Upper respiratory endoscopy is performed in a resting patient and allows excellent visualisation of the structures but gives little information about the functional ability and capacity of the larynx and pharynx.
Overground endoscopy, or exercise endoscopy, is performed by inserting a firm endoscope into the horse’s nasal passages to sit looking at the pharynx / larynx area. The horse is then exercised, and the data is sent to a computer located underneath the saddle.
The video is recorded and can then be played back in slow motion allowing visualisation and assessment of the function of the larynx and pharynx at fast (gallop) exercise.
There are numerous conditions which can only be diagnosed during exercise so an overground endoscopy is considered the gold standard for airway diagnostics. Since the advent of overground endoscopy it has been realised that a single respiratory problem rarely occurs in isolation but an overground endoscopy is required to diagnose the other, more subtle but still important, functional abnormalities.