Inventors of the DDSP Collar File for a Patent

Testing of the Cornell DDSP Collar—an external collar that prevents dorsal displacement of the soft palate (DDSP)—has been so promising that its inventors, Norm G. Ducharme, DMV, MSc, Dipl ACVS, J. Brett Woodie, DVM, MS, Dipl ACVS, and Richard P. Hackett, DVM, MS, Dipl ACVS, have filed for a patent on the collar's design and use with the U.S. Patent Office.

DDSP, also known as choking down, is an upper airway problem common in racehorses and other types of performance horses. During exercise the palate shifts position and the horse can't breath sufficiently. The horse may open its mouth and slow down rapidly or stop to swallow. Sometimes, it may make a gurgling sound when the palate is displaced. Because DDSP disrupts airflow, horses with DDSP can't exercise adequately. The condition is a major problem for the racing industry.

For years, veterinarians have treated DDSP with surgery but it's only 60 percent effective. One day while exercising horses on a treadmill to evaluate how the larynx (voice box) contributes to DDSP, veterinary surgeons Ducharme and Woodie made an interesting observation.

“We found that we could prevent palate displacement by manually holding their voice box while they were running on the treadmill,” Ducharme recalls.

With support from the Zweig Memorial Fund, they designed and tested a collar to perform the same function. Their research on the laryngohyoid stabilizer (LHS), commonly known as the Cornell DDSP Collar, was presented at the American College of Veterinary Surgeons meeting on October 10, 2003, in Washington, D.C.

“We think this collar could have widespread application for the racing industry, because nearly 90 percent of racehorses wear tongue-ties, at least partly, to stabilize the upper airway,” says Ducharme. “This collar could be used widely during training and racing to prevent palate displacement. If the tongue-tie alternative collar is not approved for racing, the collar could be used to identify horses that will respond to surgery.”

To test the collar's effects on airflow, ventilation, and its ability to prevent DDSP in exercising horses, Ducharme, Woodie, and Hackett evaluated ten adult horses in a two-phase study. In phase one, a control group of healthy horses exercised on a high-speed treadmill with and without the collar. In phase two, the surgeons performed a bilateral resection of the thyrohyoideus muscles (TH) to create exercise-induced DDSP. These horses were tested twice with and without the collar. The researchers used videoendoscopy, analyzed arterial blood gas samples, and analyzed static tracheal and pharyngeal pressures. In separate trials, they measured airflow and tracheal pressure. In each trial exercise, data were collected while the horses exercised on the treadmill at 75, 90, and 100 percent of maximum heart rate.

“From these measurements, we calculated if the airway was impeded,” says Woodie. “While the collar had no effect on exercising horses with a normal upper airway, the LHS prevented the DDSP from occurring in 13 out of 14 experimental trials. In other words, the LHS, when placed in proper position, does not reduce the integrity of the upper airway and can prevent experimentally created exercise-induced DDSP.”

The researchers now are field testing the collar on Thoroughbred racehorses at New York racetracks, thanks to funding from the New York Thoroughbred Horseman's Association, Inc.

“This collar could be used widely during training and racing to prevent palate displacement.” - Norm Ducharme