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Exercise Induced Pulmonary Hemorrhage in the Horse

EIPH or exercise induced pulmonary hemorrhage is unfortunately a common condition in equine athletes, affecting upwards of 40% of race horses and an estimated 62% of QH’s involved in racing, including other disciplines such as barrel racing.2  It is one of the main causes of decreased performance and also one of the more common respiratory problems found in competitive equine athletes, especially when involving epistaxis or nasal bleeding.  EIPH can be very frustrating for some trainers, due to the fact that a specific cause in each case is often not determined and response to therapies can decrease over time.  In many instances, the equine athletes are able to maintain higher levels of performance, while other are forced to retire.  As with many equine health conditions, with a better understanding, sometimes we can implement therapy options to improve the outcomes, helping to keep performance to a high level.

EIPH in the Horse

EIPH or exercise induced pulmonary hemorrhage is a familiar term in the equine industry, especially with those owners or trainers competing at high levels of speed and involving endurance or high outputs physically such as racing, barrel racing and even endurance in some cases.  It is not uncommon, however, to also encounter EIPH in other disciplines such as jumping and even western pleasure.  In many of those cases, horses are retired from higher levels due to EIPH, which then take on a new career at a lower level of competition, but continue to have bleeding problems due to ongoing scar tissue or pulmonary (lung) damage.

In most instances, bleeding is noted in both nostrils post competition and often seen with a cough in some. The bleeding can be obvious, sometimes dripping profusely, while in other cases, it may not be externally present but require the use of an endoscope to see blood within the trachea or lower airways.  The degree to which the blood is present dictates the severity of the condition.  In one study, on a scale of EIPH severity from 0-4, those horses with a lower level of grade 1 were 4.0 times more likely to win, 1.8 times more likely to place in the top 3 positions and 3.0 times more likely to earn above the 90th percentile compared to those horses with grade 2 or above.1

Most patients are alert, responsive with an elevated heart rate, respiratory rate and body temperature, often associated with exercise.  Some will have a cough or increased swallowing rate.  Most routine diagnostic testing, including bloodwork, is unremarkable unless there is significant blood loss. The most common diagnostic tool utilized is upper airway endoscopy to evaluate the nasal passages and trachea for evidence of bleeding.  Dependent on how much blood is present, on examination, then determines the grade of EIPH assigned to that horse on a scale of 0-4.

Underlying Mechanisms and Causes of EIPH

The exact cause of EIPH in the horse is not known, mainly due to the fact that there are many underlying contributors to the problem, with those contributors often being different from one horse to the next.

The main underlying mechanism in almost all cases of EIPH is a rupture of small blood vessels, called capillaries, located deep within the lung or pulmonary tissue.  The exact cause of their rupture is what complicates things, but overall, they are more prone to rupture when pressures exceed capabilities of those blood vessels, referred to as high pulmonary capillary pressure. Now, this is where things tend to get complicated and can vary from one patient to the next, as the cause of this rupture can be many, but include:2

  1. high cardiac output leading to higher pulmonary pressures
  2. inproper dilation or relaxation of the pulmonary capillaries to accomodate the increased pressures
  3. increased blood thickness or viscosity
  4. upper airway obstruction with lower aveolar pressure
  5. lower airway obstruction with lower aveolar pressure
  6. interstitial or lung inflammation (lower airway disease)
  7. inappropriate clotting mechanism (coagulopathy)
  8. poor vascular health or integrity

Each patient is different and the underlying contributors can vary from one case to the next, sometimes being very difficult to readily determine.  What is known is that once a horse ‘bleeds’, their risk of bleeding again in the future increases.  The risk of bleeding also increases with age and time involved with racing or high performance.  There is also an increased risk of EIPH or bleeding in those horses with underlying airway disease, which involves inflammation, such as IAD, COPD or even recurrent airway infections from bacteria or viral invaders.  Along those lines, those horses in environments with poor air circulation are also at an increased risk, likely due to inflammatory airway pathology induced by potential toxins and fumes in the environment inhaled into the lungs.

This process of inflammation is important not only as a potential contributor to EIPH development, but also in recurrence.  With each episode of pulmonary bleeding, there is a subsequent inflammatory response to the overt blood in the airways, which then may actually create lung tissue damage, impacting future pulmonary pressues, capillary blood vessel integrity.  This then can increase the liklihood of future bleeds, making them more prevalent and severe in nature.

Treatment & Management Options of Exercise Induced Pulmonary Hemorrhage

The main goal or goals with management of EIPH cases is to reduce the frequency and severity of the condition, as well as hopefully reduce the negative aftermath of the bleeding.  This aftermath is the inflammatory response which is elicited due to blood loss within the pulmonary or lung tissue, which can be a future deterent to performance.

When we mention the phrase ‘bleeder’ or EIPH, the most common association is with the medication called Lasix®, which is a diuretic. This is one of the most common ‘preventatives’ utilized with EIPH cases, usually given pre-race or pre-competition at various doses.  Lasix® actually works as a diuretic, helping to reduce fluids in the body, specifically water, thus reducing overall blood and capillary pressures.  In theory, if we can reduce those pressures, then the chances of capillary rupture are reduced as well. The problem that comes with the use of diuretics is that they can lead to dehydration and contribute to poor performance, not to mention derrangements in electrolyte levels in some cases.  Some believe that the loss of ‘water weight’ in the horse is actually beneficial to race times, but this is controversial and certainly not a justification for use. The other problem that comes is that in many horses, the required dose of Lasix® over time actually increases, which implies that the condition is progressing or worsening despite our efforts.  Overall, the use of Lasix® is well accepted in most disciplines and has demonstrated effectiveness in reducing pulmonary capillary pressures in research studies.  Despite this, we can obviously see that the use of this medication is not the ‘solution’, mainly due to the fact that many horses bleed through lasix, require higher doses or are eventually retired due to continued bleeding.

Other interesting avenues or attempts at reducing pulmonary capillary pressures revolve around the concept of nitric oxide production within the body, which helps to relax or dilate blood vessels, reducing pressures.  One main supplement that has shown some promise is the use of the amino acid, L-arginine, which is used to help produce nitric oxide in the body.  One product we have used in some cases is the Cur-OST EQ Nourish, which supplies several amino acids along with protein to benefit the athlete. The problem that comes here is that exact dose required to achieve this effect is unknown and can again vary from one horse to the next.  In some horses, there is simply no impact, which might be due to altered metabolism or pathways in the production of nitric oxide.  In these cases, another viable option is utilization of food groups which may be naturally high in nitrates, which are then more easily utilized to encourage nitric oxide production in the body.  One example would be red spinach (EQ Nitric Boost), which not only supplies natural sources of nitrates but also serves as a natural source of other nutrients to benefit overall cardiovascular health.

The exploration of blood pressure lowering medications, such as ACE inhibitors, in horses has not proven beneficial unfortunately in EIPH cases.  In regards to bleeding itself, in EIPH, there does not appear to be a problem with overall blood clotting, as often clotting times are normal.  Therefore, use of medications to increase clotting times have been mostly unsuccessful, but in some do appear to be beneificial.  The one concern with overuse of these medications would be that in theory, one could ‘thicken’ or increase the blood viscosity, which in turn could increase or contribute to higher pulmonary pressures, making matters worse.

In some cases, we do have upper airway obstructions, such as those found with laryngeal hemiplasia or even dorsal displacement of the soft palate, which can then impact alveolar pressures and contribute to EIPH.  In those case, if possible, correct of the problem may be beneficial to the patient.  In other cases, use of devices to open or dilate the nares (Flair®), have shown some benefits.

One area of interest and potentially a major contributor to EIPH is lower airway inflammation and associated fibrosis, which may be secondary to lung infections or to EIPH episodes themselves.  This inflammation and subsequent damage to lung tissue can worsen future bleeding episodes, potentially by creating damage to pulmonary blood vessels, lung tissue, impacting pulmonary pressures.  Attempts to modify this inflammatory response and impact EIPH episodes with medications such as corticosteroids has been unrewarding in most studies.  This is a topic of interest and an avenue of exploration when it comes to diet and use of herbs.

Lastly, in most cases of EIPH, forced rest from competition is generally recommended and in some disciplines, enforced.  This allows for time for the body to rest, recover and heal.  This time is beneficial in most cases, but in many, despite the rest, EIPH continues to be a problem.

Alternative Options of Consideration in EIPH

The high use of medications, such as Lasix®, along with variable results, deteriorating conditions and worsening of performance despite rest and other therapies opens the door for other options to be considered as well at theories.

One of the biggest problems or factors involved, from my perspective, is the overall health of that patient which then is reflective in cardiovascular health, vascular integrity and even pulmonary or lung health. A high percentage of these patients are highly stressed, which raises the question of the impact of cortisol on bodily functions and tissue health.  We know that in most studies, chronic stress is a negative influencer on health, reducing tissue health, performance and even impacting the gastrointestinal tract and immune health.  The second major consideration is the impact of inflammation overall on the body, being generated through stress including training and competition.  The third consideration is the diet and impact on gastrointestinal health, potentially contributing to bacterial microbiome population shifts, decreased digestive power and potentially contributing to systemic inflammation and even higher than normal lactic acid levels.  I have personally seen all 3 of these factors play a role in many patients and when we correct them, the EIPH condition becomes more easily managed.

Inflammation and oxidative stress in the body are increased as a result of stress, training and competition.  This has been proven in many research trials.  These two processes can then impact not just overall health, but cardiovascular health and likewise tissue intregrity, including blood vessels.  I would theorize that in many cases of EIPH, we actually have an underlying blood vessel weakness due to oxidative and inflammatory damage, which then makes that blood vessel more susceptible to rupture, not too dissimilar to human peripheral vascular disease.  This process can then be further complicated by the impact of stress and diets higher in carbohydrates, such as high grain intakes which then can contribute to gastrointestinal alterations and acidosis.  It is not uncommon in many cases of EIPH to have concurrent ulcers in those patients, either foregut or hindgut, which are then being managed daily with ulcer medications.  It is a matter of who came first in these cases, and how far reaching that damage is in that patient.

What we have seen in numerous patients is that if we utilize various herbs, including curcumin, boswellia and various antioxidants, we can impact the inflammatory and oxidative stress pathways positively.  This can then result in better management of a host of ailments in that patient, including EIPH, and many of those horses require lower doses of diuretics in their pre-race regimen as a result. The problem that comes here is that there is a difference between breeds and how we approach them.  As an example, we may have a lean TB race horse that bleeds that also has concurrent GI ulcers and anxiety. On the other hand, we may have an easy keeper or stockier QH that is barrel racing, that also has EIPH and concurrent GI ulcers with anxiety.  As much as we’d like to treat them the same, it is not that simple in most cases.

In the lean TB racehorse, our typical approach to exercise induced pulmonary hemorrhage is through the use of the Cur-OST EQ Plus along with the Cur-OST EQ Stomach +/- Cur-OST EQ Adapt for anxiety.

In the QH, things are different due to most of these heavier horses actually having underlying gastrointestinal issues such as leaky gut contributing to the overall problem. In these cases, our main approach is through the use of Cur-OST EQ Total Support along with the Cur-OST EQ Adapt if needed for anxiety.  In many of these cases, the underlying gastrointestinal disharmony is actually contributing to the anxiety, so if we manage that problem area well, the anxiety improves on its own.

Many horses with underlying lung disease or inflammation often benefit from the above two approaches, due to the fact that inflammatory process is one of the main targets in therapy.

Other adjunctive or additive approaches include the addition of the Cur-OST EQ Immune formula in those horses with immune related dysfunction, inflamamtory airway disease or recurrent airway infections.  The Cur-OST EQ Nitric Boost is another that can provide both dilatory benefits to reduce pressures, but also an overall enhancement of performance secondary to improved oxygen exchange in the body.  Finally, the Cur-OST EQ Revive has shown some benefits in cases of EIPH associated with overall fatigue or exhaustion, which can impair overall health.

Bottom Line

EIPH (exercise induced pulmonary hemorrhage) is a condition that simply should not be taken lightly.  It impacts performance but also impacts overall health in that patient, and its shear presence indicates that health is not optimal in that patient. There is simply no cure nor is there an easy ‘fix’ in any patient, but more so, we have to recognize the problem for what it is and try to reduce the impact on some level. Despite various medications being heavily utilized and accepted, they simply are not the answer, nor are they improving the health of that animal. If we want to manage this problem better and improve performance, we have to take a different approach, even if that means in conjunction with some medications.  Those approaches are available to you, as a horse owner and trainer.  The question is whether or not one takes advantage of them.  Many horses with EIPH can be positively improved, but time is not on our side and the longer the condition persists, the more damage that is present.  We should take a proactive approach with these cases and if done correctly, we reap the benefits on many levels.


Thank you.

Tom Schell, D.V.M.

Nouvelle Research, Inc


Image courtesy of Google Images


  1. Hinchcliff, KW et al. Association between exercise induced pulmonary hemorrhage and performance in Thoroughbred racehorses. J Am Vet Med Assoc, 2005; 227:768-74
  2. Hinchcliff, KW et al. Equine Sports Medicine & Surgery, second edition, Saunders, 2014;644


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