A racehorse running at top speed breathes about 120 times per minute, moving about 12-15 liters of air per breath or 1,400-1,800 liters per minute. With this amount of airflow, it’s not hard to imagine that any amount of airway inflammation can significantly affect performance. Unfortunately, the problem is common in horses, said Susan J. Holcombe, VMD, PhD, Dipl. ACVS, ACVECC, at the 2005 American Association of Equine Practitioners Convention, held Dec. 3-7 in Seattle, Wash.

“Airway inflammation is a key component of respiratory disease in all mammals,” she explained. “It is responsible for bronchoconstriction (narrowing of airways), mucus/edema production (which can clog airways and decrease ventilation), and cause tissue damage (possibly leading to exercise-induced pulmonary hemorrhage). It can also cause tissue remodeling and fibrosis (this can impair gas exchange) and perhaps chronic changes in the lung that can decrease a horse’s ability to perform long-term.”

Holcombe discussed two types of airway inflammation: Upper airway inflammation (pharyngitis) and inflammatory airway disease (IAD), which affects the lower airways