By Kate Allen and Geoffrey Lane
The majority of upper airway (‘wind’) disorders affect the regions of the pharynx and larynx. Most of these conditions are only present during exercise, when the upper airway is exposed to large changes in pressures associated with increased breathing rate and effort. This is the reason why performing endoscopy at rest may not give an accurate diagnosis. Endoscopy during strenuous exercise (overground endoscopy) has become key for veterinary surgeons to be able to give an accurate interpretation of upper airway function.
There are many different forms of upper airway disorders. They occur when part of the pharynx or larynx collapses into the airway, causing an obstruction to airflow. This obstruction causes turbulence to airflow, which in turn creates the abnormal noise. Observations of upper airway function during exercise enable veterinary surgeons to estimate the impact of the abnormalities with respect to race performance. Generally speaking, the more the structure collapses and the more the airway is narrowed, the greater the detrimental effect to performance. The mechanisms by which upper airway disorders affect performance are surprisingly complex, but in brief they influence the amount of air the horse can breathe in and also how hard the horse has to work to get that air into the lungs.
A full understanding of an individual horse’s upper airway function allows targeted treatments to be performed. Although the more common treatments have been included here for completeness, it is important for you to discuss individual horses with your own veterinary surgeon.
Understanding the anatomy is the first step to interpreting upper airway function during exercise. When looking at an endoscopic image, the left side of the horse is on the right side of the image as we look at it, and vice versa (figure 1).