Page 16 - 27 April 2012

Endoscopy of the upper airway while the horse is
exercising is an invaluable tool for diagnosing problems the equine athlete may experience.
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Dynamic endoscopy on a treadmill.
DYNAMIC ENDOSCOPY
Diagnosing upper airway abnormalities.
by J. Brett Woodie, DVM, MS, Dipl. ACVS
Upper airway abnormalities are common causes for poor performance in the equine athlete. Racehorses are not the only equine athletes that
suffer performance problems related to upper airway problems. Horses of all breeds and disciplines can be and are affected with upper respiratory problems.
The horse is an obligate nasal breather, so all the air needed for oxygenation must pass through the upper airway. The upper airway of the horse must accom- modate a very large increase in airflow during exercise. During maximal exertion the upper airway must handle more than a 20-fold increase in airflow com- pared to airflow at rest. The upper airway also must withstand significant negative pressure that is gener- ated during exercise. There is a nine-fold increase in the amount of negative pressure generated in the upper airway at exercise compared to resting conditions. It is easy to understand that what may seem like a minor abnormality at rest can be a big problem at exercise.
An endoscopic examination is the primary diagnostic tool used by veterinarians to evaluate the upper airway. Numerous upper airway abnormalities can be diagnosed from a resting endoscopic exami- nation. However, endoscopy of the upper airway while the horse is exercising is an invaluable tool for
diagnosing dynamic problems the equine athlete may experience. A dynamic problem is only present during exercise and will not be evident at rest or during an endoscopic examination immediately after strenuous work. Oftentimes a dynamic examination will clarify multiple problems of the upper airway. This is vital information so that all problems can be addressed. Case selection for an endoscopic examination while exercising includes horses that are experiencing unex- plainable poor performance; those making abnormal respiratory noise with a normal resting endoscopic examination; horses that have an abnormal finding on resting endoscopy but the effect still needs to
be assessed at exercise; and cases in which there is a concern for a dynamic upper airway problem.
There are two methods that can be used to evaluate the upper airway during exercise. One is a treadmill examination and the second is overground endoscopy. Overground endoscopy uses endoscopic equipment that is attached to the horse so that the upper airway can be examined while the horse is working under their natural conditions.
Once the decision has been made to evaluate the horse using a dynamic examination we must make sure that the horse is as fit as it is for competition.
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SPEEDHORSE, April 27, 2012
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