Exercise-Induced Pulmonary Hemorrhage in Racing Thoroughbreds: A Preliminary Study

SUMMARY Of 235 Thoroughbred racehorses examined with a flexible fiberoptic endoscope within 2 hours of racing to determine the frequency of exercise-induced pulmonary hemorrhage (eiph), 103 (43.8%) had various degrees of hemorrhage in the tracheal lumen. Two of these horses (0.8%) subsequently had blood flow from the nostrils. Blood seemed to originate from the lung. Statistical analysis of frequency data for 191 horses which finished in 1st, 2nd, and 3rd places did not show any relationship between eiph and horse’s age, sex, or finishing position. However, a trend toward an increased frequency of eiph with age was shown, by a greater proportion of horses 5 years and older having eiph. This trend is thought to reflect the chronicity of the pulmonary lesions and an inability of the lung to repair damaged regions while training and racing continued. The efficacy of furosemide for the treatment of eiph was questioned, since 30 of 56 furosemide-treated horses which were examined had evidence of pulmonary hemorrhage. Nineteen (8%) horses had visible functional abnormalities of the upper respiratory tract.