Received: 9 February 2024 | Accepted: 12 February 2024 DOI: 10.1111/eve.13962


C L INI C A L COMMENTA RY Pulmonary haemorrhage in athletes: Equine and beyond


Kile S. Townsend Veterinary Health Center , University of Missouri , Columbia , Missouri , USA


Correspondence: Kile S. Townsend Email: townsendks@missouri.edu


In the case report described in this issue, Kopec et al. ( 2024 ) present a hitherto unreported complication associated with a bronchoalveolar lavage (BAL) procedure in a Thoroughbred with historical exercise- induced pulmonary haemorrhage (EIPH). Haemopneumothorax was diagnosed in the gelding 2 days after the BAL procedure was per- formed. The gelding was a National Hunt horse, expected to perform as an athlete with a high level of fitness required to be successful in this type of racing competition. Although haemopneumothorax has now been reported as a pos-


sible complication (Kopec et al., 2024 ), it is an unusual outcome after performing an equine BAL. Pneumothorax has been reported as a complication in human medicine but is often seen in relation to pre- existing conditions, especially conditions causing infectious intersti- tial emphysema (Krueger et al., 1988 ). In equine medicine, BALs are utilised commonly for characterisation and diagnosis of conditions affecting the lung diffusely (Couetil & Thompson, 2020 ). Some such diffuse pulmonary conditions include equine asthma (EA), EIPH, or infectious causes such as viral, parasitic, or diffuse fungal disease. BAL is used frequently because it is relatively easy to perform, low cost, and has few reported severe complications. Analysis of BAL fluid is performed commonly to diagnose EA and is helpful in identi- fying subclinical EIPH (Couëtil et al., 2016 ). Indications for BAL fluid collection and analysis in a racehorse often include signs such as poor performance, exercise intolerance, cough, or nasal discharge. It is recommended that a BAL is performed as part of a complete workup and not in isolation to diagnose or monitor disease. The case report by Kopec et al. ( 2024 ) describes the veterinar-


ian observing blood at the nostrils immediately post- BAL procedure and subsequent diagnosis of haemopneumothorax in the following days. When epistaxis is observed in the equine athlete in a period surrounding exercise, it is more than likely a result of pulmonary haemorrhage (Crispe & Lester, 2019 ). Any time epistaxis is observed in horses, a further workup is recommended to rule out any im- mediately life- threatening conditions (i.e. guttural pouch mycosis). Pulmonary haemorrhage in equine patients is commonly associated with vigorous exercise and has been reported in humans undergo- ing strenuous exercise (Ghio et al., 2006 ). Although EIPH is encoun- tered frequently in horses, there may be other causes of pulmonary


Equine Vet Educ. 2024;36:293–295.


haemorrhage identified in horses, such as atrial fibrillation, inflam- mation, infection, or trauma. The majority of Thoroughbred race- horses are believed to have at least one episode of EIPH during their career and other high- intensity equine athletes have been shown to have EIPH episodes as well (West et al., 1993 ). Quarter Horses par- ticipating in barrel racing, endurance horses, and horses competing in high- level show jumping events have been shown to demonstrate pulmonary haemorrhage during or after athletic events (Bonomo et al., 2019 ; Hinchcliff et al., 2005 ; Sundman et al., 2020 ; Tarancón et al., 2019 ). It is a common cause of epistaxis in an equine athlete and warrants further diagnostic tests and exploration. Why does pulmonary haemorrhage occur? From human medi-


cine and exercise physiology, it is known that intense exercise (such as playing sports and running) can result in lung injury due to high pulmonary pressures and increased blood volume (Bove, 2016 ). The same can be extrapolated to equine athletes exercising intensely. Haemorrhage into the respiratory system is believed to occur when there is an increase in pulmonary arterial pressure resulting in fa- tigue and failure of pulmonary capillaries, leading to the spillage of blood into the alveoli and subsequently into the airways (if there is a large enough volume of blood) (West et al., 1993 ). Pulmonary arterial pressure rises massively in exercising horses due to the horse ' s ability to expand circulating volume by splenic contrac- tion during exercise. Horses can achieve large stroke volumes with heart rates reaching ~240 beats per minute during exercise (Poole & Erickson, 2016 ). Pulmonary capillary leakage occurs during exercise when left atrial pressure increases related to left ventricular sys- tolic or diastolic failure and low airway pressures occur (Bove, 2016 ; Crispe & Lester, 2019 ).


In humans, it is believed that pulmonary


oedema and haemorrhage during exercise occurs especially when diastolic left ventricular dysfunction results in elevated left atrial pressure (Bove, 2016 ). Pathologic changes to the lung are seen with repeated injury. Abnormalities such as pulmonary vein wall remod- elling, fibrosis, and angiogenesis are also believed to increase ve- nous occlusion, contributing to capillary rupture in EIPH (Derksen et al., 2011 ; Rocchigiani et al., 2022 ; Williams et al., 2008 ). The concept of an ‘athlete ' s heart’ is an area that has been ex- plored in human medicine with some spillover into the equine world.


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