Exercise Induced Pulmonary Hemorrhage Healthy Lungs Make Healthy Horses Jim Hamilton, DVM One of the most significant problems other than lameness that the athletic horse may have to endure is pulmonary hemorrhage - bleeding from the lungs. As the name suggests, this is a problem induced by intense exercise. Historically, racehorses have been the subgroup most plagued by this condition. The typical scenario is the horse that starts off in a race and shows great speed for 5/8 to 3/4 of a mile and then rather suddenly slows up as if he has run out of air. In the worse case, that horse comes back off the track and has blood running from his nostrils, though more commonly nothing is seen and the only sign may be a few coughs as the horse cools out. In recent years, as the event horse has had to go faster, jump higher, and recover more quickly, we have recognized EIPH in this group with greater frequency. With the event horse it is often missed because there are few, if any, warning signs - the rider writes indications off to the horse being nervous or not fit. As for the cause of EIPH, no single event or underlying pathology (disease) has been identified. However, there are several contributing factors worth discussing. Any lung disease that results in inflammation of the lung tissue predisposes the horse to EIPH; this includes both infection and allergic causes. The reason for this is that with lung inflammation comes increased blood flow as well as a decrease in airway size - the result is air being forced through smaller "tunnels" that have increased amounts of blood around them. Tissue irritation and the rupture of small blood vessels often results. Studies have shown that many healthy horses will show evidence of EIPH, but in its most mild form. Researchers thought blood pressure might be a contributing factor as well, but support for this theory is inconsistent at best. However, there is reasonable evidence to show that the horse's fitness level may contribute to development of EIPH. If a horse is asked to do more than he is prepared for, one can assume that over exertion may lead to circulatory stress with elevated blood pressure. If other factors are present at the same time, then the rupture and hemorrhage of blood vessels is more likely. Further, research may show that there is a genetic contribution as well. It may be that some bloodlines produce thin, more fragile vessels, though only time and research dollars will tell! To prevent a horse from developing EIPH, all the various issues discussed above must be addressed; it is critical that the horse has healthy lungs that are free of infection and allergic inflammatory disease! Making sure the horse's lungs are healthy is possible with the development of the broncho-alviolar lavage (BAL), a means of assessing the health of the lung tissue in a very accurate way. Tufts University's Dr. Andrew Hoffman is field testing a portable lung function test that should further improve our diagnostic abilities. If testing suggests your horse suffers from an allergic condition such as Chronic Obstructive Pulmonary Disease (COPD), then inhalation therapy with an Aeromask can help manage the disease so that athletic endeavors are possible. Other researchers have suggested that boosting the immune system with products like Equistim and Equimune help the lung fight off the sub-clinical infections before they cause damage. The unfortunate reality is that many
horses are training on a daily basis hampered by some form of respiratory
dysfunction. If that horse is doing only mild to moderate exercise,
they may be able to tolerate their respiratory inadequacies. But when
pushed to give his best, the horse may falter sadly. Due diligence is
required in order to avoid the worst scenario.
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