Exercise-Induced Pulmonary Hemorrhage (EIPH) refers to bleeding from
blood vessels within the lung (pulmonary) which occurs
during strenuous exercise (exercise-induced). Whilst
it has been documented for over 300 years that a small
percentage of racehorses show blood at the nostrils
after racing (e.g. Bleeding Childers, Herod), it was
not until the introduction of fiber-optic endoscopes
(devices for looking into the airways; they are passed
via the nostrils in the conscious horse) that it became
clear that blood observed at the nostrils during or
following strenuous exercise nearly always originated
from the lung.
With the more widespread use of endoscopy in veterinary
practice and veterinary research, it is now clear that
40-75% of Thoroughbred horses will have some blood in
their trachea (windpipe) after racing. The degree of
bleeding varies considerably between individual horses,
with horses showing visible blood at the nostrils often
being referred to as "bleeders".
