. 1997;29(1):65–72.16

Figure 8. The diuretic furosemide significantly (*) reduced exercise-induced pulmonary hemorrhage during high-intensity exercise as measured by bronchoalveolar lavage. Notes: Vials upper left and right indicate, respectively, the appearance of BAL fluid from Control and Furosemide conditions. This effect is believed to be driven by the reduction in pulmonary blood flow and thus capillary intraluminal pressures. Adapted from Kindig CA, McDonough P, Fenton G, Poole DC, Erickson HH. Efficacy of nasal strip and furosemide in mitigating exercise-induced pulmonary hemorrhage in Thoroughbred horses. J Appl Physiol. 2001;91(3):1396–1400.68 Abbreviations: EIPH, exercise-induced pulmonary hemorrhage; BAL, bronchoalveolar lavage.

Figure 9. The nasal strip pictured at right significantly (*P<0.05) reduced exercise-induced pulmonary hemorrhage during high-intensity exercise as measured by bronchoalveolar lavage. Notes: Vials upper left and right indicate, respectively, the appearance of BAL fluid from Control and Nasal strip conditions. This effect is caused by the less negative alveolar pressures and thus reduced capillary transmural pressures. Adapted from Kindig CA, McDonough P, Fenton G, Poole DC, Erickson HH. Efficacy of nasal strip and furosemide in mitigating exercise-induced pulmonary hemorrhage in Thoroughbred horses. J Appl Physiol. 2001;91(3):1396–1400.68 Abbreviations: EIPH, exercise-induced pulmonary hemorrhage; BAL, bronchoalveolar lavage.

Figure 10. Inhaled nitric oxide (80 ppm) lowered pulmonary vascular pressures substantially but significantly increased exercise-induced pulmonary hemorrhage as measured by bronchoalveolar lavage. Notes: This demonstrates that some degree of pulmonary vasoconstriction is actually protecting the fragile pulmonary capillaries under control conditions. *P<0.05. Adapted from Kindig CA, McDonough P, Finley MR, et al. NO inhalation reduces pulmonary arterial pressure but not hemorrhage in maximally exercising horses. J Appl Physiol (1985). 2001;91(6):2674–2678.148 Abbreviations: EIPH, exercise-induced pulmonary hemorrhage; BAL, bronchoalveolar lavage.

Figure 11. Concentrated equine serum decreased exercise-induced pulmonary hemorrhage during high-intensity exercise as measured by bronchoalveolar lavage. Notes: *P<0.05. Data from Epp et al.151 Abbreviations: EIPH, exercise-induced pulmonary hemorrhage; BAL, bronchoalveolar lavage.