Exercise-induced pulmonary hemorrhage in Thoroughbreds after racing and breezing.

Thoroughbred horses (n = 191) were examined with a flexible fiberoptic endoscope within 2 hours of racing on a dirt track; 147 (75.4%) had evidence of exercise-induced pulmonary hemorrhage (EIPH), and 13 (9.0%) had blood at the nostrils. Of 107 Thoroughbreds examined within the same period after breezing, 41 (38.3%) had evidence of EIPH. One horse (2.4%) of this group had blood at the nostrils. Statistical analysis of frequency data showed that a relationship existed between EIPH and the horse's age or distance raced or breezed. Relationship did not exist between EIPH and sex or finishing position. Thoroughbreds were also examined endoscopically after steeplechase, flat turf, and timber races; 67.7% (21/31), 14.3% (2/14), and 66.6% (2/3) of the horses in such races were EIPH-positive, respectively; and 14.3% (3/21), 0% (0/2), and 100% (2/2) of these EIPH-positive horses had blood at the nostrils. Of 32 breezing Thoroughbreds in a 3rd survey, 21 (65.5%) were EIPH-positive. None bled from the nostrils. Endoscopic findings of EIPH are repeatable in the horses, indicating that bleeding is not a random event.