Examining the Airway
We have previously discussed the genetics behind “roaring” and how science is starting to get to the point of being able to identify the variants within the genes responsible for a problem that all owners and trainers hate to face. It is going to take some time for this to eventuate, but in the meantime there are some very interesting developments in terms of overground videoendoscopy that will enable veterinarians, trainers and owners to better understand the upper airway under race pressure.
In a paper presented in this month’s ‘early view’ of the Equine Veterinary Journal, scientists discuss the use of an overground videoendoscopy used under race day conditions. Overground videoendoscopy provides an alternative to high-speed treadmill videoendoscopy (HSTE) for diagnosing upper airway obstructions in exercising horses. Overground endoscopy may be preferable to HSTE because it more closely approximates competition conditions (presence of full tack, track surface, weight of rider/sulky, differences in head position, actions of drivers/riders and increased motivation associated with adjacent competing horses) and comparisons between HSTE and overground training have identified important physiological differences in heart rate, blood lactate, stride length and stride frequency. As a result, treadmill speed or incline is frequently increased in order to render it as intense as overground testing.
The study looked at Forty-six Standardbred racehorses racing in qualifying races (non-wagering official qualifiers of a standard one mile [1600 m] distance with a published standard total race time i.e. qualifying standard) or schooling races (2 year also non-wagering 1600 m training races which also conforms to requirements adopted by the state racing commission). The procedure did not interfere with performance as there were no significant differences in race times between races in which horses were examined with the endoscope in place and prior unexamined races. Airway obstructions during or after the race were documented in 21 of the 46 horses. Most common causes of upper airway obstruction were observed including bilateral ventro-medial arytenoid displacement and dorsal displacement of the soft palate. Although dorsal displacement of the soft palate was the most common diagnosis made, interestingly many displacements occurred after the race when the horse was being brought back to slower paces. The study also showed that many drivers were aware of when a horse had a breathing issue as the horse would make a ‘noise’ of some description but it was also clear that there is a percentage of ‘silently’ performing horses that have abnormal upper airway morphology.