"Dynamic respiratory endoscopy is very exciting," says Jennifer Smith, DVM, DACVS, New Jersey Equine Clinic. "I really do
believe it is going to change how we look at upper airway disorders in horses. My experience with the DRS has completely changed
the way I interpret upper airway disorders in horses. Basically, what I have found is that it is impossible to predict how
a horse's upper airway will function during exercise based on its appearance on a resting endoscopic exam alone. Horses with
normal-looking airways at rest can experience severe dynamic obstructions during high-intensity exercise, or vice versa —
a horse appears abnormal at rest (ex-asymmetry of the arytenoid cartilages, intermittent displace the soft palate) and maintains
normal function during exercise. I no longer feel comfortable recommending a surgical treatment based on a resting exam alone
or without a dynamic respiratory examination to document the airway disorder."
Photo 6: DVE equipment affixed to a saddle pad.
DRS examination gives veterinarians a way to evaluate patients both for initial diagnostic purposes, pre-purchase examinations,
as well as for treatment follow-up. With DRS, veterinarians are able to compare a horse before and after surgery and provide
objective documentation that the surgical procedure performed either corrected or failed to correct the airway disorder. Ideally,
by having a definitive diagnosis on DRS examination to begin with, practitioners can make better treatment recommendations
and have more favorable outcomes.
There are additional unique advantages to the use of DRS over traditional treadmill endoscopy. For horses that only develop
abnormal noise or exercise intolerance at higher speeds over longer distances or when they are challenged in the company of
other horses, DRS is likely to be more diagnostic than traditional treadmill endoscopy. "You can breeze the affected horse
longer distances or alongside other horses to try to best replicate the conditions in which the horse typically demonstrates
the dysfunction," says Smith. "You cannot do that with treadmill exams."
Scott Hay, DVM, of Teigland, Franklin and Brokken, Fort Lauderdale, Fla., who practices at Calder and various south Florida
racetracks, has had DVE available in his practice for about 9 months. "It's a lot less traumatic for the horse," says Hay.
"For owners or trainers, it's easier to consider using DVE at their home track or training center and not have to ship their
horse to a facility where they could get a treadmill exam done."
Hay says that in south Florida, the nearest treadmill is a five-hour van ride away to the University of Florida School of
Veterinary Medicine. "The other advantage to using this piece of equipment is that it more closely mimics the racing or the
training experience — having the horses go naturally on a racetrack, rather than on a treadmill," says Hay.
Despite the many advantages, there are some minor concerns with the use of DVE. "There are things that can go wrong when you
do it, and I've experienced most of them," Hay says. "It's a somewhat sensitive piece of equipment, so you have to make sure
that everything is hooked up right and that all your pieces are functioning properly. There can be issues with mucus accumulation
on the end of the scope, but this is reported as more of an annoyance than a true problem. Additionally, scope placement can
result in difficulties. Problems have been experienced if the scope is placed improperly or slips during the examination."
During Priest's experience with DVE, there has not been a problem with mucus accumulation or the automatic lavage system,
which rinses the lens. "Once the water is pumped across the lens, you might lose a few frames of video, but it is inconsequential,"
he says. Priest suggests that if you regulate the water and adjust it properly, the mucus causes minimal problems, However,
he does admit that the visual disturbance is variable since some horses produce more mucus discharge than others.
There appears to be a definite learning curve in getting the right positioning of the scope in the horse's airway, but if
you take the time to ensure that it is placed correctly to start with, then the other issues can usually be avoided.
Veterinarians using DVE have also experienced signal abnormalities on some racetracks, preventing continuous visualization
on the monitor. However, the recording system allows the veterinarian to go back and view the examinations later.
"The main thing I tell most people is that we are probably not going to make a solid diagnosis while we are sitting there
watching the horse train," says Hay. "We are going to take the images back to the computer and see what we've got."
Being able to save and send the images to others in the diagnostic and patient loop, including clients, trainers, referring
veterinarians or other specialists, is an important feature to this new technology. "Seeing is believing, as the saying goes,"
says Smith. "And with most of the upper airway disorders, even an untrained eye can appreciate the difference in the size
of a normal airway versus an airway experiencing a dynamic obstruction."
The DVE equipment is still new to most veterinarians, and both the systems and technology are likely to continue to develop
in the future. However, the currently available systems are proving to be reliable, well-tolerated by patients and generally
user-friendly. The clinicians making use of DVE have found that experience with the equipment is invaluable.
While DVE is not designed to replace the use of standing endoscopy and other diagnostic tools, it is another resource for
diagnosing some of the more difficult upper respiratory abnormalities in performance horses.
Racetrack veterinarians may be concerned about the cost and usefulness of this device. Bryan Young, DVM, Young Equine Services,
Cypress, Texas, has some of these concerns. "We have to have a unit that is portable and affordable," he says. "Obviously
it has great application. We'd love to be able to see what these horses' throats look like under tack and at speed. I think
the technology is very exciting, and I'd love to have it. It's just a question of getting it down to where we can afford it
and where we would be able to set it up and use it effectively in a racetrack environment."
An exciting future
Several of the veterinarians currently using DVE systems are enthusiastic about the future of this technology.
"The actual endoscope and the quality of the images are so good now, and the stability of the images is far better than with
the fiberoptic scope that is used on the treadmill," Priest says. "As with all technologies, there might be room for improvement,
but the image quality is very good at this time."
Robertson says, "I think we are going to see some improvements through generations of development."
According to Robertson, audio is currently available on some of the equipment, including audio analysis of recordings, spectrographic
analysis, and graphic analysis of noise frequency. In the near future, an audio component to the video is likely to be a standard
feature, which will allow the practitioner to evaluate sounds that have been heard by jockeys or exercise riders on the racetrack
to determine how significant those sounds are. There is also discussion of incorporating a global positioning system to monitor
the speed and position of the horse on the racetrack when respiratory tract events such as a dorsal displacement of the soft
Veterinarians would also like to know additional data about these patients at the time of respiratory compromise, including
heart rate and respiratory rate. The goal is to provide practitioners with a safe, easy, useful and comprehensive tool that
is affordable to purchase and maintain in private practice.
According to Robertson, the true benefit of DVE is that it is really helping equine patients.
Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and
veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.