Upper Respiratory Obstructions

United Kingdom researchers found that dorsal displacement of the soft palate and palatal instability were to blame for poor performance in 78.5% of the horses examined in a recent treadmill study of Thoroughbred racehorses. They also found that horses were often affected by more than one airway obstruction at the same time. The study results were published in the September issue of the Equine Veterinary Journal.

University of Bristol researchers used video endoscope recordings from treadmill workouts to examine the upper airways of 600 horses brought to the university with complaints of poor performance. They reviewed the recordings both in real time and in slow motion. Of the 600 horses, researchers diagnosed upper airway disorders in 471 of them.

Researchers found that study horses with upper airway disorders were most commonly affected by dorsal displacement of the soft palate (DDSP; 50%) and palatal instability (33%). They also found that younger horses were at increased risk of DDSP, while older horses were at greater risk for palatal instability.

Dorsal displacement of the soft palate is characterized by a fluttering noise that occurs during strenuous exercise that  is caused by the soft palate (the rear roof of the mouth) moving up and over the epiglottis (a triangle-shaped piece of cartilage that prevents food from entering the windpipe) and partially blocking the airway.

Palatal instability is the vertical “billowing” of the soft palate without displacement of its caudal (toward the rear) border (similar to what causes snoring in humans). It often precludes DDSP.

The data showed that 30% of the study horses were affected by more than one disorder. Researchers said, "Complex obstructions, where more than one structure collapses into the airway, occur frequently and therefore treatments that address solitary disorders may often be unsuccessful."

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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