Exercise induced pulmonary hemorrhage (EIPH) causes serious economic losses in the horse racing industry. Besides racing horses, jumpers, polo horses, barrel racing, pullers, and ropers can be effected. Endoscopic examination indicates that 40-90% of horses exhibit EIPH following sprint exercise, but the limitations of the endoscope prevent diagnosis in many horses and the actual incidence may approach 100%. Research completed in 2009 begins to center in on the pathogenesis of this common disorder of race horses. This report contains information on what we know about EIPH and the effect furosemide (Lasix) has on EIPH and performance. Also, provided are links to related articles and summaries of recent scientific findings.

Looking at the lung tissues of effected horses finds a number of abnormalities localized to the dorsocaudal areas of the lung that help us form a picture of what is happening to these horses during exercise and over time:

• Increase in the vein wall thickness
• Broken down red blood cells (haemosiderin) accumulation.
• Capillary Neovascularization
• Scaring and fibrosis (collagen)

These results support the hypothesis that during repeated strenuous exercise increases in pulmonary venous blood pressure cause the vein walls to remodel with collagen accumulation leading to venous occlusion and cappillary hypertension. Subjected to these high pressures, there is capillary stress failure, bleeding, haemosiderin accumulation and, subsequently, lung fibrosis.