ENDOSCOPIC ANATOMY AND MAP OF THE EQUINE BRONCHIAL TREE

To develop a bronchoscopic map of the equine respiratory tree, the maj or airways of the lungs of 6 healthy Thoroughbred horses were systemat ically explored with a flexible fibreoptic endoscope through a tracheo stomy while the horses were sedated in stocks. With the carina as the reference point, measurements were made of distances to the branches o f the major airways using markers on the shaft of the endoscope. All b ranches were explored until the narrowing of their diameters prevented further advancement of the endoscope. Positions of origins of branche s from the parent bronchus were recorded in relation to a 12 h clock. Branching patterns of the right and left lungs were similar. Seventeen branches of the principal and caudal lobar bronchi of the left lung, and 18 branches of the principal and caudal lobar bronchi of the right lung were identified. Mean explorable distances from the carina to th e ends of the right and left caudal lobar bronchi were 34.0 +/- 3.5 (s d) and 34.5 +/- 3.0 cm, respectively. Generally, smaller horses had sh orter explorable bronchial lengths. Branching patterns of the parent b ronchi were fairly consistent among horses, particularly the branches closest to the carina. After endoscopy and euthanasia, the lungs were removed, and dried with pressurised air flowing through them for 7-10 days. Attempts to explore the airways of the dried lungs endoscopicall y were relatively unsuccessful, because airways were much smaller in t he dried lungs, and many of the branches were distorted when compared with their antemortem appearances. However, having a dried lung specim en as a reference during the bronchoscopic procedure was useful for ma intaining orientation in the lungs. Radiographs were used to estimate the location of the origin and destination of each airway branch in re lation to the nearest intercostal space. This makes the airway map use ful when lesions identified radiographically are to be lavaged.